2021 Vol. 36, No. 11

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Gas exchange process of two-stroke engine based on multi-objective optimization
HU Chunming, TIAN Mengyuan, LIU Na, SONG Xijuan
2021, 36(11): 2241-2250. doi: 10.13224/j.cnki.jasp.20200554
Abstract FullText HTML PDF(4754KB) icon806 icon219
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The gas exchange process of two-stroke aviation piston engine directly affects the combustion effect and the performance of the engine.Taking a two-stroke aviation piston engine as an example，a simulation model was established，and multi-objective optimization based on dynamic performance，economic performance，and scavenging performance was conducted.The optimization analysis of structure parameters of scavenging ducts and exhaust ducts was also performed.In addition，the parameters of the ducts structure under different altitude operating conditions （speed of 5 600 r/min，100% throttle opening） were optimized.The conclusion showed that the optimization of the engine ducts structure using the NSGA-Ⅱ algorithm can effectively improve the engine scavenging efficiency and power （speed of 5 600 r/min），by 0.841 kW and 2.712 kW respectively，and reduce the fuel consumption by 22.08 g/(kW?h)；in addition，under different altitude operating conditions，as the altitude increased，the length of the scavenging duct showed a trend of decrease，while the length of the exhaust duct gradually increased，and the trend changed more obviously when the altitude was greater than 1 800 m.
Turbofan engine performance degradation prediction based on gas path parameter fusion
GUO Qing, LI Yinlong
2021, 36(11): 2251-2260. doi: 10.13224/j.cnki.jasp.20200420
Abstract FullText HTML PDF(3662KB) icon592 icon170
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In view of the problem of low accuracy in predicting performance degradation of turbofan engine driven by a single parameter，a turbofan engine performance degradation prediction method based on gas path parameter fusion was proposed.By monitoring multi-source parameters in the process of engine performance degradation，a combination of expert experience and nuclear principal component analysis was used to select and integrate engine performance indicators to construct health parameters.The turbofan engine degradation model was constructed based on the nonlinear Wiener process，and the maximum likelihood method was used to obtain the offline parameter estimates of the engine degradation model secondly，due to the difference of performance degradation of different engines，real-time updating of random parameters based on Bayesian updating concept can realize real-time prediction of performance degradation of single engine.Finally，through the verification of examples，the root mean square error at the end of prediction using this method was 0.028 3，and the overall prediction accuracy was improved by 54.5%，which can assist in guiding maintenance decision-making.
Design of test system for large-scale propeller power simulation in wind tunnel
LEI Hongsheng, CHEN Zhengwu, WANG Zheng, DOU Manfeng, ZHAO Yu
2021, 36(11): 2261-2270. doi: 10.13224/j.cnki.jasp.20210191
Abstract FullText HTML PDF(4933KB) icon694 icon222
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In order to study the aerodynamic and aeroacoustic properties of a certain type of aircraft propeller，a set of power simulation test system was designed in 5.5 m×4 m aeroacoustic wind tunnel.Taking the 300 kW high power density permanent magnet motor as the core，the system realized the power simulation of large-scale propeller by matching the corresponding power supply，drive，control，support and so on.Meanwhile the test verification was carried out.The results showed that the speed and torque of the equipment were as high as 5 000 r/m and 573 N·m respectively，and the speed control accuracy was better than ±0.5 r/min.And also it had low noise level and good electromagnetic compatibility，and the test repeatability accuracy was better than 0.000 7.The establishment of the system can effectively meet the requirements of the large-scale propeller power simulation and further expand the low-speed aerodynamic test simulation capabilities.
Calculation method of shaft power and its uncertainty of turboshaft engine under small environmental deviation
QI Bin, LIU Tao, LENG Lintao, ZHONG Huagui, WU Feng
2021, 36(11): 2271-2277. doi: 10.13224/j.cnki.jasp.20210166
Abstract FullText HTML PDF(2294KB) icon618 icon168
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The performance processing method of turboshaft engine high altitude simulation test was studied.The shaft power calculation method of turboshaft engine was studied and the calculation formula of shaft power under the condition of small deviation of environment simulation was derived by using small deviation and traditional similarity conversion theory.The experimental results showed that under the condition of small deviation，the calculation error of this method was 0.2%-0.6% lower than that of similar conversion.The formula of converted shaft power and the formula of uncertainty under the condition of small deviation were given.The shaft power calculation method and uncertainty calculation method proposed can provide a technical reference for relevant engineering and technical personnel.
Scheme optimization of yaw control of flying-wing aircraft based on jet flow control
ZHU Jiachen, SHI Zhiwei, GENG Xi, FU Junquan, SUN Quanbing, CHEN Yongliang
2021, 36(11): 2278-2291. doi: 10.13224/j.cnki.jasp.20200466
Abstract FullText HTML PDF(7933KB) icon639 icon376
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There are difficulties in yaw control of a flying-wing aircraft due to the cancellation of vertical tail.A variety of control schemes were designed based on the jet flow control technology to assist in and optimize the yaw control.The jet control actuator was designed and manufactured.Through the wind tunnel force measurement experiment and two-dimensional numerical simulation，the control effect and mechanism of each scheme were analyzed，and the optimal control scheme was selected.The results showed that under the same jet momentum coefficient，it was easier to obtain yaw moment by producing resistance than by applying thrust.After turning on the excitation，the more inverse components the jet contains in relation to the incoming flow，the more obvious the interaction with the incoming flow；the larger the separation zone formed，the better the control effect.The forward symmetric blowing was proved to be the optimal control scheme，which can produce about rudder effect equivalent to a split drag rudder deflection of 70°，and the coupling degree of moment was small.
Aerodynamic performance of new conceptual configuration of high speed vehicle's heat flux and drag reduction
ZHANG Shuai
2021, 36(11): 2292-2305. doi: 10.13224/j.cnki.jasp.20200477
Abstract FullText HTML PDF(6482KB) icon455 icon126
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A heat flux and drag reduction conceptual configuration combining the forward-facing cavity and the channel was proposed with high speed.The ength-to-depth ratio of forward-facing cavity was set as 1.The first series of channel height with 0,10,20,30,40 mm,and the second series of channel entrance height with 30 mm and channel exit height with 35,40,45,50 mm were taken into consideration.The wall heat flux distributions and drag coefficient were extracted from the flow field structures to evaluate the heat flux and drag reduction characteristics via solving Navier-Stokes （N-S） equations.The results showed that the cavity-channel configuration can achieve the expected heat flux and drag reduction.Compared with the baseline blunt cone,the cavity-channel configuration （the channel entrance height to exit height ratio of 30/50） had the optimal but not best heat flux and drag reduction performance within the range considered,and the heat flux and drag reduction rates reached approximately 40.1% and 16.8%,respectively.Higher channel height indicated better the drag reduction,but the heat flux protection effectiveness became weakened.Moreover,higher channel exit height with a constant channel entrance height could enhance the drag reduction effectiveness without any heat flux reduction penalty.
Airfoil optimization design based on Gaussian process regression and genetic algorithm
CHANG Linsen, ZHANG Qianying, GUO Xueyan
2021, 36(11): 2306-2316. doi: 10.13224/j.cnki.jasp.20200402
Abstract FullText HTML PDF(4252KB) icon1014 icon211
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In view of the problems that the leading edge curvature of the wind turbine airfoil with high lift-to-drag ratio has large radius，the traditional airfoil parameterization method has insufficient leading edge control ability，and there exists poor prediction accuracy based on the panel method XFOIL，an enhanced class function/shape function transformation （CST） parameterized method was used to control the shape change of airfoil，Latin hypercube experimental design，computational fluid dynamics （CFD） flow field calculation module，Gaussian process regression model and genetic algorithm，based on high-confidence Reynolds average Navier -Stocks （RANS） and Gaussian regression model-assisted genetic algorithm for airfoil optimization design method.The results showed that the airfoil optimization method based on the Gaussian regression model can reduce the number of CFD calculations for optimization by one order，thereby greatly improving the optimization design efficiency.The resistance reduction design of the supercritical airfoil RAE2822 of the standard calculation example showed that the resistance of the CFD frequency in the order of hundreds of times was reduced by 43.16%，the shock wave was weakened and the lift，moment and area could strictly meet the constraints.The maximum lift-to-drag ratio of the wind turbine airfoil NACA64618 showed that the designed airfoil not only greatly increased the lift-to-drag ratio at the design angle of attack and the secondary design angle of attack，but also improved its aerodynamic performance in the entire range of the small angle of attack.And there were two main design points，without bad resistance.
Analysis and prediction of noise-induced combustion instabilities of coaxial swirl injector
YANG Shangrong, WANG Yong, YANG Baoe
2021, 36(11): 2317-2324. doi: 10.13224/j.cnki.jasp.20200404
Abstract FullText HTML PDF(3487KB) icon367 icon93
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The combustion dynamics of a coaxial swirl injector was investigated with the mixture ratio of oxidant and fuel as the system control parameter.The mixture ratios at which the transitions between combustion noise and oscillatory state occurred were different for the forward path and for the reverse path.This difference indicated that the transition to the oscillatory state observed was subcritical Hopf bifurcation in nature.Noise-induced instabilities were observed in the bistable regime.The viability of three early warning measures such as lag-1 autocorrelation，variance and conditional heteroskedasticity （CH） to predict transition in the combustor was analyzed based on critical slowing down theory.It was found that lag-1 autocorrelation showed an increasing trend as the critical point was approached，enabling to predict catastrophic transitions as early warning signals.Variance may be less generic as an indicator of noise-induced instability.Significant CH showed an increasing trend，which can be used as an auxiliary judgment condition.An online prediction method of good adaptability and reliability for noised-induced instability based on Kendall rank correlation coefficient was proposed.
Experiment on discharge coefficients for outlet lateral dilated hole
WAN Buming, CAO Jun, LI Chaochao, CHEN Jiang
2021, 36(11): 2325-2330. doi: 10.13224/j.cnki.jasp.20200548
Abstract FullText HTML PDF(2308KB) icon440 icon120
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The experimental study on the discharge coefficient of outlet lateral dilated hole was conducted to investigate the trend of discharge coefficients with different structure parameters and aerodynamic parameters.Research showed that the diacharge coefficient of outlet lateral dilated hole cylindrical segment diameter 0.6 mm 3% larger than 0.8 mm.When the hole inclination angle was reduced from 30° to 25°，the discharge coefficient increased，and when the inclination decreased to 20°，the discharge coefficient remains unchanged.When the expansion angle grew from 20° to 40°，the discharge coefficient increased first and then decreased，and reached the maximum value when the expansion angle was 25°.Meanwhile the discharge coefficient was proportional to the secondary flow Reynolds number，and the larger secondary flow Reynolds number indicated the smaller pressure drop needed to reach the limit coefficient value.When the preesure drop was greater than 0.9，the difference of the discharge coefficient at different secondary flow Reynolds number was about 2%.
Film cooling performance and flow resistance characteristics of single/triple-row fan-shaped holes based on actual density ratio
WEI Hong, ZU Yingqing
2021, 36(11): 2331-2343. doi: 10.13224/j.cnki.jasp.20210306
Abstract FullText HTML PDF(5446KB) icon316 icon150
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The heat transfer and flow resistance characteristics of single/triple-row of fan-shaped film cooling holes under the condition of true density ratio were experimentally studied.The pressure-sensitive paint （PSP） technology was used in the wind tunnel to test the film cooling performance of the fan-shaped holes with a constant outlet width，and the differences in heat transfer and flow resistance characteristics of fan-shaped film cooling holes with different hole shape parameters under the condition of real density ratio were studied.The hole shape parameters of fan-shaped holes implementing the critical blowing ratio of the coolant jet blowing away from the hot-side wall surface and the hole shape parameters with highest span-wise average film cooling effectiveness were obtained.The experimental results indicated that：within the range of hole shape parameters studied，for fan-shaped holes，when blowing ratio was less than 1.5，the coolant jet wasn't blown away from the hot-side wall surface，and the film cooling performance of the fan-shaped hole with inclination angle of 20° and diffusion angle of 15° was the best.However，when blowing ratio equaled to 2.0，partial coolant jet was blown away from the hot-side surface，the film cooling effectiveness of the fan-shaped hole with inclination angle of 25° and diffusion angle of 10° was the largest.In addition，the discharge coefficients of the fan-shaped holes with inclination angle of 25° and diffusion angle of 13° and those of the fan-shaped hole with inclination angle of 30° and diffusion angle of 10° were the highest.
Simulation study on combustion flow in low-pressure condition of hydrogen-oxygen torch ignitor
WANG Yan, FANG Jie, YANG Jinhui, CAI Guobiao
2021, 36(11): 2344-2352. doi: 10.13224/j.cnki.jasp.20200552
Abstract FullText HTML PDF(4745KB) icon309 icon108
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The effects of hydrogen-oxygen injection interval and droplet mean diameter on the combustion flow of the low-temperature liquid hydrogen and liquid oxygen torch electric ignitor in low-pressure condition were investigated by numerical simulation.Discrete phase model（DPM） and 16-step，6 species hydrogen-oxygen chemical reaction mechanism were applied for the analysis.Considering the turbulent combustion effect，the eddy dissipation concept combustion model was utilized for simulation calculation.The temperature results obtained by simulation were in good agreement with those obtained by experiment，and the deviations of pressure were within 5%，thereby verifying the accuracy of the numerical models.As the results shown，under low-pressure condition，when the hydrogen-oxygen injection interval increased，the ignitor head inner wall temperature increased，the chamber pressure decreased，and the combustion length decreased.The larger liquid hydrogen droplets diameter resulted in the longer combustion length and higher head inner wall temperature，besides，the pressure in the ignitor chamber was slightly reduced.The diameter of liquid oxygen droplets had little effect on combustion flow of the ignitor.
Numerical study on effect of film ejections in rotating detonation engine combustor
WANG Yuanshuai, TAN Xiaoming, TIAN Jia, ZHANG Jingzhou
2021, 36(11): 2353-2362. doi: 10.13224/j.cnki.jasp.20200403
Abstract FullText HTML PDF(5179KB) icon775 icon130
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To solve the problem of high thermal load on the wall of the RDE （Rotating Detonation Engine），a numerical simulation of film cooling on the combustor wall of an RDE was carried out to explore the interaction between film outflow and detonation wave，oblique shock wave and flow field，as well as the film cooling characteristics on RDE wall.The results showed that the detonation wave had an obvious effect on the compression of the film and blockage of the cooling holes.The film had little effect on the overall propagation characteristics of the detonation wave.Affected by the detonation wave and the flow field of the combustor，the film outflow had periodic oscillations，which affected the cooling effect of the wall to a certain extent.Under the film cooling，the decrease of peak wall temperature was limited in the area covered by the detonation wave，but the decrease of time-average wall temperature was more than 26.9%.In the area covered by the oblique shock wave，with the increase of cooling air quantity，the decrease of peak wall temperature and time average wall temperature was more than 32.5% and 51.3%，respectively，and the cooling effect of the film on the wall covered by oblique shock wave became more significant.
Numerical analysis on cooling capacity of transpiration cooling system
ZHOU Zihe, SU Hao, HE Fei, WANG Jianhua
2021, 36(11): 2363-2371. doi: 10.13224/j.cnki.jasp.20200544
Abstract FullText HTML PDF(3631KB) icon459 icon124
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The maximum heat flux that the system can withstand under a specific amount of coolant consumption，was numerically investigated.The strict theoretical analysis and simulation results indicated that the transpiration cooling capacity was restricted by the coolant heat absorption capacity of the coolant and the heat exchange capacity between the fluid and solid.Under a small coolant mass flux，the transpiration cooling capacity was mainly determined by the coolant heat absorption capacity，while the effect of the heat exchange capacity between the fluid and solid on the transpiration cooling capacity increased with the coolant mass flux.Due to this crucial change，the effects of solid thermal conductivity，particle diameter of porous media and coolant specific heat on the transpiration cooling capacity under a small coolant mass flux were quite different with those under a larger coolant mass flux.
Creep-fatigue life prediction method of tail edge holes in turbine blade for a turboshaft engine
QIAN Zhengming, LI Gaiqi, MI Dong, AI Xing
2021, 36(11): 2372-2378. doi: 10.13224/j.cnki.jasp.20210130
Abstract FullText HTML PDF(2914KB) icon625 icon194
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A creep-fatigue life analysis method considering stress relaxation was established for turbine blade in a turboshaft engine.The nonlinear creep deformation of a superalloy was predicted by coupling creep damage in the framework of viscoplastic theory.The results revealed that based on the elastic-plastic creep analysis of a turbine blade，the creep damage and its evolution law of the leading edge and trailing edge of the blade were clarified，and a method was provided for determining the local dangerous points on the blade.The calculation error of the model for the elastic-plastic stress-strain curve was less than 5%，while the simulation accuracy for the creep curve was within the dispersion range of the inherent properties of material creep deformation.With the help of the linear damage cumulative life theory，the creep-fatigue life of the trailing edge hole of a turbine blade considering the stress relaxation was obtained，providing a more reasonable and better engineering application method for the blade life evaluation.
Ablation characteristics of carbon/phenolic at converging section in semi-submerged nozzle
GONG Lunkun, DENG Zhe, WEI Xiaolin
2021, 36(11): 2379-2388. doi: 10.13224/j.cnki.jasp.20200413
Abstract FullText HTML PDF(3987KB) icon319 icon100
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By solid-gas heat coupled numerical method and the ALE （arbitrary Lagrangian-Eulerian） adaptive meshing technique，the ablation of carbon/phenolic at the converging section in semi-submerged nozzle was investigated，and the results were validated by comparing the results with the experiment data.The results showed that the Al/Al2O3 particles and droplets had great effect on the heat transfer and ablation process at the converging section.The effects of Al/Al2O3 on the ablation can be ignored when the gas traveled almost parallel to the surface.Based on the decomposition mechanism of phenolic，the ablation characteristics of carbon/phenolic can be predicted assuming that the fully charred material was ablated immediately，and the ablation rate was about 0.3 mm/s.The char formation process after the motor burnout was very important for the carbon/phenolic.The thickness of pyrolysis zone was about 2.0 mm during the operating process of the motor，and may increase to 4.0 mm considering the pyrolysis process after motor burnout.The ablation of carbon/phenolic in contact with the carbon/carbon throat can be enhanced owing to the heat flux through carbon/carbon throat heat transfer.
Bionic topology optimization method based on graph method
DING You, ZHOU Zhou, ZHU Xiaoping
2021, 36(11): 2389-2399. doi: 10.13224/j.cnki.jasp.20210013
Abstract FullText HTML PDF(5070KB) icon349 icon133
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For taking the advantages of the fractal system in automatically generating graph topological forms，an implicit method was presented to express the structure topology and optimization.This stepped method was firstly based on the results computed by the ground structure method，then a homogenization operation was performed to get the discrete data in the design domain.Through the data got from the previous step to guide the new structure topology direction for the next level from the fractal system，which was similar to the plant growth to get the final structure topology.At last a finite element calculation with parametric modeling was used for the evolution method to get the optimal result.Two cases respectively presented specific implementation process of the optimization system and verified the feasibility of the method.In the first case，an approximate Michell structure was obtained through bionic method under the multi-objective optimization method.In the second case，the buckling load factor of the wing skin was increased by 10.61%，and the mass was reduced by 10.85%，which verified the feasibility of our method to the similar planar structure topology optimization.
Reliability evaluation of bearings based on small samples and zero-failure life test data
WANG Ruixiang, XU Lingtian, CHEN Xiaoyang, WANG Peng, CHEN Shijin
2021, 36(11): 2400-2409. doi: 10.13224/j.cnki.jasp.20200522
Abstract FullText HTML PDF(3361KB) icon403 icon145
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A reliability evaluation model of small samples and zero-failure life data was proposed.The Bayes theory was used to construct a sampling function subjecting to the original small samples.The Bootstrap method was used to generate a large of random numbers subjecting to the sampling function as augmented samples.Both of the original and augmented samples were analyzed by the best linear invariant estimation method to obtain the two-parameter estimation value of Weibull distribution for reliability evaluation.The Monte-Carlo method was used to generate random numbers subjecting to the Weibull distribution.These random numbers were evaluated by the model，the match distribution curve method and the existing Bayes theory respectively.The results showed that the parameter estimates obtained by the model were closer to the Weibull two-parameter true value than the existing Bayes theory and the match distribution curve method.Meanwhile，the relative error of the estimated value of the shape parameter and the scale parameter was less than 10%，indicating the feasibility of the model to analyze the small sample of zero-failure data for reliability evaluation.The model was verified with examples in reference，and the results showed that the reliability evaluation obtained by the model was closer to that used in actual engineering practice than the other two methods；moreover the model's two-sided reliability confidence interval length was smaller than the other two methods，effectively improving the accuracy of reliability evaluation of small samples and zero-failure data .
Fretting fatigue test of ZSGH4169 dovetail structure
XING Zeyu, ZHANG Hongjian, YU Ziqiang, CUI Baolong, WEN Weidong
2021, 36(11): 2410-2417. doi: 10.13224/j.cnki.jasp.20200509
Abstract FullText HTML PDF(3345KB) icon438 icon122
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The fretting fatigue of ZSGH4169 Nickel-based superalloy dovetail structure was studied under different temperatures and loads.It was found that under different working conditions，the fretting fatigue cracks were generated at the lower edge of the mortise contact area，and cracks were generated on both sides.The fretting fatigue life of dovetail structure decreased significantly with the increase of test temperature and load.Both temperature and load affected the slip amplitude and the fretting fatigue life decreased with the increase of slip amplitude.The high-temperature fretting fatigue life prediction model containing fretting fatigue parameters was used to verify the fretting fatigue test of ZSGH4169，and the predicted life was within the double error band.
Fault diagnosis of tooth surface spalling of planetary gearbox based on GWO-TVF-EMD method
CAO Wei, GOU Zhenyuan, HAN Zhao, GUO Yahong, YANG Zhuangzhuang, WANG Dong, QU Jinxiu
2021, 36(11): 2418-2429. doi: 10.13224/j.cnki.jasp.20210226
Abstract FullText HTML PDF(5563KB) icon438 icon103
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In order to overcome the shortcomings of the time varying filter for empirical mode decomposition （TVF-EMD） method，the sample entropy was used as the fitness function.The gray wolf optimization （GWO） algorithm was used to optimize the bandwidth threshold and B-spline order core parameters，and the optimal combination solution was obtained to decompose the vibration signals of different fault impact tests.The selection process of intrinsic mode function （IMF） components was optimized，and multiple weighted indexes were used to calculate all the IMF components，and finally the optimal IMF component was selected.Then，the spalling fault features of planetary gear were extracted by envelope spectrum analysis.In the planetary gear box fault test，the root mean square method was used to identify the spalling fault initially，and the optimal IMF component of each spalling fault signal was obtained by GWO-TVF-EMD，and the envelope spectrum analysis was used to judge the fault frequency of the planetary gear clearly.The method can extract the detailed features of three different degrees of tooth surface spalling faults，and the relative error between the theoretical value and the actual value was 1.68%.
Analysis of oil-off tolerance of angular contact ball bearing under condition of high speed and heavy load
LIU Lu, ZHAO Cong, FENG Xiaochuan, WANG Liqin
2021, 36(11): 2430-2436. doi: 10.13224/j.cnki.jasp.20200526
Abstract FullText HTML PDF(2836KB) icon416 icon122
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According to the study of the oil-off fault recurrence phenomenon of the angular contact ball bearing，the initial failure mode was three-point contact between balls and inner rings.The three-point contact analysis method was used to calculate the bearing's oil-off tolerance；in combination with the calculation and analysis results of similar bearings，it was found that the larger the shim angle，the worse the bearing's oil-off capacity.The bearing had poor resistance of oil-off when the shim angle was 25°.Through analysis of the transient temperature distribution of the bearing after the oil-off，combined with the three-point contact analysis method，it was determined that the bearing oil-off withstand time of the original design state was 25 s，without the ability to withstand the oil-off for 30 s.According to the conclusion of the analysis，the shim angle of the bearing was reduced to 19°，and the improved bearing passed the oil-off verifications of test rig and engine test verification.
Construction and experiment of point contact gear pair with certain contact trace
PENG Shuai, ZHANG Jing, WANG Linxiang
2021, 36(11): 2437-2446. doi: 10.13224/j.cnki.jasp.20200530
Abstract FullText HTML PDF(3951KB) icon374 icon169
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A type of point contact gear pair was proposed.Based on a given tooth surface，the flexible contact trace was selected according to the design requirements，and the conjugated curve was derived.A tooth surface was established by sweeping along the conjugated curve，and the meshing pair gear was constructed.The sliding coefficient calculation method of the this gear pair was studied.Taking the involute internal gear as the given tooth surface，the parabolic tooth surface was designed as the matching gear.The gear pair was manufactured and efficiency experiment was carried out.The results showed that during the whole meshing process，the gear pair kept point contact state，and the meshing point moved along the theoretical contact trace，which was consistent with the theoretical analysis.The variation range of the sliding coefficient mainly depended on the involute parameter values at the approach point and the recess point.After the experiment，the actual contact trace was consistent with the theoretical contact trace，and the efficiency was kept stable within a range from 97.2% to 98.5%.
Mechanism and influencing factors analysis of windage losses from aeronautic spiral bevel gear
LI Linlin, WANG Sanmin, ZHANG Xuyang, LI Fei, LI Zhibin
2021, 36(11): 2447-2457. doi: 10.13224/j.cnki.jasp.20200524
Abstract FullText HTML PDF(4290KB) icon355 icon113
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Based on the computational fluid dynamics （CFD） theory，the airflow characteristic and the mechanism of gear windage losses around the single spiral bevel gear were simulated and analyzed using shear stress transfer （SST） k-ω turbulence model and multi-reference rotation model （MRF） technology and the Coupled decoupling algorithm.The influence of gear speed，rotation direction and shroud configuration on windage power loss was researched.Then the windage moment was studied by orthogonal experiment and numerical simulation analysis with the difference clearance value between the shroud and the tooth surface，the heel and toe of the gear.By means of variance analysis and data fitting，the functional relationship between the windage losses and the clearance value of the gear was obtained.The results showed that when the shroud clearance value was 1mm，the windage moment was the smallest，and the effect of reducing the windage power loss was the best.The optimal reference value of the clearance between the shroud and the gear was given by using the single-objective optimization analysis method，which provided the theoretical basis and research method for further studying the multi-objective optimization of the shroud clearance and also a reference for the engineering application of the windshield.
Influence of transverse variable acceleration on design of insulation structure for solid rocket motor
SUN Di, LI Yongzhou, LIU Xiaowei, GAN Xiaosong
2021, 36(11): 2458-2464. doi: 10.13224/j.cnki.jasp.20200435
Abstract FullText HTML PDF(2723KB) icon598 icon154
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Targeting the high-mobility characteristics of the new generation antiaircraft missiles，the influence of the complex transverse variable acceleration trajectory on the engineering design for the solid rocket motor insulation structure was studied.It considered the instantaneous changes of acceleration value and angle，meshed the insulation structure，and calculated its ablation thickness by programming，and then the design thickness of the heat insulation layer at different positions was obtained according to the safety margin design criterion.Compared with traditional design results，considering the change of transverse acceleration significantly reduced the structural mass of the motor，and improved the overall performance；the heat insulation mass of the motor was reduced by 53.7%，and the total impulse was increased by 6.84%.

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