2021 Vol. 36, No. 4

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Large eddy simulation on the staggered tube bundle of the compact precooler
CHEN Yiming, LI Zepeng, ZHANG Junqiang, ZOU Zhengping
2021, 36(4): 701-712. doi: 10.13224/j.cnki.jasp.2021.04.003
Abstract PDF(7614KB) icon474 icon285
Abstract:
The large-eddy simulation was carried out to research convective heat transfer in the staggered tube bundle of the compact precooler. Besides, the dynamic mode decomposition (DMD) method was used to analyze the coherent structure and statistical characteristic of heat transfer of cross-row tube bundles. Results showed that within the simulated operating range (Re≤6 000), the flow structure of the front tube bundle exhibited regular shear layer movement and wake vortex shedding. The flow structure of the rear tube bundle was an irregular small-scale vortex structure, and the disorderly flow field of the rear tube bundle was presented. The instantaneous Nusselt number on the surface of the front rows had a relatively fixed wave frequency, while the instantaneous Nu on the back rows had no fixed wave frequency because of the irregular impact of the falling vortex of the front rows. Under the condition of Re=2 600, the entropy production in the bundle mainly came from heat transfer rather than dissipation. The main flow structure contributed to the dissipative entropy production and heat transfer entropy production in the location of the boundary layer and free shear layer on the tube wall. It contributed greatly to the entropy production in the front row tubes, but less to the entropy production in the back row tubes.
Experiment and numerical simulation on aerodynamic performance of low-loaded and highly-loaded compressor cascades
YUAN Ze, ZHENG Qun, YUE Guoqiang, DONG Jingtao, JIANG Yuting
2021, 36(4): 724-733. doi: 10.13224/j.cnki.jasp.2021.04.005
Abstract PDF(5699KB) icon589 icon301
Abstract:
To clarify the difference in aerodynamic performance and flow transition between compressors using highly-loaded design and general design (low-loaded), the cascade experiments including suction side flow pattern and parameter measurement were performed. Based on the experimental boundary conditions, numerical researches on the suction boundary layer with γ-θ transition model were also conducted. Result showed that, compared with the low-loaded cascade, as the incidence angle increased, the flow boundary layer in highly-loaded cascade transformed from the attached flow to the separated flow, which enhanced wake width and loss and made wake integrate with corner separation loss region into a “strip-shape” loss region. Meanwhile, the flow boundary flow in low-loaded cascade was still an attached flow and the corner separation maintained open separation close to the endwall. The results indicated that highly-loaded design enhanced the inverse pressure gradient in the cascade, causing the flow more easily separated, the surface shape parameter presented a wide range of “peak” distribution, and the transition mode also changed from local bypass transition to all-span separation-induced transition.
Analysis of influencing factors of fretting wear with helicopter floating involute spline
XIAO Li, XU Yingqiang, CHEN Zhiyong, SHI Xinxin, LI Mingxu
2021, 36(4): 751-766. doi: 10.13224/j.cnki.jasp.2021.04.008
Abstract PDF(7083KB) icon485 icon191
Abstract:
In order to explore the influence of different wear influencing factors on the wear of floating spline, a fretting wear prediction model of spline pair was established based on the energy dissipation theory. The influences of torque, load fluctuation, spline material, friction factor, axial misalignment and angular eccentricity on the wear of floating splines were analyzed. Meanwhile, an entropy weight-fuzzy correlation analysis model was established to objectively analyze the correlation degree of different influencing factors on the wear of floating involute splines. The results showed that the calculated difference of the maximum wear depth at the top, middle and root of tooth for the spline based on the energy dissipation wear model was lower than 6.9%, 2.4% and 14%, respectively. The angular eccentricity of the spline caused poor contact at the start and stop positions of some teeth, resulting in uneven distribution of wear on both ends of the spline. The angular eccentricity, axial misalignment and material properties were more sensitive to the fretting wear of the spline pairs, providing a technical support for the research on the anti-wear method of the floating spline.
Natural characteristics and sensitivity analysis of a coaxial contra-rotating encased differential gear train
ZHANG Donglin, ZHU Rupeng, LI Miaomiao, FU Bibo, TAN Wuzhong
2021, 36(4): 767-775. doi: 10.13224/j.cnki.jasp.2021.04.009
Abstract PDF(2491KB) icon336 icon229
Abstract:
Based on the torsional vibration lumped-parameter model of the coaxial contra-rotating encased differential gear train, the natural frequencies and vibration modes of the system were solved. The results showed that all vibration modes of the planetary gear train can be categorized into three classes: rotational mode, stepped planet mode and planet mode, corresponding to the distinct frequency, L (Number of planet gear)-1 and N (Number of star gear)-1 multiple frequency respectively. The number of planets had no effect on the magnitude of the multiple frequency. When the change rate of stiffness was positive, the change rate of natural frequency was positive, and the change rate of natural frequency was negative when the change rate of moment of inertia was positive. Frequency loci veering occurred when two frequencies in the same vibration mode were approaching. The correctness of the theoretical analysis was verified by an example, providing a basis for the analysis and optimization of the natural characteristics design of the coaxial contra-rotating encased differential gear train.
Effect of gas compressibility on flow coefficient
HU Wencheng, ZHANG Baohua, SHEN Chen, WANG Dongdong, DOU Yitao, SHAO Zhiqiang
2021, 36(4): 776-782. doi: 10.13224/j.cnki.jasp.2021.04.010
Abstract PDF(3716KB) icon564 icon213
Abstract:
The effect of gas compressibility on the effective flow area was studied by theory and experiment. The regression analysis method was used to fit the experimental data, and compared the degree of the coincidence between different theoretical models and experimental data. Results showed that the pressure of gas compressibility can be neglected when the gas pressure ratio was less than 1.081. When the pressure ratio was greater than 1.081, the fitting curve of the compressible gas theory model was consistent with the experimental data, and the value of effective flow area was stable at different pressure ratios. Fitting curves of the incompressible flow theory model deviated from the experimental data. The value of the effective flow area changed with different pressure ratios.
Calculation of airfoil anti-icing/deicing characteristics based on water film flow and coupled heat transfer
XIN Miao, ZHONG Guo, CAO Yihua
2021, 36(4): 783-794. doi: 10.13224/j.cnki.jasp.2021.04.011
Abstract PDF(2826KB) icon366 icon177
Abstract:
Numerical simulation methods for airfoil anti-icing/deicing system based on water film flow and coupled heat transfer model were established to solve the coupled mass and heat transfer phenomena among air/water film/ice layer/airfoil on the airfoil surface in the aircraft anti-icing/deicing process. The numerical computation methods for runback flow water, ice accretion on the airfoil surface as well as inner temperature distribution under the effect of the thermal load of anti-icing/deicing system were established based on the Myers water film flow model. For the heat transfer process in the airfoil and ice layer, the enthalpy theory and the finite volume method were used to establish the numerical simulation method of heat transfer in the complex multilayer structure. For the phase change process in the ice layer, the phase change correction method based on enthalpy theory was proposed to consider the effect of phase change latent heat on temperature change. Finally, coupled calculation of the airfoil anti-icing/deicing process was realized. The results showed that through the coupled calculation of the water film flow and airfoil/ice layer heat transfer model with combination of the heat transfer boundary conditions at different interfaces and the enthalpy theory considering the latent heat effect of phase change, the temperature distribution can be accurately computed in the airfoil/ice layer, meanwhile the effective prediction and analysis of the flow and ice accretion characteristics of the runback water during the airfoil anti-icing/deicing process can be realized.
Method of blade vibration response analysis under airflow excitation
TIAN Shaojie, QI Wenkai, XU Zhenghua
2021, 36(4): 826-838. doi: 10.13224/j.cnki.jasp.2021.04.015
Abstract PDF(4461KB) icon665 icon390
Abstract:
In order to study the method of blade vibration response analysis under airflow excitation, the aerodynamic excitation force prediction method was established. The nonlinear harmonic method was used to conduct three-dimensional unsteady flow analysis of the blades, obtain the fluctuating pressure on the blade surface, compile the flow-solid conversion program, and calculate the aerodynamic excitation force on the blade. The aerodynamic damping analysis method for blades was established. Based on the energy method and the weak coupling analysis method, the fluid-solid weak coupling analysis was carried out for blades and flow fields. The aerodynamic negative work done by aerodynamic forces on moving blades was equivalent to the work done by viscous damping force, and the modal aerodynamic damping ratio of rotor blades was obtained. The vibration response analysis method of blade excited by airflow was established, and based on aerodynamic excitation force and modal aerodynamic damping ratio of blade, modal superposition method was adopted. Using this method, the aerodynamic excitation force, the modal aerodynamic damping ratio of the first eight modes and the vibration response of the rotor blade under the combined action of the aerodynamic excitation force and the aerodynamic damping were calculated for the rotor stator blade array model of the 1.5-stage compressor in the engine. The results showed that the vibration stress reached 100 MPa.
Spray angle model of gas-liquid pintle injector unit
ZHANG Botao, LI Wenlong, LI Ping
2021, 36(4): 839-850. doi: 10.13224/j.cnki.jasp.2021.04.016
Abstract PDF(4071KB) icon434 icon202
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In order to accurately predict the spray angle of pintle injector unit, the theoretical model of spray angle of liquid jet impinging on gas sheet was established based on momentum conservation. The deformation factor was obtained by experimental results. Moreover, the influence of structure parameters and operation parameters on spray angle was analyzed. The results showed that the local momentum ratio had the greatest influence on the spray angle, and other structure parameters and operation parameters further determined the spray angle by influencing the local momentum ratio. As the local momentum ratio increased, the deformation of the liquid jet decreased. The effective momentum ratio was less than the geometric momentum ratio due to liquid jet deformation. According to the experimental results, the value of the deformation factor was given in sections. When the local momentum ratio ranged from 0 to 3, the recommended value of the deformation factor was 0.61. When the local momentum ratio ranged from 3 to 4.5, the recommended value of the deformation factor was 0.70.When the local momentum ratio ranged from 4.5 to 7.2, the recommended value of the deformation factor was 0.75. The theoretical predicted value of the deformation factor was in good agreement with the experimental results. This model can provide a reference for the theoretical research and engineering design of gas-liquid pintle injector.
Thermal coupling analysis of variable cross-section circular hole grain under temperature impact
LIU Yuanxiang, LU Yingying, HU Shaoqing, FU Xuejin, LI Hongyan, ZHANG Haoyuan
2021, 36(4): 851-860. doi: 10.13224/j.cnki.jasp.2021.04.017
Abstract PDF(4564KB) icon456 icon190
Abstract:
In order to study the influence of temperature impact load on the structure integrity of a modified double-base propellant grain, mechanical relaxation tests of the modified double-base propellant at different temperatures were carried out based on the basic theory of thermo-structure coupling. The sixth order Prony series of relaxation modulus at different temperatures and the time-temperature equivalent W.L.F (Williams-Landel-Ferry) equation with 293.15 K as the reference temperature were obtained. Ansys finite element method software was used to analyze the structure integrity of the grain under the temperature impact condition from 333.15 K to 218.15 K. The results showed that the temperature and strain of the grain changed sharply in the early stage of temperature impact, and basically reached balance at 12 000 s. Two corners of the grain front face were damaged in the early stage of temperature impact. In order to verify the simulation results, from 333.15 K to 218.15 K temperature impact test was carried out. The results showed that: in the process of temperature impact, the propellant column cracks appeared along the axial and radial directions, and the crack initiation points were at the front two corners of the propellant grain. The temperature impact test results verified the accuracy of the simulation calculation, which showed that the calculation process can be used to analyze the structural integrity of grain.
Fault diagnosis of abnormal fuel injection of small aviation piston engine
SHEN Huan, ZHAO Fei, MAO Jianguo, ZHANG Chen, HU Wei
2021, 36(4): 861-873. doi: 10.13224/j.cnki.jasp.2021.04.018
Abstract PDF(5060KB) icon545 icon177
Abstract:
Considering the abnormal fuel injection failure of small aviation piston engines, based on the engine’s in-cylinder pressure and cylinder head vibration signal, a fault diagnosis method combining variational modal decomposition and cuckoo search optimization support vector machine was used to diagnose abnormal fuel injection failure of the engine. The method used variational mode decomposition to process the in-cylinder pressure signal and cylinder head vibration signal of the engine to obtain an intrinsic mode function, perform singular value decomposition and energy feature extraction on the intrinsic mode function, and the data sets of in-cylinder pressure and cylinder head vibration were input into the support vector machine optimized by the cuckoo search algorithm for training and testing. Results showed that this method can better identify the faults of abnormal fuel injection of the engine, and the accuracy of the fault recognition classification of the pressure in the cylinder and the vibration signal of the cylinder head was 95.32% and 92.47%, respectively, verifying the effectiveness of the method.
Safety analysis method of aero-engine systems based on Simscape model
CHU Nana, ZHANG Shuguang, GAO Yanlei, WEI Zhiyuan, SHAO Nian
2021, 36(4): 885-896. doi: 10.13224/j.cnki.jasp.2021.04.020
Abstract PDF(2846KB) icon761 icon481
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In view of the problem of coupling influence in the system safety analysis of aero-engines, the coupling fault modeling and safety analysis of aero-engines based on Simscape model were studied. Combined with the general characteristics of fault extension in model based safety analysis (MBSA), two ways of fault external expansion and internal fault expansion based on modeling language of Simscape model were analyzed, so as to establish a model considering the coupling faults. Taking the main fuel control subsystem in full authority digital engine control (FADEC) as a research example, formal safety analysis of the independent and coupling fault was conducted. The results showed that the Simscape model of aero-engines system safety analysis based on the system design environment can be used as a common tool for system design and safety analysis, which can ensure the consistency of design and safety analysis. Based on the principle of fault mathematics, the model expansion method and modeling language can flexibly and quantitatively describe the component independency and coupling fault characteristics in different physical domains of the actual system. The safety analysis based on the extended fault model had the advantages of formalization, intuitiveness and objectivity.

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