2021 Vol. 36, No. 8

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Combustion, Heat and Mass Transfer
Research on mixture formation of two-stroke heavy fuel direct injection engine
ZHAO Zhenfeng, YU Chuncun, DONG Xuefei, WANG Lei
2021, 36(8): 1569-1577. doi: 10.13224/j.cnki.jasp.20200370
Abstract FullText HTML PDF(3821KB) icon658 icon311
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In view of the problems of difficulty in evaporation of aviation kerosene and high fuel consumption of two-stroke engines,a three-dimensional simulation model of a two-stroke direct injection engine fueled with aviation kerosene was established,and the accuracy of the model was verified through experiments. On this basis, scavenging and mixture formation process was studied. The research results showed that postponing fuel injection reduced the short-circuit time of fuel, and at the same time avoided the free exhaust phase with large exhaust mass flow, which can improve the fuel capture rate. Utilizing the high temperature of exhaust gas can speed up the evaporation process of kerosene. Injection too late could lead to incomplete evaporation and uneven mixture of fuel and fresh charge. For this engine,80° before bottom dead center indicated an appropriate injection timing enabling fuel evaporation and uniform mixing while increasing the fuel capture rate. At this time, the engine had higher indicated power and lower indicated thermal efficiency, which were 84. 0 kW and 360. 3 g/kWh, respectively. The research results can provide theoretical support for the optimization of the fuel injection parameters of the two-stroke direct injection engine.
Effects of temperature and pressure on laminar flame characteristics of low heat value fuel
ZHENG Weilin, ZHANG Shijie, PANG Liyao, XIE Fan, ZENG Wen
2021, 36(8): 1578-1585. doi: 10.13224/j.cnki.jasp.20200453
Abstract FullText HTML PDF(3351KB) icon585 icon213
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In order to illustrate the combustion characteristics of low heat value fuel under operation conditions of gas turbines, the laminar flame velocity of blast furnace gas, with volume fraction of 7%H2, 21. 72%CO, 21. 45%CO2, 49. 83%N2, was measured in a constant volume vessel, under initial pressures of 0. 10, 0. 15, 0. 20 MPa, initial temperatures of 303, 353, 403, 453 K, and equivalent ratios within the range of 0. 8~1. 6,in comparison with calculation results using the Gri-Mech 3. 0 kinetic mechanism. It was concluded that the laminar flame velocity of low heat value fuel increased with the decrease of the initial pressure and the increase of the initial temperature. The change of the laminar flame velocity was not monotonous and thus was fitted by high-order polynomials based on the experimental data. Further sensitivity analysis showed that the main reactions with positive sensitivities were R99 and R46,and the main reactions with negative sensitivities were R45 and R36,respectively. The laminar flame velocity was highly dependent on reactive free radicals,and affected by the competition between chain termination reactions and chain branching reactions. The mole fraction of active free radicals increased with the decrease of initial pressure and the increase of initial temperature, resulting in an increase in the laminar flame speed.
Pulse detonation gas expansion process and evaluation method of energy conversion difficulty degree
LI Xiaofeng, XIAO Junfeng, HU Mengqi, WANG Wei, WANG Feng
2021, 36(8): 1586-1593. doi: 10.13224/j.cnki.jasp.20200474
Abstract FullText HTML PDF(2545KB) icon422 icon193
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In order to improve the energy conversion efficiency of pulse detonation gas, the expansion process of pulse detonation gas in the turbine was analyzed, and a calculation method for evaluation method of energy conversion difficulty degree was established. Based on the numerical model of the pulse detonation combustor with the axial turbine, the turbine efficiency was adopted to verify the calculation method for gas energy conversion difficulty degree. The results showed that:(1) in the process of detonation wave expansion,the thermal choking phenomenon appeared in the turbine static vane and formed a back-propagating compression wave.(2) The expansion of the detonation gas in the turbine was mainly comprised of primary expansion, over-expansion and secondary expansion; the enthalpy drop of the detonation gas in the turbine mainly occurred in the primary and secondary expansion stages. In the over-expansion stage,the gas did negative work in the turbine.(3) The gas energy conversion difficulty degrees for the three calculation conditions with equivalent ratios of 0. 72, 0. 89 and 1. 00 were 0. 396, 1. 000 and 0. 803, respectively, and the turbine efficiency for the three calculation conditions was 0. 473 6, 0. 597 2 and 0. 570 3, respectively, verifying the accuracy of the calculation method for gas energy conversion difficulty degree.
Thermal protection model of apogee engine
ZHANG Yang, ZHAO Jianfeng, HAN Chongwei, ZHANG Ningli, NING Bo, DU Zhuolin, ZHAO Xin, ZHAO Qiwei
2021, 36(8): 1594-1604. doi: 10.13224/j.cnki.jasp.20200371
Abstract FullText HTML PDF(6105KB) icon374 icon169
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To solve the problem of modifying thermal model on thermal protection of apogee engine with multi-parameter and strongly thermal coupling, a single-parameter modified method was proposed by grading thermal environment and classifing thermal parameters. By analysing heat transfer network,the system was divided to two thermal environments. Only few parameters were debugged in each thermal environment. By analysing thermal resistance network, the undetermined thermal parameters were figured out. By analysing the influence degree of parameters, the debugging sequence was determined. The temperatures of two Beidou Navigation satellites were employed. The thermal model was built by I-DEAS TMG. The debug result showed that all the temperature deviations were less than 2℃, so the modified thermal model can be used to verify and optimize thermal protection design. The principle of single-parameter modified method was based on different influence degrees of the undetermined parameters. Through several times debugging, the problem can be solved with high precision and stability. The single-parameter modified method is available to debug multi-parameter and strongly thermal coupling model.
Experimental and numerical investigation of thermo-acoustic instability in single-sector, sector and full annular combustors
GAO Xianzhi, HE Pei, FENG Xiaoxing, DENG Xiangyang, JIANG Jingjing
2021, 36(8): 1605-1613. doi: 10.13224/j.cnki.jasp.20200482
Abstract FullText HTML PDF(4262KB) icon377 icon195
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Self-excited periodic combustion instabilities in a staged lean burn combustor could be generated by operating the combustor at single-sector,sector and full annular combustor test rigs,but differences existed in oscillation modes and frequencies.In order to investigate the differences and establish the relationship among them, and to verify the thermo-acoustic instability simulation method, experiments and numerical simulations of combustion instabilities were carried out on these three kinds of test rigs, the oscillation characteristics of different test rigs were obtained, and the results were compared between simulations and experiments. The results showed that there were two unstable modes in full annular combustor, while only one unstable mode existed in sector combustor and single-sector combustor.The single-sector and sector com-bustors can represent one of the unstable modes in full annular combustor,but cannot represent another unstable mode. The three-dimensional finite element method thermo-acoustic simulation method accurately predicted the combustion instabilities of these three different kinds of test rigs, and the predicted dimensionless unstable frequencies were consistent with the experimental results with an error within 2%.
Fuel/air mixing characteristics of scramjet combustor based on acetone-PLIF technology
WANG Linsen, TU Xiaobo, WANG Yuhang, CHEN Shuang, SONG Wenyan, YANG Shunhua
2021, 36(8): 1614-1620. doi: 10.13224/j.cnki.jasp.20200444
Abstract FullText HTML PDF(7208KB) icon667 icon152
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In order to study fuel/air mixing characteristics in scramjet combustor,a non-invasive flow visualization system was designed based on acetone-PLIF(planar laser-induced fluorescence) technology. The acetone fluorescence images of four kinds of shaped struts were obtained at different sections, and the effects of nozzle position and trailing edge angle on fuel/air mixing were studied. The results showed that the flow field of the "standard" NL1 strut was of a transverse "S" curve,which had normal mixing effect in the four struts. The NL2 strut increased a few acetone diffusion range, but decreased mixing area with fluorescence signals. The EL1 strut with an expanded trailing edge angle can greatly improve effect, since the acetone molecules filled over a half of the cross section at 54 mm downstream the strut.
Heat transfer and flow resistance characteristics of multi-row jet impingement cooling in double-wall cooling structure
WEI Hong, ZU Yingqing
2021, 36(8): 1621-1632. doi: 10.13224/j.cnki.jasp.20200486
Abstract FullText HTML PDF(6429KB) icon524 icon204
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The heat transfer and flow resistance characteristics of the jet impingement cooling in double-wall cooling structure were experimentally and numerically studied. The cooling structure with inline and staggered patterns were experimentally studied in the wind tunnel with steady-state thermo-chromic liquid crystal technology, and the differences of heat transfer and flow resistance characteristics of two structures were studied. The experimental results indicated that both the discharge coefficient and Nusselt number on the target plate increased with the increase of Reynolds number, and the influence of impingement hole arrangement on the averaged Nusselt number was small. However, the discharge coefficient of the staggered cooling structure was higher than that of the inline pattern, and the heat transfer on the target plate was more uniform. Furthermore, the numerical results showed that distribution of the mass flow rate and the heat transfer in the central region of target plate increased with the increase of impact distance, while the opposite phenomenon occurred in the downstream area.
Experimental research progress in combustion of metal under microgravity
XU Peihui, LIU Jianzhong, YUAN Jifei, YANG Weijuan, ZHOU Junhu
2021, 36(8): 1633-1645. doi: 10.13224/j.cnki.jasp.20200378
Abstract FullText HTML PDF(6412KB) icon390 icon195
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The combustion characteristics of metal aerosols,particles,and rods in a microgravity environment were reviewed based on three typical microgravity experiment methods, including free fall, parabolic flight, and simulating microgravity flow field. The metals include magnesium, aluminium, titanium and so on. The influence mechanism of microgravity on metal combustion speed, flame structure, phase transition process, and unique combustion phenomena was introduced in detail. The advantages of the microgravity environment in revealing the inherent properties of metal combustion were described. The advantages and disadvantages of existing microgravity experimental system and the feasibility of simulating the microgravity flow field were summarized. Results showed that the researches on the inherent properties of metal combustion and the influence of weak effects were limited due to the costly and uncommon microgravity environment. It is suggested to further investigate the microgravity experimental methods,the influence of weak effects on the combustion characteristics of metals, and the microscopic influence mechanism of heat and mass transfer changes on combustion chemical reactions under microgravity.
Study on controlling liquid fuel spray combustion instability by multi-aperture perforated plate
LIU Zihua, ZHOU Hao, FANG Hao
2021, 36(8): 1646-1656. doi: 10.13224/j.cnki.jasp.20200478
Abstract FullText HTML PDF(6309KB) icon434 icon181
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The sound absorption characteristics of the multi-aperture perforated plate acoustic dampers with adjustable back cavities were studied. The sound absorption characteristics of the perforated plates were predicted via an acoustic model. The experiment was conducted to research the control effect of the perforated plates on the dynamic pressure and heat release rate in the chamber and plenum under a bias flow. The multi-aperture perforated plates had two apertures:the radius of the small holes was 1. 0 mm,and the radii of the large holes were 1. 5,2. 0,2. 5, 3. 0 mm, respectively. It was found that the sound absorption performance of perforated plates with large difference in aperture was not good. However, perforated plates with small difference in aperture had a significant attenuation effect on the thermoacoustic oscillations in the chamber. After installing the perforated plate, the pressure in the chamber was reduced by 59%-84%, the heat release fluctuation was reduced by 47%-87%,and the flame shape can be stabilized.
Structure, Strength and Vibration
On the vibration reduction performance of underplatform dampers considering parameter correlation
LI Lin, GAO Qian, WU Yaguang, FAN Yu
2021, 36(8): 1657-1668. doi: 10.13224/j.cnki.jasp.20200373
Abstract FullText HTML PDF(5527KB) icon439 icon142
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The correlation between principal parameters of wedge underplatform dampers (UPDs) was established to reveal the influence of these relevant parameters on the damping effect, and then to summarize the design guidelines considering parameter correlation. Based on the lumped parameter model of a two blades-UPD system which can describe the motion containing phase lag between blades,the steady state response of the system was simulated by the multi-harmonic balance method(MHBM), and the reduction of the resonance amplitude was used to quantify the damping performance. In order to improve the convergence and efficiency of the algorithm,the Jacobian matrix was deduced analytically. Results showed that it was necessary to consider the parameter correlation. The damper performance of wedge UPDs can be optimized to 4. 57% by choosing larger material density and appropriate wedge angles. Asymmetric wedge dampers can further improve the damping effect under excitation with phase lag.
Influence of small hole on thermal mechanical fatigue in single crystal superalloy DD6
JING Fulei, TANG Shibai, YANG Junjie
2021, 36(8): 1669-1679. doi: 10.13224/j.cnki.jasp.20200469
Abstract FullText HTML PDF(4552KB) icon389 icon276
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Mechanical strain -controlled thermal mechanical fatigue(TMF) tests under in-phase(IP) and out-of-phase(OP) cycles were performed on specimens with/without small hole made of nickel based single crystal superalloy DD6, and the impacts of stress concentration induced by small hole and phase shift between the mechanical strain and temperature on lifetime on crack initiation were studied. The results indicated that the life of the specimens with small hole whose cracks initiated at the location of maximum principal stress around the hole was one order of magnitude lower than that of smooth ones. Moreover,the OP life was lower than IP for specimens with small hole,which was consistent with that for specimens without small hole. The distribution and evolution of stress and strain in the specimens were obtained with the aid of numerical simulation with viscoplastic constitutive model based on slip systems. The correlation between the damage generated in single crystal superalloy under TMF loadings and the macro-/micro-parameters was identified. Based on the above-mentioned results, a new life model which could consider the effect of stress concentration and phase shift was proposed for the TMF life prediction. The predicted life of DD6 specimens with and without small hole under IP and OP TMF loadings was approximately within a factor 2 of the experimental life.
Application of ant colony algorithm in wide-chord fan blade sequencing optimization
XIE Li, LIU Zheng, ZHANG Jijun, LONG Changjiang, ZHANG Yong
2021, 36(8): 1680-1689. doi: 10.13224/j.cnki.jasp.20200476
Abstract FullText HTML PDF(1749KB) icon470 icon116
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Based on the mechanical model of the fan rotor, the formulas for the calculation of static unbalance and couple unbalance considering three-dimensional mass moment were deduced, the assembly and test result of a set of fan blades showed that this unbalance calculation method can significantly reduce the use of counterweight block and the times of balancing. An improved ant colony algorithm based on neighborhood search was proposed to optimize the sequencing of fan blades. The improved ant colony algorithm had an obvious superiority, its optimal unbalance was 88. 9% less than the conventional ant colony algorithm, and 36. 8% less than the improved genetic algorithm.
Dynamic strain reconstruction of rotating blade based on response transmissibility
ZHU Yuda, QIAO Baijie, FU Shunguo, AO Chunyan, CHEN Xuefeng
2021, 36(8): 1690-1701. doi: 10.13224/j.cnki.jasp.20200440
Abstract FullText HTML PDF(7936KB) icon538 icon208
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A dynamic strain reconstruction method of rotating blades based on response transmissibility was proposed. Based on the characteristics of system strain frequency response, an analytical expression of the strain-strain response transmissibility with respect to the modal shape was obtained within the frequency domain,and the mapping between the measured and unmeasured strains on the blade was established. Experiments for the blade dynamic strain measurement were conducted under the high-speed rotating condition. Then, the finite element model of the blade was established and updated by using the first four natural frequencies from experiments. The modal analysis of the rotating blades was conducted considering the prestress of rotational speed. The blade strain mode shapes were extracted from the finite element model and the strain-strain response transmissibility on single-mode resonance was calculated. Experimental results showed that the relative errors between the measured dynamic strains measured by strain gauges and the reconstructed dynamic strains based on the response transmissibility were less than 10%.
Interface failure analysis of thermal barrier coatings under CMAS penetration
ZHANG Zifan, HAN Yandong, WANG Weizhe, CAI Zhenwei
2021, 36(8): 1702-1711. doi: 10.13224/j.cnki.jasp.20200374
Abstract FullText HTML PDF(6172KB) icon405 icon126
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Influences of different calcium, magnesium, aluminum, silicon and other oxides(CMAS) penetration depths under the influences of temperature gradients and the influences of the interface roughness on the interface temperature distribution under CMAS penetration were considered based on the influences of penetration on the properties of the ceramic layer of the thermal barrier coating(TC). The influences of thermally growth oxide(TGO) thickness and interfacial stress behavior were also studied. The results showed that the penetration of CMAS increased the thermal conductivity of the ceramic layer, which further increased the interface tem-perature, the thickness of TGO, and also made the stress state of the interface more serious. The increase of the interface roughness led to an increase in the temperature difference between the peaks and valleys of the interface, the uneven growth of the interface TGO, and finally caused the change of the stress distribution of the interface.
Aerothermodynamics and Aeroengine Design
Noise reduction technology in test section of continuous transonic wind tunnel
CHEN Jiming, LÜ Jinlei, LIAO Daxiong, WU Shenghao, PEI Haitao, SHI Zhiwei
2021, 36(8): 1712-1719. doi: 10.13224/j.cnki.jasp.20200375
Abstract FullText HTML PDF(3796KB) icon402 icon129
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According to the acoustic experimental conducted in the 0. 6m continuous transonic wind tunnel of CARDC(China Aerodynamics Research and DevelopmentCenter), the noise generation process in test section and the propagation process in tunnel circuit were researched. Acoustic treatments were performed on both the compressor rear cone and the fourth corner to prevent the emitted noise from propagating forward. Meanwhile the wind tunnel was running with second throat throttling to suppress the downstream noise. With those effective means to reduce the circuit noise, the optimization design of active noise reduction schemes with different ventilation wall types and different design parameters was carried out, then an excellent design for the test section wall was achieved. The wind tunnel pressure fluctuation coefficient reached the target of less than 0. 8%,the advanced international level.
Ground vortex distortion flow characteristics of inlet for a transport aircraft
ZHAO Haigang, LIU Yu, WANG Junqi, YANG Liu, REN Dingding
2021, 36(8): 1720-1728. doi: 10.13224/j.cnki.jasp.20200429
Abstract FullText HTML PDF(10696KB) icon319 icon172
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Based on idle and engine driving of a military transport aircraft equipped with a large bypass ratio turbofan engine in unpaved runway ground,a full-scale three-dimensional simulation model was established, By means of numerical simulation, the ground vortex distortion flow characteristics under different wind speed, wind direction and running speed were studied. The result showed that the ground vortex intensity first increased and then decreased under the 270 degree crosswind condition. The ground vortex intensity was maximal under wind speed range from 2 m/s to 4 m/s. The ground vortex disappeared when wind speed was more than 6 m/s. The ground vortex intensity was maximal and it had strongest suction capacity to foreign objects at 210 degree wind direction under the wind speed of 3 m/s. Also it had greatest influence on the inlet's outlet flow field. The ground vortex intensity and scope was weak under the condition of aircraft running compared with stationary,headwind.
Transonic natural laminar flow nacelle optimization design at high Reynolds number
CAO Fan, HU Xiao, ZHANG Meifang, TANG Zhili
2021, 36(8): 1729-1739. doi: 10.13224/j.cnki.jasp.20200459
Abstract FullText HTML PDF(4454KB) icon344 icon144
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To solve the problem of high-dimensional optimization design of laminar flow nacelle with large bypass ratio under high Reynolds number,three datum planes of nacelle were extracted to realize the optimal design of axisymmetric natural laminar flow.A wide range of laminar flow was obtained to reduce the surface friction resistance of the nacelle. An optimization system for the natural laminar flow(NLF) nacelle was established in combination with class and shape transformation (CST) parameterization, γ-Reθt transition model and the genetic algorithm. It showed the feasibility of establishing a three-dimensional NLF nacelle design method by optimizing the nacelle datum plane.Then, a three-dimensional non -axisymmetric NLF nacelle was constructed through the secondary development of CATIA, which solved the problem of efficiently importing a large number of data points and surface generation after the datum plane optimization. For the designed three-dimensional non-axisymmetric NLF nacelle,a transition sensitivity analysis of the angle of attack,sideslip angle,incoming Mach number,and turbulence intensity near the design point was conducted. The results showed that:under the condition of transonic speed,the laminar flow range decreased with the increase of the angle of attack; the laminar flow range increased with the increase of incoming Mach number; the sideslip angle and turbulence intensity had little effect on the laminar flow range.
Aerodynamic performance for bionic drag-reducing airfoil
ZHANG Ziliang, ZHANG Mingming
2021, 36(8): 1740-1748. doi: 10.13224/j.cnki.jasp.20200485
Abstract FullText HTML PDF(2193KB) icon487 icon183
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By adopting a bionic riblet model based on the slip-boundary theory, the aerodynamic performance for the bionic drag-reducing airfoil was numerically investigated. The results suggest that the total drag of the bionic drag-reducing airfoil could reduce by 1.73%-3.07% and the lift-drag ratio could increase by 2.10%-4.08% when riblets are applied in turbulence regions of both pressure and suction surfaces.The main reason for the total drag reduction was attributed to the decrease of the viscous drag.Flow field analysis indicated that the velocity profile of the bionic drag-reducing airfoil had an uplift compared with the smooth airfoil,resulting in an increase of the viscous-sublayer thickness.The aerodynamic performance was then improved.
Power Transimission
Three degree of freedom visualization experimental device of GMA oil film bearing
YIN Xuemei, JI Shuaicheng, WU Chao, MA Mingfei, ZHANG Shaolin
2021, 36(8): 1749-1755. doi: 10.13224/j.cnki.jasp.20200380
Abstract FullText HTML PDF(12102KB) icon318 icon181
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A three-degree-of-freedom visual experimental device for a controlled oil-film bearing with giant magnetostrictive actuators(GMA) was presented. The basic structure,working principle and adjustment method of the experimental device were introduced. A turbo-wormscrew drive mechanism was used to adjust the vertical height of the experimental spindle. And a cross sliding table,GMA and a mold spring were adopted to adjust the position of the experimental bearing on the horizontal plane. It was convenient to change the eccentricity of the experimental bearing and to control the bearing seat by using a GMA to reduce the vibration of the rotor. The pressure and temperature of the oil film of the elliptic bearing were measured on the adjusted experimental bench. Adjustment experiments of static balance position of the rotor supported by the elliptic bearing were also carried out. Results showed that it was obvious to change the static balance position of the rotor system by controlling the short axis oil film of the elliptical bearing. The experimental device can be used to conduct experiments such as axis trajectory acquisition, rotor power frequency vibration control,formation and fracture observation of oil film and cavitation with rotating speed between 0~10 000 r/min,laying a certain foundation for the subsequent experiments on the dynamic performance of GMA oil film bearing.
Analyse bending fatigue strength test of cylindrical gear of third-generation aviation gear steel
TANG Xin, ZHU Rupeng, LIAO Meijun, XIONG Xingbo, TANG Peng
2021, 36(8): 1756-1764. doi: 10.13224/j.cnki.jasp.20200559
Abstract FullText HTML PDF(5089KB) icon580 icon224
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Taking the third-generation aviation gear steel gear as the research object, the bending fatigue test of the cylindrical gear made of this material was carried out. The cylindrical gear for bending fatigue test was designed, and the calculation formula of the GB standard gear bending fixture was revised. The bending fatigue test was carried out for the gear of the material. The experimental data were analyzed, and the log -normal distribution and two -parameter Weibull distribution data processing methods were used to fit the data. The bending fatigue limit and R-S-N curve of the test gear were obtained. The performance of test gears and 9310 steel gear was compared and analyzed. The results showed that under the condition of 95% confidence degree and 99% reliability, the bending stress limit of 9310 steel gear was 602 MPa and the bending stress limit of the third-generation aviation gear steel gear was 687. 6 MPa. The bending fatigue performance of the third-generation aviation gear steel gear was 14. 2% higher than that of the 9310 steel,presenting great advantage in aviation gear transmission.
Influence of error on static load-sharing performance of coaxial six-branch twist herringbone gear transmission system
LI Zhibin, WANG Sanmin, LI Fei, LI Linlin, PENG Qi'an, WANG Weikang
2021, 36(8): 1765-1775. doi: 10.13224/j.cnki.jasp.20200423
Abstract FullText HTML PDF(6046KB) icon357 icon95
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The static equilibrium equation of the system is fulfilled based on the stress state of each gear with coaxial six-branch twisted herringbone gear transmission system as the research object. Considering the manufacturing error,installation error and dislocation caused by input and output wheel floating, the existence of error is analyzed based on the theory of equivalent meshing error. The system deformation coordination equation is established according to the closed characteristics of system power. The static load coefficient and branch static load coefficient of coaxial six-branch herringbone gear transmission system are obtained by examples. The results showed that when there was no error or the gear error was the same constant value, the static meshing force of the first grade gear was 1. 773×105 N and the second grade gear was 3. 673×105 N. The system has good static load-sharing performance and the system branch static load-sharing coefficient was 1, and the closed loop error of the system can be eliminated from each other. When the amplitude of manufacturing and installation error was 50 μm at the same time,the variation amplitude of branch static load coefficient under manufacturing error was larger than that under installation error,and it can be seen that the manufacturing error had a great influence on the static load performance of the system. When the amplitude of partial torsion and parallel error was 50 μm at the same time,the static load-sharing per-formance of parallel level at the two-stage transmission system was more easily affected by the error than the torsion level, so the output member should have a floating amount. To sum up, with the increase or decrease of the system error, it would have a bad effect on the static load-sharing performance of the system. The research results can provide scientific basis for the determination of manufacturing error and installation error accuracy of coaxial reducer transmission system and the de-termination of average load coefficient.
Turbomachinery
Analysis of dynamic characteristics of sand particles in air intake and compressor cascade of aero-engine
XU Qiannan, HU Feng, XIAO Youhong, ZHANG Hai
2021, 36(8): 1776-1782. doi: 10.13224/j.cnki.jasp.20210803
Abstract FullText HTML PDF(10204KB) icon632 icon206
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In order to improve the sand swallowing and sand control capabilities of the aeroengine, it is necessary to understand the law of sand movement in the engine and its impact on engine performance. The Euler-Lagrangian method was used to analyze and calculate the coupling effect of sand particles and airflow on the E3 engine fairing,fan and supercharger stage,and the particle collision model and erosion model were added. The simulation analysis results showed that the sand movement trajectory and erosion area conformed to the engine usage law. The sand particles entered the engine and collided with the pressure surface of the fan blades, and most of the sand particles entered the outer culvert flow channel after the collision. The collision position of sand particles was mainly concentrated at the pressure surface of the fan blades. The fan had the most significant influence on the particle movement trajectory. The particles after collision had an obvious radial movement trend, and the particle concentration in the tip area was relatively high. The fairing,the pressure surface of the fan blades and the wall of the outer casing all had serious sand erosion,while the sand erosion of the booster stage blades was not obvious.
Leakage characteristics and formula establishment of nonmetallic labyrinth seal based on fluid-solid-thermal coupling
ZHOU Min, SUN Dan, ZHAO Huan, ZHI Qiang, ZHANG Guochen
2021, 36(8): 1783-1792. doi: 10.13224/j.cnki.jasp.20200467
Abstract FullText HTML PDF(3715KB) icon557 icon291
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Fluid-solid-thermal coupling numerical model of nonmetallic labyrinth seal leakage characteristics was established considering the deformation of tooth.The flow field, structure mechanical characteristics and leakage characteristics of polyether ether ketone (PEEK),30% carbon fiber-filled reinforced polyether ether ketone (PEEK-CA30) and aluminium alloy in three kinds of material labyrinth seal under different pressure ratios and temperature were studied on the basis of the validation to solve the model accuracy,and based on the formula for Vermes,the nonmetallic labyrinth leakage theory formula was constructed considering the deformation of tooth. The results showed that the fluid-solid-thermal coupling model of labyrinth seal can accurately calculate the deformation of nonmetallic seal teeth and the leakage rate. Among the three materials studied, PEEK-CA30 material had relatively small deformation of sealing teeth, accounting for 0.35%-0.67% of radial length of sealing teeth.Its sealing performance was good,and compared with the leakage rate without considering deformation of teeth,it only increased by 1.2%-6.8%. When the pressure ratio was more than 3 and the temperature was higher than 500 K,the equivalent stress of the seal teeth using aluminium alloy material reached the yield limit of the material, leading to the failure of the seal.The theoretical formula of leakage rate can accurately predict the leakage rate of nonmetallic labyrinth seal considering deformation of tooth,providing a theoretical basis for analysis of the leakage characteristics of nonmetallic labyrinth seal.

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