2016 Vol. 31, No. 11

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Combustion Heat and Mass Transfer
Experiment on spiral pulse detonation chamber
WANG Wei, XIAO Jun-feng, QIU Hua, LI Xiao-feng, WANG Feng
2016, 31(11): 2561-2566. doi: 10.13224/j.cnki.jasp.2016.11.001
Abstract PDF(1078KB) icon1373 icon721
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For the purpose of reducing the axial length of pulse detonation chamber and the DDT(deflagration to detonation transition) distance by the spiral pulse detonation chamber, the results of experimental investigation on spiral pulse detonation chamber using liquid gasoline and air mixture were presented. Results show that, compared with straight pulse detonation chamber, the DDT distance has reduced 11.2% at least by the spiral pulse detonation chamber; the spiral pulse detonation chamber can work stably under the frequency of 5~20Hz; the spiral pulse detonation chamber design is a successful one.
Numerical investigation of flow and heat transfer characteristics in rotating square U-duct
YANG Ke, WEN Jie, XU Guo-qiang
2016, 31(11): 2567-2574. doi: 10.13224/j.cnki.jasp.2016.11.002
Abstract PDF(1104KB) icon1117 icon656
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k-ω SST (shear stress transport) two-equation turbulence model was used to analyze the flow and heat transfer characteristics in rotating square U-duct at different inlet Reynolds numbers (10000~60000) and rotation numbers (0~2.013). Results show that both in stationary and rotating state, Nusselt numbers are augmented with the increase of inlet Reynolds number. Comparing with stationary state, at the same Reynolds number, the intensity of heat transfer in radial outward passage is dramatically enhanced by rotating, while the radial inward passage is just enhanced a little. Rotation number influences the U-duct heat transfer through changing the values of Coriolis force and buoyancy force. Coriolis force enhances greatly the heat transfer of trailing surface in radial outward passage, while the leading surface weakens. Buoyancy force causes flow separation in the vicinity of the wall, so it alters the heat transfer characteristics. In different positions of the radial inward passage, the heat transfer intensity of the leading surface firstly decreases and then increases with the rise of rotation number. The critical rotation numbers got by calculation are in good agreement with the experimental results. The product of dimensionless distance parameter and critical rotation is a constant.
Experiment on axis locus of rotor and leakage characteristics of finger seal
DU Chun-hua, JI Hong-hu, HU Ya-ping, LUO Jian, MA Dan, TANG Li-ping, LIAO Kai
2016, 31(11): 2575-2584. doi: 10.13224/j.cnki.jasp.2016.11.003
Abstract PDF(1134KB) icon1095 icon651
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Experimental research on the axis locus of rotor and leakage characteristics of finger seal tests of clearance, transition and interference fit was conducted. The axis locus of rotor was measured by eddy current sensors. The results show that the higher the rotor rotation speed, the smaller the offset of the axis. And the offset does not affect the fit state if the wear is not considered, which assured the reliability of the test rig. And then the influences of factors such as the rotation speed, the pressure drop and the sealing clearance on the leakage characteristics was studied. The results show that the leakage coefficient slightly decreases with the increase of the rotation speed. For the case of clearance and transition fit, the leakage coefficient increases with the increase of the pressure drop which is below than 0.3MPa and then almost keeps constant while the pressure drop exceeds 0.3MPa. For the case of interference fit the pressure drop almost has no influence on leakage coefficient. The leakage coefficient reduces with the decrease of the sealing clearance and with the increase of interference.
Experiment on ignition of kerosene in supersonic flow based on cavity floor injection
LI Xi-peng, LIU Wei-dong, PAN Yu, LIU Shi-jie, SU Yi
2016, 31(11): 2585-2594. doi: 10.13224/j.cnki.jasp.2016.11.004
Abstract PDF(1025KB) icon1189 icon667
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Experiment on ignition of kerosene injected from cavity floor in scramjet combustor with two-staged cavities were conducted at the inflow conditions of Mach number of 2.52, total temperature of 1486K, total pressure of 1.6MPa. The influences of injector diameter and injection position on ignition ability were analyzed. Results showed that when kerosene was injected from the upstream cavity floor using large diameter injector and ignited by the spark in the downstream cavity, it led to a reliable ignition with large margin of flame stability (kerosene overall equivalent ratio range of 0.102-0.206). The upstream propagation of pressure disturbance had an obvious hysteresis phenomenon and interacted with the formation of separating zone. The kerosene spray distribution was governed by the fuel injection scheme, and influenced the ignition characteristics on the other hand.
Effects of back pressure induction methods on scramjet isolator flow characteristics
WANG Yu-hang, SONG Wen-yan, BAI Han-chen, CHEN Liang
2016, 31(11): 2595-2603. doi: 10.13224/j.cnki.jasp.2016.11.005
Abstract PDF(1217KB) icon1298 icon649
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Experimental and numerical methods were utilized to investigate the back pressure effect on isolator flow characteristics by combustion or by flow choking. Combustion experiment with different hydrogen fuel equivalent ratios and wedge-blocked were conducted under the same airflow condition and the same isolator exit pressure ratio. Combustion and corresponding flow choking situations with different isolator exit pressures were investigated numerially to compare the flowfield details in the isolator under two situations. Experimental results indicate that when the shock train is about to enter the isolator, the same pressure distribution is achieved with these two choking methods; but when the isolator exit pressure ratio reaches 2.3, which means the shock train has entered the isolator, there is a significant difference between these two situations.Numerial result for these two situations suggest that separation zone for the combustion situation originally appears in the lower wall, but in the flow choking situation it appears in the upper wall, indicating that the shock train under combustion situation deflects upward and differs from that under the flow choking situation. When isolator exit pressure ratio reaches 3.0, the difference between two situations decreases, indicating that the difference may disappear eventually with the increasing back pressure. These results show that, only when the back pressure field by combustion and by flow choking experiment simulation is confirmed similar, flow choking experiment result can be used to assess the inlet unstart risk by back pressure.
Flamelet/progress variable approach for turbulent combustion
XIONG Mo-you, LE Jia-ling, HUANG Yuan, SONG Wen-yan, YANG Shun-hua, ZHENG Zhong-hua
2016, 31(11): 2604-2612. doi: 10.13224/j.cnki.jasp.2016.11.006
Abstract PDF(1275KB) icon1642 icon742
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Adding flamelet/progress variable approach to computation platform developed by ourselves, two kinds of progress variable were adopted to simulate methane/air coaxial jet combustor. Comparing the results with each other and also with steady flamelet model, literature reference and experiment result, it is indicated that the results of flamelet/progress variable approaches can compute unsteady phenomenon in combustion, such as lifted flame which can not be observed in steady flamelet model, and agree reasonably well with the literature reference and experiment result, namely, they can reflect the actual process of combustion accurately; at the same time it is learnt that different definitions of progress variables lead to different results; it is proved that flamelet/progress variable approaches do better in simulating main auxiliary production carbon monoxide, and are closer to experiment result.
Influence of injection location on upstream struts in a dual-struts supersonic combustor
TIAN Liang, XU Xu, ZHU Shao-hua
2016, 31(11): 2613-2620. doi: 10.13224/j.cnki.jasp.2016.11.007
Abstract PDF(1080KB) icon1190 icon616
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Directly-connected test on dual-struts supersonic combustor fueled by liquid kerosene was made to test the influence of three different injection locations in upstream strut on combustion. The wall pressures were processed by one-dimensional impulse analysis method. Results showed that the position of thermal coking was influenced by the injection location in the upstream strut. Moreover, when fuel was injected respectively from the first and the second positions in upstream strut, the wall pressure distributions were nearly the same, but 6.3%-7.5% and 16.7%-17.4% higher than from the third injection location in conbustion efficiency and in thrust separately. Test results showed that fuel injected from the first injection position in the upstream strut could hold steady combustion but couldn't do from the third one. The results of simulation showed that the fuel had a high mixing efficiency with the air combusted steadily when the L≥80mm, where L was the distance between injection position and trail of strut.
Simulation calculation of hot air anti-icing system based on internal-external comjugate heat transfer
GUO Tao, LIN Li, ZHU Cheng-xiang
2016, 31(11): 2621-2627. doi: 10.13224/j.cnki.jasp.2016.11.008
Abstract PDF(1080KB) icon1264 icon588
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Based on the principle of conjugate heat transfer between the external and internal chamber, AMESim simulation model was established for the hot air anti-icing system. The change rules of the flux, pressure and skin temperature in different bleeding conditions were researched. The internal flow characteristics and the conjugate heat transfer characteristics of the aircraft wing anti-icing system were calculated using this model. The predictions of the flux, temperature and pressure were verified against those in the flow distribution experimental data of the wing anti-icing system, showing a satisfactory agreement. The maximum error was less than 9%. Its accuracy and validity were validated with the comparison of results. On the basis of modeling, a nacelle hot air anti-icing system was simulated. The transient characteristics of key parameters under a certain flight envelop, such as the heat flux, temperature and heating efficiency, were analyzed. The results can be provided as a reference for design, analysis and optimization of hot air anti-icing system.
Investigation of bonding with micro structures starting fromdouble layers to multi-layers
YUAN Xing, TAO Zhi, LI Hai-wang, TAN Xiao, SUN Jia-mian
2016, 31(11): 2628-2634. doi: 10.13224/j.cnki.jasp.2016.11.009
Abstract PDF(945KB) icon1328 icon614
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The technique of multi-layers' direct bonding with micro structures was investigated by both theoretical analysis and experimental validation. The adopted method of chemical energy activation in silicon wafer surface was hydrophilic treatment. The adopted bonding process was to firstly pre-bond wafers in bonding machine and then carry out high temperature annealing in annealing furnace. In the process, the parameters in pre-bonding procedure decided whether the bonding could succeed eventually. The three main parameters (temperature, pressure, time) in pre-bonding procedure were elaborately analyzed using orthogonal experiments, significantly reducing the time of experiments. The infrared images of bonded wafers were analyzed by silicon-silicon bonding analysis software prepared by the research group to calculate the bonding rate. Applying the best pre-bonding process parameters concluded by experiments, the bonding rate of multi-layers reached 86.6527%.
Hot wire test on the flow fields in a rotating square channel
WEI Kuan, TAO Zhi, DENG Hong-wu, LI Hai-wang
2016, 31(11): 2635-2640. doi: 10.13224/j.cnki.jasp.2016.11.010
Abstract PDF(965KB) icon978 icon609
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To apply the hot wire technique in rotation condition and accurately measure the flow fields in a rotating square channel, a rotating test rig was built.Two connection modes were applied in the hot wire calibration tests, and the relative error in measuring the averaged velocity was estimated to be ±6%. The measurements were conducted in a rotating channel with the Reynolds number and rotation number varying in the range of 5000-10000, and 0-0.222, respectively. The results show that there is a shift of the velocity profile to the trailing side(Y/D=-0.5), the drift of velocity profile increases with the bigger X/D and rotation number. When the rotation number is 0.222, there is a velocity profile inflection point near the trailing side that likely is related to the secondary flow induced by Coriolis force instability.
Thermal conductivity prediction of unidirectional composites based on microstructure identification
JIANG Hua, MAO Jun-kui, TU Ze-can, SHEN Kai, SONG Jin-rong, GUO Wen, HUANG Wei-na
2016, 31(11): 2641-2651. doi: 10.13224/j.cnki.jasp.2016.11.011
Abstract PDF(1195KB) icon1171 icon625
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Taking the T300 carbon fiber/epoxy resin matrix unidirectional composites as an example, an equivalent thermal conductivity prediction method based on microscopic image recognition was established, in consideration of the influence of the interface defect. The microstructure scanning electron microscope photos were processed first through image recognition. Then according to the fiber volume fraction stability criterion, the representative volume element(RVE) were built by geometry reconstruction technique. Meanwhile, the thermal contact resistance was added at the interfaces in the RVEs to represent the influence of the interface defects. Finally, the prediction results of equivalent thermal conductivity (ETC) were obtained by the finite element method. Results show that the randomness of the interface defect's position affects ETC weakly, while ETC decreases significantly with the increasing proportion or the thickness of the interface defect. When the the interface defect proportion is greater than 0.8 and the dimensionless thickness of the interface defect is less than 0.15, the most significant influence on ETC appears. Compared with the simulations of ignoring the interface defect between fiber and matrix, the biggest drop of ETC can reach 52.1% considering the interface defect.
Surrogate formulation methodology of coal-based jet fuel based on neural network mixing model
LIU Zhen-tao, XU Quan-hong, ZHANG Chi, HUO Wei-ye, LIN Yu-zhen
2016, 31(11): 2652-2658. doi: 10.13224/j.cnki.jasp.2016.11.012
Abstract PDF(912KB) icon1119 icon592
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In order to build spray model of aviation fuel for the high-fidelity numerical simulation of spray combustion, a surrogate formulation methodology was proposed for coal-based jet fuel based on artificial neural network mixture model. An implicit prediction model was developed on the blended physico-chemical properties using the multi-component fuel properties data set to train the neural network. And then the surrogate of coal-based jet fuel was formulated from the neural network mixing model by the stochastic points' optimization method, which could well simulate the target physico-chemical properties focusing on its atomization.Result shows that the surrogate is composed of 5 hydrocarbons(n-decane,n-dodecane,n-tetradecane,iso-octane and methylcyclohexane),their mole fraction are 11.46%, 23.29%,49.87%,6.66% and 8.72%, respectively. Compared with the real fuel, the atomization simulation of the surrogate was evaluated by experiments. This surrogate formulation methodology can solve the nonlinear issue in the mixing process, and formulate different surrogates for various requirements.
Aerothermodynamics and Aeroengine Design
Investigation of variable geometry RBCC inlet with double passage
LIU Xiao-wei, LI Yong-zhou, ZHANG Meng-zheng, LÜ Qi-wei
2016, 31(11): 2659-2664. doi: 10.13224/j.cnki.jasp.2016.11.013
Abstract PDF(971KB) icon1128 icon535
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A two-dimensional inlet variable geometry scheme with double passage regulation was put forward. The regulation of inlet compress angle and contraction ratio was achieved by the switch of the downstream compress passage to accommodate wide operation range, and the integrative design with aircraft and combustion was also considered. The investigation shows that,this scheme can reduce the staring Mach number to near the ejector/ramjet mode transition point; the starting Mach number hereto is 2.8; higher total pressure recovery coefficient of 0.62 at coming flow Mach number of 3.0, higher mass flow rate of 0.79 at coming flow Mach number of 3.0, and lower resistance are attained during low coming flow Mach number range (which is reduced to more than 30%), while the inlet performance during high coming flow Mach number range is unvaried.
Factors influencing the accuracy of Kriging surrogate model in two-dimensional aerodynamic problem
MA Yang, ZHANG Qing-bin, HAN Qi-long, HUA Ming-jun, LI Hong-xia
2016, 31(11): 2665-2672. doi: 10.13224/j.cnki.jasp.2016.11.014
Abstract PDF(1142KB) icon1154 icon557
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The factors influencing the accuracy of Kriging surrogate model including the number of sample points, the parameters of model and their types, were researched. The drag property of two-dimensional transonic airfoil was used to construct the surrogate model. The computational fluid dynamics (CFD) was employed to compute the drag coefficient. Three kinds of errors,i.e. average error, maximal error and standardized cross-validated residual were employed to measure the accuracy of the Kriging surrogate model while the cross validation was applied as the accuracy validation method. The results obtained are summarized as follows. First, the Kriging surrogate model performs well when predicting the aerodynamic drag of the two-dimensional transonic airfoil. Second, the accuracy of model improves with the increase of sample number, and when the ‘bizarre airfoil’ whose responses based on Kriging surrogate model are opposite with the normal ones are deleted, the accuracy of the model is improved obviously, and the average error and maximal error decrease 5%-38% and 13%-77% respectively. Third, the model accuracy is mainly affected by type of kernal function, followed by the correlation parameter, while the regression model has little influences. The Kriging surrogate model with Gauss correlation function, second order regression model and optimal correlation parameter has the best accuracy.
Design and verification of engine air particle separator for vehicle gas turbine engine
YANG Han-jie, TU Meng-pi, GONG Ai-dong, XIE Mai-xiang, WANG Chang-rong
2016, 31(11): 2673-2681. doi: 10.13224/j.cnki.jasp.2016.11.015
Abstract PDF(1062KB) icon1136 icon504
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The design method of engine air particle separator for vehicle gas turbine engine was presented. According to the design target, a design scheme and a design flow were proposed. The vortex tube with grille and the air cleaner assembly were designed. The internal three-dimensional gas-solid two phases flow was analyzed by numerical simulation. Taking the air cleaner assembly as the test object, the verification test was performed. Both the numerical simulation and the test results indicate that the design method is feasible for the engine air particle separator,this method can simulate three-dimensional gas-solid two phases flow of vortex tube accurately,calculation result is credible.
Conformal asymmetry S-shaped inlet design and optimization of flying wing unmanned aerial vehicle
ZHANG Le, ZHOU Zhou, XU Xiao-ping
2016, 31(11): 2682-2690. doi: 10.13224/j.cnki.jasp.2016.11.016
Abstract PDF(1155KB) icon1314 icon551
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Based on domestic power constraint and stealth design requirements, conformal S-shaped inlet was designed for twin-engine flying wing unmanned aerial vehicle. In order to further improve the inlet performance, the optimization research on the inlet design was carried out. First, a verification on the wind tunnel test model of conformal inlet was made by CFD (computational fluid dynamics). And then CFD numerical simulation was carried out combining with parametric modeling and automatic mesh generation technique. Finally, RBF (radial basis function neural network) surrogate model and multi-island genetic algorithm were used to take an optimization on the inlet parameters. Results indicated:(1)The aerodynamic performance of optimized inlet improved, and especially it improves significantly after the attack angle of 4°. The total pressure recovery coefficient increased by 5.46%,and the distortion coefficient decreased by 38.7% at the Mach number of 0.6 and attack angle of 4°. (2)Compared to the initial configuration, the area distribution of optimized inlet changed gently in the front but increases slightly behind; while the centerline of former 1/3 was consistent with the initial configuration, and after that the curvature changed more smoothly. (3) The conformal inlet has strong secondary flow at the exit. The sideslip angle made a little influence on the inlet performance under small attack angle but it had greater influence at large attack angle. So the sideslip performance under large attack angle should be paid more attention.
Analysis and evaluation about radar target scattering characteristics of helicopter wing components
JIANG Xiang-wen, ZHAO Qi-jun
2016, 31(11): 2691-2700. doi: 10.13224/j.cnki.jasp.2016.11.017
Abstract PDF(1271KB) icon1020 icon529
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Considering quasi-stationary principle, analysis and evaluation about helicopter wing components on the radar scattering characteristics were investigated based on electromagnetic high-frequency method. Firstly, in order to obtain effects about the radar scattering characteristics of the helicopter wing components, the RCS(radar cross section) changes, the strong scattering regions, and the time-frequency domain of echo signal were analyzed considering the dynamic features of rotor high-speed rotation; as a result, the scattering mechanisms of wing components were revealed. Then, according to the strong scattering distributions and multiple response characteristics of the helicopter, the radar detection range of the helicopter with different wing components was compared, four levels warning mechanism and angle domains about azimuthal, pitch and roll attitudes were proposed, and the corresponding strategy against the radar detection was given. It shows that the radar exposure distance of helicopter fuselage with difference wing components such as the horizontal stabilator, wingstub and their combinations, increase by 11.54%, 14.88% and 18.06%, respectively, and comprehensive radar stealth performances of the helicopter are declined.
Couplings in helicopter hovering longitudinal motional modes
CHEN Yuan, CHEN Ren-liang, LI Pan
2016, 31(11): 2701-2709. doi: 10.13224/j.cnki.jasp.2016.11.018
Abstract PDF(999KB) icon1135 icon518
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A quantitative analysis method was put forward, concentrating on couplings among state variables in helicopter motional modes. In the method, based on motional modes resulting from a decoupling procedure, couplings among state variables in motional modes were quantitatively described in combination with the matrix of aerodynamic derivatives. And all couplings were distinguished quantitatively by instantaneous characteristics and integrated characteristics. With the application into helicopters, Lynx, Bo105, and Puma, coupling characteristics of hovering longitudinal motional modes were analyzed. It showed that the coupling on pitching rate from longitudinal velocity by speed stability played a vital role in the unsteady hovering longitudinal oscillatory mode. Based on the quantitative analysis of examples, simplified models were obtained with the selection of main couplings, and the resulted deviation of natural frequency and damping ratio of motional modes was less than 2%, superior to simplified models in references. So it is feasible to obtain simplified models on the basis of the quantitative analysis.
Relationship between noise sources spatial distribution and radiation characteristic of airfoil trailing edge
BAI Bao-hong, LI Xiao-dong
2016, 31(11): 2710-2716. doi: 10.13224/j.cnki.jasp.2016.11.019
Abstract PDF(1078KB) icon1009 icon537
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The relationship between the airfoil turbulent boundary layer trailing edge noise spatial distribution and radiation characteristic was studied in detail. A Reynolds averaged Navier-Stokes (RANS) based airfoil trailing edge noise prediction method was employed to investigate the NACA0012 airfoil turbulent boundary layer trailing edge noise source spatial distribution and radiation characteristic at four different operating conditions. The spatial distribution of NACA0012 airfoil turbulent boundary layer trailing edge noise source at different frequencies was calculated firstly. It indicated that the turbulence within boundary layer was responsible for the airfoil turbulent boundary layer noise. Meanwhile the source region approached to the trailing edge of airfoil with increase of the noise frequency; it was also shown that the spatial dimension of source and the strength of the source increased first and then decreased with the increase of frequency; meanwhile, the noise radiation characteristic from different source regions in boundary layer was computed secondly. It demonstrated that the noise from source region in boundary inner layer was concentrated on high frequency and the boundary outer layer was responsible for the low frequency of noise. The noise energy moved to low frequency with increase of angle of attack or decrease of incoming flow velocity.
Design and performance analysis of the three-dimensional asymmetric nozzle with lateral expansion
NIU Yan-feng, XU Jing-lei, MO Jian-wei
2016, 31(11): 2717-2722. doi: 10.13224/j.cnki.jasp.2016.11.020
Abstract PDF(894KB) icon1188 icon526
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Design method based on the quasi two-dimensional method of characteristics (MOC) was proposed for the three-dimensional (3-D) rectangular cross-section asymmetrical nozzle with lateral expansion. The corresponding asymmetrical nozzle design program based on MOC was obtained. Then, according to different lateral expansion laws, a series of asymmetrical nozzles were designed by using this method. And comparisons were made between these nozzles and the optimal configurations designed by optimization method. The comparisons show that:the up and down ramps of asymmetrical nozzles designed by the two methods are basically coincident and the pressure distributions on the expansion ramp are consistent, verifying the reliability of quasi-two-dimensional method of characteristics; the difference in thrust between the MOC design and the optimization design is lower than 0.60% and in lift is lower than 8.07%. This design method can reduce the time spent by the design from 30.5h to 2h, presenting a satisfactory approach for the preliminary design.
Structure, Strength and Vibration
Structure safety design strategy of rotor-support system due to fan blade loss
HONG Jie, XU Mei-ling, MA Yan-hong, LIANG Zhi-chao, ZHANG Li
2016, 31(11): 2723-2730. doi: 10.13224/j.cnki.jasp.2016.11.021
Abstract PDF(960KB) icon1064 icon563
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Taking the high bypass ratio turbofan engines as the research object for the rotor-support system under the load of blade loss, the strategies of structural safety design were put forward for the supporting scheme with loading distribution, variable stiffness support structure and the deformation control of support structure. Combined with the dynamic design on rotor, the safety design was realized. Research showed that, the variable stiffness support design at the rear bearing could reduce the critical speed and corresponding vibration amplitude, leading to local vibration of the fan during the process of slowing down. Through the design on cone angle of the conical shell at the ball bearing, decreasing the influence of shaft deformation on the ball bearing and the support could withstand the big axial direction load. The design of drum-like matching interface between the bottom of bearing case and rotating shaft could avoid the support deformation through the matching surfaces slipping upon each other, thus ensuring the safety of the bearing. The research results can provide a technical reference for safety design on high bypass ratio turbofan engines under severe loadings.
Control effect study on thermal boundary loading in optimization design of turbine disk
DING Shui-ting, SUN He-xing, LI Guo
2016, 31(11): 2731-2737. doi: 10.13224/j.cnki.jasp.2016.11.022
Abstract PDF(946KB) icon993 icon495
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For the optimization design of aeroengine turbine disk structure, the reasonable temperature and stress distribution was obtained by changing the thermal boundary loading coefficients of rim and hub under the constant heating and cooling condition. An optimization design process including modeling,CFD analysis, FE(finite element analysis) was developed based on ISIGHT softwave which is used to solve fluid-heat-structure coupling problems and the effect of optimization design of turbine disk structure imposed on thermal boundary loading was explored. Result shows that the optimization result varies from the different thermal boundary loading coefficients.The maximum equivalent stress of disk hub decreases 5.93% and 12.01% respectively, the mass of disk decreases 1.25% and 2.24% respectively when the thermal boundary loading coefficients of 0.1 and 0.2.
Experiment on acoustic vibration fatigue properties of the aero-engine rotor blade
WANG Yan, GUO Ding-wen
2016, 31(11): 2738-2743. doi: 10.13224/j.cnki.jasp.2016.11.023
Abstract PDF(862KB) icon1161 icon544
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Vibration load, sound load and other factors may result in high cycle fatigue of aero-engine rotor blade. The acoustic vibration fatigue properties of aero-engine rotor blades were studied experimentally. Firstly, the effects of blade root boundary conditions on the acoustic responsiveness properties of aero-engine rotor blade were studied. Three different clamping forces were applied to three groups of rotor blades. Then sound loads were applied to each group of blades from low to high. The relationship between the acoustic responsiveness and the sound pressure under different boundary conditions was therefore got. The results showed that blade root boundary condition was an important influential factor to the blade acoustic responsiveness. Then the acoustic vibration fatigue properties of the blade were studied. Conclusions could be drawn as follows:rotor blade could be damaged under sound loads; blade frequency decrease is slightly different when applying two different vibration excitations to two rotor blades,i.e. random vibration and sinusoidal vibration. The lifespan of blade under sinusoidal excitation is much longer than under random excitation if both are at the same dynamic stress level.
Flutter boundary prediction based on natural excitation technique
LI Yang, ZHOU Li, YANG Bing-cai
2016, 31(11): 2744-2749. doi: 10.13224/j.cnki.jasp.2016.11.024
Abstract PDF(995KB) icon933 icon536
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In order to predict the flutter boundary of the wing under the turbulence excitation, the natural excitation technique was used to obtain the free decaying signal from the turbulence response, and the matrix pencil method was adopted to identify the modal parameters, then the flutter margin was calculated by the Z-W(Zimmerman-Weissenburger) method, and finally the flutter boundary was extrapolated by the fitting margin curve. Plate wing numerical simulation model was analyzed and responses of alone wing model wind-tunnel flutter test were calculated. Results show that the natural excitation technique and the matrix pencil method can identify the modal parameters more accurately with the error of identified frequency less than 6% and identified damping ratio error less than 30%,and the flutter boundary can be predicted early at a low airspeed before the flutter point when combined with the Z-W method thus be helpful to protect the modal and improve the test safety.
Turbomachinery
Integrated throughflow design method of variable-cycle compression system
LIU Bao-jie, JIA Shao-feng, YU Xian-jun
2016, 31(11): 2750-2756. doi: 10.13224/j.cnki.jasp.2016.11.025
Abstract PDF(1005KB) icon1124 icon516
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Targeting the two typical variable-cycle compressor system of turbofan engines, double-bypass engine and triple-bypass engine, an integrated throughflow design method based on streamline curvature method was proposed for simplifying the design process of a variable-cycle compression system and shortening the design cycle. By solving the flow filed of a triple-bypass variable-cycle compression system, the feasibility of the method and the capability of the code was proven. Three main conclusions were drawn:(1) The connection of the first and second bypasses complicates the aerodynamic correlations of the components and correctly reflecting the correlations is the key of an integrated design method. (2) Streamline curvature method is suitable for variable-cycle compression system design and its mass flow boundary conditions can be used for modeling the function of the front area-variable bypass injector. (3) The mixing process of the first and second bypasses flow will not influence the upstream blade flow field, and simple mixing model can meet the requirements for simulation of such a process.
Performance contrast experiment of prototype single cascade and redesign tandem cascade at high inlet Mach number
XIANG Hong-hui, GE Ning, HOU Min-jie, MA Chang-you, YANG Rong-fei, YANG Yong
2016, 31(11): 2757-2764. doi: 10.13224/j.cnki.jasp.2016.11.026
Abstract PDF(1024KB) icon1252 icon518
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Based on the redesign requirement of stator blade with high critical inlet Mach number of a highly-loaded axial flow fan, the performance contrast experiment of prototype single cascade and redesign tandem cascade was presented. The improvement effect of tandem cascade at high inlet Mach number was also evaluated by analyzing the internal flow field parameters of both types of cascade.Results show that the tandem cascade has significant advantages in reducing flow loss and increasing compression capacity than the single cascade. Compared with the single cascade, the total pressure loss coefficient and the static pressure ratio of the tandem cascade reduced by 19% and enhanced by 3.1%, respectively. Accordingly, the flow blockage phenomena of the single cascade at original design condition are eased basically. The front blade can restrain the boundary layer development on suction surface of the rear blade of the tandem cascade, thus the rear blade has good operating performance.
Outlet clearance optimization on axial-force of inducer and impeller combination aero fuel centrifugal pump
LI Jia, LI Hua-cong, WANG Shu-hong, XU Xuan
2016, 31(11): 2765-2772. doi: 10.13224/j.cnki.jasp.2016.11.027
Abstract PDF(1156KB) icon1083 icon484
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As the research object of inducer and impeller combination aero fuel centrifugal pumps, the outlet clearance optimization on axial-force of the pump was carried out. Through comparing the axial-force simulation data with theoretical calculation data, the axial-force trends of the two methods were identified similar and the simulation's accuracy was verified by Pumplinx because of the error less than 4%. Then the outlet clearance's influence on axial-force was analyzed. Simulation results show that expanding the clearance to 0.2mm increases the axial-force value, and reduces the pressure charging; but reducing the clearance to 0.1mm and 0.13mm can make optimizations of the axial-force, and the clearance of 0.1mm is the best. The axial-force performance of the model with clearance of 0.1mm was analyzed finally, showing that this model's inner performance of different sections is normal and steady; the axial-force value at design point is 3620N, so reducing the outlet clearance to 0.1mm can make a high optimization about axial-force of the inducer and impeller combination centrifugal pump.
Power Transmission
Influence of radial clearance and processing technology on structural properties of gas foil bearing
FENG Kai, ZHANG Jun, WANG Fa-yi
2016, 31(11): 2773-2780. doi: 10.13224/j.cnki.jasp.2016.11.028
Abstract PDF(1050KB) icon1044 icon491
Abstract:
In order to analyze the static stiffness, structure stiffness and viscous damping of bearing under different factors, the experiment rigs for gas foil bearing (GFB) static and dynamic characteristic experiment were established. By changing the size of the journal of a same bearing, the influences of radial clearance on the static and dynamic properties of experiment bearings were studied. Additionally, the different bump foils, foil materials, ways of heat treatment and other factors affecting bearing elastic structure properties were also investigated. Result shows that, with the decreasing radial clearance of the bearing, the static stiffness and dynamic structure stiffness increase gradually and equivalent viscous damping increases first and then decreases; different bump foils and foil materials play a major role in GFBs' structural properties.
Bearing pedestal looseness dynamic model of dual rotor system and fault feature
XU Hong-zhi, WANG Nan-fei, JIANG Dong-xiang
2016, 31(11): 2781-2794. doi: 10.13224/j.cnki.jasp.2016.11.029
Abstract PDF(1772KB) icon974 icon502
Abstract:
For the bearing pedestal looseness fault of dual rotors system, after taking into account three DOF(degree of freedom) planar rigid motion of loose bearing pedestal and introducing collision recovery coefficient, a dual rotor system dynamics model including loose bearing pedestal was set up based on the dual rotor structure of experiment rig. Using the finite element method and rigid body kinematics, and adopting the Newmark-β algorithm for numerical simulation based on Timoshenko beam elements, the dynamic characteristics of the inner and outer rotors and the bearing pedestal plane rigid body motion in occurrence of bearing pedestal looseness fault were studied. Meanwhile, the loose experiments of dual rotor system under two different speeds' combination were carried out, and the experimental results were basically the same. The simulation results with the bearing pedestal looseness fault of dual rotors bench were compared, indicating loose rotor vibration displacement waveforms had "clipping" phenomenon. When the bearing pedestal looseness fault occurred, the inner and outer rotors' vibration spectrum not only contained the difference and the sum frequency between the two rotors' fundamental frequency, but also contained loose support rotor second and third harmonics components, etc; there were more low frequency spectrums containing dividing component, etc; the rotor displacement spectrum also contained fewer combination frequency components, etc; when unilateral bearing pedestal was loosened, the inner rotor axis trajectory was drawn into similar-ellipse shape.
Effect of negative clearance on dynamic characteristics of high-speed high-temperature thin-walled cylindrical roller bearings
MAO Yu-ze, WANG Li-qin, GU Le
2016, 31(11): 2795-2800. doi: 10.13224/j.cnki.jasp.2016.11.030
Abstract PDF(968KB) icon1174 icon510
Abstract:
A equivalent radial preload analytical model was developed by taking negative clearances and elastic deformation of cylindrical roller bearings into account. Loading characteristics and internal hoop stress of rings were calculated by this model. Results showed that negative clearances decreased the maximum contact pressure and cage sliding ratio, but made the fatigue life decline at the same time. So it's necessary to take cage sliding ratio and fatigue life both into account when designing negative clearance roller bearings.
Artocontrol
Acceleration process optimization control of turbofan engine based on variable guide vane adjustment
ZHENG Qian-gang, ZHANG Hai-bo, YE Zhi-feng, MIAO Li-zhen
2016, 31(11): 2801-2808. doi: 10.13224/j.cnki.jasp.2016.11.031
Abstract PDF(1077KB) icon1112 icon520
Abstract:
Acceleration process optimization control research was conducted based on the variable vane adjustment and feasible sequential quadratic programming (FSQP) algorithm. Using the adjustment of the guide vane during acceleration, the air mass flow of high pressure compressor and fan can be optimized. In this case, the fuel flow can be increased at a faster speed. Thus, the acceleration performance was significantly enhanced. Then, compared with conventional two-variable (fuel flow and nozzle throat area) optimization method, three-variable optimization method simulations were carried out based either on guide vane of fan or on that of high pressure compressor. The results show that fuel flow rate is better than the traditional ways. Moreover, the guide vane of high pressure compressor plays a more important role than that of fan during the process. The acceleration pass after optimization is close to the surge margin boundary with restraint in the feasible region. The acceleration time of the three methods are 5.5s, 4.9s and 4.5s respectively.
Rocket Engine
Temperature dependent adhesive interfacial mechanical properties of EPDM film
JIA Deng, ZHENG Jian, CHEN Xiong, YU Jia-quan
2016, 31(11): 2809-2816. doi: 10.13224/j.cnki.jasp.2016.11.032
Abstract PDF(1117KB) icon976 icon467
Abstract:
The double cantilever sandwich beam(DCSB) specimen was used to study the temperature-dependent mode I fracture behavior of the interface between the ethylene propylene diene monomer(EPDM) films, the mode I fracture energy was determined by the linear elastic fracture mechanics(LEFM) method, then used simultaneously with the cohesive strength, which was obtained by uniaxial tension test as the parameter of a bilinear cohesive zone model(CZM) to simulate the fracture behavior of the DCSB specimen under different temperatures. Results showed that, there existed a large deviation between the test and simulation results, because the fracture energy determined by the uncorrected LEFM was not accurate. At last, by the means of adjusting the parameters of the CZM to make the simulation curves match the test curves better, the accurate mechanical property parameters were obtained, and the simulation result using these accurate properties matched well with test curve, proving the usability of this model to the fracture of the interface.

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