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Effect of throat size of turbine guide on performance of gas turbine starter
FAN Xiaoqian, WANG Yangbing, LIU Yiming, BAI Jie
, Available online  , doi: 10.13224/j.cnki.jasp.20230775

This article takes a gas turbine guide used on a gas turbine starter as the research object, and the effect of throat size of gas turbine guide on the performance of gas turbine starter and components were studied using experimental methods and numerical simulation. The results of experimental reseach on A、B、C three types of gas turbine guide (average outer diameter of the throat is ϕ111.27 mm、ϕ111.94 mm、ϕ112.34 mm) indicates: type C starter compared to type A starter, normal starting time becomes shorter by 14%, output shaft disengagement speed of lose efficacy starting increases by 7.1%, maximum output power increases by 11.6%, the performance of starter is improved significantly. Numerical research results indicates: type C compared to type A, the flow rate of turbine stage increases by 3.6%, maximum output power of power turbine increases by 12.2%. The increase in power turbine power is attributed to the combined effect of increased flow rate、increased temperature and increased temperature drop. In summary, the outer diameter of gas turbine guide throat changes the matching point of entire gas turbine by affecting the performance of turbine stage, then the overall performance exists a certain degree of dispersion.

Numerical study on the flow and sound characteristics of split three-stream nozzle
YANG Yuming, ZHOU Li, SHI Jingwei, WANG Zhanxue
, Available online  , doi: 10.13224/j.cnki.jasp.20230078

The influences of the three-stream introduction and the tertiary bypass ratio on the flow and noise characteristics of the three-stream nozzle were studied by the numerical simulation method. The results showed that the three-stream introduction increased the length of the bypass potential core, shortened the axial distance of the direct mixing between the end of the primary potential core and the free stream, and reduced the peak value of the turbulent mixing between them by about 2.63%. However, due to the increase of the shear layer thickness, the low-speed three stream had limited noise reduction effect in all directions. The increase of the tertiary bypass ratio was easy to achieve, at the cost of reducing fuel consumption, and it can increase the engine thrust and reduce the broadband noise of the exhaust system. The increase of tertiary bypass ratio to 2.52 weakened not only the turbulent mixing intensity at the end of the primary potential core, but also the mixing intensity of the strong shear layer between the three stream and the free stream. Compared with the design condition, the mixing intensity at the end of the primary potential core decreased by 8.57%, and the overall sound pressure level decreased in all directions, with a peak value of about 2.37 dB.

Effect of reaction progress on temperature measurement system error of gas analysis method
LI Hao, LIU Yong, ZHANG Xiang, YANG Chen, LIU Chongyang
, Available online  , doi: 10.13224/j.cnki.jasp.20230075

It is generally believed that the error of gas temperature calculation based on enthalpy conservation method is caused by the error of direct measurement and the influence of high temperature decomposition. However, in the test of a certain high temperature combustion chamber, it was found that, taking thermocouple measurement results as the reference standard to evaluate the performance of gas analysis method under high temperature environment may introduce a large response error, so the turbulent flame experimental data of Sandia laboratory were used as reference standard to compare and analyze the temperature of each measuring point. The results showed that the overall average error of the temperature calculated by the enthalpy conservation method was small compared with the temperature measured in the experiment, but there were large errors in the initial reaction region and the combustion region. Further research found that: the uncertainty of temperature measurement in gas analysis was mainly derived from reaction progress. The uncertainty of temperature calculation results can be quantified by using reaction progress variable, and the applicable range of gas analysis method can be judged and limited, providing a reference for further research on the application of the enthalpy conservation temperature measurement method in the temperature measurement of turbulent flame and engine combustion chamber and the evaluation of uncertainty.

Numerical simulation method for the random vibration response of thin-walled conical shells of composite materials
WANG Zhizhou, MA Yanhong, HAN Ding, WANG Yongfeng, HONG Jie
, Available online  , doi: 10.13224/j.cnki.jasp.20230073

A specific tail nozzle of a supercharged ramjet engine was selected as the object of analysis. A three-dimensional finite element analysis method was employed to establish a finite element model of the tail nozzle, enabling investigation of the vibration characteristics of the thin-walled conical shell, structural dynamic response analysis under random vibration conditions, and validation through dynamic experimental tests. The results indicated that the tail nozzle exhibited a diverse range of modal characteristics, primarily characterized by multi-order nodal circle and nodal diameter vibrations. Under axial random vibration loads, the dominant vibration mode observed was m=6, n=1, with the aft section of the nozzle experiencing significant amplitudes and notable amplification of acceleration. This section may be considered as a vulnerable area for dynamic design considerations. The simulation results agreed well with the experimental data, with modal frequency errors within 10%, meeting the requirements for engineering calculations. Therefore, the simulation method with practical value can provide a reference for the dynamic design and evaluation of supercharged ramjet engines.

Flow loss mechanism of high subsonic compressor blade vibration under low Reynolds number conditions
CHEN Caiyan, ZHANG Yanfeng, ZHANG Jianshe, ZHANG Yingqiang, DONG Xu, WANG Mingyang, LU Xingen
, Available online  , doi: 10.13224/j.cnki.jasp.20230086

In order to investigate the influence of high subsonic compressor blade vibration on the flow state of the surface layer under low Reynolds number (Re) conditions, numerical simulations were conducted to analyze the rule of separation, re-attachment, transition and flow loss of compressor blade surface boundary layer under different vibration frequencies. According to the simulation results, under the condition of Re=1.5×105, the increase in the normal relative velocity of the vertical wall of the surface layer caused by blade vibration could trigger the mixing of the separated surface layer with the mainstream in advance, which promoted the advance of transition. In this case, the normal velocity pattern at normal position near the wall was fuller, which improved the ability of the boundary layer to resist separation and limited the development of the separation bubble. In addition, the boundary layer and separation bubble thickness became "thin" due to blade vibration, which reduced the accumulation of low-energy fluid at the trailing edge, and weakened flow blockage near the trailing edge and wakes mixing, thereby reducing flow loss and improving the aerodynamic performance of the high subsonic compressor blade under low Re conditions.

Numerical simulation for the hypersonic flow structure and thermal environment of non-rectangular cavities in the rarefied slip regime
JIN Xuhong, YAO Yuzhu, CHENG Xiaoli, ZHOU Jingyun
, Available online  , doi: 10.13224/j.cnki.jasp.20220755

In order to quantify the local high pressure and heat loads due to cavities or imperfections on the surface of hypersonic vehicles, the direct simulation Monte Carlo (DSMC) was utilized to simulate the rarefied hypersonic flows over cavities in the slip regime. Three kinds of cavities were taken into account: the standard rectangular cavity, the shallower-front cavity, and the shallower-back cavity, for the purpose of gaining the effects of cavity-floor shape on flow characteristics inside the cavity, surface pressure and heat transfer to the cavity surfaces. Results showed that the cavity-floor shape had little influence on flow characteristics, including the streamline pattern, vortex-core position and density distribution, inside the upper part of cavities. Therefore, the surface pressure and heat transfer to the upper part of the aft wall of the cavity was kept unchanged when the front or back part of the cavity floor became shallower. However, in comparison with the standard rectangular cavity, both the shallower-front and shallower-back cavities suffered more severe heat loads on the cavity floor. Especially, the peak value of heat transfer to the cavity floor in the case of shallower-back cavity was 100 times larger than the corresponding value in the standard rectangular cavity. In the design of spacecraft, the cavity floor is exactly taken as the spacecraft surface, so much attention should be paid to the pressure and heat loads on the cavity floor in case of shallower-back cavity.

Structural parameters of pintle on transcritical combustion efficiency of liquid oxygen/methane engine
TAN Tianjun, ZHANG Bin, LI Zhiqiang, XIANG Jixin, XU Jifeng, REN He, ZHENG Xiaoxia
, Available online  , doi: 10.13224/j.cnki.jasp.20220825

To study the effects of pintle structural parameters on the combustion efficiency in transcritical combustion, a standard k-ε turbulence model and a non-adiabatic stable diffusion flamelet model were utilized to numerically study the transcritical combustion of an LOX/CH4 pintle engine considering the real gas properties of fluid. The study analyzed the impact of various methods for calculating physical properties on the flow field within the thrust chamber, and the effects of radial and axial annular seam width of pintle injector on engine combustion efficiency were analyzed. The results showed that the size of both the central recirculation zone and the high temperature zone was reduced when considering the transcritical effect. Within a certain range, as the radial annular seam width increased, the combustion efficiency initially decreased and then increased, as the axial annular seam width increased, the combustion efficiency decreased. A greater combustion efficiency can be achieved by reducing the axial annular seam width and increasing the radial annular seam width. When the total momentum ratio was less than 1, increasing axial momentum can effectively improve mixing. However, if the total momentum ratio was greater than 1, increasing axial momentum can hinder the improvement of mixing. The combustion efficiency decreased with the increase of the total momentum ratio. When the total momentum ratio for different operating conditions was similar, the operating condition with a higher momentum ratio exhibited a higher combustion efficiency.

Optimization of kinematic parameters of 3D forward flapping wing
XU Qiyan, ZHU Jianyang, ZHU Mingkang, XIE Peng
, Available online  , doi: 10.13224/j.cnki.jasp.20220083

In order to improve the lifting efficiency of the flapping wing, the analyzing of the three kinematic parameters of reduced frequency, flapping amplitude and pitching amplitude influence on the aerodynamic performance of flapping wing were carried out by the combination of the Taguchi test and numerical solution of three-dimensional N-S equation. The results show that compared with the worst parameters combination, the average lift coefficient and lifting efficiency of the best parameters combination flapping wing are increased by 52.1% and 85.52% respectively. The range of the influence on the aerodynamic performance of flapping wing is reduced frequency, flutter amplitude and pitch amplitude in turn. Further, through the analysis of the flow field on the flapping wing surface, it is found that the best parameters combination can enhance the intensity of the vortex attached to the flapping wing surface and promote the formation of von Karman vortex street in the wake of the flapping wing, so as to lead the flapping wing to have better aerodynamic characteristic.

Parametric modeling method and mechanical behavior of 3D woven composites with warp insertion
GUO Yingzhao, CUI Haitao, WEN Weidong, ZHANG Hongjian, ZHAO Siyu, JU Hongkui, GUO Junhua
, Available online  , doi: 10.13224/j.cnki.jasp.20220950

To describe the microstructure and mechanical behavior of woven composites more accurately, a parametric model construction method for 3D woven composites with warp insertion was established. The equality constraints among the parameters in the geometric model were investigated, and the geometric constraint model was developed to realize the parametric description of the geometric model. Based on the geometric constraint model, the construction method of the parametric model was discussed, and the mapping relationship between the geometric model and the actual structure was established by input parameters, which not only improves the reduction degree of the geometric model to the actual structure but also provides guidance for material analysis and design. The progressive damage model was applied to predict the strength of 3D woven composites in the warp direction, and the prediction results were compared with the experimental results. Under the tensile load, the failure mode of the warp and binder yarn is mainly longitudinal fracture, the failure mode of the weft yarn is transverse fracture, and the failure mode of the resin-rich region is tensile fracture. The predicted strength of the material in the warp direction is 853.6 MPa, with a relative error of 2.3%, which is basically consistent with the experimental results.

Characteristics of shaped holes on the pressure surface of turbine vane
JIANG Yan, LI Haiwang, XIE Gang, TAO Zhi, ZHOU Zhiyu
, Available online  , doi: 10.13224/j.cnki.jasp.20220963

Numerical simulations were employed to investigate the performance on the flow fields and heat transfer characteristics of four types of film holes, cylindrical holes, laidback fan-shaped holes, fan-shaped holes and laidback holes, on pressure surface of the turbine vane. Fan-shaped holes equipped with the lateral divergence angle of 12 degrees compared to cylindrical holes, and laidback holes equipped with the forward divergence angle of 7 degrees. Furthermore, laidback fan-shaped holes expanded in both directions. The adiabatic film cooling effectiveness, the heat transfer coefficient ratio and the net heat flux reduction were estimated parameters for quantitative comparative analysis. Results showed that fan-shaped holes and laidback fan-shaped holes showed the maximum adiabatic film cooling effectiveness in the range of blowing ratios. When the blowing ratio was 2, the film cooling effectiveness of fan-shaped holes and laidback fan-shaped holes were improved to the greatest extent by 128.9% and 146.9% in contrast to cylindrical holes, respectively. Additionally, laidback fan-shaped holes had the largest net heat flux reduction, 28.8% higher than cylindrical holes, which indicated the laidback fan-shaped hole was the best scheme. And the forward divergence angle had less influence on the flow and heat transfer characteristics than the lateral divergence angle due to advantages of laidback holes were not obvious. Besides, the effect of the film cooling effectiveness on net heat flux reduction was dominant on account of similar distributions of net heat flux reduction and the film cooling effectiveness.

Numerical analysis on cooling performance of quasi-elliptic multi inclined holes in CMC combustion liner
YU Guoqiang, SUI Zhengqing, CHEN Zhengyang, NI Zheng, DU Jinkang, GAO Xiguang, SONG Yingdong
, Available online  , doi: 10.13224/j.cnki.jasp.20230084

In order to improve the cooling performance of ceramic matrix composite combustion liner wall, a new quasi-elliptic multi-inclined hole cooling structure was designed on the basis of the existing circular multi-inclined hole cooling structure. Meanwhile, the cooling effects of two kinds of multi-inclined hole structures were compared by using three-dimensional numerical simulation method. The results showed that: compared with the circular hole feature simulator, the high temperature area on the wall of the new quasi-elliptic inclined hole simulated part was obviously narrower, the hot spots at high temperature were reduced, and the temperature distribution was more uniform. In the warp yarn direction, the high stress area of the simulated part with quasi-elliptic inclined hole features was reduced, and the stress concentration phenomenon was weakened. In the weft yarn direction, the high stress regions in the feature simulators of quasi-elliptic inclined hole and circular hole were found.

Dynamic characteristics analysis of the complex rotor-blade system for the aero-turboshaft engine
JIN Miao, WANG Ailun, WANG Qingshan, YIN Yijun, HENG Xing, ZHANG Haibiao
, Available online  , doi: 10.13224/j.cnki.jasp.20220739

The equivalent contact model of the end-tooth connection including three stages such as the elastic, elastoplastic and plastic deformation was proposed using the Hertz contact theory in conjunction with the mathematical statistics method. In view of the complex structure of the aero-turboshaft engine, the general dynamic model of the complex rotor blade system, including the end tooth connection considering the contact effect, was established based on the finite element method and Hamilton's variance principle. The concrete finite element results demonstrated the validity and correctness of the analytical model. And on the basis, the effects of the pre-tightening forces on the natural frequencies, transient and steady unbalance responses were further investigated. The results showed that the effects of the pre-tightening forces had a significant effect on the contact state of the end-tooth connection. In the relaxation state of the pre-tightening force, the slippage of contact interface can reduce the bending and torsional stiffness of the end-tooth connection, leading to a decrease in the connection stiffness of the end-tooth connection. For the transient and steady-state unbalanced responses, there existed obvious amplitude amplification phenomena in the rotor vibration in x direction, torsional direction and bending vibration of the blade tip. The saturation stage of the pre-tightening force was selected at the range of 2.0×104—2.0×105 N, the end tooth connection was approximately equivalent to the rigid connection. The results provide a quantitative reference for the design of the aero-turboshaft engine considering the end-tooth connection under the action of the pre-tightening forces.

Research and application of SST turbulence surrogate model based on neural network
LIANG Shuang, GUO Mingming, YI Miaorong, TIAN Ye, SONG Wenyan, YANG Maotao, ZHANG Yi, LE Jialing
, Available online  , doi: 10.13224/j.cnki.jasp.20220759

In view of the problem that traditional turbulence model has many parameters and is slow to obtain complex flow data, various kinds of neural network algorithms were studied to construct the turbulence surrogate model of the Navier-Stokes solver in supersonic flow. The cavity under supersonic flow conditions was taken as the research object, and the Latin hypercube sampling method was used to obtain the sample space of nine parameters of the standard SST turbulence model. The independently developed hypersonic internal and external flow coupling numerical simulation software AHL3D was used to carry out numerical simulation at the incoming flow Mach number of 2.92 Ma to obtain the wall pressure data, and then the dataset was constructed. Various kinds of models such as deep neural networks (DNN), residual neural network (ResNet), and long short-term memory (LSTM), which were trained by the training dataset, were used to build the SST turbulence surrogate model. The experimental results showed that: under certain SST turbulence model parameters, these three neural network surrogate models can predict the wall pressure with high accuracy, and the coefficient of determination was above 0.99, which was basically consistent with the results of the numerical simulation solver, and can be used to quickly obtain the wall pressure under different turbulence model parameters.

Film cooling performance and optimization of ellipse conical holes onturbine vanes leading edge
JIANG Yan, LI Haiwang, XIE Gang, ZHOU Zhiyu
, Available online  , doi: 10.13224/j.cnki.jasp.20220736

Simulations were employed to study the film cooling effectiveness of ellipse conical holes on the leading-edge of turbine vane. The influences of two geometry parameters, forward and lateral expansion angle, on the adiabatic film cooling effectiveness were studied comparatively. And optimization was also conducted within the range of forward and lateral expansion angle, 0°—18° and 0°—16°, respectively. Results showed that the ellipse conical hole with a forward expansion angle of 1.4° and a lateral expansion angle of 11.1° presented the highest film cooling effectiveness, which was 147.5% higher than that of the cylindrical hole. Moreover, the relationship between the two geometry parameters and the film cooling effectiveness can be fitted to quartic function. When lateral expansion angle was low, the film cooling effectiveness increased with forward expansion angle. Otherwise, the film cooling effectiveness decreased with forward expansion angle. Additionally, when forward expansion angle was lower, the film cooling effectiveness increased and then decreased with lateral expansion angle. And the film cooling effectiveness was roughly constant or showed a small increase with lateral expansion angle.

Study on airworthiness compliance demonstration method of aeroengine components fabricated through selective laser melting technique
GUO Jing, HE Xin, ZHOU Chenyang, FU Qiuju, LIU Wei, WANG Tianyuan, WU Yu
, Available online  , doi: 10.13224/j.cnki.jasp.20230765

Motivated by the demand of airworthiness compliance of civil aeroengine components fabricated using selective laser melting (SLM) technique, this paper summarizes applications of SLMed aeroengine components. Additionally, reference related to airworthiness compliance of SLMed components are analyzed. Meanwhile, airworthiness compliance demonstration method of SLMed aeroengine components is investigated. Presently, some SLMed aeroengine components have passed the airworthiness certification in foreign countries. However, China is still in the initial stage in this field. According to the related reference and airworthiness compliance demonstration method of aeroengine components manufactured through traditional processing techniques, it is supposed that the airworthiness compliance demonstration method of SLMed aeroengine components should mainly contains the following parts: establishment of selective laser melted material specifications, certification of selective laser melting process, identification of material quality and determination of material properties.

Experimental study on transient characteristics of solid rocket motor exhaust plume
WEI Tianyu, FU Debin, LIU Haotian, FENG Zirui, LIU Lingyue
, Available online  , doi: 10.13224/j.cnki.jasp.20220088

Based on the image data collected by the solid rocket motor mooring experiment, the image mean and variance analysis, the fast Fourier transform (FFT) of the time series of the brightness of the typical position of the flame, and the improved Hilbert-Huang transform (improved HHT) are used to analyze the data. Transient characteristics are analyzed and processed. The analysis results show that: in the obtained frequency band, there is no obvious main pulsation frequency in the entire exhaust plume, and there are small pulsation components at each frequency, and the pulsation amplitude in the core area is smaller than that in the turbulent mixing zone. There is a correlation between the pulsations in the core region and that in the turbulent mixing zone, and the improved HHT transform based on the improved adaptive noise complete set empirical mode decomposition algorithm (ICEEMDAN) can be used as an effective means to analyze the transient characteristic change mechanism of non-stationary signals such as solid rocket engine flames.

Simulation and experiment on contact stiffness of aviation splines
LI Yingjie, ZHAO Guang, YUAN Yunbo, HOU Zhiqiang, GUO MEI, ZHANG Dayi
, Available online  , doi: 10.13224/j.cnki.jasp.20230070

The high magnitude of the contact stiffness of aviation splines leads to the difficulty in direct measurement and notable test error. A spline structure model was established through reasonable simplification and scale design according to the actual spline connection structure of an aero-engine. Simulations were made to determine the spline contact stiffness and its variation with transmission torque and lateral force. A test bench consistent with the simulation model was built to test the contact stiffness. The results showed that when the transverse force was constant, the contact stiffness of the spline increased nonlinearly with the increase of transmission torque, and was inclined to be unchanged gradually. When the spline was under the same torque and lateral force, the contact stiffness of the spline was different during loading and unloading, and the hysteresis phenomenon occurred. The average contact stiffness of splines measured under all torques was 20.48 MN/m. The test and simulation results were in good agreement, with an average error of 8.54%. This study provides a reference for studying the contact stiffness of aviation splines.

Lateral force regulation characteristic of a three-tab mechanism
ZHANG Ruheng, YANG Jun, YAO Baojiang, YANG Shilin, ZHANG Bingfeng
, Available online  , doi: 10.13224/j.cnki.jasp.20220733

In view of the layout feature of three tabs in circular symmetry and action mode of radial rotation, a lateral force calculation scheme with only three-tab rotation angles as variables was proposed. Numerical and experimental results showed that the lateral force on the wall of nozzle expansion section was almost non-existent when thrust vector was adjusted by the mechanism, and lateral force was mainly generated by differential action of three tabs. The pitch force was positively correlated with difference value between average rotation angle of spoiler 2 and spoiler 1, spoiler 3. The yaw force was positively correlated with difference value between rotation angle of spoiler 1 and spoiler 3. In small angle adjustment within 52°—23°, the aerodynamic interference between three tabs was small to be within 3%, and the thrust loss was approximately linear with tab rotation angle. The deviation of the calculation result of lateral force from the test result was less than 6%, which verified the correctness of this method. The proposed formula had closed solvability, and the rotation angle of the target can be solved according to thrust loss and expected lateral force in reverse solving, thus providing a method for attitude adjustment of three-tab mechanism.

Effect investigation of combined variable speed of rotor/turboshaft engine power turbine on the performance
YI Weilin, CUI Zhiwei, ZHENG Tingkai
, Available online  , doi: 10.13224/j.cnki.jasp.20220077

The rotor speed of traditional helicopter is constant, so the power turbine of turboshaft engine operates at a constant speed, resulting in high rotor power demand, low efficiency and high engine fuel con-sumption under some flight conditions. In this paper, the calculation model of rotor optimal speed and power demand considering flight conditions and the performance analysis model of turboshaft engine with variable speed power turbine were established respectively. Based on these models, the performance analysis method and code of rotor/turboshaft engine power turbine were developed, and the perfor-mance analysis under typical flight envelope was carried out for UH60A helicopter and T700 turboshaft engine. The results show that when the flight altitude, weight and speed change, the rotor speed has an optimal value, the required power will be significantly reduced, and the power turbine speed of tur-boshaft engine needs to be variable. Compared with the constant speed operation mode, after complet-ing a typical flight mission, the coordinated variable speed operation of rotor / turboshaft engine can reduce fuel consumption by nearly 5%. When the speed of power turbine is variable, the steady-state matching working line of compressor and high-pressure turbine change slightly, but the isentropic efficiency of power turbine decreases significantly with the decrease of speed, and its performance needs to be further improved.

Heat transfer and resistance characteristics of shell side of novel finned tube heat exchanger
DING Tianxiang, PENG Hao, MA Jie
, Available online  , doi: 10.13224/j.cnki.jasp.20230076

A new type of slotted fin was designed. The flow and heat transfer characteristics of the novel slotted fin were studied by experiment and numerical simulation. The influences of fin pitch and relative slotted height on the heat transfer and resistance characteristics of the novel slotted fin were analyzed. The relevant flow and heat transfer correlation was obtained by power function multivariate nonlinear fitting. Research showed that the shell-side comprehensive heat transfer performance of the novel finned tube was 1.46—1.64 times higher than that of the plain finned tube. When Reynolds number Re=9500 and relative slotting height was 0.5, the fin pitch decreased from 1.6 mm to 1.0 mm, the air side Nu increased by 19.44%, the air side f increased by 39.54%, and comprehensive heat transfer performance increased by 6.88%. When the Reynolds number Re=9500 and fin pitch was 1.2 mm, relative slotting height increased from 0.4 to 0.7, the air side Nu increased by 11.55%, the air side f increased by 3.14%, and comprehensive heat transfer performance increased by 9.84%. The calculation correlations of Nusselt number and resistance coefficient with average deviation less than 10% were finally proposed.

Temporal super-resolution imaging of 3D OH concentration field in turbulent flame based on deep learning
ZHONG Yue, CAI Minnan, XU Wenjiang, YANG Fan
, Available online  , doi: 10.13224/j.cnki.jasp.20230071

In response to the difficulty and high cost of high-speed measurement of flame hydroxyl concentration field, a Cycle-3D-CNN model based on deep learning was proposed for temporal reconstruction of three-dimensional (3D) hydroxyl concentration fields in turbulent flames. It achieved a higher temporal resolution by utilizing a data-driven approach with a 3D convolutional neural network (3D CNN) based on cycle consistency. In the experimental analysis, the model was used to achieve a two-fold and three-fold increase in temporal resolution of the 3D hydroxyl concentration field time series, respectively. In both experimental results, the mean peak signal-to-noise ratio (PSNR) reached 33.57 dB and 30.37 dB, respectively, the structural similarity (SSIM) indices reached 0.899 and 0.813, respectively, outperforming traditional frame reconstruction method.

Effects of blade single and coupling errors on axial flow compressor performance
CHU Wuli, HE Xudong, YANG Jibo, LIU Kaiye
, Available online  , doi: 10.13224/j.cnki.jasp.20220941

Due to the limitation of processing technology and other factors, there is always a small error between the theoretical blade profile and the actual blade profile in the actual processing. For transonic compressor Rotor 37, the influences of axial position and stagger angle errors on the uncertainty of compressor aerodynamic performance were studied by numerical simulation and NIPC (Non-Intrusive Polynomial Chaos method). The conclusion indicated that, for machining errors with zero mean standard normal distribution of axial position and stagger angle, the sensitivity of rotor aerodynamic performance was approximately the same when they changed singly or in coupling, only individual parameters were different. The correlation between the aerodynamic performance of axial flow compressor and each error was strong or weak, and attention shall be paid to the performance parameters with strong correlation during processing. The influence of blade coupling error on compressor lied in the superposition of the influences of blade axial position error and stagger angle error.

Cooling characteristics analysis on impingement film with effusion under constant pressure difference
WU Jiazhou, ZHANG Jingyu, WANG Long, HE Xiaomin
, Available online  , doi: 10.13224/j.cnki.jasp.20220785

In response to the problem of short continuous liner wall and poor film stacking effect in a certain type of oblique flow vortex combustor, a combined impingement film and effusion cooling structure was constructed. Under the conditions of equal pressure difference, experimental study of multiple cooling schemes on the overall cooling effectiveness was carried out, and the influence laws of pressure difference between coolant and hot gas, the distance ratio between slit and effusion, and the impact spacing ratio on the flow and overall cooling effectiveness were obtained by combining the numerical simulation. The results showed that compared with the single effusion or impingement film structure, the impingement film composite effusion scheme solved the problems of low cooling effectiveness in the film initial section and uneven distribution of axial wall temperature, and average area overall cooling effectiveness was about 3.2% higher than effusion cooling. The increase of the pressure difference significantly improved the overall cooling effectiveness. The larger distance ratio between slit and effusion was not conducive to the stacking of the downstream cooling-film, while the reduction of the impact spacing ratio can improve the overall cooling efficiency of the impingement film section.

Effect of bolthead/ nut constraint state on thread loosening characteristics
ZHANG Gongping, LIU Wenguang, HUANG Zheng, LI Kehao, CHENG Long
, Available online  , doi: 10.13224/j.cnki.jasp.20230675

In order to investigate the effects of the constraint state of bolthead/nut on the thread loosening characteristics, two kinds of anti-loosening structures with bolthead constraint or nut constraint were proposed firstly. Subsequently, the fine finite element model of a single-lapped and single bolted joint structure was developed, and the thread loosening process of different kinds of anti-loosening models under transverse vibration was simulated. Thereafter, the thread loosening characteristics of different models under different loading, friction factors of the threaded surfaces, and friction factors of the bearing surfaces were analyzed. A thread loosening test was carried out to verify the anti-loosening effect in the end. Results indicated that under the same conditions, for the ordinary bolted joint without constrained bolthead and nut, the preload loss was the largest in the pre-vibration period, and the easiest to occur loosening. For the new type of bolted joint with constrained bolt head, the preload recession was the slowest, the loss was the smallest, and it had excellent anti-loosening effect. For the bolted joint with constrained nut, the loosening was the fastest, and no anti-loosening effect was achieved. In the project application, the bolted joint of constraining the bolthead can be considered in design to improve the anti-loosening capability.

Research progress on flow characteristics and control of supercooled water film on aircraft surface
JIA Yingxuan, SHEN Yizhou, LIU Senyun, XU Yangjiangshan, SHEN Ruxun
, Available online  , doi: 10.13224/j.cnki.jasp.20230199

In order to deeply understand the importance of the flow control of supercooled water film on the aircraft surface for anti-icing/deicing, the influence of supercooled water film on aircraft icing was elaborated from supercooled water film formation process and water film icing model, and then the main ideas and methods of supercooled water film flow control were proposed. The influential factors of supercooled water film flow were introduced, and the effects of environmental parameters such as wind speed and intrinsic characteristics of material surface, including roughness on the flow of supercooled water film, were systematically analyzed. On this basis, the research status of indirect control of supercooled water film flow by regulating the movement of droplets was summarized, a new idea of using gradient non-wetting surface to directly control the movement of supercooled water film was proposed. and the important problems and development trends to be solved urgently in the development of supercooled water film flow control were comprehensively prospected.

Vibration characteristics of angular contact ball bearing with local defect considering impact excitation
LEI Chunli, SONG Ruizhe, FAN Gaofeng, LIU Kai, XUE Wei, LI Jianhua
, Available online  , doi: 10.13224/j.cnki.jasp.20230211

In order to characterize the operation state of angular contact ball bearing(ACBB) with local defects in detail, a dynamic model of ACBB with local defects considering the impact force was proposed to solve the problems of incomplete factors and inadequate description in the traditional model. According to the time-varying displacement excitation model of ACBB with local defects, the instantaneous impact force function related to defect size and bearing speed was established. Based on Hertz contact theory and impact force function, the dynamic calculation method of ACBB with a local defect in outer ring was presented. The vibration characteristics of the ball bearing with faults were investigated, and the dynamic response of the bearing under different working conditions was analyzed. The results showed that with the increase of defect size and load, the fault characteristics frequency of bearing was kept unchanged, but its amplitude increased. With the increase of speed, the frequency of bearing also increased and the amplitude changed. The increase of these three factors could aggravate the vibration of bearing.

Influence study of flow angularity on measuring device in wind tunnel flow field calibration
CONG Chenghua, ZHAO Fang, YI Xingyou, YU Yongsheng, WANG Ning
, Available online  , doi: 10.13224/j.cnki.jasp.20220081

In order to determine the influence of flow angularity on design parameters of measuring device in low speed wind tunnel flow field calibration, wind tunnel experiment and numerical simulation were both used to prove that the method of assessment this paper adopted is feasible. Numerical simulation method was carried out to study the influence of local flow angularity on measuring device blockage, offset, angle of attack and probe length. The law of influence was obtained and the mathematical model of influence was established. The results show that: 1) the angle of attack, the offset of measuring device and the length of probe has obvious influence on the local flow angularity experiment results, 2) if the measuring device or test method is not properly designed, the error of flow angularity test results will be too large, and even the wrong experimental conclusion about flow angularity will be obtained.

Model solving and size optimization of dryout threshold for vertical micropillar evaporators
GAO Shenbao, JIAO Feng, HE Yongqing
, Available online  , doi: 10.13224/j.cnki.jasp.20220723

The existing dryout threshold model was optimized by adding gravity and combining with capillary force and permeability solution methods, so as to obtain the best combined model (Darcy_avg(S)+SE) for characterizing the heat transfer performance of a vertical micropillar evaporator with an average error of about 7%. The effect of micropillar geometry was investigated using this model. Model predictions indicated that the maximum heat transfer capacity of the evaporator was balanced between permeability and capillary pressure; those geometries close to the optimal pitch ratio (d/l≈0.35) and higher micropillars correspond to greater heat dissipation capacity; and that micropillar arrays with smaller receding contact angles correspond to greater dryout thresholds. The increase of the dryout length under gravity led to a significant decrease of the dryout threshold, and the genetic algorithm can be effectively used to solve for the optimal size at different dryout lengths. The arrangement method affected the dryout threshold, the forked-row arrangement of the micropillar arrays increased the heat transfer capacity by nearly 13% compared with the smooth-row arrangement at optimal spacing ratio.

Multi-objective optimization design of binary variable geometry inlet regulating mechanism for aircraft
QI Haitao, LIU Xu, LIU Duo, MENG Haoyang, SU Hang
, Available online  , doi: 10.13224/j.cnki.jasp.20230118

Considering the design requirements of hypersonic aircraft’s binary variable geometry inlet regulating mechanism for light weight, low energy consumption and high accuracy, multi-objective optimization was carried out for the mechanism, the design scheme with the best comprehensive performance was obtained and the feasibility of the scheme was verified. Firstly, through force analysis and ADAMS software simulation, the minimum driving force required for the wedge plate and throat plate was obtained. Then the mathematical model of the mass, energy consumption and stiffness of the mechanism was established, the design variables and constraints of the mechanism were determined, and the Pareto solution set was obtained by multi-objective optimization using NSGA-Ⅱ optimization algorithm. The visualization of Pareto frontier was realized by drawing the level diagram, and a group of optimal solutions were selected for the design scheme. Finally, the feasibility of the scheme was verified by mechatronics concept designer (MCD) kinematics simulation analysis. The results showed that the weight of the mechanism was reduced by 6.48% and the energy consumption reduced by 8.35% compared with that before optimization, and also it can meet the displacement demand of actuation.

Investigations on thermal environment of launch pads during the two-nozzle launch vehicle launching
ZHAO Chengeng, LE Guigao, SU Yifei, SUN Zhongyi, WANG Yichen
, Available online  , doi: 10.13224/j.cnki.jasp.20220717

Taking the launch pads consisting of two-nozzle launch vehicle power system as the research object, the thermal environment of launch pads during the rocket launching was studied by numerical simulation method. Based on three-dimensional compressible Navier-Stokes equations, k- ε turbulence model and second order TVD (total variation diminishing) upwind scheme were used to establish the gas jet model of two-nozzle launch vehicle. The research showed that the intersections of the nozzle central axis and the flame deflectors withstood the greatest impact of the guide surface, where the temperature and pressure were extremely high. The back splash caused by the rocket tail jet impinging on the flame deflectors may further deteriorate the thermal environment of the launch pad. The drift of the rocket during launching could increase the impact of the jet on the launch pad, rapidly increase its surface temperature and pressure, and reduce its service life. The research method provides an effective method for the thermal environment assessment of launch pads during launch vehicle takeoff and has important engineering application value for the safety design of thermal protection system.

Application of 3D ice shape laser measurement technology in icing wind tunnel
WEI Longtao, ZUO Chenglin, GUO Xiangdong, LIU Senyun, GUO Qiling
, Available online  , doi: 10.13224/j.cnki.jasp.20220958

The principle of measuring 3D structure for ice accretion in icing wind tunnel with ROMER measuring instrument was introduced, and a fast reconstruction method for model with ice shape was proposed. Typical rime ice, rough ice and horned ice were obtained by wind tunnel test. The 3D morphology of ice accretion was measured by ROMER instrument, and the 3D data of ice accretion on the surface of the model were obtained. The results showed that 3D results of rime ice were highly consistent with the actual ice shape, and the detailed characteristics of ice accumulation can be accurately measured. 3D scanning technology can measure the rough ice results which can not be obtained by hot knife method. Compared with the ice trajectory of the shorn ice obtained by the hot knife method, the ice trajectory of the 3D ice shape in the same section had the same icing range and icing level, with the average thickness deviation of ice up to 2.5 mm.

Control strategy of mass flow rate and pressure in an air supply system of gas turbine engine
XUE Yongjian, LIU Gaowen, MA Jiale, BAI Yang, GONG Wenbin, LIN Aqiang
, Available online  , doi: 10.13224/j.cnki.jasp.20220781

The mass flow rate and pressure control scheme of the gas supply system was studied, and the improved control method of using multiple linear regression prediction and adaptive proportional regulation was put forward to integrate the control of the electric valve of each flow path of the experimental platform. The design of a measuring control system operation table, using Siemens programmable logic controller (PLC) as the main controller, can realize automatic control of 46 electric valves, and retain the remote manual control function. The control mode can be adjusted according to different electric valve speed change/increase amplitude, making the valve adjustment more smooth. Based on the pipeline condition of the experimental platform, compared with the conventional proportion integral differential (PID) control, the control mode can reduce the overshooting of the pressure and mass flow rate of each gas path of the experimental platform by more than 20%, shorten the adjustment time by more than 40 s, and improve the steady-state performance by more than 2% for the large mass flow rate condition.

Numerical investigation for influence of chute seal configuration of a counter-rotating turbine cavity on hot gas ingestion
SONG Yanqing, SUI Xiuming, TONG Xin, SONG Quanbin, ZHAO Wei, ZHAO Qingjun
, Available online  , doi: 10.13224/j.cnki.jasp.20220955

The numerical simulation method was used to study the influence of the oblique sealing geometry of the high-pressure wheel flange on hot gas ingestion, and the results showed that under low sealing flow, the radial expansion of the end of the high-pressure wheel flange caused the decrease of pressure gradient in the wheel flange gap, which delayed the separation of the boundary layer of the low-pressure wheel flange, while the radial expansion of the high-pressure wheel flange caused the increase of mainstream flow velocity in the endwall region, and the ability of the fluid to resist the inverse gradient was enhanced. As a result, the sealing efficiency increased by 46.95%; with the increase of the sealing flow, the pressure of the sealing flow in the disk cavity gradually increased, the sealing efficiency was gradually improved due to the enhancement of the sealing flow outflow capacity, and the radial upward movement effect of the sealing vortex core induced by the radial expansion of the high-pressure wheel flange was weaker than the influence of the increase of the sealing flow on the sealing efficiency, so with the increase of the sealing flow, the increase of sealing efficiency gradually decreased.

Hypersonic modification and verification of Langtry-Menter transition model
LI Chengrui, JIANG Zhongzheng, WU Changju, YANG Yuxin, DENG Sichao
, Available online  , doi: 10.13224/j.cnki.jasp.20220970

For the prediction of hypersonic boundary layer transition flow, three types of high-speed modified methods were studied based on the traditional Langtry-Menter transition model and SST (shear stress transport) turbulence model. The modification of hypersonic cross-flow criterion, compressibility modification of turbulent kinetic energy pressure dilatation term and modification of pressure gradient coefficient were introduced into the original transition model to expand the simulation capacity of the model in hypersonic flow. The modified transition model was validated by using several typical cases: supersonic plate, hypersonic cone with zero angle of attack, hypersonic cone with small angle of attack and hypersonic HIFIRE-5. The results showed that the predicted transition-start position, transition-end position and transition zone length of the modified model were basically consistent with the experimental results. The calculated results of skin friction and heat flux were basically consistent with the experimental measurement data. The modified transition model performed well in predicting hypersonic transition flow.

Combustion and emission numerical simulation of shape morphing jet-stabilized combustor
QI Zhiwei, WANG Jifei, LIU Qiuhong
, Available online  , doi: 10.13224/j.cnki.jasp.20220725

According to the requirements of low pollution emission of gas turbine in recent years, in order to take advantage of an elliptical combustor and improve poor matching between its outlet and the gas turbine, a concept of shape morphing was proposed, which made the inlet of the jet-stabilized combustor elliptical and the outlet circular. Using numerical simulation methods, the combustion characteristics and flow and emission characteristics at the outlet of the combustor were studied. The influence of shape morphing on the emission and flow characteristics of the combustor was investigated. Shape morphing combustor reduced NO emission by 51.26% compared with circular combustor, maintaining the advantage of low emissions from the elliptical combustor; compared with the elliptical combustor, 2.85% of NO emission was sacrificed, but the uniformity of outlet temperature was improved by 4.27%. At the same time, it can provide a more matched temperature distribution for the blades in the rear gas turbine, and prove the feasibility of the cross section gradual change concept, which can serve as a reference for further research on cross section gradual change technology.

Influence of tapered bridge holes on impingement double wall cooling for gas turbine blade
LIU Yusong, ZHU Hua, YAN Biao, LI Liang
, Available online  , doi: 10.13224/j.cnki.jasp.20220718

In order to investigate the influence of the bridge holes on flow and thermal behavior of impingement double-wall cooling for gas turbine leading blades, the impingement double-wall cooling configurations with 0°, 5°, 10°, 15° and 20° tapered bridge holes were calculated by using ANSYS CFX numerical simulation. Results indicated that the tapered bridge holes can significantly enhance the comprehensive heat transfer capacity. As the angle of bridge holes increased from 0° to 20°, the angle of holes did not have a significant influence on flow loss of inner and outer chambers for the blades. Likewise, the cooling performance of the inner chamber target wall was not sensitive to the change of the bridge hole angle. With the growing angle of bridge holes, the thermal behavior of the target wall for the outer chamber increased at first and then decreased, reaching the biggest value at 15°. When the angle of bridge holes increased to 15°, its average heat transfer intensity was 19.7% higher than the case with 0° bridge holes. Similarly, the thermal performance factor of the whole configuration also became larger at first and then became smaller. The largest thermal performance factor occurred at 15° too, which was 12.15% higher than the case with 0° bridge holes.

Multi-view visiual measurement of three dimensional dynamic position and orientation of aero engine casing
GUO Jianying, LIANG Jin, YE Meitu, WANG Mingming, LIU Hui, TEN Guangrong
, Available online  , doi: 10.13224/j.cnki.jasp.20220967

In view of the difficulty of measuring the relative position and orientation in the rigidity test of aero engine casing, the conventional method of binocular visual measurement for position and orientation was improved, a global multi-view visual dynamic position and orientation measurement method based on video dynamic measurement technology was proposed. The global coordinates of coded point on the casing under initial coordinate system were obtained by close-range photogrammetry and converted to custom numerical model coordinate system of the casing by vector coordinate transformation. The external parameters of multi-view camera were solved by using the coded point coordinates under numerical model coordinate system, and the coordinate system of each measuring camera was unified, so that the measuring data can be analyzed in the customized coordinate vector. The three-dimensional coordinates of measuring points on the inner and outer rings of the casing under each deformation state were obtained by multi-view visual dynamic position and orientation measurement method, and then the position and orientation of the measuring points on the inner and outer rings of the casing in the numerical model coordinate system as well as their relative changes were calculated. The test results showed that the displacement measurement error of the proposed method was less than 0.005 mm compared with the traditional micrometer measurement method, which made up for the disadvantage of the traditional measurement method in extracting difficultly the relative orientation of different parts of the test piece, thus providing a convenient measurement method and reliable data source for the rigidity test of aero engine casing and related shells.

Thrust stand model analysis and thrust position based on screw algebra
LI Dong, ZHANG Leile, ZHENG Guoliang, XING Yanchang, YOU Guangfei
, Available online  , doi: 10.13224/j.cnki.jasp.20220960

The screw theory and coordination between deformation and displacement were applied to research the octagonal orthogonal box-type thrust stand in screw modeling, model solving, error compensation, and thrust positioning. Screw model of the stand was established based on the two major characteristics of load eccentricity and force coupling. And constraint equations for model solution were derived based on the branches deformation constraint relationship. Numerical examples and simulations showed that the maximum relative error of the screw model was 9.147‰. An error compensation model was established based on the coordinated relationship between the branches deformation and the stand displacement. Numerical examples and simulations showed that the minimum compensation for force was 78.03%. The Poinsot’s central axis theorem of the screw theory was used to clarify the uncertainty of vector thrust positioning, which was caused by ignoring the influence of pure couple in the resultant force. The analytic method indicated that the effect of mass center offset on vector thrust uncertainty was linear.

Compound fault feature extraction of rolling bearing based on parameters adaptive CYCBD
XIANG Wei, LIU Shujie, LI Hongkun, CAO Shunxin, LYU Shuai, YANG Chen
, Available online  , doi: 10.13224/j.cnki.jasp.20220716

In view of the difficulty to accurately extract and separate the features of the early fault signals of rolling bearings, a compound fault feature extraction method of rolling bearing based on parameters adaptive maximum second-order cyclostationarity blind deconvolution (CYCBD) was proposed. Based on different fault types, the harmonics energy ratio index was used as the fitness function, and the sparrow search algorithm was used to adaptively obtain the optimal filter length and cycle frequency of deconvolution. The obtained optimal parameters combination was used to extract the fault components in the original signal one by one, and the envelope spectrum analysis of the deconvolution signal was carried out to realize the diagnosis of compound fault of the bearing. The analysis results showed that the proposed method can clearly and accurately separate 1—4 times of the inner ring characteristic frequency and 1—6 times harmonic component of the outer ring fault from the measured signal of bearing fault under the background of strong noise, while other common methods can only extract a few fault frequencies with low resolution. The proposed method has obvious diagnostic effect, higher application value and promotion performance.

Discrete-adjoint optimization of axial turbine blade using free-form deformation technique
KANG Wei, WANG Yanqing, XU Quanyong, HU Shilin
, Available online  , doi: 10.13224/j.cnki.jasp.20220943

A discrete adjoint CFD method based on the free-form deform was developed for aerodynamic performance optimization of the axial turbine stage. Optimization analysis of the two-dimensional turbine stator and single turbine stage was carried out, and the optimal shape of the blade shape under the constraints was given. In the stator blade optimization, the leading edge radius and thickness of the blade obtained were significantly reduced. The total pressure recovery coefficient decreased by 12.44% after optimization, while the flow outlet angle was constrained to −74.66° with the variance of 0.047% during the optimization. For the single-stage turbine optimization problem, the camber of the rotor blade was enhanced, and the total efficiency was improved by 0.79% considering the rotation effect. The constraint condition lied in the flow outlet angle with the variance of 0.068% during the optimization. The results showed the effectiveness of the proposed method on the aerodynamic performance optimization of turbine stage. Compared with the traditional finite difference method, the discrete adjoint method costed only 3% CPU time for single-stage optimization.

Life calculation and test method of RV reducer based on fatigue strength
ZHANG Yueming, LI Yiwan, JI Shuting
, Available online  , doi: 10.13224/j.cnki.jasp.20220957

To accurately calculate the life of Rotate Vector (RV) reducer under actual operation and reduce the cycle and cost of durability life test, taking RV reducer for industrial manipulator as research object, a fatigue life calculation method of RV reducer based on fatigue strength theory was presented, and a device was designed and built for accelerated life test. Combined with Stress-Fatigue life N (S-N) curve and Palmgren-Miner rule, the basic life model of RV reducer was established. The mathematical expression of the RV reducer’s rated life and service life was constructed, the law between the load and service life of the RV reducer was systematically studied, and the accelerated life test based on the S curve acceleration and deceleration control algorithm was designed. The test device was set up and the data were analyzed to verify the accuracy of the life calculation method. The results showed that the relative error between the life obtained by the fatigue life calculation method and the test results was only 6.3%, the acceleration factor was 20.7, and the test cycle and cost reduction effect were remarkable.

Aerodynamic-propulsion coupling characteristics of distributed electric propulsion system
XU De, XU Xiaoping, XIA Jiyu, ZHOU Zhou
, Available online  , doi: 10.13224/j.cnki.jasp.20220681

A momentum source method (MSM) for solving the Reynolds average Navier-Stokes (RANS) equations based on the $k {\text{-}} \omega $ SST (shear stress transpot) turbulence model was adopted. For the two-dimensional simplified model of the distributed propulsion wing with lift flaps, research on the aerodynamic-propulsion coupling characteristics and physical mechanism in the vertical take-off, transition and cruise flight state was carried out. The research showed that the suction effect of the duct made the distributed propulsion wing show the phenomenon of increasing lift and reducing drag, and delayed the flow separation of the wing. Compared with the freestream condition, the stall declination angle of the lift flaps in the ducted jet significantly increased from 12° to 34°, and at the same time the lift flaps induced jet deflection, so that the total lift of the distributed propulsion configuration was effectively raised.

Theoretical and experimental investigation on measurement error of pivot point excursion of flexible joint
ZHANG Jinyao, REN Junxue, XUE Muyao, TONG Yue, ZHENG Qing
, Available online  , doi: 10.13224/j.cnki.jasp.20220710

In order to quantitatively analyze the measuring error source of pivot point excursion for flexible joint, the pivot point excursion at different vector angles under 10 MPa vessel pressure was calculated using ANSYS software. According to the experimental results of flexible joint, the influences of pendulum rod deformation, horizontal displacement sensor push rod measurement error, push rod measurement error and horizontal deviation of vertical displacement sensor on the measurement results of pivot point excursion were studied respectively. In addition, the influence of the structural error of flexible joint was studied by simulations. Results showed that the measured pivot point excursion was in good agreement with the simulation after correcting four kinds of errors. The error sources in the measurement of pivot point excursion were confirmed, in which the push rod measurement errors of horizontal and vertical displacement sensors accounted for 65.98% of the cylindrical envelope height error, and 77.32% of the cylindrical envelope radius error, respectively. And these led to a great influence on the axial and radial drifts of flexible joint. Moreover, the structural error of flexible joint also affected the measurement of pivot point excursion. The distribution of pivot point excursion caused by the thickness error of elastomers and reinforcements was consistent. The results can provide a theoretical guidance for the error analysis of pivot point excursion measurement of flexible joint.

Simulation on steady-state characteristics of aero-engine fuel regulation device
YANG Shiyu, LIN Yuanfang, XU Xianghua, LIANG Xingang
, Available online  , doi: 10.13224/j.cnki.jasp.20220776

In order to study the steady-state operating characteristics of fuel regulation device and improve the flow control performance, a one-dimensional steady-state flow simulation program for aero-engine fuel system was developed based on Python language. By establishing a complete component library and efficient solution algorithm, the simulation of a fuel flow regulation system with pressure control components was realized. From the view of system, the working characteristics of the regulation device and the influence of parameters on the flow were analyzed. The results showed that under the working condition of the design point, the normal-working opening range of the metering valve was 0.3—0.85, and too large or too small opening was not conducive to the control of fuel flow. Only the preload can change the opening boundary of the metering valve. The influences of differential pressure valve parameters on the oil supply varied monotonically with the opening of the metering valve. Under the function of differential pressure valve, the oil supply to the combustor was less sensitive to the parameters of the system, and the change was less than 10%. It was found that internal leakage of the fuel pump served as an important factor affecting the fuel supply.

Flow field structure of stealth inlet under ground state e
ZHAO Qingwei, XIE Wenzhong, LI Tengfei
, Available online  , doi: 10.13224/j.cnki.jasp.20220994

In order to find out the cause of bad flow field of the stealthy inlet under the ground state, the flow field structure of the triangular and M-shaped inlets with equal inclined cut surface under the ground state was numerically simulated and analyzed, and the influences of the lip ratio and internal channel offset on the ground working characteristics of the M-shaped inlet were studied. The results showed that a large three-dimensional separated vortex (half flow field) was formed near the inlet symmetry plane in the triangular inlet, while a pair of relatively small vortices were formed at the intersection of the side lip and the upper lip in the M-shaped inlet. Moreover, the distortion index at the outlet of the triangular inlet was too large to meet the inlet/engine matching requirements. With the increase of the proportion of the M-shaped lip, the low total pressure area of the inlet exit section deflected counterclockwise along the sidewall, and the direction of the vortex changed. The total pressure recovery coefficient gradually increased, and the distortion index decreased first and then increased. The increase of internal channel offset could further aggravate the deterioration of flow field under ground conditions.

Natural characteristics calculation and analysis of fiber reinforced truncated conical shell
XU Zhuo, XU Peiyao, ZHENG Lisheng, LI Hui, LI He, GU Dawei, HE Mingyang, HAN Qingkai, WEN Bangchun
, Available online  , doi: 10.13224/j.cnki.jasp.20220876

The natural characteristics of composite conical shells were calculated and verified by combining theory and experiment. Based on the classical lamination theory and considering the influence of anisotropy of composite structures, the theoretical model was established by introducing half-cone angle coefficients. Then, the natural characteristics of the structures were obtained by utilizing the Rayleigh-Ritz method and orthogonal polynomial method. A natural characteristic experiment system of composite conical shell was established and the natural characteristics were acquired. The results showed that the error between the calculated and test results was between 1.4% and 2.3%, which further verified the correctness of the proposed model. Finally, the influences of different parameters, such as the half cone angle, the boundary conditions and the fiber ply angles, on the natural characteristics of the structure were discussed.

Research status and prospect of aircraft heat pipe anti-icing technology
LI Yundan, CHEN Xiaoming, GONG Huan, LI Miao, LIAN Wenlei
, Available online  , doi: 10.13224/j.cnki.jasp.20220771

In order to deeply understand and develop the anti-icing technology of heat pipe, the research status of different types of heat pipes in aircraft anti-icing field was mainly discussed, the theoretical and experimental results of loop heat pipe, rotating heat pipe and gravity heat pipe used in anti-icing of aircraft wings and engine front parts were summarized, the main characteristics of loop heat pipe and rotating heat pipe for anti-icing were sorted out, and the development direction of heat pipe anti-icing technology was prospected. The results showed that the researches on heat pipe anti-icing technology were still at initial stage, and most of them stayed in the design and feasibility verification of heat pipe anti-icing system. These suggested that subsequent research should be concentrated on experiments, and the method of combining numerical calculation and experimental research should be adopted, with a focus on the operation characteristics of heat pipe anti-icing system under the aircraft environment and icing meteorological conditions; moreover, the influences of factors such as the characteristics of the working medium, working temperature and liquid filling rate on the heat transfer performance of the heat pipe anti-icing system were determined, thus providing a theoretical and experimental support for the design optimization and practical application of heat pipe anti-icing system.

Simulation on filling process of gas generator head with gas injecting
HAN Jianing, ZHOU Chenchu, LU Jiawei, YU Ruibo, ZHANG Lihui
, Available online  , doi: 10.13224/j.cnki.jasp.20220772

Based on the starting process of high-pressure combustion liquid oxygen kerosene rocket engine, the filling process of the head cavity of the gas generator with gas injecting was studied. Firstly, experiments indicated that the coefficient n required for the Marquinelli empirical relation was determined to be 2.29, which verified the accuracy of the empirical relationship. Secondly, the finite element segmentation was used to establish a one-dimensional distribution parameter model of the head cavity of the gas generator with gas injecting, and the experimental data were compared and analyzed with the empirical relationship and the simulation results of the one-dimensional distribution model, which proved the accuracy of the model. The results showed that the error between steady-state pressure and the mean value of experimental data of the one-dimensional distribution parameter model was 0.429%, and the error of the empirical relationship (centralized parameter model) was 1.464%; the flow area of the injecting increased, the pressure built into the head cavity slowed down, and the stable pressure value decreased; the volume of the head cavity increased, and the pressure building speed slowed down, but the pressure stability value was kept unchanged; the resistance coefficient of the head cavity increased, and the pressure stability value and filling speed decreased.

Influence of helium cycle flow ratio on SABRE4 design point hydrogen flow rate
ZHENG Shangzhe, CHEN Yuchun, WANG Zhihua, DU Jinfeng, GAO Yuan, HUANG Xinchun
, Available online  , doi: 10.13224/j.cnki.jasp.20220774

The thermodynamic calculation model based on component method for synergistic air-breathing rocket engine (SABRE) design point was established. The minimum hydrogen flow rate required by the engine was analyzed. To save the hydrogen flow rate, two simplified schemes of SABRE4 were proposed by adding two helium branches based on the SABRE3 configuration. Combining two simplified schemes, SABRE4 scheme was proposed. The influences of the helium branches flow ratios on engine design point parameters and hydrogen flow rate were analyzed. The results showed that: the minimum hydrogen flow rate was proportional to the helium flow rate through Heat Exchanger 3. The less helium flow rate through Heat Exchanger 3 indicated the less hydrogen flow rate required. A smaller branch one flow ratio one was conductive to reducing the hydrogen flow rate, meanwhile the required helium compressor pressure ratio was increased. A smaller branch two flow ratio two was conductive to reducing the hydrogen flow rate and the required helium compressor pressure ratio. The decrease of flow ratio one and flow ratio two caused heat exchangers to approach their limits. When the Heat Exchanger 1 inlet helium temperature was lower than 310 K and the pressure ratio of helium compressor was lower than 11.0, the minimum hydrogen flow rate of SABRE4 was 83.3% of SABRE3.

Experiment on flash-boiling spray characteristics of single-orifice/dual-orifice nozzle
MIAO Junjie, WU Weiqiu, LI Xiankai, YIN Chao, JIANG Kailin, FAN Yuxin
, Available online  , doi: 10.13224/j.cnki.jasp.20220940

The flash boiling spray characteristics of RP-3 aviation kerosene inside single-orifice/dual-orifice nozzle were experimentally studied to analyze the influence of superheat degree and nozzle structural parameters on in-nozzle flow and near-nozzle jet. Results showed that increasing the length-diameter ratio of single-orifice nozzle can inhibit the cavitation effect inside the nozzle, helping to increase the kerosene gasification rate from wall boiling inside the nozzle, resulting in better atomization effect of fuel jet. The expansion chamber of dual-orifice nozzle could play the role of increasing the discharge-orifice’s gasification rate; however, excessive aspect ratio of expansion chamber may decrease the superheat degree inside the nozzle, which impaired the near-nozzle atomization effect and spray symmetry. Compared with single-orifice nozzle, dual-orifice nozzle allows more easily to promote the transformation of aviation kerosene from subcooled spray to flash boiling spray by increasing the residence time for phase transition, helping to improve the fuel atomization and obtain larger spray width and spray cone angle. Thus, using dual-orifice nozzle is a potential technical way to realize flash-boiling spray in the combustion chamber of aero-engine.

Reliability analysis of intermediate casing based on adaptive Kriging
DI Haoyuan, LI Hongshuang
, Available online  , doi: 10.13224/j.cnki.jasp.20220707

In order to explore the structural reliability analysis method of the intermediate casing under multiple failure modes, a parametric finite element model was established for the deterministic analysis of an aero-engine intermediate casing. Considering the uncertainty of material properties, geometric parameters and external loads of the aero-engine intermediate casing, the limit state functions were constructed for the two most typical failure modes of the intermediate casing: static strength failure and stiffness failure. By constructing an adaptive Kriging surrogate model for two failure modes and combining with the generalized subset simulation method, the failure probability of the intermediate casing structure was predicted. And the correlation of the two failure modes was modeled based on the Copula function theory to determine the mutual influence between them, and the calculation results were compared with AK-GSS method. The results showed that the failure probability of the intermediate casing structure system was in the order of $ {R_2} $. Compared with the conventional method, the computational time of the AK-GSS method for solving the failure probability was reduced by 87.7% almost without loss of computational accuracy. In addition, the AK-GSS method still had high accuracy when considering the correlation between the two failure modes of the intermediary magazine.

Numerical simulation on infrared radiation characteristics of a vertical take-off and landing nozzle
ZHAO Haiyu, WANG Wei, SONG Jingyuan, WANG Qingshan
, Available online  , doi: 10.13224/j.cnki.jasp.20220864

In order to improve the infrared stealth and maneuverability of aircraft exhaust system, a multi-axis cascade rotary vertical take-off and landing nozzle was developed and proposed, and the infrared radiation characteristics of nozzles in conventional cruise, vertical takeoff and landing and intermediate form S stealth modes were studied parameterized by using Malkmus statistical narrow band model and The reverse Monte Carlo method (RMCM). The results showed that compared to the conventional cruise mode nozzle, the infrared radiation intensity of the vertical takeoff and landing mode nozzle was reduced by a maximum of 23% and the S stealth mode nozzle by a maximum of 47%. And the relative angles of the cabins had a significant effect on the infrared radiation characteristics of the S stealth mode nozzle, and the relative angles of the cabins near the exit had little effect on the infrared radiation characteristics of the nozzle in vertical takeoff and landing mode.

Numerical simulation on drag and heat reduction of hypersonic spike-aerodisk-self-coupled stamping lateral jet concept
WANG Ziyu, FANG Shuzhou, GUO Jian, NI Zijian
, Available online  , doi: 10.13224/j.cnki.jasp.20220775

The drag and heat reduction effect of hypersonic spike-aerodisk-self-coupled stamping lateral jet configuration was numerically simulated. Compared with the simple spike-aerodisk, the spike-aerodisk-self-coupled stamping lateral jet configuration pushed the shear layer away from the wall, enlarged the recirculation zone near the blunt body, and pushed the separating shock away from the spike. The strength of the attachment shock was significantly weakened, and the drag and heat reduction characteristics of the combined configuration were significantly improved. The drag and heat reduction mechanism of the spike-aerodisk-self-coupled stamping lateral jet configuration was studied, and the influences of different parameters on the drag and heat reduction effect were discussed. Within the study range, the drag and heat reduction effect was continuously improved when the lateral jet angle increased from 30° to 90°, but when the lateral jet angle increased from 90° to 120°, the drag and heat reduction effect decreased slightly. For lateral multiple jets, the farther the second lateral jet was from the blunt body wall surface, the better the drag and heat reduction performance. The configuration with the best drag and heat reduction effect was compared with the configuration with the same parameter spike-aerodisk, finding that the peak value of Stanton number on blunt body wall was reduced by 39.7%, and the drag coefficient of configuration was reduced by 19.3%.

Analysis of the influence of manufacturing error on the modal characteristics of disc-drum combined rotor
ZOU Cunjian, HAN Qingkai, ZHANG Hao, LU Chongshao, ZHAI Jingyu
, Available online  , doi: 10.13224/j.cnki.jasp.20220727

In order to explore the influence of manufacturing errors on rotor modal characteristics, the mechanisms of rotor modal localization, mode step, and frequency steering characteristics were described based on rotor dynamics and perturbation theory. According to actual rotor assembly engineering, the manufacturing error forms of typical mating surfaces were characterized by user-defined functions, and point cloud data were generated. The skin model method was used for the first time to introduce manufacturing errors into the rotor finite element model, and the characteristics of manufacturing errors on its frequency steering, mode step, and mode localization were analyzed for this model. The mode displacement localization factor was used to quantify the degree of rotor vibration mode localization caused by manufacturing errors. The results showed that when the manufacturing error was considered to a certain extent, it could induce the rotor detuning, leading to the change of the rotor system stiffness and aggravating the frequency steering characteristics; at the same time, through analysis of the mode confidence criterion diagram, it can be seen that the mode shape had the phenomenon of dislocation step and sequence step; the detuning effect caused by manufacturing error could make the vibration energy gather in some areas of the rotor, so some frequencies falling in the frequency pass band of the ideal model may fall into the frequency band gap after detuning, and the phenomenon of mode shape localization occurred; further quantitative analysis showed that the mode displacement localization factor can effectively characterize the degree of vibration mode localization. The research methods and results can provide a reference for complex rotor assembly technology.

Multi-objective optimization of propeller airfoil for general aviation aircraft
WANG Zhi, WANG Heming, WANG Zijing, XIANG Song
, Available online  , doi: 10.13224/j.cnki.jasp.20220636

In order to obtain an airfoil with higher aerodynamic performance and lower aerodynamic noise, the RAF-6 airfoil for a general aviation aircraft propeller was optimized. The flow field and sound field of the airfoil were simulated by CFD/FW-H method. The influence laws of four design variables, i.e. the maximum thickness, the position of the maximum thickness, the downbending angle and position of trailing edge, on its aerodynamic performance and aerodynamic noise were studied respectively. Taking the cruise state as the design point, the airfoil multi-objective optimization design was carried out with higher lift-drag ratio and lower aerodynamic noise as the optimization objectives, and the Pareto solution set was obtained. The experimental results verified that the optimized airfoil increased the propeller thrust by 14.7% and reduced the aerodynamic noise by 2.3 dB.

Improved GRU-based self-attention optimization algorithm for aero-engine remaining useful life prediction
GUO Xiaojing, XU Xiaohui, GUO Jiahao
, Available online  , doi: 10.13224/j.cnki.jasp.20220984

Multivariate, high-dimensional and time-ordered aero-engine performance parameters can characterize life regressions, which are prone to gradient disappearance using conventional model training. A self-attention optimization algorithm was proposed to improve the gated recurrent units (GRU). Row gradients of source domain and inter-column correlations were analyzed. The feature weights were optimized by augmenting the strongly correlated lifetime columns, with its aim to accelerate model convergence and improve prediction accuracy. Experiments on the engine life prediction dataset (C-MAPSS) showed that the root mean square error (RMSE) of life obtained by the algorithm fell in the interval [10.52, 18.91] and the over-prediction index (score) in the interval [48.69, 204.98]. Compared with the traditional method, the effect of life prediction was greatly reduced, and an effective solution was provided for engine life prediction and advanced maintenance.

Effect of ship airwake active control on helicopter trimmed controls
YE Yi, CHEN Renliang
, Available online  , doi: 10.13224/j.cnki.jasp.20220646

In order to investigate the effect of ship airwake on helicopter trimmed controls, a method of combining numerical simulation and helicopter flight dynamics model was adopted. The ship airwake was obtained by computational fluid dynamics (CFD) numerical simulation method, and the characteristics of ship airwake under active control were explored; at the same time, considering the effect of ship airwake on helicopter, the flight dynamics model coupled with the ship airwake was established. The results of relative hovering trim with/without airwake were calculated, and the effect of active control on helicopter trimmed controls was further compared and analyzed. The results showed that theship airwake had a significant impact on the helicopter take-off and landing, compared with the interference of the ship airwake on the helicopter controls when there was no control, the addition of the blowing device can effectively suppress the downwash of the ship airwake, reduce the required collective pitch control by 7.8% and pedal control by 7.5%, improve other corresponding controls and alleviate the pilot control load.

Influence of variable temperature circulating air on turbine guide vane life
CHEN Yingtao, LIANG Shuwei, AI Yanting, LIANG Zijian
, Available online  , doi: 10.13224/j.cnki.jasp.20220834

To improve the reliability and service life of gas turbine guide vane, the concept of variable temperature circulating air conditioning is introduced in this paper. Taking a turbine vane as an example, the thermal shock cycle fatigue life of a gas turbine vane was studied, three-dimensional fluid-solid thermal coupling finite element analysis of stress state under start-stop cycle load spectrum of turbine guide vane is carried out. According to the change law of thermal shock stress of the vane in the cold air of the variable temperature cycle, the temperature field distribution and stress field distribution of the vane in the steady state and transition state in the cycle were obtained, and then the structural strength and fatigue life of the vane under each calculation condition were analyzed and evaluated. Build a test bench, thermal impact fatigue test is carried out on the turbine guide vane of this type of gas turbine under constant temperature cold air circulation, compare with the results of finite element analysis, come to a conclusion: the large area of blade stress obtained by three-dimensional fluid-solid thermal coupling finite element analysis is the trailing edge of blade and the middle of blade basin, consistent with the failure zone obtained by thermal shock test, the thermal fatigue life of vane can be effectively improved by changing the cooling circulation temperature.

Impact of cross-flow on the aerodynamic load of propeller for stratospheric airship
NIE Bo, WANG Haifeng, DU Chenxi, MA Jiexiang
, Available online  , doi: 10.13224/j.cnki.jasp.20230207

The validity of sliding mesh technology and detached eddy simulation (DES) with non-steady numerical methods was verified by wind tunnel tests of a scaled propeller model, and numerical calculations of aerodynamic loads under different cross-flow conditions were performed. The results showed that the instantaneous aerodynamic load coefficient of the rotating propeller exhibited periodic unsteady characteristics, and the flapping torque along the blade radius increased significantly with cross-flow angle, with an instantaneous value equivalent to the axial moment at 30°, and more than twice the axial moment at 60°. Along with an increasing number of blades, the frequency of fluctuations within one cycle increased. Compared with the two-bladed propeller, the amplitude of the thrust and torque coefficients of the four-bladed propeller relative to their mean values was reduced by 76.6% and 70.1%, respectively. Research method can provide effective input basis for the design of blade structure and related support mechanism.

Effect of valve opening time difference on working process of 150 N hypergolic propellant liquid rocket engine
CHEN Ruida, TIAN Zeng, CHEN Hongyu, XU Hui
, Available online  , doi: 10.13224/j.cnki.jasp.20220683

In order to study the effect of the valve opening time difference on the working process of the space liquid rocket engine using hypergolic propellants, the high-altitude simulated thermal test of a 150 N engine was carried out. The engine working stability, ignition thrust peak and response time were investigated when the oxidant valve and fuel valve were opened 40, 100, 500, 1000 ms in advance, respectively. The test results showed that the engine can be successfully ignited, and the thrust after stabilization was basically unchanged. When the oxidant valve and the fuel valve were opened first, the ignition thrust peak of the engine was about 1.01—1.05 times and 1.04—1.07 times of the stable thrust, respectively, which was equivalent to the opening of the two-way valve synchronous signal. When the fuel valve was opened first, the startup response time was extended by about 16 ms. When the valve was opened alone, the oxidant was fully vaporized, the ice particles were ejected in the middle area of the flow field, and the fuel was partially vaporized. When the valve opening time difference reached 500 and 1000 ms, while the oxidant valve and the fuel valve were opened separately, the output thrust of the engine was about 11 N and 6 N, respectively, accounting for 7% and 4% of the stable thrust respectively, and the output thrust of the latter fluctuated and kept falling.

Optimization of cargo aircraft packing and stowage combination
ZHAO Xiangling, ZUO Lei
, Available online  , doi: 10.13224/j.cnki.jasp.20220844

Aircraft Weight and Balance (AWB) and Air Cargo Palletization (ACP), two crucial components of the present air cargo loading plan, were carried out independently, which restricted the optimization of the aircraft payload and center of gravity (CG). To guide the packing operation, raise aircraft payload, and boost transportation effectiveness, models of the combination of ACP and AWB were developed. The Bi-level Optimization Model (BOM), the Combinatorial Optimization Model (COM), and the Improved Combinatorial Optimization Model (IOM) were proposed, and the objectives of the models were the maximum payload and the minimum CG deviation from a defined target CG. The models also took into account a wide range of restrictions in real packing and stowing operations, such as limitations on capacity, weight, loading position, aircraft balance, and other factors in aircraft and ULDs. Four scenarios with various conditional data for three models were tested and analyzed using the commercial solver Gurobi, by taking the B777F as an example. Experiments showed that while the BOM had the greatest CG deviation and the smallest mean payload (97 412.37 kg), it also had the fastest solution speed. For cases solved within the time limit, the mean computational time was 87.77 seconds, but the mean CG deviation was 1.35% mean aerodynamic chord (MAC). And there were some unacceptable cases where the maximum approached 3.66% MAC. The COM test required the longest time for completion; 48% of the cases cannot be solved in the given time limit, and the mean took 880.25 seconds for completion, making it a challenge to accept in real-life scenarios. The IOM had an acceptable solution time, with a mean of 424.79 s, the best target optimization effect, and the greatest payload, with a mean of 97679.7 kg; all CG deviations were controlled within 1.16%MAC, with a mean of 0.79%MAC.

Development and application of finite element methods in research field of thermal barrier coatings
LIU Yankuan, WANG Yuansheng, WANG Lulu
, Available online  , doi: 10.13224/j.cnki.jasp.20220762

Three major aspects, including thermally grown oxides (TGO) growth behavior and stress-strain, overall thermomechanical properties of thermal barrier coatings (TBC), structural optimization and life prediction of TBC, were reviewed. The development and application of finite element method in these researches in recent years were analyzed, then the problems and limitations in current researches were summarized. At present, the research directions mainly focus on the combination of failure theory, multi-physics coupling and Python subroutines with complex physical models to obtain more accurate finite element analysis results. However, due to many problems such as irregular morphology of TGO, insufficient physical parameters of materials under high temperature conditions, and random distribution of microscopic pores in ceramic layers, there is still a gap between the calculated and actual results. In the future, more in-depth research can be carried out from the aspects of physical model fineness, interlayer boundary conditions and dynamic growth simulation, etc.

Efficient optimization design method of helicopter rotor airfoil
CUI Senrun, LI Guoqiang, ZHANG Weiguo, YANG Xiaoquan, CHANG Shuyu
, Available online  , doi: 10.13224/j.cnki.jasp.20220819

The adjoint-based design optimization method of rotor airfoil is inefficient in combination with a Dual Time Stepping method, making it difficult to meet the optimization requirements of multi-point and multi-objective optimization in engineering. Considering the problem of unsteady optimization design of rotor airfoil, coupled with efficient Time Spectral method and multigrid method, a multi-point and multi-objective optimization design method suitable for multiple motion states of helicopter, such as hovering, forward flight and maneuvering, was developed. The Navier-Stokes equation and adjoint equation were solved by using the Time Spectral method to discretize the physical time term. In addition, the multigrid method was used to improve the optimization efficiency. The rotor airfoil NACA0012 and OA209 were selected to carry out multi-point, multi-objective steady and unsteady optimizations. The results showed that the static and dynamic aerodynamic shape optimization design methods had high accuracy, and can realize the multi-point and multi-objective optimization design of rotor airfoils under complex motion states; compared with Dual Time Stepping and adjoint-based design optimization method, the Time Spectral and adjoint-based design optimization method can improve the calculation efficiency of airfoil optimization by more than 5 times.

Experiment on the tail supersonic jets characteristics of an underwater vertically moving vehicle
ZHANG Chun, XU Tonghua, LIU Xinhui, WANG Baoshou
, Available online  , doi: 10.13224/j.cnki.jasp.20220824

Aiming at the interaction between the flow around underwater vehicles and the supersonic gas jets, supersonic gas jets submerged in liquid ambient from a vertically moving vehicle are experimentally studied. In the experiments, a high-speed camera system is used to observe the evolution of the gas jet bubble, and a dynamic pressure measurement system is used to measure the pressure fluctuation at underwater vehicle bottom. The results show that the main shape of the cavity formed by the supersonic gas jet in still water gradually changes into quasi-ellipsoid. Due to the influence of Rayleigh-Taylor instability, the bulge phenomenon occurs in some domains close to the nozzle outlet. The jet penetration distance decreases with the increase of nozzle expansion ratios. For the tail jets characteristics of an underwater vertically moving vehicle, asymmetric cavity walls may be formed at the start-up stage of ventilation. The interaction between the flow around underwater vehicles and supersonic gas jets leads to the phenomenon of cavity oscillations, which gradually disappears in the working stage. The supersonic gas jets continuously disturbed the near-field flow, and the vehicle bottom pressure successively presents the characteristics of transient impact pressure peak, wide fluctuation in the initial stage, high frequency fluctuation in the working stage, and stable atmospheric pressure after water exit. The shear flow generated by the high-speed motion of the vehicle can suppress the high frequency oscillation of the tail jets, and the pressure oscillation in the 200—1200 Hz frequency band is significantly reduced.

Influence mechanism of different axial spacing on aerodynamic and acoustic characteristics of counter-rotating propeller
FENG Heying, CUI Panwang, TONG Fan, CHEN Zhengwu, LI Qiangbin
, Available online  , doi: 10.13224/j.cnki.jasp.20220838

Based on the nonlinear harmonic method and acoustic analogy theory, the influences of rotor axial spacing on the aerodynamic characteristics and noise of counter-rotating propeller and its physical mechanism were studied. Taking a certain type of counter-rotating propeller as the research object, six kinds of counter-rotating propeller models with different rotor axial spacings were studied. The calculation results showed that change of the axial spacing of the counter-rotating propeller rotor had a certain influence on the overall efficiency of the counter-rotating propeller, but had little influence on the total pull coefficient and total power coefficient. The increase of rotor axial spacing had a significant impact on the axial velocity between the front and rear rotors, but had little impact on the axial velocity of air flow behind the rotor. With the increase of the axial distance between rotors, the radial velocity between the front and rear rotors decreased gradually, and then the slipstream contraction between rotors of counter-rotating propeller was weakened. By changing the axial spacing of the rotor, compared with the minimum axial spacing, the maximum noise of the counter-rotating propeller was reduced by about 10 dB, the interference noise was reduced by more than 10 dB, and the efficiency was increased by 1.4%. With the increase of rotor axial spacing, the amplitude of the first harmonic pressure on the pressure surface and suction surface at 85% of the blade height of the front rotor decreased by 1836 Pa (89%) and 1277 Pa (90%), respectively, at the trailing edge, and the amplitude of the third harmonic pressure on the pressure surface and suction surface at 75% of the blade height of the rear rotor decreased by 266 Pa (78%) and 209 Pa (85%), respectively, at the leading edge.

Numerical study of stator serrated trailing-edge to control turbine broadband noise
XIANG Kangshen, CHEN Weijie, LIAN Jianxin, QIAO Weiyang
, Available online  , doi: 10.13224/j.cnki.jasp.20230120

Using delayed detached eddy simulation/analogy acoustics (DDES/AA) hybrid simulation method, the noise reduction effects and physical mechanism of upstream stator with “arch” distributed trailing edge (Bionic S) and downstream rotor with “arch” distributed leading edge (Bionic R) on turbine turbulent wake interaction broadband noise were studied. The research found that, except for individual frequencies, the upstream “arched” trailing edge stator blades (Bionic S) and the downstream “arched” leading edge rotor blades (Bionic R) can reduce the turbulent wake interaction broadband noise at most of frequencies below 10 kHz. Based on this, the wake characteristics and physical mechanism of noise reduction of Bionic S were preliminarily explored. Bionic S can change the characteristics of the stator wake, making it show periodic changes in the span direction, and then periodical distribution of the time-space correlation coefficient of pressure fluctuation, indicating that the bionic configuration greatly enhanced the phase-delay of pressure fluctuation at different spanwise positions. The influence existed in the entire interaction between wake and suction surface during downstream transport. And the discontinuous characteristics of spatial correlation coefficient distribution of the pressure fluctuation showed the necessity of noise reduction study of bionic configuration in the future to be carried out in the three-dimensional flow.

Helicopter rotor blade model updating method based on sensitivity analysis
S1 Zixian, HAN Dong, CUI Zhao
, Available online  , doi: 10.13224/j.cnki.jasp.20220869

In order to reduce the deviation between the modal response results of the finite element model and the actual model of the helicopter rotor blade structure, a model updating method based on sensitivity analysis was used. In view of traditional sensitivity method without consideration of the influence of the change of design parameters on the sensitivity calculation results, as well as the problem of non-uniform quantification, the method was appropriately improved for the helicopter rotor blade model. Taking the carbon fiber composite helicopter rotor blade model as an example, the natural frequencies of the first six modes of the actual model and the finite element analysis model were obtained through experiments and finite element analysis, respectively, and the main design parameters of the finite element model of the rotor blade were optimized by using the sensitivity method. The average error between the rotor blade finite element model and the actual model was reduced from 8.15% to less than 1%. The error was significantly reduced and the accuracy was significantly improved. The updating results showed that the model updating method based on sensitivity analysis can effectively improve the accuracy of the helicopter propeller structure model.

Study of supercritical kerosene combustion characteristics on single-head combustor
ZHENG Yushan, WANG Shiwei, XIAO Baoguo, ZHOU Yu, LI Tianyu
, Available online  , doi: 10.13224/j.cnki.jasp.20220823

In order to deeply understand the combustion characteristics of supercritical kerosene in aeroengine, a series of direct-connect experiments and numerical simulations were carried out under different ambient pressures and equivalent ratios based on a single head model of an aeroengine dual-swirl combustion chamber. The influence of kerosene injection state on combustion characteristics was obtained. The results showed that, under the same test conditions, the transition of kerosene from subcritical to supercritical state had no obvious effect on the outlet center temperature, but it improved the outlet temperature uniformity to a certain extent, as the outlet temperature distribution coefficient decreased from 0.315 to 0.294. When kerosene was injected in supercritical state, the uniformity of outlet temperature increased with the increase of equivalent ratio, as the outlet temperature distribution coefficient decreased from 0.294 to 0.195 at 380 kPa, and from 0.394 to 0.210 at 580 kPa. Numerical simulations of combustor flow field under various conditions were carried out based on our own CFD software, and the temperature distribution trend obtained was consistent with the tests. The results showed that kerosene injected in supercritical state can enhance fuel and air mixing, advance combustion, migrate the main combustion zone upstream and improve the uniformity of outlet temperature distribution.

Numerical simulation on the effect characteristics of belly temperature rise for short/vertical takeoff and landing aircraft proximity of ground
LI Chun, LI Guangchao
, Available online  , doi: 10.13224/j.cnki.jasp.20220831

The two-order response surface regression functions of the belly temperature rise of the aircraft about the nozzle pressure ratio (NPR), velocity of cross wind and the height of the nozzle exit were obtained by CFD method and the Response Surface method, and the key factors significantly affecting the belly temperature rise were also acquired. The interaction effects of NPR, velocity of cross wind and height of nozzle exit above ground on aircraft belly temperature rise were analyzed, and the maximum belly temperature rise in certain range working state was obtained. The study showed that when considering single factor the belly temperature rise decreased with the increase NPR, velocity of cross wind and the height of nozzle exit above the ground. When considering the interaction of the two factors, only height and NPR had interaction effects on the belly. When considering the two-order influence of single factor, there were two order effects of height of nozzle exit, velocity of cross wind and NPR. According to the maximum belly temperature rise obtained by optimization, the height of rear nozzle exit above ground was treble the diameter of rear nozzle exit, the NPR was 3, and the velocity of cross wind was 0 m/s. In this case, the belly temperature change was 13.92%.

Error analysis and uncertainty assessment of intake momentum measurement
YANG Qiao, WU Feng, WANG Jingyuan, XU Quanyong, LI Hongli
, Available online  , doi: 10.13224/j.cnki.jasp.20220846

In the high altitude simulation test, the measurement method of intake momentum required for engine thrust statistics and the components of measurement uncertainty were introduced. The measurement error of flow coefficient affected by Reynolds number and the calculation error of inlet velocity caused by boundary layer velocity loss were given. The uncertainty of these two errors was analyzed theoretically. Taking the typical flight condition of a turbofan engine as an example, numerical simulation and test measurement were carried out, and the corresponding uncertainty of intake momentum measurement was obtained. The results showed that the uncertainty of intake momentum in thrust measurement was about 1.2%—1.4%. The error of flow coefficient caused by Reynolds number deviation and the calculation error of intake velocity cannot be ignored, and should be taken into account in the calibration method or correction method.

Semiempirical prediction of Sauter mean diameter for pressure swirl atomizer based on instability theory
GAO Zhao, LIU Yuying, ZHANG Quan, HUANG Yong, WANG Donghui
, Available online  , doi: 10.13224/j.cnki.jasp.20220626

Based on the liquid atomization instability theory, a semiempirical model was established to predict the Sauter mean diameter (SMD) of pressure swirl atomizers, considering the Kelvin-Helmholtz (K-H) instability and Rayleigh-Taylor (R-T) instability generated by the interactions between air and liquid film. The experiments were also conducted using phase Doppler particle analyzer (PDPA) technique and digital off-axis holography with liquid temperature ranging from 240 to 300 K and liquid pressure ranging from 0.5 to 3 MPa. The results showed that: there were circumferential waves and axial waves on the surface of liquid sheet. With the decrease of liquid pressure and liquid temperature, the instability of liquid film was inhibited, which led to the increase of the SMD. Compared with the K-H instability, the effect of the liquid pressure on R-T instability was more significant; the effects of liquid physical properties, geometrical structures and operating conditions were included in the semiempirical correlation. The predictions showed good agreement with the experimental results, and the maximum uncertainty of the semiempirical correlation to predict the SMD was about ±15% for the available experimental data, making it valuable for the prediction of atomization performance and the optimization of the structure of pressure swirl atomizers.

Numerical study on static and dynamic characteristics of an integral floating ring seal with shallow groove dynamic pressure
ZHAO Huan, JIANG Jinyu, SUN Dan, WANG Shuang, LI Yanpeng
, Available online  , doi: 10.13224/j.cnki.jasp.20220697

A multi-frequency elliptic vortex solution model for static and dynamic characteristics of the monolithic floating ring seal with shallow groove dynamic pressure was established. On the basis of verifying the accuracy of the numerical calculation method, the static and dynamic characteristics of the integral floating ring seal with no groove, rectangular groove, spiral groove and T-groove were analyzed. The changes of leakage, buoyancy and dynamic characteristics of the integral floating ring seal under different structures and working condition parameters were studied. The influence of groove type on the stability of the integral floating ring seal rotor was analyzed, and the influence mechanism of dynamic pressure groove type on the dynamic characteristics of the integral floating ring seal was revealed. The results showed that the leakage and the lift force increased with the increase of eccentricity. Compared with the non-slotted floating ring seal, the rectangular groove had the largest leakage, and the T-shaped groove had the largest buoyancy, which was 434.7% of that without groove. Under the same vortex frequency, the effective damping of the rectangular groove was maximum and positive, and the tangential flow force was opposite to the rotor vortex direction, which can restrain the rotor vortex and improve the rotor stability.

Prediction of the swing fatigue life of flexible joint based on cracking energy density
ZHANG Jinyao, REN Junxue, XUE Muyao, TONG Yue, ZHENG Qing, TANG Haibin
, Available online  , doi: 10.13224/j.cnki.jasp.20220826

In order to accurately predict the swing fatigue life of flexible joint, the cracking energy density (CED) was used as the damage parameter to drive the fatigue crack growth of elastomers. The swing fatigue life prediction model of flexible joint was established by means of fatigue crack growth test and uniaxial tensile fatigue test. The CED of flexible joint under 12.3 MPa and 6° swing angle was calculated by using the finite element analysis results, and then the swing fatigue life of flexible joint was predicted. The results showed that the predicted swing fatigue life of the flexible joint under the experiment condition was 107 cycles, which was consistent with the measured fatigue life of 120 cycles, and the predicted crack location and crack plane were in good agreement with the failure position of test. The ratio of predicted life to measured life was 1/1.12 within the double dispersion factor, which was acceptable in engineering.

System design of hybrid distributed electric propulsion aircraft
LI Jiacheng, SHENG Hanlin, CHEN Xin, SHI Haolan, ZHANG Tianhong
, Available online  , doi: 10.13224/j.cnki.jasp.20220693

The Y-7 aircraft was used as the reference model to carry out the overall design and performance analysis of the distributed electric propulsion aircraft. The power system of the distributed electric propulsion aircraft was designed, including design of propeller parameters, correction of wing parameters, calculation of motor power and type selection and aerodynamic design of propeller, and finally the design of hybrid power system was completed. The mass increase and decrease of each part of the distributed electric propulsion aircraft were completely calculated and its flight performance was analyzed. Compared with the reference model, the range and duration increased by 540 km and 1.2 h respectively, up by 20%. Finally, the three-dimensional modeling was established and aerodynamic characteristics of the distributed electric propulsion aircraft were analyzed. The result provides a theoretical basis for the modeling, simulation and control of distributed electric propulsion aircraft and its engineering applications.

Fast automatic correction method for component characteristics of the identification dynamic model of VCE
ZOU Zelong, HUANG Jinquan, ZHOU Xin, ZHOU Wenxiang, LU Feng
, Available online  , doi: 10.13224/j.cnki.jasp.20220680

To realize the engineering requirement for fast automatic correction of model component characteristics, an enhanced automatic correction strategy of the identification model component characteristics was proposed. Taking steady-state test data as input, the designed correction strategy allowed to analyze and select suitable characteristic correction coefficient combinations based on sensor measurements. The proposed method also coupled individual rig test data of engine to design the equilibrium equations, and used the double-loop strategy of multi-point model correction to quickly and automatically correct component characteristics. Finally, the fast automatic correction of the identification model of a certain variable cycle engine was realized. The inverse flow path disturbance, damping coefficient self-adjustment method of Newton-Raphson method and characteristic map interpolation protection logic were adopted to improve the operation rate and stability of the algorithm. The simulation results showed that the maximum output error of the corrected model was less than 0.1%, and the consuming-time was reduced by more than 98.6% compared with the common component-level model, which was simulated in single and double bypass modes on a computation with 2.10 GHz processor. The corrected model can be used for control law design and also provide a reference for determining the current real state of the engine.

Influence of secondary combustion reaction on the performance of air-underwater dual-mode turbines
ZHANG Anjing, QIN Kan, WANG Hanwei, WANG Qian, LUO Kai
, Available online  , doi: 10.13224/j.cnki.jasp.20220671

In order to make the trans medium vehicle adapt to underwater and air medium navigation at the same time, research on the secondary combustion reaction process of a new dual-mode turbine was carried out. The turbine used kerosene and air as fuels when it worked in the air, and used Yutui-3 propellant as fuel when it worked underwater. At the stage of turbine water take-off, kerosene and Yutui-3 propellant need to be burned at the same time. As the combustion products of Yutui-3 propellant contain a large amount of CO, H2 and CH4, it will produce secondary combustion after mixing with the residual air from kerosene combustion. In order to analyze the influence of secondary combustion reaction during takeoff, the influence of secondary combustion reaction on the performance of air-water dual-purpose turbine was studied by numerical simulation. The results showed that these two kinds of fuel gases had chemical reaction, and CO, H2 and CH4 in Yutui 3 fuel gas were almost completely burned; the secondary combustion reaction mainly occurred in the front section of the nozzle. The maximum temperature of the combustion section increased from 712 K to 2 185 K, which increased the outlet velocity of the nozzle and made the thrust increase by about 30.24%. This study provides an idea for the increase of thrust of air water turbine during takeoff.

An improved EWT method for fault diagnosis of rolling bearings
SHENG Jiajiu, CHEN Guo, KANG Yuxiang, HE Zhiyuan, WANG Hao, WEI Xunkai
, Available online  , doi: 10.13224/j.cnki.jasp.20220677

Considering the problem of empirical wavelet transform (EWT) in extracting optimal frequency band of the rolling bearing fault signal, an improved EWT method based on extracting energy envelope trend line to adaptively divide frequency band was proposed and applied to rolling bearing fault diagnosis. The Teager energy operator was used to convert the spectrum into energy spectrum, and the energy envelope was obtained by repeated Hilbert transform. Local maximum values were extracted and smoothed to obtain the energy envelope trend line, and the first-order difference was performed to select effective extreme points to adaptively divide the frequency band. A normalized fault characteristic frequency saliency index was constructed as an effective criterion for fault diagnosis and optimal resonance frequency band selection. The algorithm was verified by rolling bearing fault simulation and experiment data. The results showed that compared with the original EWT, the proposed method can effectively identify the early faults of rolling bearings and reasonably select the optimal resonance frequency band. The proposed indexes for the outer and inner race fault data can be increased by 48.0% and 174.1% on average.

Experimental study of low pressure turbine cascade under high Mach number and low Reynolds number conditions
DUAN Wenhua, CHEN Weijie, ZHAO Xinyu, QIAO Weiyang
, Available online  , doi: 10.13224/j.cnki.jasp.20220827

A high speed low pressure turbine cascade was experimentally and numerically studied under high Mach number and low Reynolds number conditions. The loss characteristics of cascade under isentropic outlet Mach number range of 0.66—1.23 and Reynolds number range of 1.1×105—9.0×105 were studied experimentally, and the flow field under typical conditions was simulated. The influence of Reynolds number on cascade performance under high subsonic speed conditions and the influence of shock wave on boundary layer flow under different Reynolds number conditions were mainly analyzed. The results showed that when the Reynolds number decreased from 1.1×105 to 9.0×105 under high subsonic speed conditions, the suction side boundary layer developed from no separation to a closed separation bubble, and finally to an open separation. In the absence of shock wave, the starting position of laminar separation was not greatly affected by Mach number, which mainly affected the transition and reattachment position of the separation boundary layer. Shock laminar boundary layer interactions occurred on the suction surface of the blade under transonic conditions. The development of the boundary layer after interaction relied on the Reynold number and the strength of shock. The numerical results were in good agreement with the experimental results, but there were differences in the prediction of the pressure coefficient at very low Reynolds numbers.

Numerical calculation on resistance characteristics of metal foam
ZHANG Lifen, GE Xin, HU Xinglong, WEI Ruirong, YU Bangtuo, LIU Zhenxia
, Available online  , doi: 10.13224/j.cnki.jasp.20220638

The cell structure of the metal foam was reconstructed using the body-centered cubic structure and Kelvin structure, respectively, and the internal resistances of the metal foam under single-phase flow and two-phase flow at different cutting angles were analyzed and compared. The results showed that: 1) the body-centered cubic structure can achieve a porosity e range of 68.01% < e < 98.01%; while the Kelvin structure can achieve a porosity range of 72.1% < e < 98.7%; 2)the pressure drop calculated by two-phase flow was about 5% higher than that calculated by single-phase flow when the mass fraction of oil droplets was 9.1% and the inlet velocity was less than 20 m/s; 3) the resistance characteristics of the Kelvin structure metal foam with a cutting angle of 30° were in high agreement with those of the actual metal foam, and can better characterize the resistance characteristics of the metal foam.

Application and technical analysis of ceramic composite combustor liner
ZENG Qinghua, CHEN Xuanwu, ZENG Qi, LI Ziwan, XIE Pengfu
, Available online  , doi: 10.13224/j.cnki.jasp.20220629

Based on the development trend and characteristics of aero-engine and combustor, the demand of ceramic composite materials for new generation aero-engine combustor was analyzed, the composition, type characteristics and high temperature corrosion resistance of ceramic composite liners were expounded, the process principle, advantages and disadvantages of ceramic composite liners under different fabrication methods were summarized, and the application status of ceramic composite materials in combustor liner was discussed in detail, finally, combined with the significant anisotropic characteristics and challenges of ceramic composite materials, the key technologies for the design of ceramic composite liner of combustor were proposed. The result showed that the ceramic composite liner had obvious technical advantages in the application of combustor, and its service status on multiple advanced military and civil aviation engines verified the feasibility of developing the technical route of ceramic composite liner. However, due to the high sensitivity of ceramic composite to thermal stress and its complex heat transfer and mechanical characteristics, its engineering application still faced great technical challenges; the key technologies that need to be solved urgently in the engineering application of ceramic composite liner include the cooling design of ceramic composite liner, the combustion organization design of ceramic composite combustor, the connection design of ceramic composite liner components, and the forward strength design of ceramic composite liner.

Early fault alarm method of rolling bearing based on wavelet analysis and convolution neural network
LIU Xiyang, CHEN Guo, WEI Xunkai, LIU Yaobin, WANG Hao, HE Zhiyuan
, Available online  , doi: 10.13224/j.cnki.jasp.20220622

In view of the problems in condition monitoring of aero-engine main bearing, such as the difficulty in obtaining the real fault samples, the limitation in defining the general alarm threshold under variable conditions and the difficulty to identify the early weak faults, a general alarm method for early faults of rolling bearings was proposed. This method only trained convolutional neural networks based on normal samples, constructed evolution state indicator by the characteristic distance between degraded data and normal data, and unified the alarm thresholds of different working conditions based on training labels; at the same time, the sensitivity of wavelet band envelope signal to early high-frequency fault was used to realize early warning; then, the evolution stages were divided based on the Pauta criterion, according to which the degradation and failure thresholds were determined; finally, the remaining useful life was predicted step by step based on particle filter. Three groups of test results showed that the degradation threshold and failure threshold of wavelet analysis and convolution neural network (Wavelet-CNN) based on different fault test data can be normalized around 0.6 and 1.0, and the predictions of degradation start time were 13.01%, 12.33% and 13.70% earlier than those of non wavelet methods respectively.

Modal test and model modification of spiral bevel gears
HE Hongtu, CAO Xuemei, XU Hao, HOU Shengwen
, Available online  , doi: 10.13224/j.cnki.jasp.20220978

To accurately extract spiral bevel gears’ modal parameters and construct an accurate dynamic model, a combination of experimental and simulation methods were used to conduct modal tests using the moving force hammer method to extract modal parameters; an accurate simulation model was established based on measured data and modal analysis was conducted; the elementary rotation transformation method was used to correct the simulation mode shapes, and the accurate confidence of the test and simulation modes was obtained to improve the analysis accuracy; taking the experimental modal frequency as the target, the response surface method was used to correct the material parameters of the model. After the correction, the maximum relative error of natural frequency was reduced from 0.83% to 0.353%, which improved the accuracy of the simulation model. The experimental and simulation frequency response analysis results showed that the frequency shift phenomenon and acceleration amplitude error caused by inaccurate simulation models were effectively controlled, verifying the accuracy of the dynamic model. The research method lays the foundation for further structural optimization and vibration reduction and avoidance of spiral bevel gears.

Structural robust optimization design of beam seal
LIU Yong, REN Xinjiang, YAN Fangchao
, Available online  , doi: 10.13224/j.cnki.jasp.20220868

In order to improve the sealing performance of the beam seal, the structural parameters of the beam seal were used as design variables, and the robust optimization design was carried out. A finite element model of the beam seal with elliptical arc groove was established. Taking the maximum contact pressure and contact surface width of these two seals on the sealing contact surface as quantitative indicators of sealing performance, second-order response surface models were established, and the response surface models were solved by multi-objective optimization using genetic algorithm. The additional sensitivity term representing the robustness of the objective function was added to the multi-objective optimization model, and the robust design parameters combination of the beam seal was obtained. The effectiveness of the robust optimization results was verified by the finite element’s numerical simulation. The results showed that when the elliptic semi-major axis was 1.156 mm, the elliptic semi-minor axis was 0.315 mm, and the nominal width of the first seal was 0.429 mm, the sealing robustness of the beam seal was better, and the robust design achieved the expected goal.

Effect of equivalence ratio on kerosene-hydrogen-air rotating detonation propagation at room temperature
HUANG Hanli, LYU Yajin, ZHENG Quan, WU Mingliang, XIAO Qiang, WANG Fang, WENG Chunsheng
, Available online  , doi: 10.13224/j.cnki.jasp.20220712

In order to study the effect of equivalence ratios and hydrogen mass fractions on the propagation characteristics of a rotating detonation wave, the evolution process was numerically simulated by utilizing the kerosene and hydrogen as fuel and air as oxidant. The propagation characteristics of rotating detonation wave, the component distribution characteristics of internal flow field and the stability of detonation wave were analyzed. The simulated results showed that with the increase of hydrogen mass fractions, the range of equivalence ratios for successful initiation of a rotating detonation in the combustor was narrowed gradually. At the same time, the recorded peak pressures of detonations decreased, while the propagation speed increased with the velocity deficits showing a non-monotonous variation with the equivalence ratio. Under the fuel-lean condition, the fuel and oxidant in the fuel-rich zone were not evenly mixed and the oxygen was distributed in strips; under the fuel-rich condition, the deflagration zone increased and its reaction strength was intensified, and the edge of the oxygen-rich zone was in wavy shapes. The propagation stability of rotating detonations was higher when the equivalence ratio was 1.0 to 1.2, and the time interval from ignition to the formation of a stable rotating detonation wave reached the minimum at the stoichiometric equivalence ratio, but increased with the increase of hydrogen mass fractions.

Workable mode optimization design method for dual-rotor system with inter-shaft bearing
WANG Rui, LIAO Mingfu, CHENG Ronghui, CONG Peihong, LEI Xinliang
, Available online  , doi: 10.13224/j.cnki.jasp.20220623

In order to solve the problem that the dual-rotor system of aero-engine cannot avoid the critical speed, a model of dual-rotor system with inter-shaft bearing was established. Considering the influence of unbalance sensitivity, damper effect and the load effect of inter-shaft bearing, the tolerability evaluation functions of low-pressure and high-pressure rotor excited modes were constructed, the tolerability objective function and the constraint condition for optimization design on workable mode of dual-rotor were confirmed, and the optimization design method for the workable mode of dual-rotor system with inter-shaft bearing was established. It was found that compared with the traditional critical speed margin design criterion, the maximum amplitude of the disk of the dual-rotor system with inter-shaft bearing was reduced by 39.83%, the total mass of the shafting was reduced by 2.32%, and the external force of the fulcrum was reduced by 64.98% by using the optimization design method for the workable mode, indicating that the optimization design method for the workable mode of dual-rotor system with inter-shaft bearing was effective.

Scheme and Performance Analysis of a Hybrid Power System for Two Stroke Aviation Heavy Fuel Piston Engine
WANG Yukun, SHAO Longtao, YU Tao, GENG Tai, XU Zheng, ZHOU Yu
, Available online  , doi: 10.13224/j.cnki.jasp.20230203

In response to high power density and low fuel consumption, an aviation piston-turbine hybrid system configuration was proposed, wherein the piston subsystem adopted a two-stroke aviation heavy oil piston engine with horizontally opposed cylinders, and the turbine subsystem consisted of a burner and a turbocharger. Based on the GT-POWER platform, the accuracy of the simulation model was verified using a comparative study of cylinder pressure. The effects of turbocharger efficiency, turbine efficiency, reheat fuel flow, and altitude on the performance of hybrid system were studied, and the system performance was evaluated based on brake specific fuel consumption and output torque. The research results showed that the hybrid system can increase the output torque by about 30% compared with the aviation piston engine at the limit state. The torque gain generated by a 10% increase in compressor efficiency was greater than the torque gain generated by a 10% increase in turbine efficiency. When the fuel flow rate in front of the turbine was 0.2 g·s−1, the exhaust temperature can be increased by about 150 K, and the output torque at all operating points can be increased by more than 20%. Therefore, reheating in front of a turbine is an effective means to improve the performance of an aviation piston-turbine hybrid system.