2020 Vol. 35, No. 1

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Effect of warhead shape on penetration into metal-ceramic lattice sandwich structure
ZHANG Jun, JIA Guangchen, XU Guojun
2020, 35(1): 1-8. doi: 10.13224/j.cnki.jasp.2020.01.001
Abstract PDF(3789KB) icon669 icon502
Abstract:
A structural model of composite materials composed of the metal skeleton,ceramic rods, epoxy, front and back metal plates was proposed. Based on the finite element method, the validity of numerical method was proved by the available experiments. Then, anti-penetration mechanisms of the composite structures were simulated in the process of penetration with three types of steel projectiles (flat-warhead, hemispherical-warhead and conical-warhead). The sub-structures failure modes, energy absorption efficiency, plastic deformation, ballistic performances, velocities and accelerations of the projectiles target plate were analyzed. The results showed that the warhead shape had a great effect on the damage mechanisms and energy absorption characteristics. The flat-warhead and hemispherical-warhead projectiles mainly resulted in crushing damage to the target plate, and the peak acceleration time was shorter. However, the conical-warhead projectile penetration into the target plate mainly resulted in piercing and reaming. The peak acceleration time was greater and the penetration efficiency was the highest. During the projectile penetration, the shear hole and plastic deformation of the metal skeleton, the fracture of the ceramic rod and the plastic deformation of the metal front plate and the metal back plate significantly improved the anti-penetration ability of the structure.
Parameter identification of linear time-varying systems based on chirplet transform under environmental excitation
ZHANG Jie, SHI Zhiyu, LI Lirong
2020, 35(1): 9-17. doi: 10.13224/j.cnki.jasp.2020.01.002
Abstract PDF(1833KB) icon545 icon481
Abstract:
The assumption that frequencies of responses of linear time-varying systems vary linearly in a short-time was proposed. By fitting the time-varying responses to multi-component line frequency modulation signals, a physical parameter identification method of time-varying systems under random white noise excitation was obtained according to the cross-correlation theory of line frequency modulation signals. The mass and stiffness coefficients of time-varying structures were identified only using the acceleration response. Due to the introduction of frequency modulation factor to describe the variation of frequencies of response signals in a short-time, this method could track fast changes or even abrupt changes of parameters better than traditional identification method, so it had important application value for time-varying structures in practical engineering. In the simulation example, a 3-degress of freedom time-varying structure model was constructed to identify linear, periodic and abrupt changes of physical parameters. The error analysis showed that the identification errors were all within 5%. The results verified the correctness and applicability of the method.
Study on damage of aero-engine blades caused by different metal hard materials
SHU Chang, CHENG Ming, XU Yu
2020, 35(1): 18-29. doi: 10.13224/j.cnki.jasp.2020.01.003
Abstract PDF(5704KB) icon784 icon506
Abstract:
In order to analyze the characteristics difference of foreign object damage caused by different metal hard materials on the aero-engine fan blades, beads made of steel, copper, aluminum and lead were regarded as foreign objects, the intake edges of real blades were impacted at two angles and different speeds, and the dynamic damage process was simulated by numerical methods.The experiment results showed that when the steel and copper beads impacted, the blade damage morphology could be divided into pits, tears and gaps, when the tearing appearance occurred, the small angle impact required higher speed compared with large angle impact. Furthermore, copper beads impact required higher speed compared with steel beads impact; aluminum beads and lead beads had large deformation when they were impacted, which only caused extrusion deformation of the blade. The simulation results showed that, when the impact energy was 22 J, there were two significant peaks of contact force in the process of tear damage caused by copper beads and steel beads, accompanied by the phenomenon of “kinetic energy recovery”; more kinetic energy of the copper bead was transformed into the blade and its own strain energy, so its penetration ability to the blade was not as good as that of the steel bead; the aluminum bead had the highest impact force, and the ratio of its kinetic energy to its own strain energy was the highest; the impact force peak of the lead bead was not obvious, and most of its kinetic energy was converted into heat consumed by friction.
Numerical simulation method and investigation of cold expansion processing parameters of nickel-based superalloy GH4169
JIN Shengzhe, HU Dianyin, LIU Hui
2020, 35(1): 30-40. doi: 10.13224/j.cnki.jasp.2020.01.004
Abstract PDF(3870KB) icon790 icon481
Abstract:
In order to investigate the usage of cold expansion technology in nickel-based superalloy GH4169, the numerical simulation method was established to study the influence of mandrel materials, interference value and friction coefficient on circumferential residual stress distribution. The validity of the numerical method was verified by experimental data. According to the simulation results, the upper limit of interference value was 186% and there existed a favorable range of interference value and friction coefficient. In addition, the depth of compressive residual stress had a positive linear correlation with the interference value on both entrance and exit surfaces, while an optimal interference value existed. The choice of mandrel material should be based on yield strength and ultimate strength due to mandrel’s plastic deformation. The friction coefficient only affected the distribution of compressive residual stress on the edge of the hole. In case of insufficient lubrication, exit surface became a critical section resulting from material accumulation.
Compressive sensing identification method of blade tip timing signals based on arbitrary sensor arrangement
ZHANG Xiaopu, TIAN Jie, SUN Zonghan
2020, 35(1): 41-51. doi: 10.13224/j.cnki.jasp.2020.01.005
Abstract PDF(4889KB) icon721 icon619
Abstract:
Based on the characteristics of blade vibration and tip timing system, the regulation of blade vibration response under arbitrary sensor angle distribution was studied. Based on the sparsity in frequency domain of tip timing signal, the application of compressive sensing method in reconstruction of blade tip timing signal and mode identification was explored. Through a large number of numerical experiments of synchronous and non-synchronous signals, the influences of signal reconstruction errors, number of sensors, number of sampling cycles, frequency resolution and signal to noise ratio on the identification effect were analyzed, and the basic methods and steps of the compressive sensing method to reconstruct the timing signal of blade tip were determined. Finally, the method was applied to the reconstruction of vibration response data of a titanium alloy wide chord fan blade from the finite element simulation. The results show that the excitations with large amplitudes can be accurately identified under three rotating speed conditions of 80%, 90% and 100% with blade tip position error and 30 dB noise signals. The compressive sensing method based on arbitrary sensor angle distribution is effective in identifying the timing signal of blade tip and has value of engineering application and promotion.
Double local resonance effect acoustic metamaterial muffling performance
ZHANG Xiaoguang, L Haifeng, L Chuanmao
2020, 35(1): 52-59. doi: 10.13224/j.cnki.jasp.2020.01.006
Abstract PDF(1673KB) icon732 icon454
Abstract:
In order to effectively control low-frequency broadband noise, a dual local-domain resonance effect acoustic metamaterial based on Helmholtz resonator was proposed. The acoustic metamaterial was used to combine the Helmholtz resonance effect with the spring mass resonance effect, and control the deformation of the film by the driving voltage to realize the simultaneous change of the resonance frequencies of the two systems. On the basis of establishing the mathematical model of the system, the calculated natural frequency of the Helmholtz resonance system was 4141 Hz, the natural frequency of the flexible film system was 2868 Hz, and the theoretical deviation of the resonant frequency from the flexible film was 44%. The theoretical calculation deviation of the resonant frequency of the resonant cavity was 097%. The acoustic properties of acoustic metamaterials were studied using the acoustic-solid coupling physics of COMSOL software, and the acoustic metamaterials were tested using the dual load method. Results showed that the acoustic metamaterial had good noise control effect in the low frequency range, and generated two transmission loss peaks, forming a double local resonance effect, which can simultaneously control the noise in the two frequency ranges. When the driving voltage increased from 0 V to 350 V, the spring mass system transmission loss peak frequency was shifted from 30 Hz to 110 Hz, and the rate of change was 228%, which can realize adaptive control of noise and provide a method for active control and optimization of acoustic metamaterials.
Experiment of identifying semi-active particle damping loss factor based on steady-state energy flow method
XUE Cheng, XU Xiangxi, SU Zhanfa
2020, 35(1): 60-65. doi: 10.13224/j.cnki.jasp.2020.01.007
Abstract PDF(2095KB) icon628 icon461
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The relationship between semi-active particle damping loss factor and response signal was derived by steady-state energy flow method, and semi-active particle damping loss factor was identified through experimental method. The internal and external features affecting semi-active particle damping loss factor were explored by changing particle filling rate and voltage. The experimental results showed that the semi-active particle damping loss factor can increase by increasing the voltage, and gradually become stable after reaching a certain voltage; in addition, the semi-active particle damping loss factor could increase through increasing particle filling rate. After reaching 70% particle filling rate, the loss factor increased slowly and became stable gradually.
Effects of gas state equation on n-dodecane jet combustion
QIN Wenjin, LU Dengbiao, LIU Hao
2020, 35(1): 66-74. doi: 10.13224/j.cnki.jasp.2020.01.008
Abstract PDF(4543KB) icon525 icon417
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The n-dodecane was selected as an alternative fuel of aviation kerosene in this study. Its jet combustion characteristics under supercritical condition were studied by using large eddy simulation and detailed chemical reaction kinetics. The effects of gas state equations on jet morphology, penetration, temperature, and mixing fraction were also investigated. The simulation results showed that ideal gas and real gas state equations had negligible effect on the jet penetration and macroscopic shape, while the real gas state equation had advantage to reflect the liquid fuel jet characteristics under supercritical condition, such as mixing fraction and temperature. In terms of combustion, there was an error of 10% between the simulated ignition delay and the experiment, the flame lift-off length, flame shape and soot were also well predicted, and the distribution of NOx and OH was highly consistent with the temperature field.
Preliminary experiment on the lean blow-off of an integrated cavity-based strut flameholder
LIU Yuying, ZHOU Chunyang, XIE Yi
2020, 35(1): 75-80. doi: 10.13224/j.cnki.jasp.2020.01.009
Abstract PDF(1132KB) icon609 icon444
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The incoming air temperature was within the range of 773-1 073 K. The incoming flow Mach number ranged from 020-032. The results showed that, the lean blow-off (LBO) fuel/air ratio of integrated cavity-based strut flameholder (ICBSF) was within the range of 0001 3-0002 7 and had a wide lean blow-off limit because of the cavity structure favorable for evaporation and atomization of fuel. LBO fuel/air ratio of ICBSF increased with the increase of incoming flow Mach number and decreased with the increase of flow temperature, similar to that of conventional bluff-body stabilizers. When the temperature of incoming flow was significantly increased, the influence of the incoming Mach number on fuel/air ratio of ICBSF was weakened; similarly, when the incoming Mach number was significantly increased, the influence of the inflow temperature was also weakened.
High-altitude ignition characteristics of three fuels in ramjet combustor
WANG Jianpei, LI Na, LI Jiangning
2020, 35(1): 81-87. doi: 10.13224/j.cnki.jasp.2020.01.010
Abstract PDF(2277KB) icon714 icon596
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To investigate the ignition characteristics of three liquid fuels (aviation kerosene (RP-3), high thermal oxidation stability fuel (RP-3+100), high-density liquid hydrocarbon fuel (LUAN)), high-altitude ignition simulated experiment in a small-scale ramjet combustor was conducted. The results showed that the three fuels can be ignited successfully under all selected conditions. With the increase of temperature and pressure of inlet air, the range of ignition equivalence ratio of three fuels became wider. But the increased velocity narrowed the range of ignition equivalence ratio. The range of ignition equivalence ratio of RP-3+100 was the widest among the three fuels at any time. RP-3 and LUAN had a similar range of ignition equivalence ratio. As the extraneous factors, like temperature, pressure, and velocity, changed, RP-3+100 had the narrowest variation of the range of the ignition equivalence ratio, while RP-3 was the widest one.
Influence of tube length on flow resistance and temperature reduction characteristics of tubed vortex reducer
XIA Zilong, WANG Suofang, HOU Xiaoting
2020, 35(1): 88-96. doi: 10.13224/j.cnki.jasp.2020.01.011
Abstract PDF(3510KB) icon749 icon408
Abstract:
Numerical simulation and model experiment method were combined to research the tubed vortex reducer, and the influences of the tube length on the pressure loss coefficient, temperature reduction coefficient and their weights between each section were analyzed. Model experiment results verified the reliability of numerical simulation method. The results showed that increasing the tube length can reduce the pressure loss obviously and increase the temperature reduction of the tubed vortex reducer at the same time. Co-rotating cavity and the tube are the key factors influencial factors to the flow resistance and temperature reduction characteristics of the tubed vortex reducer, with the shift of the weight. When the tube length increased, the pressure loss in tubed vortex reducer was reduced by sacrificing the pressure loss in the tube and reducing the pressure loss in the co-rotating cavity. The rapid increase of the temperature reduction in the tube contributed a lot of to the increase of the temperature reduction coefficient of the tubed vortex reducer. The pressure loss coefficient of the tubed vortex reducer decreased by 8370% and the temperature reduction coefficient increased by 4502% compared with the smooth co-rotating cavity model when the tube length L/b was 0786.
Experiment on cold start of piston aviation kerosene engine
SU Siyuan, HU Chunming, LIU Na
2020, 35(1): 97-105. doi: 10.13224/j.cnki.jasp.2020.01.012
Abstract PDF(2727KB) icon889 icon418
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Targeting the influencing factors such as starting speed, fuel temperature and ignition energy, an experimental research on the cold start performance of aviation kerosene engine was carried out on a single-cylinder testing machine with a displacement of 650 mL. The results showed that with the increase of the starting speed, the starting time became shorter but then longer, the starting time was the shortest when the starting speed was 1 200 r/min. The rise of the fuel temperature improved the cold starting performance and combustion characteristics. Under the given test conditions, the engine can be successfully started when the fuel temperature was 50 ℃. Increasing ignition energy had a positive effect on the formation of the fire core and the flame propagation, which can significantly shorten the starting time, but when the ignition energy increased to 75 mJ, the improvement effect was not obvious.
Drag reduction performance of tube-baffle composite vortex reducer
HOU Xiaoting, WANG Suofang, ZHANG Kai
2020, 35(1): 106-113. doi: 10.13224/j.cnki.jasp.2020.01.013
Abstract PDF(3164KB) icon591 icon444
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To research the effects of tube-baffle composite vortex reducer on drag reduction performance of radial internal flow in co-rotating disc cavity, numerical simulation was carried out to calculate the de-rotating system with varied structure of tube-baffle composite vortex reducer under different rotating speeds. The flow structure, total pressure loss and distribution curve of total pressure loss along the way under varied conditions were obtained. The results showed that the total pressure loss in the disk cavity of the tube-baffle composite vortex reducer can be obviously reduced with respect to the basic tube vortex reducer. The drag reduction effect of the upstream installation partition of the tube vortex reducer was better than that of the downstream installation of the disc cavity. There existed optimal dimensionless baffle length of 0118 and 0065 for upstream and downstream baffles. Compared with the basic model, the optimal drag reduction effect increased by 17% and 5%, respectively. And at the optimum baffle length, the drag reduction effect of the upstream and downstream baffles installed at the same time was 19% higher than the basic model.
Numerical study of transonic separation flow using an anisotropic turbulence model
YAN Wenhui, PENG Tengfei, YONG Yan
2020, 35(1): 114-125. doi: 10.13224/j.cnki.jasp.2020.01.014
Abstract PDF(2793KB) icon539 icon394
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A transonic turbulent separation flow in a converging-diverging transonic diffuser was studied, when there existed a separation bubble on the top wall of the diffuser triggered by strong shock-wave-boundary-layer-interaction (SWBLI). To capture the essential behavior of this complex flow, the current study utilized an anisotropic turbulence model developed on the basis of a statistical partial average scheme. The first order moment of turbulent fluctuations, retained by a novel average scheme, and the turbulent length scale, can be determined from the momentum equations and mechanical energy equation of the fluctuation flow, respectively. The two physical quantities were readily used to construct the nonlinear anisotropic eddy viscosity tensor and to significantly improve the computational results. Comparisons between the computational results and experimental data were carried out for velocity profiles, pressure distribution, skin friction coefficient, Reynolds stress as well as streamline vectors distribution. Without using any empirical coefficients and wall functions, the numerical results were in good agreement with the available experimental data, further confirming that the nonlinear anisotropic eddy viscosity tensor is the decisive factor for the success of the computational results.
Performace of novel synthetic jet actuator under high ambient temperature
HONG Liang, Eriqitai, GONG Jian
2020, 35(1): 126-134. doi: 10.13224/j.cnki.jasp.2020.01.015
Abstract PDF(4375KB) icon895 icon394
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The flow field of the piston-type synthetic jet actuator (SJA) under high ambient temperature was investigated numerically and experimentally. The effects of the actuation frequency and orifice diameter on conventional SJA and novel SJA were analyzed. The results indicated that the auxiliary air inlet can significantly increase the SJA performance under high ambient temperature. Compared with the conventional SJA, the novel SJA can increase the inlet mass flow rate, peak cylinder pressure ratio and peak jet momentum, despite of a little decrease of the peak jet velocity. The peak efficiency of the auxiliary air inlet lied in high actuation frequencies or small orifice diameter. Compared with the conventional SJA, the inlet mass flow rate, peak cylinder pressure ratio and peak jet momentum of novel SJA increased up to 23073%, 10397%, and 10737%, respectively, of conventional SJA at actuation frequency of 250 Hz, orifice diameter of 2 mm.
Control of hypersonic boundary layer instability by transverse rectangular micro-cavities
GUO Qilong, TU Guohua, CHEN Jianqiang
2020, 35(1): 135-143. doi: 10.13224/j.cnki.jasp.2020.01.016
Abstract PDF(5262KB) icon542 icon440
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The spatial-developing flat-plate boundary layer of Mach number of 6 was simulated. The influences of the two-dimensional transverse micro-cavities on the base flow and the second mode instability wave were studied by adding them on the flat-plate surface. Results indicated that the two-dimensional micro-cavity configuration had a larger size (more than 100 μm) compared with the conventional porous coating. The comparison of the base flows showed that the micro-cavities had little effect on the streamwise velocity. No new instability mode appeared on the spectrum of the sampling point. The micro-cavities could be helpful to reduce the frictional drag. The drag caused by the pressure difference in the cavities was one to two orders of magnitude lower than the frictional drag. As the porosity increased, the total drag decreased. A reduction over 40% on the total drag can be reached when the porosity was 06. Two ways were employed for adding second mode instability waves at the inflow boundary, including a single-mode disturbance and a superposition of multi-modes disturbances. The downstream evolution indicated that the transverse micro-cavities had apparent suppression effect on the amplification of the second mode within a broadband frequency range, and the control effect became stronger with the increasing porosity.
Influence of starting position of ship surface flow field on rotor transient aeroelastic response
ZHAO Jiachen, HAN Dong, YU Lei
2020, 35(1): 144-152. doi: 10.13224/j.cnki.jasp.2020.01.017
Abstract PDF(4334KB) icon538 icon402
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In order to study the influence of starting position of helicopter on rotor transient aeroelastic response in ship surface flow field, the velocity distribution information of ship surface flow field was simulated by CFD method. Nonlinear quasi-steady aerodynamic model and moderately deformed beam assumption were used in rotor dynamics modeling, and the dynamic equations were solved by combining different starting positions. The results showed that if the starting position of helicopter was closer to the bow and the port side, the negative swing of blade was greater. Within 1 m of the deck center, the maximum negative displacement near the port side of the bow can reach 159% of the rotor radius, while the maximum negative displacement at the center was only 85% of the rotor radius. The vertical airflow gradient near the port side and the bow was obviously higher than that near the starboard side and the stern. The results show that the vertical airflow gradient has a significant effect on the transient aeroelastic response of the rotor. Changing the starting position of helicopter can effectively reduce the transient aeroelastic response of the rotor.
Frequency band optimization of Morlet complex wavelet and its application in fault diagnosis of inter-shaft bearing
AI Yanting, TIAN Bowen, TIAN Jing
2020, 35(1): 153-161. doi: 10.13224/j.cnki.jasp.2020.01.018
Abstract PDF(4097KB) icon586 icon391
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According to the characteristics of fault signal of inter-shaft bearing, a new band optimization parameter-the peak factor of local envelope spectrum, was proposed, which can not only reflect the strength of impulse component in the signal, but also highlight the characteristics of periodic impulse. It was applied to optimize the frequency band of Morlet complex wavelet resonance demodulation of fault signal of inter-shaft bearing. In order to verify the superiority of this method, a double-rotor test-bed was built to simulate the outer ring and inner ring faults of inter-shaft bearings. The Morlet complex wavelet optimized by the local envelope spectrum peak factor band was used to analyze the collected test data. Taking the inter-shaft bearing with the inner and outer ring speeds of 600 r/min as an example, the theoretical value of the outer ring fault frequency was 88 Hz, and the outer ring fault frequency obtained by the local envelope spectrum peak factor band optimization was 8725 Hz. The results show that the index can extract the peak fault frequency of the inter-shaft bearing, effectively separate the fault information from the vibration signal, and realize the fault diagnosis of the inter-shaft bearing.
High-speed skidding suppression characteristics of cylindrical roller bearing with beveled cage pocket
LIU Yanbin, ZHANG Zhanli, LIU Hongbin
2020, 35(1): 162-168. doi: 10.13224/j.cnki.jasp.2020.01.019
Abstract PDF(2182KB) icon577 icon398
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In order to solve skidding problem of aero-engine mainshaft cylindrical roller bearing, a cylindrical roller bearing with beveled cage pocket was proposed, and its high-speed skidding suppression characteristics was researched. By use of the Hertz contact theory, elastohydrodynamic lubrication and hydrodynamic lubrication formulas, contact model between roller and inner/outer ring races, contact model between cage pocket and roller, and contact model between cage and guiding surface of outer ring were built, and based on multibody kinematics and the Newton-Euler dynamics theory, three degree of freedom bearing dynamics model in the bearing radial plane was built. On this basis, using the Runge-Kutta numerical integration method, bearing dynamics numerical simulations were carried out, influence laws on bearing skidding by inclination angles of the front and rear walls of cage pocket were discussed, and bearing high-speed skidding characteristics was analyzed in case of inclination angle of the front wall of cage pocket was equal to 5° and inclination angle of the rear wall was equal to 10°, and the simulation results show: influence on bearing high-speed skidding by inclination angles of the front and rear walls of cage pocket is remarkable, and by optimizing this two inclination angles, bearing high-speed skidding can be effectively controlled.
Lubrication characteristics in contact state of journal bearings inside aero gear pump
ZHU Jiaxing, LI Huacong, FU Jiangfeng
2020, 35(1): 169-177. doi: 10.13224/j.cnki.jasp.2020.01.020
Abstract PDF(5027KB) icon692 icon385
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In order to solve the problem of aero-gear pump gear-shaft/bearing gap lubrication under high load condition, CFD simulation and gear-shaft rigid model were combined to realize the transient lubrication calculation based on the CFD radial motion coupled analysis. The bearings film three-dimensional thermohydrodynamic lubrication calculation model and rough surface micro-asperity contact model were established. On the basis of calculation of the gear-shaft radial motion orbit on the gear pump transient field influence, the model was used to achieve the analysis of the characteristics under high eccentricity/contact condition. Results showed that: the error between gear pump simulation results and experimental results was less than 10%. And the transient behavior of pressure distribution caused by gear pump transient field had an impact on the fluctuation shape of gear shaft radial load, leading to the change of bearings lubrication characteristics. By the numerical calculation for bearings lubrication model, it was found that: compared with non-contact condition, journal bearings lubrication state was more serious on the contact condition, with the higher temperature and lower viscosity.
Identification method for parameter uncertain model of aero-engine
BAI Jie, LIU Shuai, WANG Wei
2020, 35(1): 178-184. doi: 10.13224/j.cnki.jasp.2020.01.021
Abstract PDF(1552KB) icon667 icon403
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The linear model of aero-engine is effective within a small application range. According to this problem, the identification method for parameter uncertainty model of aero-engine was proposed. The identification problem was solved by calculating nonlinear programming. The parameter uncertainty was considered in the identification method for an uncertainty model of aero-engine. A parameter uncertainty model of aero-engine with large range of application can be obtained. This method was used for DGEN380 aero-engine. Two parameters, the deviation parameter of actual working conditions and the maximum deviation parameter of model, were defined for describing error range. Compared with experimental data, the uncertainty model of DGEN 380 can simulate the real state of DGEN380 within 1% error range when the variation of the power lever angle was less than 22%.
Cold start control strategy of spark igniting type heavy oil piston aero-engine
GENG Zhao, ZHAO Zhenfeng, LI Hong
2020, 35(1): 185-195. doi: 10.13224/j.cnki.jasp.2020.01.022
Abstract PDF(3983KB) icon691 icon399
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In view of the problem of low temperature starting of the ignition heavy oil piston engine, the air-assisted in-cylinder direct injection technology was adopted to carry out the cold start control strategy research and experiment verification research, and the strategy solved the problem of low temperature starting of the engine at -10 ℃. The key control parameters affecting the cold start were extracted and studied. The optimal matching results and experiment verification of the ambient temperature were obtained. The cold start stage of the ignited heavy oil engine was defined. According to the matching and experiment results, the mapping relationship between key parameters and cylinder temperature was obtained, and the cold start strategy was designed and verified by experiments. Results showed that the best fuel injection advance angle was between 50° and 85° before top dead center when the cylinder temperature was between -10 ℃ and 20 ℃. The optimal ignition advance angle was 45° before top dead center, ensuring the smooth start of heavy oil engine and the starting time was less than 3 s.
Aerodynamic robustness of centrifugal compressor impeller under multi-source uncertainty coupling
TANG Xinzi, WANG Zhe, WANG Xiaoyu
2020, 35(1): 196-204. doi: 10.13224/j.cnki.jasp.2020.01.023
Abstract PDF(2745KB) icon537 icon398
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Considering the manufacturing error and aerodynamic boundary multi-source uncertainty coupling, taking a centrifugal compressor impeller as the research object, the numerical calculation method, the Latin hypercube test design method, the surrogate model, and the Monte Carlo method were combined to analyze the correlation of geometric design variables and performance. The influences of impeller manufacturing error and speed fluctuation on compressor performance were quantified. An aerodynamic robust optimization design method for centrifugal compressor impeller was proposed for considering multi-dimensional diverse uncertain factors. Results showed that, under the coupling effect of manufacturing error and speed uncertainty, the fluctuation range of pressure ratio increased from 350% to 1414%. The aerodynamic robustness was enhanced after optimization, the mean value of pressure ratio and isentropic efficiency increased by 69% and 49%, respectively, and the standard deviation of pressure ratio and isentropic efficiency decreased by 154% and 184%, respectively.
Experimental and numerical investigation on aerodynamic stability of steam ingestion in a compressor
FU Wenjun, TU Baofeng, HU Jun
2020, 35(1): 205-214. doi: 10.13224/j.cnki.jasp.2020.01.024
Abstract PDF(2966KB) icon514 icon412
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In order to investigate the effect of steam ingestion and swirl distortion on the aerodynamic stability of the compressor, a two-stage low-speed axial compressor was used as the experimental research object. The compressor test bench for steam ingestion and swirl distortion was established. The experimental results showed that steam ingestion caused the inlet total pressure and total temperature distortion. With the increase of rotating speed, the total pressure distortion intensity increased and the total temperature distortion intensity decreased. Steam ingestion caused the decrease of total pressure ratio and stability margin. When the compressor rotating speed was 600 r/min and 800 r/min, the stability margin was reduced by 15% and 63%, respectively. The stability margin decreased more significantly when the steam ingestion and the reverse bulk swirl distortion were combined. When the compressor rotating speed was 600 r/min and 800 r/min, the stability margin was reduced by 630% and 1264%. Numerical simulation investigated the effect of steam ingestion on the experimental compressor. The results showed that the stability margin decreased by 321% and 812% when the compressor rotating speed was 600 r/min and 800 r/min, respectively.
Mechanism of symmetry breaking of flow field induced by shock separation in supersonic nozzle and its control
JIA Ruidong, FENG Xiping, CHEN Hui
2020, 35(1): 215-224. doi: 10.13224/j.cnki.jasp.2020.01.025
Abstract PDF(4907KB) icon601 icon527
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In order to mitigate or eliminate side force, the mechanism of symmetry breaking of flow field induced by flow separation was studied in detail. The finite volume second-order upwind interpolation scheme and k -ε turbulence model were used to simulate the working process of a supersonic nozzle on the ground. The flow structures inside the nozzle were studied, and the transition process of shock separation mode from freedom shock separation to restricted shock separation near the nozzle wall was analyzed in detail. In order to reduce the side force of over-expansion nozzle under the condition of low altitude and high back pressure, the flow field characteristics and flow separation mode under different length-diameter ratios and expansion ratios of nozzle were studied numerically. The results showed that a great side force can be induced in the process of shock mode transition, and the flow patterns or structures can be optimized by changing the nozzle configuration. And the side force can be effectively reduced by properly shortening the length-diameter ratio and expansion ratio. As the length-diameter ratio was 105, the side force was more than 4 000 N. But as the length-diameter ratio was 095 or 115, the side force didn’t exceed 20 N in the whole stage. And as the expansion ratio was 539, the peak value of side force reached more than 4 000 N, while as the expansion ratio was reduced to 45, the side force decreased obviously.

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