2016 Vol. 31, No. 9

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Temperature field test for aeroengine combustor with five nozzles based on gas analysis
WANG Ming-rui, XIAO Yang, HAN Bing, LI Ya-juan, JIA Lin-yan, MA Zheng
2016, 31(9): 2049-2054. doi: 10.13224/j.cnki.jasp.2016.09.001
Abstract PDF(884KB) icon1352 icon773
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Sampler and gas analysis system were introduced for temperature field of aeroengine combustor, and error was analyzed as a result of gas system simplification. Method of computing combustion temperature was expounded, the average of combustion efficiency and combustion temperature and fuel-air ratio was computed. The temperature field for combustor with five nozzles by gas analysis and thermocouple was analyzed, indicating that combustion efficiency by thermocouple was 4% less than that by gas analysis, and combustion temperature was 55℃ lower at 1500℃. Gas analysis was proven to be dominant in measuring high temperature gas from aeroengine combustor. High quality data can be gained by gas analysis, which is hardly influenced by environment.
Combustion reaction mechanism of three-component simulation surrogate fuel for RP-3 kerosene
LIU Yu, ZENG Wen, MA Hong-an, CHEN Bao-dong
2016, 31(9): 2055-2064. doi: 10.13224/j.cnki.jasp.2016.09.002
Abstract PDF(1037KB) icon1620 icon693
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A kind of combustion reaction mechanism of surrogate fuel was developed, including 65% n-decane, 10% toluene and 25% propyl cyclohexane for RP-3 kerosene. The mechanism consisted of 150 species and 591 elementary reactions. The ignition and combustion characteristics of surrogate fuel at various conditions were simulated by this reaction mechanism, and the simulation results were compared with those of another one-component surrogate fuel (n-decane) and the experimental data, respectively. Results show that the chemical reaction mechanism of three-component surrogate fuel can accurately calculate the ignition and combustion characteristics of RP-3 kerosene. The calculation deviation of the ignition delay time can be controlled within 5%, and the calculation error of the laminar burning velocity can be controlled within 10%, better than those of n-decane. The combustion reaction mechanism of three-component surrogate fuel was also modified by sensitivity analysis, showing that the calculation error of the laminar burning velocity was improved from 10% to 5%. This means the modified mechanism can predict the ignition delay time and laminar burning velocity of RP-3 kerosene better.
Numerical investigation of shaped-hole film cooling on turbine rotor blade
ZHU Xing-dan, ZHANG Jing-zhou, TAN Xiao-ming, GUO Wen, SU Yun-liang
2016, 31(9): 2065-2072. doi: 10.13224/j.cnki.jasp.2016.09.003
Abstract PDF(1462KB) icon1373 icon667
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Numerical simulations were conducted to investigate the shaped-hole film cooling on the pressure side of a turbine rotor under engine operating conditions, including the effects of blowing ratio and rotational Reynolds number. Results showed that the film jet was deflected towards the blade tip subjecting to the combined influences of centrifugal force and Coriolis force under rotational conditions, due to the change of the film vortex structure. The film jet was deflected towards the blade tip more sharply with the increase of rotational Reynolds number. The laterally-average cooling effectiveness slightly improved owing to more uniform film coverage. In the same rotational speed, the fan-shaped hole and console hole enabled to effectively restrain the film separation with high blowing ratios compared with the cylindrical hole. The laterally-average cooling effectiveness monotonously decreased downstream and increased with the blowing ratio. Besides, the film jet bent to the tip more notably with a small blowing ratio. As a result, the fan-shaped hole and console hole still have a pronounced advantage over the cylindrical hole under rotational conditions.
Effect on working characteristic of fuel injection pump in aircrafts of temperature
SHAO Lei, LIU Wei-hua, PAN Jun, LIU Wen-yi, FENG Shi-yu
2016, 31(9): 2073-2079. doi: 10.13224/j.cnki.jasp.2016.09.004
Abstract PDF(912KB) icon1194 icon636
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A mathematical model of the injection pump was set up and its working characteristic was simulated using numerical computation method, the experiment apparatus was constructed and RP-3 fuel was adopted as the working fluid to verify the validity of this model. The flow ratio under various operating pressures was calculated from -40 degree to 40 degree by employing RP-3 fuel and JET-A fuel as working fluids, respectively. Result shows that if the fuel's temperature is above 0 degree, the effect of the fuel temperature on the working characteristic of injection pumps can be ignored. However, with the decrease of the temperature, the deviation of the performance with that at standard temperature(20 degree) increases definitely, especially the pressure ratio is high. When the temperature is above 0 degree, the performance of injection pump using RP-3 fuel is slightly better than that using JET-A fuel, but if the temperature is extremely low, the performance using RP-3 fuel is much better than that using JET-A fuel. It can be concluded that when the temperature is low and the pressure ratio is high, the effect caused by the temperature on the performance of injection pump should be considered carefully.
Influence of chamber length on rotating detonation engine performance
SUN Jian, ZHOU Jin, LIN Zhi-yong, LIU Shi-jie
2016, 31(9): 2080-2086. doi: 10.13224/j.cnki.jasp.2016.09.005
Abstract PDF(945KB) icon1304 icon693
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Numerical simulations using single step chemical model were carried out to investigate the influence of chamber length on rotating detonation engine (RDE) with an equivalence ratio of 1.0. By analyzing the gas condition parameters of chamber inlet and outlet, the internal mechanism of the influence of chamber length on RDE performance was revealed clearly. The results show that when the chamber length is too short, the detonation wave is not fully formed; the momentum thrust is the main part of thrust; within the range of chamber lengths simulated, the specific impulses are 5410-5566s, thus the chamber length has little effect on RDE performance.
Envelope protection method for pitch attitude holding mode under flight icing conditions
WANG Xiao-long, XUN Hao-jun, XUE Yuan, ZHU He-quan, PEI Bin-bin
2016, 31(9): 2087-2094. doi: 10.13224/j.cnki.jasp.2016.09.006
Abstract PDF(1005KB) icon1378 icon639
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An envelope protection method with autopilot systems was proposed based on the research of wing stall and tailplane stall under icing conditions. The angle of attack was identified as a critical parameter, and the pitch angle was identified as a command parameter. The detection of hinge moment coefficient could early warn aircraft stall and increase the margin of envelope protection. The flight longitudinal dynamics equation in pitch attitude holding (PAH) mode was built. Results show that, the envelope protection system works at the 2 degrees before the stall angle of attack through the detection of hinge moment under icing conditions, increasing the flight safety margin. With the control command limitation, the angle of attack of the automatic flight under icing conditions could be limited to the stall angle of attack.
Effects of sleeve mixing length of swirl cup on the ignition characteristics
KANG Yao, LIN Yu-zhen, JIANG Yao, WANG Xiao-feng
2016, 31(9): 2095-2103. doi: 10.13224/j.cnki.jasp.2016.09.007
Abstract PDF(1315KB) icon1656 icon1629
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A research was performed done to study the effect on the ignition performance by the too long mixing length of sleeve. Two variations of sleeve mixing length were made to test the ignition performance using a single module test combustor under normal temperature and atmospheric pressure. Melvin was used to test the spray particle size, and the software Fluent was used to analyze the experimental results. The research results show:the hardware geometry of sleeve mixing length has a great influence on the flow fields, and spray distributions of the dome. The spray drops will impact on the wall of sleeve when the mixing length of sleeve is long enough, and the radial movement of swirl jets and spray drops will be confined, leading to the decrease of spray cone angle by 32% and the increase of fuel air ratio(FAR) of lean ignition about 20%.
Aeroacoustic and flow field features of ultrasonic atomizer based on Hartmann resonance tube
RUAN Can, HUANG Yue, CAI Jiang-qian, LIU Chen, XING Fei
2016, 31(9): 2104-2114. doi: 10.13224/j.cnki.jasp.2016.09.008
Abstract PDF(1744KB) icon1281 icon649
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Experimental and numerical studies were carried out to investigate the effects of operation parameters, such as diameter of resonance tube, resonance tube depth, jet nozzle hole to resonance tube spacing and nozzle pressure ratio(NPR), on the flow and acoustic field characteristics of a ultrasonic atomizer based on the Hartmann resonance tube(HRT). The modifications of the geometry of HRT in spectral and flow field characteristics were studied in detail. Result shows that that,when NPR is higher than 2, the increase of NPR has little effect on the frequency, however, when NPR is lower than 2, the lower frequencies of the acoustic field are obtained. The simulation results of flow field suggest that when the length of the resonance tube is smaller than diameter of jet nozzle hole, the reciprocating phenomenon of flow in the cavity is dampened, leading to a decrease of acoustic field frequency compared with cases having longer resonance tube length, and the classical relation between acoustic field frequency and tube resonance length is not appropriate for these situations. Also, the oversized diameter of resonance tube (typically,the diameter of resonance tube more than 1.75 times the diameter of jet nozzle hole) results in a lower oscillation acoustic field frequency for the interaction of the reciprocating and the shock is weakened. Furthermore, resonance occurs when the cavity is put in the regions where pressure arises for free jet.
Effect of width of skirted mixer on performance of mixing diffuser with par-allel intake
LIU You-hong, CHEN Zhong-yuan, XU Hua-sheng, ZHONG Shi-lin, HUANG Yi-yong, XIE Jian-guang
2016, 31(9): 2115-2123. doi: 10.13224/j.cnki.jasp.2016.09.009
Abstract PDF(1180KB) icon1067 icon606
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In order to clarify the effects of width of skirted mixer on flow field, streamwise vorticities, thermal mixing efficiency, total-pressure recovery factor,average speed and speed factor as well as temperature evenness of outlet of mixing diffuser, different widths of skirted mixer were studied quantitatively through the three-dimensional numerical simulations based on Navier-Stokes(N-S) equations, and the principle of effects on aerothermodynamic performance was obtained. Results show that, when width of skirted mixer varies from 40mm to 130mm, stream-wise vorticities increase at the outlet of mixing diffuser with the growing width, and the flow mixing of internal and external bypass can be promoted. Thermal mixing efficiency firstly increases and then decreases as the width increases, and the total-pressure recovery coefficient linearly decreases as the width increases generally. The average speed and speed factor of outlet of mixing diffuser linearly decrease as the width increases, and the temperature evenness of outlet of mixing diffuser increases with the growing width.
Optimization design of two dimensional convergent and divergent nozzles' profile based on surrogate models
SHI Xiao-juan, JI Hong-hu
2016, 31(9): 2124-2131. doi: 10.13224/j.cnki.jasp.2016.09.010
Abstract PDF(916KB) icon1456 icon703
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Based on the influence research of design parameters on the aerodynamic performance of two dimensional convergent and divergent (2D-CD) nozzle, the optimization design of 2D-CD nozzles' profile was conducted. The goal of optimization design was to get thrust coefficient as high as possible. The design variables of optimization design were throat aspect ratio, throat radius ratio, convergent half angle, divergent half angle. In the design process, the initial sample points were selected using the orthogonal experiment design method, then the Kriging surrogate model of thrust coefficient for design parameters was established. The analysis and optimization was conducted with the Adaptive Simulated Annealing Algorithm (ASA). The results show that when the throat aspect ratio is 6, throat radius ratio is 0.3, convergent half angle is 15°, divergent half angle is 5.64°, the maximum thrust coefficient of the 2D-CD nozzle is 0.97847, and the flow coefficient is 0.98778.
Investigation on the performance of a supersonic inlet with diversing flow control on the exit
WEN Yu-fen, YAN Jia-min, CHEN Hao, MA You-lin
2016, 31(9): 2132-2139. doi: 10.13224/j.cnki.jasp.2016.09.011
Abstract PDF(1037KB) icon1730 icon647
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Due to the flow separation induced by the severe curved shape of the inlet, a flow-control method based on the diversing flow grid was brought forward. Three different diversing flow grids were designed and a comparison of the supersonic inlet performance was conducted with a computational fluid dynamics method. Effects on the flow structure and working performance of the inlets with different diversing flow grids were attained. Results indicate that taking the grid as the flow control measure could avoid flow separation on the exit of the inlet by improving the flow structure and pressure distribution of the curved duct. It is proven that the performance of the inlet could be obviously improved by optimizing the diversing grid. Stability and total pressure recovery coefficient of the inlet with adoption of the airfoil shape grid could be raised by 10.3% and 9.8% at utmost while its interior resistance could be reduced by 5.3% at Mach number of 3.5.
Wind tunnel side wall boundary layer control based on vortex generator
LIU Guang-yuan, WANG Rui-bo, DENG Ji-long, CHEN Hong-tao
2016, 31(9): 2140-2145. doi: 10.13224/j.cnki.jasp.2016.09.012
Abstract PDF(972KB) icon1388 icon686
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Combined with former numerical simulating results, vortex generators applicable for 2.4m transonic wind tunnel half-model test section were designed and validated to reduce side wall boundary layer effect. Results show that 20%-30% boundary layer thickness is reduced using trapezia-shaped flat vortex generators in subsonic conditions, and the influence on flow field uniformity is neglectable. The decrease of zero-lift drag and increase of lift-slope are found after vortex generators installation, meanwhile pressure center moves toward fuselage. Both trends are distinct evidence of thinner boundary layers. The developed vortex generators can be applied to half-model tests for subsonic conditions.
Investigation of rod-airfoil interaction noise using large eddy simulation and FW-H equation
CHEN Wei-jie, QIAO Wei-yang, WANG Liang-feng, XU Kun-bo, TONG Fan
2016, 31(9): 2146-2155. doi: 10.13224/j.cnki.jasp.2016.09.013
Abstract PDF(1328KB) icon1278 icon657
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Large eddy simulation (LES) and Ffowcs Williams-Hawkings (FW-H) equation were used to investigate the spectral characteristics of the rod-airfoil interaction noise and the influence of the quadrupole source. The flow field prediction was in good agreement with experiment data, and the spectral shape of the acoustic radiation was consistent with experiment results. The front 30% chord length at the leading edge of the airfoil is the main interaction noise source. For the reason of the different span-wise length between simulation and experiment, a new group of formulas was derived based on the hypothesis of trigonometric correction function and the results were compared with the rectangular, exponential and Gaussian functions. The correction deviation for different correction methods is as large as 7.6 dB. The correction effect of the trigonometric function is similar to the rectangular function and better than Gaussian function, whilst the exponential function has the poorest correction effect. Solid wall surfaces and permeable data surfaces were used for acoustic calculation to investigate the effect of quadrupole source. The results show that the impact of quadrupole source is negligible at low Mach number.
Ionization effects on aerodynamic heat for vehicle in hypersonic rarefied flow
QU Cheng, WANG Jiang-feng
2016, 31(9): 2156-2163. doi: 10.13224/j.cnki.jasp.2016.09.014
Abstract PDF(1000KB) icon1421 icon558
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Effect of ionization reaction on aerodynamic heat characteristics for vehicle in hypersonic rarefied flow was studied by using direct simulation Monte Carlo (DSMC) method in which ionization reaction model was added. For the actual difficulties added by electron in rarefied flow, a bundling method was used to deal with electron motion. The ionization reaction model and the processing method of ionization reaction were presented. Firstly, taking the example of shape of RAM-C Ⅱ vehicle, DSMC code with addition of ionization reaction was validated. Then, a numerical experiment was made to investigate the effects of ionization reaction on aerodynamic heat characteristics of the Stardust blunt body at different altitudes by use of 5 species gas model(without ionization) and 11 species gas model(with ionization) in chemical non-equilibrium flow. The results show that the treatment scheme proposed can simulate ionization reaction for hypersonic rarefied flow. At 60km altitude, ionization reaction effect on the aerodynamic heat characteristics becomes the strongest, reducing heat flux at stagnation point by 5.12%,and the effect decreases with the increase of the rarefied content of gas.
Reconstructing technique of forebody shock system andits applicationin hypersonic inlet
LI Cheng-hong, TAN Hui-jun, NING Le, LI Guang-sheng
2016, 31(9): 2164-2170. doi: 10.13224/j.cnki.jasp.2016.09.015
Abstract PDF(923KB) icon1256 icon609
Abstract:
A reconstructing technique for the forebody shock system of hypersonic vehicles was proposed. The flow mechanism and the control law of the technique were investigated numerically. The application of the technique in the variable hypersonic inlet with fixed geometry was also explored. The results showed that the first ramp shock was deflected outward effectively and the second ramp shock was weakened and even eliminated when the controlling activity was employed, indicating the forebody shock system was reconstructed entirely. The required secondary mass flow to drive the first ramp shock to the shock-on-lip condition decreased with the increase of the injection angle. The shock-on-lip condition can be maintained within the operating Mach number range of 5 to 6 at a maximum secondary flow ratio of 2.04%. Furthermore, as compared with the variable inlet using previous fluidic shock control technique, the required secondary mass flow ratio of the newly developed variable hypersonic inlet is less and the total pressure recovery at the exit of the inlet is higher.
Analysis on damping effect of dry friction damper under wideband multi-harmonic excitation
LI Lin, LIU Jiu-zhou, LI Chao
2016, 31(9): 2171-2180. doi: 10.13224/j.cnki.jasp.2016.09.016
Abstract PDF(1110KB) icon1201 icon579
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The key points of multi-harmonic balance method, time-marching procedure of obtainning the friction force in time domain and alternating frequency-time (AFT) domain procedure were introduced. The analysis on damping effect of under-platform damper in aero-engine was investigated using a multi-harmonic balance method combined with an AFT domain procedure, showing that this method is precise and its computational efficiency is much higher than the direct integral method. Influence of the number of harmonics on forced response indicates that more harmonic components should be kept when investigating the damping effect of under-platform damper in aero-engine under wideband multi-harmonic excitation. The optimal normal contact loads of the resonant peaks induced by various excitation frequencies are different; in practice, the design parameters of the friction damper should be optimized in line with the frequency components of excitation and the requirement of vibration attenuation to obtain the minimum response in the whole frequency range.
Impact factors to friction characteristics of space lubricating oil No.4116
WANG Yan-shuang, LI Gang, CHENG Jun-wei
2016, 31(9): 2181-2187. doi: 10.13224/j.cnki.jasp.2016.09.017
Abstract PDF(919KB) icon1143 icon553
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Friction coefficients of a space lubricating oil No.4116 were experimented on the ball-on-disc experiment rig at various operating conditions, especially in high and low temperature conditions. The influences of rolling speed, sliding speed, the maximum working pressure and oil inlet temperature on friction coefficient were researched by adopting the orthogonal experimental design method. The curves of the friction coefficient versus each impact factor were plotted respectively. The research results show that the sliding speed and rolling speed have significant influence on the friction coefficient, while the oil inlet temperature and the maximum working pressure have only a certain influence on the friction coefficient. The friction coefficient of the oil increases with the increase of the sliding speed but the increase amplitude becomes smaller and smaller. When the rolling speed increases, the friction coefficient decreases quickly until the rolling speed exceeds 20m/s and finally keeps at a stable value. The oil inlet temperature below 0℃ has a bigger influence on the friction coefficient. The friction coefficient increases slowly with the increase of the maximum working pressure.
Application of cyclic symmetry property in transient response solution of mistuned bladed disks
YAO Jian-yao, XIN Jian-qiang, WANG Jian-jun
2016, 31(9): 2188-2194. doi: 10.13224/j.cnki.jasp.2016.09.018
Abstract PDF(930KB) icon1258 icon571
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Theory and algorithm for using cyclic symmetry property to calculate transient response of mistuned bladed disk was presented. The mistuning parts were moved to the right-hand side of the equations of motion, and were treated as the nonlinear excitation force of the corresponding tuned bladed disk. Therefore, the mistuned problem was transformed to a nonlinear tuned one, and could be solved using only one sector of the bladed disk. The iterative and prediction-correction time-marching schemes were proposed to handle the nonlinear mistuning force, and were validated using a single degree of freedom(DOF) model. A simplified mistuned bladed disk finite element model was used as the numerical example to validate the effectiveness of the proposed method. Result shows that,the number of DOF is reduced from 3888 to 324 by using the cyclic model, and it only takes 2-3 iterations to obtain the converged solution for each time step. The response results obtained using full model and cyclic model agree very well with the maximum amplitude error of 0.14%.
Probabilistic risk assessment method for turbine disk
SUN Yang-hui, YANG Kun, HOU Nai-xian, CHEN Jian, BAI Guo-juan
2016, 31(9): 2195-2202. doi: 10.13224/j.cnki.jasp.2016.09.019
Abstract PDF(957KB) icon1228 icon572
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For the turbine disk probabilistic risk assessment requirement of CCAR 33.70 airworthiness regulation, the applications of response surface method used in definition of failure zone and estimation of crack growth life were studied. A method of variance reduction of sampling and improving sampling efficiency was demonstrated based on the response surface method to allocate the failure sampling zone during Monte Carlo simulation. It was shown that importance sampling method could significantly improve sampling efficiency:samples rate between failure samples and total samples was 94% by importance sampling method, bigger than traditional direct sampling method (only 33%). The importance sampling method can minimize the total number of samples required to achieve a desired analysis accuracy results. In addition, the life approximation function by response surface method was presented to significantly reduce the computation time of crack growth life:computation time for 104 samples was only 2 minutes by using life approximation function, which was much shorter than traditional life model (288 min). The life error analysis showed that the maximum error was only 1.0%, which had good agreement with traditional method of crack growth life. These results can be applied to improve the efficiency of turbine disk probabilistic risk assessment.
Stiffness modification and dynamic modeling of a rod fastening rotor
LU Ming-jian, SUN Yan-hua, ZHOU Jian, ZHAO Shi-quan, GENG Hai-peng, WANG Wei-ming
2016, 31(9): 2203-2209. doi: 10.13224/j.cnki.jasp.2016.09.020
Abstract PDF(987KB) icon1107 icon619
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In order to analyze the rotor dynamics of a rod fastening rotor and compare its differences with the integral rotor, a model based on lumped parameter method was proposed. By modification of the stiffness of the beam element, the effects of contacts between the disks, pre-stresses in the disks produced by the axial preload and the rods can be considered. Firstly, the effects of the three factors on the stiffness of the beam in static were analyzed, and the modified coefficients were obtained. The results show that, contacts and rods compared with the pre-stresses in the discs had relatively large effects on the dynamics of the rod fastening rotor. Then the modification coefficients for each beam element of an experimental rod fastening rotor were calculated and the dynamic model of the rotor was established. The critical speeds were calculated and agreed well with the experimental results. The error was just 0.8%, validating the method proposed. The results are very useful in dynamics analysis and design of other combined structures.
Magnetic field analysis and optimization of giant magnetostrictive electro-hydrostatic actuator
YANG Xu-lei, ZHU Yu-chuan, FEI Shang-shu, JI Liang, GUO Ya-zi
2016, 31(9): 2210-2217. doi: 10.13224/j.cnki.jasp.2016.09.021
Abstract PDF(1255KB) icon1130 icon554
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A structure of giant magnetostrictive electro-hydrostatic actuator (GMEHA) was designed. The control coil was combined with permanent magnet to provide driving magnetic field. Mathematical model of the magnetic circuit was established, and the analytical calculation of magnetic flux density inside giant magnetostrictive rod was performed. Secondly, finite element analysis (FEA) for the above structurewas conducted, and the mapping principle between the main parameters of the structure and the magnetic field uniformity was got. Finally,the study of actuator magnetic field experiment was conducted, the result of the study was compared with the result of FEA, verifying the predictability of theory and finite element model, then the structure design method of this electro-hydrostatic actuator was presented. Results show that the maximum no-load output volume flow is 0.85 L/min around 250 Hz of the best driving frequency, while the maximum blocked force was close to 120N.
Sand erosion damage test on TC4 titanium alloy and TiN/Ti multilayer coating
CAO Xin, WANG Guan, HE Wei-feng, ZHANG Yi-fei, HE Guang-yu, YANG Zhu-fang
2016, 31(9): 2218-2225. doi: 10.13224/j.cnki.jasp.2016.09.022
Abstract PDF(1609KB) icon1305 icon569
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A sand erosion test system was set up. The relationship between gas pressure and sand particle velocity was obtained by using particle image velocimetry method, and the erosion performance of TC4 titanium alloy and TiN/Ti multilayer coating was tested at the condition of sand concentration 28.91g/m3, sand particle velocity 80m/s, and impact angle 30°. The results show that, the anti-erosion performance of TC4 titanium alloy is poor with average mass loss rate about 0.7mg/min. TiN/Ti multilayer coatings can withstand sand erosion more than 200 minutes. TiN/Ti multilayer coating with modulation ratio of 1:3 is superior to that with the modulation ratio of 1:1 on the anti-erosion performance. Micro-spalling caused by the vertical impact component of sand particle velocity is the main reason for erosion damage of coating. Therefore, the key to improve anti-erosion performance of multilayer coating is enhancing the toughness.
Cross-sectional feature parameters extraction of blade based onunorganized point cloud
LIU Shu-gui, MAO Chen-li, ZHANG Hai-tao
2016, 31(9): 2226-2232. doi: 10.13224/j.cnki.jasp.2016.09.023
Abstract PDF(825KB) icon1181 icon541
Abstract:
According to the practical requirements for extracting the cross-sectional feature parameters of aircraft engine blade, algorithms based on unorganized point cloud were studied. For the point cloud sorting, the distance-dichotomy based on rectangular corrosion was presented in consideration of the advantages of distance method and dichotomy. The approach based on minimum contain regional linear fitting and least square circle approximation was proposed for partitioning automatically the cross-sectional data of blade into four parts of leading edge, trailing edge, pressure face and suction face.The algorithms of feature parameters extraction were studied as well, and realized with VC++ and simulated using the unorganized point data generated by UG/OpenGrip. The experiments show that the precision of the calculation can reach 10-4 mm, indicating that algorithm calculation error can be ignored in the practical measurement and parameter extraction.
Effect of bulk swirl on performance and stability of transonic single rotor
TU Bao-feng, HU Jun, ZHANG Kai
2016, 31(9): 2233-2238. doi: 10.13224/j.cnki.jasp.2016.09.024
Abstract PDF(1099KB) icon1136 icon521
Abstract:
In order to investigate the effect of bulk swirl on performance and stability of axial compressor, blade swirl generator was designed and numerically simulated with a transonic single rotor. The results showed that counter-rotating bulk swirl caused significant drop in coefficient and stall margin and increase in choke mass flow, angle of attack and total pressure ratio. Co-rotating bulk swirl led to decrease of choke mass flow, attack angle, total pressure ratio and stable operating range, and increase of coefficient. Co-rotating bulk swirl caused suction surface boundary layer separation beyond 50% blade span, and more serious tip leakage blocking, contributing a lot to unstable compressor.
Aerodynamic rotating instability and fluctuated characteristics of tip clearance flow in low speed axial flow compressor
WANG Hao, WU Ya-dong, OUYANG Hua
2016, 31(9): 2239-2250. doi: 10.13224/j.cnki.jasp.2016.09.025
Abstract PDF(1551KB) icon1105 icon625
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To investigate the relationship between aerodynamic rotating instability and fluctuated characteristics of tip clearance flow, experiment and numerical studies were conducted on a 1.5 stage low speed axial flow compressor. The rotating instability was detected through casing mounted dynamic pressure sensors. The phase-locked and root mean square(RMS) pressure contours showed that the interaction of tip clearance flow with the neighboring blade was the most likely cause of casing flow field fluctuation. From the calculated results of whole-annulus cascade, it is found that the tip clearance vortex structure oscillates periodically at low flow rate conditions. Furthermore, phase lag of pressure fluctuations exist between two neighboring passages, which induces a rotating pressure wave of multiple frequencies. The frequency characteristics of this rotating pressure wave caused by fluctuation of tip clearance flow are coincident with the frequency of rotating instability. This suggests that the fluctuation of tip clearance flow is the major contributor to the initiation of rotating instability.
Numerical simulation method of roughness induced transition
LI Hong-yang, ZHENG Yun, LIU Da-xiang
2016, 31(9): 2251-2257. doi: 10.13224/j.cnki.jasp.2016.09.026
Abstract PDF(979KB) icon1283 icon568
Abstract:
For the purpose of simulating roughness induced transition, the boundary conditions of turbulent dissipation rate and eddy viscosity for rough surface were added to Langtry's γ-Reθ transition model; furthermore, equivalent sand surface roughness height was introduced to rewrite the correlation equations of the transition momentum thickness Reynolds number, making it appropriate for roughness-induced transition. Numerical simulation was made by referring to the wind tunnel data of several rough flat plate experiments and variable-pressure-gradient plate experiment, in which the results were satisfactory. Main conclusions are made as follows:surface roughness will enhance the heat transfer, increase the skin friction coefficient and shift the transition position upstream in general compared with smooth cases; effects for natural transition is significant, as surface roughness of 0.15 mm could shift the transition position upstream about 40%; while affect for separating induced transition is weaker; with the increase of surface roughness, transition position and separating bubble position are shifted backwards a little, the strength of separating bubble becomes weaker while the friction coefficient increases.
Analysis on tip flow structure in transonic fan rotor
YANG Xi-qiong, LIU Bo, CAO Zhi-yuan, MAO Xiao-chen, XIA Shu-dan
2016, 31(9): 2258-2267. doi: 10.13224/j.cnki.jasp.2016.09.027
Abstract PDF(1248KB) icon1079 icon486
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In order to analyze the tip flow structure and explore the intersection of shock and tip clearance vortex, a transonic fan rotor was studied using three dimensional numerical calculation and comparative analysis of flow field with various clearances. Further study of the intersection of tip leakage vortex and shock were obtained by establishing the 3-D flow model of the process, thus enhancing the comprehensive understanding of tip leakage flow. The research indicated that the performance was improved with the decrease of the clearance, including efficiency and pressure ratio. Moreover, with the increase of tip gap, the intensity of tip leakage vortex(TLV)was enhanced and the scope of high-entropy area was expanded along the circumferential direction and spanwise direction. The pressure difference between pressure surface and suction surface provided the impetus for the migration of the leakage flow, and lateral gap offered the migration channel. Under h/c=1.0%, the circumferential movement tended to be more notable and the secondary leakage turned more dramatic with the increase of tip height. Propagating of TLV led to the rapid reduction of the normalized streamwise vorticity, while the constant value of the normalized helicity showed that the concentrated vortex feature was maintained. What's more, the shock was distorted by the tip leakage vortex near suction, weakening the shock wave and pushing the shock upward.
Modeling and simulation of compressor system with actuators
SU San-mai, SUN Zhan-heng, LÜ Ye, LIU Jun-jie
2016, 31(9): 2268-2275. doi: 10.13224/j.cnki.jasp.2016.09.028
Abstract PDF(1019KB) icon978 icon545
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For the requirement of compressor model for active stability control purpose, the multi-dimensional space state compressor model was built by discreting the Moore-Greitzer model in space and representing the flow disturbance using discrete points around compressor circumference. Then the multi-dimensional compressor model with air injector was established considering the time lag of actuators and the momentum and mass effects caused from adding of air injector. Simulation on compressor stall and the suppression effect of air injection indicates that the rotating stall behavior is captured by the model established herein, the stable compressor operating range is expanded and stall is suppressed by air injection. The compressor model with air injectors is available for the analysis and design of active stability control system.
A multivariable frequency-domain dynamic pseudodiagonalization method and design of aero-engine decoupling controller
PENG Kai, FAN Ding, GUO Ya-nan, BU Zhen-peng, JIAO Chun-bo, XUE Yuan
2016, 31(9): 2276-2282. doi: 10.13224/j.cnki.jasp.2016.09.029
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Abstract:
For Hawkins's pseudodiagonalization method in multivariable Nyquist-class frequency domain design, an improved dynamic pseudodiagonalization method was presented to enhance the diagonal dominance of the system in order to improve the decoupling and robustness of the system together with relevant analysis. Finally, the dynamic pseudodiagonalization method was used to design an aero-engine steady controller. The simulation results show that the compensated system given by improved dynamic pseudodiagonalization method has good dynamic and static decoupling and robustness compared with standard Hawkins's method.
Effect of momentum ratio on atomization characteristics of unlike-doublet impinging jets injector
ZHENG Gang, FENG Wei, NIE Wan-sheng, ZHOU Li-xin
2016, 31(9): 2283-2289. doi: 10.13224/j.cnki.jasp.2016.09.030
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Abstract:
Numerical simulation was carried out on the atomization process of unlike-doublet impinging jets injector based on the CLSVOF (coupled level-set and volume of fluid) method. The simulation results were compared with the experiment results, and the effect of momentum ratios on liquid sheet characteristics was investigated in detail. The results show that:(1) The CLSVOF method can efficiently capture the liquid sheet characteristics formed by jet impact. The calculated liquid sheet agrees well with the experiment result. (2) In the impinging process of jets, part of the jet flow of large diameter nozzle is not involved in the impact, while the velocity of liquid in the central position drops rapidly after impact, and at the same time, the surrounding liquid maintains the velocity before impact, which results in the formation of cured liquid sheet. (3) Under the conditions of different momentum ratios, the resultant angle in the axis position after impact mainly depends on the momentum ratio of impinging jets. The simulation results are in good agreement with the theoretical calculation results, with the errors less than 10%.
Numerical simulation of nozzle damping characteristics in solid rocket motor
SUN Bing-bing, LI Jun-wei, SU Wan-xing, WANG Ning-fei
2016, 31(9): 2290-2297. doi: 10.13224/j.cnki.jasp.2016.09.031
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Abstract:
For the purpose of investigating the key factors affecting the nozzle damping characteristics of solid rocket motor, numerical simulation of nozzle damping characteristics were carried out to study the influence of the nozzle throat area-to-grain port area ratio and the chamber length, based on the simplified two-dimensional model of the typical columnar grain of solid rocket motor and with use of pulse attenuation method.It was found that the numerical simulation results and empirical formulas theoretical estimate values were in good agreement, confirm the validity of the numerical methods; the study further explored what the empirical formula cannot deal with well, such as the change rules of nozzle convergent half-angle and nozzle convergent surface. The results show that the nozzle convergent half angle plays a vital role in nozzle damping constant. Small convergent half angle is beneficial to the nozzle damping; the convex nozzle provides more damping than the conical nozzle, which in turn provides more damping than the concave nozzle.
Test rig design and experiment of gas thrust foil bearing
XU Fang-cheng, LIU Zhan-sheng, ZHANG Guang-hui, ZHANG Wen, SUN Yi
2016, 31(9): 2298-2304. doi: 10.13224/j.cnki.jasp.2016.09.032
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Abstract:
A gas thrust foil bearing test rig was designed and manufactured, and a piston loading mechanism with a foil seal was used to apply the load to thrust foil bearing. A thrust foil bearing with cooling air channels and radial radiation distribution bump foil was tested. The bearing load capacity at the speed of 15000, 20000, 25000r/min was measured by using friction torque method. Results show that the piston loading mechanism with this foil seal structure can supply enough load to the thrust foil bearing and the successful test rig design was certificated. Moreover, this type thrust foil bearing can achieve 145,195,260N respectively at these different speeds. The bearing load capacity has a nonlinear relationship with gas film thickness.

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