2020 Vol. 35, No. 2

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Effect of fresh air/exhaust gas combination on performance of wave-rotor-topped gas turbines
XING Fei, ZHANG Linqi, CHAN Shining
2020, 35(2): 225-234. doi: 10.13224/j.cnki.jasp.2020.02.001
Abstract PDF(2733KB) icon864 icon799
Abstract:
For the wave-rotor-topped gas turbines, the exhaust gas recirculation and the fresh air exhaustion phenomena in wave rotors were considered and the status how the fresh air or exhaust gas splits and merges due to the phenomena was studied. The thermodynamic governing equations were derived, comparison and parametric investigation on the general designs was conducted, and regulations in the parametric investigation results were analyzed based on thermodynamic models. Results showed that: the exhaust gas recirculation and the fresh air exhaustion reduced the work output and the thermal efficiency by different degrees; the effect of the exhaust gas recirculation was smaller than the fresh air exhaustion; an appropriate increase in the wave rotor pressure ratio could keep the general performance of the wave-rotor-topped gas turbine with the effects of the exhaust gas recirculation and the fresh air exhaustion.
Numerical simulation of flow field characteristics of impacting T-junction duct in wind tunnel
CONG Chenghua, QIN Honggang, REN Zebin
2020, 35(2): 235-243. doi: 10.13224/j.cnki.jasp.2020.02.002
Abstract PDF(4618KB) icon742 icon690
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Cracks may occur at the connection of the impacting T-junction and the position of the clapboard at regular intervals in intake pipelines of 24 m transonic wind tunnel. In order to understand the causes of cracks and provide a basis for improving design,CFD (computational fluid dynamics) was used to compare the existing tee and optimization schemes in wind tunnel. The governing equations are three-dimensional viscous incompressible Navier-Stokes equations. The results showed that the flow in the tee was the most common type without clapboard. There were three separation zones in the branch pipe. The first separation zone was horseshoe vortex, followed by the second separation zone. A pair of reverse rotating eddies, Dean eddies, and a third separation zone were formed on the top wall of the tee. The flow field was basically symmetrical along the y=0 mm and z=0 mm planes. When there was a clapboard, the left and right structures of the flow field were asymmetrical and the upper and lower structures were also asymmetrical. A small range of standing vortices were formed at the corner between the clapboard and the outer wall, and unstable spiral separation vortices were formed in the branch pipe, resulting in air flow oscillation and causing cracks in the pipe wall at the tee connection and the clapboard. According to the above flow pattern, pipeline optimization scheme and flow control device were designed. Separation zones could be effectively reduced or eliminated. Removal of the clapboard was the simplest and easiest way to solve the problem of cracks in the pipe.
Characteristics of shear-layer flow field of open-jet wind tunnels
NI Zhangsong, ZHANG Jun, WANG Mao
2020, 35(2): 244-251. doi: 10.13224/j.cnki.jasp.2020.02.003
Abstract PDF(3642KB) icon816 icon686
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Simplified theoretical formulae for the calculation of the axial and the transversal speeds of open-jet flow were presented. And the effects of two control parameters, ie, the offset parameter and the spreading rate, on the speed profile were analyzed. Experimental studies were performed in two wind tunnels respectively. The distributions of shear-layer speed profile, shear-layer thickness, turbulence intensity and turbulence spectrum were obtained. And the obtained data were compared with theoretical predictions. Results indicated that: beyond a distance from the nozzle, the axial speed profile was strongly self-similar, while the transversal speed profile was weakly self-similar; the shear-layer thickness linearly increased with stream-wise distance; the turbulence intensity was small and stable in the core flow region, slowly but linearly increased in the fully developed region, and rapidly increased in the shear-layer region; the shear-layer turbulence spectrum was broadband, no peaks can be identified in the spectrum.
Experiment on thickness noise of rotor based on control of active trailing edge
HE Xiang, MEI Xiaoning, DU Yihua
2020, 35(2): 252-262. doi: 10.13224/j.cnki.jasp.2020.02.004
Abstract PDF(6206KB) icon641 icon682
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An on-blade control technique to reduce thickness noise was developed based on the principle of sound field cancellation. A high-accuracy method for calculation of helicopter rotor aerodynamic noise was established based on the Ffowcs Williams-Hawkings (FW-H) equations with the control of active trailing edge. The overall experimental scheme was designed and the open-loop experiment of active noise control was carried out in a fully anechoic chamber, and the experiment data were compared with theoretical calculation to verify the validity of the method and experiments results. The parameter influences of the amplitude, frequency and initial phase of the trailing edge deflection on the thickness noise reduction of the rotor were analyzed. The influences of the observation distance on the cancellation of rotor thickness noise were then deeply assessed. The experimental results demonstrated that there was an optimal phase at each frequency to minimize the noise at the observations, and it varied with different frequencies; the reasonable trailing edge control law can effectively reduce the thickness noise of the observation points in the plane of the rotor up to 2-3 dB.
Experiment and numerical simulation on characteristic of front variable area bypass injector
CHEN Jia, HU Wenbing, CHEN Xiaowen
2020, 35(2): 263-271. doi: 10.13224/j.cnki.jasp.2020.02.005
Abstract PDF(3795KB) icon825 icon612
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In order to study the effects of inlet total pressure ratio and back pressure on the front variable area bypass injector’s (FVABI) performance and mixing mechanisms, experiment method and three-dimensional numerical simulation approach were applied to analyze the injector’s performance with various inlet total pressure ratios and change regularity of main flow and secondary flow mixing flow fields under different inlet total pressure ratios and back pressures. Results revealed that the standard k -ε model had great accuracy in simulating injector mixing flow field. With the enlargement of inlet total pressure ratio, the total pressure loss of the injector increased. When the inlet total pressure ratio was constant, the total pressure loss increased firstly and then decreased as the back pressure ascended. The injector had an operating point with the minimum total pressure loss as the back pressure changed. When the back pressure reduced, there was a critical operating point for the injector, furthermore the injector’s back pressure was higher at its critical operating point if the inlet total pressure ratio got higher, meaning the adjustable bypass ratio range was narrowed down. The mixing process of the main flow and secondary flow was mainly concentrated in the position of x/l=03-06. The momentum and mass adequately exchanged, and the distribution of velocity was radically uniform along the flow direction.
Acoustic characteristics test on aft-fan duct with titanium alloy annular acoustic liner
HUO Shiyu, YANG Jiafeng, DENG Yunhua
2020, 35(2): 272-279. doi: 10.13224/j.cnki.jasp.2020.02.006
Abstract PDF(2672KB) icon827 icon667
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Considering the potential application environment properties of titanium alloy honeycomb acoustic liner, an experimental method of the acoustic test of the annular acoustic liner with the influence of temperature gradient was proposed, and a simulated engine aft-fan duct acoustic test rig was developed. Then the acoustic test on titanium alloy annular acoustic liner was carried out. In view of the noise of 2 500 Hz and 2nd-order circumferential mode and the grazing flow with Mach number of 02, a titanium alloy annular acoustic liner was designed and prepared. The acoustic characteristics of the titanium alloy annular acoustic liner were studied by the means of duct acoustic mode test and far-field directivity test, respectively. Results showed that the noise reduction of the designed titanium alloy liner in the duct was 319 dB under the target operating conditions, and the 1 m far-field noise reduction appeared to be over 20 dB between 30° to 120°. Increasing the velocity of grazing flow expanded the bandwidth of the noise reduction spectrum and shifted the peak value of the spectrum from low frequency to high frequency. Increasing the temperature of the backplane of liner had little effect on the bandwidth of noise, but it shifted the peak value of noise reduction spectrum from low frequency to high frequency.
Effect of mass ejection on boundary layers stability
LI Jin, SU Wei, HUANG Zhangfeng
2020, 35(2): 280-293. doi: 10.13224/j.cnki.jasp.2020.02.007
Abstract PDF(6303KB) icon1022 icon638
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The effect of the mass ejection on the evolution of the second-mode disturbances in a boundary layer of Mach number of 6 on a blunt plate was investigated by using direct numerical simulation (DNS) method and linear stability theory (LST). Different parameters of the mass ejection and disturbances, such as the ejection velocity, width, location, combination and volume flowrate, were considered. Results showed that: the mass ejection destabilized the two-dimensional and three-dimensional disturbance waves, and the effect was the strongest when the ejection position was close to the lower bound of the neutral curve of disturbances; the volume flowrate was an important factor to determine the effect on the evolution of disturbances; the combined mass ejection had the superposition effect when its volume flowrate was small; the value of N predicted by LST was close to the direct numerical simulation result, implying that LST can quantitatively determine the effect of the mass ejection on the stability of boundary layer.
Effect of combustion chamber pressure pulsation on mixing ratio of liquid-liquid coaxial swirl injector
FU Qingfei, JIA Boqi, YANG Lijun
2020, 35(2): 294-297. doi: 10.13224/j.cnki.jasp.2020.02.008
Abstract PDF(858KB) icon822 icon577
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Based on the theory of liquid injector dynamics, the dynamic response of coaxial injector mixing ratio to the pressure pulsation in combustion chamber was theoretically studied, and the transfer function between the mixing ratio pulsation and combustion chamber pressure pulsation was also derived. The amplitude-frequency characteristics of the transfer function were calculated with a model liquid oxygen-kerosene bipropellant injector. Results showed that as the pulsation frequency increased, the pulsation amplitude of mixing ratio increased first, then decreased. The amplitude of transfer function increased when the supply system pressure increased, and decreased when the injector pressure drop increased. The frequency corresponding to the maximum amplitude was independent of supply system pressure and injector pressure drop, meaning that this frequency was dependent on the injector characteristics.
Large eddy simulation of low swirl premixed flame stabilization mechanism
LIU Yingjie, LIU Xiao, ZHOU Bo
2020, 35(2): 298-304. doi: 10.13224/j.cnki.jasp.2020.02.009
Abstract PDF(3368KB) icon1304 icon710
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The large-eddy simulation (LES) method was used to compare the premixed combustion characteristics of high and low swirls, and the flame stability mechanism of low swirl was analyzed. Results showed that LES coupling with PaSR combustion model can accurately capture the small structures and flow field distribution of premixed flame. The low swirl flow had a weak recirculation zone (sometimes just a low velocity zone), while a high swirl flow produced a strong recirculation zone with a low frequency vibration of the precession vortex core (PVC). By analyzing the change of vortex and flame temperature field, it was found that vortices generated from swirl and center jet flow were the main factors of stability mechanism to stabilize flame in the low velocity region, forming alternating W and V flame.
Circumferential seal characteristics with thermal-fluid-structure multi-physics field coupling
YAN Yutao, WEI Rong, HU Guangyang
2020, 35(2): 305-317. doi: 10.13224/j.cnki.jasp.2020.02.010
Abstract PDF(3921KB) icon756 icon707
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Based on the analysis of circumferential seal conditions, a three-dimensional multi-physics coupling simulation model of flow field, temperature field and structural field was established. The correctness of the model was verified by comparing the results of the thermal-fluid-structure coupling method with the theoretical model and the experimental results. The characteristics of flow field, temperature field and structure field of circumferential seal, and the distribution of von Mises stress and deformation in multi-physics coupling field were analyzed, and the effect of typical condition parameters on the performance of circumferential seal was obtained. The results showed that the pressure in the flow field decreased along the negative directim of z axis, and the pressure drop gradient was negatively correlated with the seal dam width. The seal gas generated irregular vortex motion, and the flow velocity decreased along the radial direction. The temperature field was uniformly distributed, and the maximum temperature was located at the lap joint. It was found that the maximum deformation and maximum von Mises stress were located at the convex lap joint by static structural analysis. The maximum deformation of the seal ring under thermal-fluid-structure coupling was 161% higher than that of the fluid-structure coupling and 09% smaller than that of the thermal-structure coupling, and the temperature field had a significant effect on the deformation of the seal ring. The maximum von Mises stress shifted to the transition between the seal dam and the lap joint, 83% higher than that under the fluid-structure coupling and 23% higher than that under the thermal-structure coupling; and both the flow field and temperature field had great influence on the von Mises stress of the seal ring. The change of seal temperature difference plays an important role in the deformation. The change of seal pressure difference plays a major role in the maximum von Mises stress and a decisive role in the leakage.
Operating range and performance analysis of oxygen consumption based inerting reactor
FENG Shiyu, XIE Huihui, PENG Xiaotian
2020, 35(2): 318-324. doi: 10.13224/j.cnki.jasp.2020.02.011
Abstract PDF(2558KB) icon581 icon518
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A two-dimensional pseudo-homogeneous reactor model of porous media coupled with chemical reaction was established by CFD method to research the operating range of the reactor in the oxygen consumption based inerting system as well as the impact on the reactor performance under different working conditions. The single-temperature model of porous media in Fluent 170 software was adopted, and the solid phase energy equation was added through UDS(user defined scalar). RP-3 fuel was taken as the object, and the chemical reaction heat was added to the solid phase energy equation in the form of source term. The operating range of the reactor was analyzed under the condition of different superficial gas velocity and different RP-3 mole fraction without temperature runaway, the indicator of oxygen consumption rate was introduced to evaluate the influence of the reactor on the inerting system, and the influence of the inlet gas temperature on the operating range and reactor performance was discussed. Results showed that the reactor had a certain operating range, and increasing the inlet gas temperature would reduce the operating range; the oxygen consumption rate tended to be constant with the increase of inlet gas velocity; the oxygen consumption rate would be greatly increased by RP-3 mole fraction and the temperature rise of the inlet gas. Therefore, these factors should be fully considered in the future design of oxygen consumption based inerting reactor.
Performance of the SOFC-GT hybrid system based on aviation kerosene reforming
HU Jiaoying, MAO Junkui, HE Zhenzong
2020, 35(2): 325-336. doi: 10.13224/j.cnki.jasp.2020.02.012
Abstract PDF(3230KB) icon907 icon548
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A simulation model of the solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system on the basis of the aviation kerosene reforming was established. The effect of two heat recovery methods on the reformers and the effect of the turbine positions on the system efficiency were studied to obtain the optimal system architecture. The performance of the SOFC-GT hybrid system was evaluated by studying the effects of the compressor pressure ratio, fuel utilization ratio, fuel flow rate and air flow rate. Results showed that the efficiency of the best hybrid system can reach 45% at the design condition, and the system demonstrated excellent performance. The efficiency and power of the system reached the peak with the fuel utilization ratio equaling to 082. Moreover, the efficiency and power could be improved with the growing fuel flow rate (from 0051 1 mol/s to 0058 4 mol/s), while the increasing compressor pressure ratio (from 25 to 33) or air flow rate (from 37 mol/s to 44 mol/s) could result in the reduction of the efficiency and power.
Investigation of flamelet modeling for bluff-body stabilized jet flame
HAN Zongying, HE Changsheng, LI Jinghua
2020, 35(2): 337-347. doi: 10.13224/j.cnki.jasp.2020.02.013
Abstract PDF(4524KB) icon696 icon519
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Based on the concept of flamelet, the Sydney University CH4/H2 bluff-body stabilized flame was studied using steady laminar flamelet model (SLFM) and Eulerian particle flamelet model(EPFM), respectively. The revised Reynolds stress model (RSM) was used and two different chemical reaction mechanisms were also considered. The numerical results of the turbulent flame structure, major species concentrations and nitrogen oxides predictions by using different models were compared with the experimental data. The comparison showed that the prediction of the temperature, and major species calculated with these two mechanisms were basically same, the SLFM can accurately predict the combustion field; the OH results of the EPFM in some regions were closer to the experiment. The result of the SLFM coupled with the GRI-Mesh 211 mechanism reduced by two times after being post-processed by the EPFM model can predict the NO concentration more accurately, testifying the importance of the chemical reaction mechanism and the unsteady effect on the prediction of nitrogen oxides.
Deposition characteristics of RP-3 aviation kerosene under high temperature conditions
LIU Tianchi, FAN Yuxin, ZHAO Shilong
2020, 35(2): 348-357. doi: 10.13224/j.cnki.jasp.2020.02.014
Abstract PDF(2330KB) icon1025 icon508
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In order to understand the aviation kerosene’s deposition characteristics under high temperature conditions, the RP-3 aviation kerosene’s deposition boundary temperature and characteristics under static state, the influences of different fuel inlet conditions and wall temperatures were studied by test. The results indicated that the deposition boundary temperature under static state was between 437-450 K, and the deposition rate decreased with the increase of test time. Increasing the flow velocity, and decreasing the fuel inlet temperature and the wall temperature can effectively reduce the deposition amount, and decreasing the fuel inlet temperature had the most effective impact. From the perspective of time scale, deposition accumulated slowly in the early stage, but increased significantly when a certain deposition amount had been formed. Taking the 400 K fuel inlet temperature, 800 K wall temperature and 05 m/s flow velocity test as example, the deposition amount of 8 h and 12 h test was about 15 times and 7 times that of the 4 h test, respectively.
Damage tolerance of titainum alloy wheel with internal defects based on fracture analysis
WU Yinglong, XUAN Haijun, SHAN Xiaoming
2020, 35(2): 358-367. doi: 10.13224/j.cnki.jasp.2020.02.015
Abstract PDF(3591KB) icon709 icon486
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In order to carry out the damage tolerance design of wheel, the crack propagation characteristics were studied by fractographic restrostimation and crack propagation simulation analysis. The crack growth rate was determined according to the fatigue striation. Close to crack length of 2 mm, the crack growth rate increased significantly, acting as the transition region of the first and second loading stages; in the stable crack growth zone, crack length had a bilinear logarithmic relationship with the crack growth rate; the list gradient method and Paris formula method were used to reversely calculate the fatigue life, and the fatigue life was 163% higher than the cycles of the second loading stage. The simulated values of crack growth in the stable stage of crack propagation coincided with the values of fracture inversion, but the simulated values in the unstable stage were less than the values of fracture inversion, and the error was -215%. Based on the above research, a reasonable table for a centrifugal wheel was determined. The life of wheels in unstable stage accounted for 248%-357% of the life of internal crack surface growth stage, so accurate calculation was of great significance.
Clamp assembly stress test of aero-engine and assembly parameter control method
LIU Zhonghua, JIA Duo, WANG Xin
2020, 35(2): 368-377. doi: 10.13224/j.cnki.jasp.2020.02.016
Abstract PDF(3888KB) icon949 icon486
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The main parameters affecting the assembly stress of clamps were derived through theoretical formulas and analyzed. Further more, the factors affecting the assembly stress of the clamps were systematically analyzed and researched by test method. In the test, the effects of bolt tightening torque, loading times, and assembly plans on the stress of the clamps were tested and statistically analyzed by using 3 types of clamps with 5 samples of each type as the test object. According to the research results, the surface of the clamp near the bolt hole was a stress concentration position. The stress of the clamp decreased with the increase of loading times, but the repeated loading times should not be too much, otherwise the local area of the clamp had large deformation and wear. The test results also showed that the method of adding a 2 mm gasket had the best effect on reducing the stress level of the clamp, and the reduction rate can reach 468%. In contrast, the reduction rate was 364% and 286% respectively by means of loading after restricting the displacement of the clamp and the method of correction after loading.
Epoxy resin formulation and its composite properties for high efficiency wet winding
LIU Li, LI Yong, HUAN Dajun
2020, 35(2): 378-387. doi: 10.13224/j.cnki.jasp.2020.02.017
Abstract PDF(2514KB) icon1013 icon604
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According to the requirement for high-efficient production of high quality solid rocket motor shell, the epoxy resin formulation with different functionalities was studied by focusing on its formulation design and mechanical properties. The curing characteristic temperature, curing reaction kinetics and pot life were tested by DSC (differential scanning calorimetry) and viscosity test, respectively, the unidirectional laminates and NOL (the Naval Ordnance Laboratory) rings were prepared to test and analyze the properties of composites. The results showed that the epoxy resin with three functionalities can meet the requirements of high efficient wet winding. When the mass fraction of TDE-85 with three functionalities was 25%, the comprehensive properties reached the optimum, the tensile strength (973 MPa), the bending strength (115 MPa) and the glass transition temperature (466 K) increased by 363%, 159% and 258% respectively, while the applicable period was 120 min. The resin system had good adaptability to fibers, demonstrated by the excellent properties of composites, about 256 GPa in tensile strength and 744 MPa in interlaminar shear strength of the NOL rings, respectively. The utilization ratio of fiber strength reached 766%, demonstrating that the epoxy resin system was suitable for the wet winding process of the solid rocket motor.
Inter-laminar stress analysis of laminated composite fan blade dovetail
KANG Yongqiang, CHEN Yong
2020, 35(2): 388-396. doi: 10.13224/j.cnki.jasp.2020.02.018
Abstract PDF(3924KB) icon850 icon625
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The finite element simulation technique was used to study the inter-laminar stress characteristics of dovetail under tensile and tension and bending coupling conditions. Based on the FiberSIM-ACP interaction module, the finite element modeling and inter-laminar stress analysis process of the fan blade dovetail were established. A finite element model of the fan blade dovetail satisfying the requirements of inter-laminar stress analysis accuracy was determined. The effectiveness of the finite element model was verified by comparison with the experimental results. Results showed that the high stress area of S33 under the tensile condition was located at the variable thickness position of the dovetail, 14 layers near the pressure surface were subjected to tensile stress; the high stress zones of S13 and S23 were in the same region, the shear stress was closely related to the ply angle, the 0° ply was subjected to a large shear stress S13, the ±45° ply was simultaneously subjected to large shear stresses S13 and S23.The high stress area of the S33 between the layers was extended to the upper end of the dovetail after adding the bending load, and the number of layers subjected to tensile stress increased; the high stress area of the shear stress was close to the bearing surface of the dovetail, and the number of layers in the high stress area also increased.
Polynomial-based continuous-curvature leading edge design method and its application
SHI Hengtao, LIU Baojie, YU Xianjun
2020, 35(2): 397-409. doi: 10.13224/j.cnki.jasp.2020.02.019
Abstract PDF(6336KB) icon1222 icon573
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To optimize the leading edge (LE) shape for improving airfoil aerodynamic performance, a polynomial based continuous-curvature LE design method was proposed. By specifying derivatives of camber-line and thickness distribution at the junction point, the continuous surface curvature was guaranteed. The length and the fullness of the LE portion could be specified according to design need. The method was used to optimize the LE portion of two subsonic airfoils with inlet Mach number of 075 and 060, respectively. Simulations indicated that the LE optimized airfoils had much lower suction spike strength, which decreased the gradient of adverse pressure caused by flow diffusion. Therefore, the LE separation bubble was suppressed and the premature transition of boundary-layer was avoided. Due to these two factors, the LE optimized airfoils had much lower loss level at off-design conditions and the useful operation range were increased by 31°and 38° compared with circular LE airfoil, respectively. The leading edge of a transonic compressor stage was also modified by this method, the increase of adiabatic efficiency for rotor and stage were 07 percent and 11 percent at near stall condition, respectively, with stall margin also extended.
Effect mechanism of pulsating flow on unsteady aerodynamic performance of turbine
JI Bing, LI Jun, WANG Zhiduo
2020, 35(2): 410-421. doi: 10.13224/j.cnki.jasp.2020.02.020
Abstract PDF(7908KB) icon845 icon486
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A periodic pulsating incoming flow was used to simulate the flow field at the outlet of a rotating detonation combustor. The effect mechanism of the amplitude and frequency of the incoming pulsation on the unsteady internal flow characteristics of the GE-E3 high pressure turbine stage was studied. Results indicated that the increase of the pulsation amplitude of the inflow could enhance the unsteadiness of the internal flow field and amplify the difference of the parameters in the internal flow field in time and space. With the increase of the pulsation frequency, the pulsation amplitude of the internal flow field gradually weakened, and the distribution of the time averaged loading of the blade was inclined to be consistent. Under the condition that the incoming pulsation frequency was 5 244 Hz, when the pulsation coefficient increased to 04, the turbine efficiency was reduced by 1399%; under the condition that the incoming pulsation coefficient was 03, when the pulsation frequency increased to 10 488 Hz, the turbine efficiency was reduced by 1557%. Increased pulsation amplitude and frequency could enhance the endwall secondary flow and cascade flow separation, make the inlet attack angle of blades deviate from the design state, and reduce the turbine working efficiency.
Influence of S3 area ratio gradient at trailing edge on turbine rare frame
LI Shulei, JIN Donghai, GUI Xingmin
2020, 35(2): 422-431. doi: 10.13224/j.cnki.jasp.2020.02.021
Abstract PDF(5006KB) icon545 icon467
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For the intergraded design of support plate and outlet guide vane, where it's difficult to apply the three-dimensional blade design, the secondary flow in the outlet guide vane can be controlled by changing S3 area ratio gradient at the trailing edge. The numerical results of inner flow field and aerodynamics performance of three designs were compared in a 15 stage turbine. The results showed that when the gradient reduced from 001 to -005, the overall total pressure recovery coefficient of the outlet guide vane increased from 0979 to 0991, and the S parameter on 5% span reduced from 0011 to 0005. The back-flow zone on the hub endwall and the suction side of the blade disappeared, and the corner separation was effectively controlled. When gradient reduced from -005 to -010, the flow velocity in the corner zone increased, and at the 5% span, corner blockage lessened, axial velocity density ratio (AVDR) increased, total pressure recovery coefficient increased, yet the S parameter didn't change.
Fatigue life prediction under random loading for accessory transmission system based on grey estimation and polynomial mutation theory
LIANG Song, YAN Ming, CHEN Zhuo
2020, 35(2): 432-439. doi: 10.13224/j.cnki.jasp.2020.02.022
Abstract PDF(1439KB) icon565 icon459
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Considering the problem of life prediction of aero-engine accessory drive system under random fatigue load, a method of fatigue life prediction based on grey estimation and polynomial variation theory was proposed. Based on the grey model and polynomial variation theory, two-dimensional load spectrum and equal amplitude fatigue median surface were obtained. Taking parallel shaft-gear transmission structure as an example, the fatigue median life of the risk point was about 135×107 using Miner fatigue cumulative damage theory. During the verifying test, standard 40Cr-workpieces were under condition of equivalent stress state. The processing process could satisfy the strength standard for aero transmission shaft in conformance to GB3077-82. In life test with equal censored time, the number of samples was 45. Median life for samples was about 142×107. As the result, the calculated value of fatigue median life was slightly less than the test value. The proposed method is reliable and conservative for improving the fatigue life of accessory drive system.
Inverse prediction of flow-path structure parameters based on intershaft bearing lubrication efficiency
ZHU Donglei, CHEN Guoding, LI Yanjun
2020, 35(2): 440-448. doi: 10.13224/j.cnki.jasp.2020.02.023
Abstract PDF(2180KB) icon582 icon464
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An inverse prediction method considering the constraints of flow-path structure parameters was proposed to satisfy the designing requirements of aero-engine intershaft bearing lubrication system while obtaining feasible structure parameters corresponding to the given bearing lubrication efficiency. Lubrication efficiency function was constructed to demonstrate the fitting relation between structure parameters and lubrication efficiency according to the neural network model. By virtue of structure parameters optimization, the distraction between lubrication efficiency function values and the given lubrication efficiency was mininized, the constraints of each parameter were considered to obtain, the flow-path structure parameters satisfying the given lubrication efficiency(minimized distraction). In comparison with the present analytical methods, the proposed inverse prediction method could improve the prediction precision by 439%, shorten the average calculation time by 175 minutes, and predict multiple parameters simultaneously, providing an approach to the design of intershaft bearing lubrication system.

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