2014 Vol. 29, No. 1

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Nonlinear numerical simulation for dynamic characteristic of gas cylinder film seal
MA Gang, HE Jun, SUN Xiao-jun, SHEN Xin-min
2014, 29(1): 1-8. doi: 10.13224/j.cnki.jasp.2014.01.001
Abstract PDF(1931KB) icon1412 icon1069
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Aiming at solving the dynamic characteristic as a problem in the research and design of gas film seal,the seal dynamic behavior of gas cylinder film seal was studied theoretically by employing the nonlinear numerical simulation method.The dynamics analysis model of gas cylinder film seal system was established to solve the coupling with the Reynolds equation (including time terms).Through finite element numerical simulation,the trajectory diagram of the sealing ring,the critical dimensionless mass of the seal system and the response to a displacement impact were obtained.The influence of the sealing ring dimensionless mass on dynamic stability was studied.The results show that the critical dimensionless mass of the smooth gas cylinder film seal could be found,and the whirl at the stability threshold is under "half-frequency" state.With the increase of the sealing ring dimensionless mass,the time of returning to a stable state becomes longer and the stability becomes worse.
Experiments of flow resistance characteristic in turbine casing
ZHANG Li, ZHU Hui-ren, ZHANG Shu-hua
2014, 29(1): 9-13. doi: 10.13224/j.cnki.jasp.2014.01.002
Abstract PDF(1403KB) icon1437 icon1161
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The pressure distribution and flow resistance characteristic in cavity of turbine casing was summarized by experiment of measuring the pressure distribution of whole cavity of turbine casing with different Reynolds numbers (80000 to 260000). The experiment results show that: (1) the pressure drop is obvious, and there is a large pressure loss in the transition zone between the second and third tanks; (2) the static pressure coefficient increases with the increasing Reynolds number, and the maximum increament is about 19%; (3) the total pressure loss coefficient varies stably with the Reynolds number increasing, and the difference is below 10%.
Combustion characteristics of scramjet combustor
LI Jun-hong, PAN Hong-lu, SHEN Qing, CHENG Xiao-li
2014, 29(1): 14-22. doi: 10.13224/j.cnki.jasp.2014.01.003
Abstract PDF(2124KB) icon2332 icon1088
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Based on a kind of kerosene-fueled scramjet combustor with low internal drag slick configuration, numerical simulation based on finite difference method was performed for its supersonic flowfield. The inviscid flux was discretized by WENO (weighted essentially non-oscillatory) scheme, and the turbulent model was SST (shear stress transport) k-ω model. The single step chemical reaction mechanism was adopted for kerosene (C12H23). Predicted value of the wall static pressure along the side wall of the combustor is consistent with previously reported test data, indicating the present algorithm is applicable for the simulation of supersonic combustion in kerosene-fueled combustor. The effects of inflow static temperature, fuel/air equivalence ratio and jet location on the kerosene supersonic flow and combustion in this combustor were discussed. Results show that combustion is concentrated near the wall boundary layer at the side of the jet nozzle, and the ignition location is very sensitive to the local static temperature. The lower inflow static temperature, fuel/air equivalence ratio and the larger combustor expansion angle mean the less combustion efficiency and combustion performance, and the ignition location moves towards the combustor exit, with the shock cluster inspired by combustion disappearing. Staggered arrangement of the jet nozzles on the upper and lower walls of the combustor can improve the combustion efficiency. Therefore, preliminary critical boundary conditions are obtained to achieve ignition in the slick kerosene-fueled combustor.
Numerical simulation of icing parameters along S-shaped intake
HU Ya-ping, PANG Li-gang, JI Hong-hu, CAO Guang-zhou, FENG Xiao-xing
2014, 29(1): 23-30. doi: 10.13224/j.cnki.jasp.2014.01.004
Abstract PDF(1690KB) icon1583 icon1027
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Under atmospheric icing conditions and at low incoming flow Mach number, a two-phase flow field of air and super-cooled water droplets along S-shaped intake was numerically simulated with the Euler-Euler method. The distributions of the icing parameters along the S-shaped intake and on the outlet surface were studied. The results show that with the increase of incoming flow Mach number from 0.1 to 0.5, air temperature drop relative to the incoming flow near the entrance increases from 6K to about 17K; the distortion index of temperature on the outlet increases gradually, while the distortion index of liquid water content increases rapidly at first and then decreases slowly with the maximum value at incoming flow Mach number of 0.2.
Comparison of CH4 moderate or intense low-oxygen dilution combustion characteristics based on cross-flow jet mixing and swirl mixing
HUANG Ming-ming, SHAO Wei-wei, ZHANG Zhe-dian, XIONG Yan, LIU Yan, LEI Fu-lin, XIAO Yun-han
2014, 29(1): 31-41. doi: 10.13224/j.cnki.jasp.2014.01.005
Abstract PDF(2233KB) icon1940 icon1030
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Two axially-staged moderate or intense low-oxygen dilution(MILD) configurations, based on cross-flow jet mixing and swirl mixing, were numerically and experimentally studied to compare their mixing performance from flow field pattern and species distribution, and to compare their combustion property from flame behavior and NO and CO emissions. The experiment fuel was methane and the heat load was regulated in the range of 16.2 to 25.9kW. The mixing between fuel and air stream is delayed in the cross-flow jet mixing configuration compared to the swirl mixing configuration, and thereby the recirculated hot flue gas preheats and diluts the fuel and air stream before spontaneous reaction in the former configuration. Compared to the swirl mixing configuration, higher flame lift-off height and more spatially distributed flame are observed in the cross-flow jet mixing configuration, of which flame behavior is also closer to MILD combustion. Furthermore, lower NO and CO emissions are observed for the cross-flow jet mixing staged combustor; at gas recirculation ratio of 0.5 and equivalence ratio of 0.6, the volume fractions of NO and CO in the flue gas are both 4×10-6.
Numerical investigation of high altitude performance of 2-D ejector nozzle and infrared supperssion of unmanned aerial vehicle
SI Ren, JI Hong-hu, LIU Fu-cheng, LIN Lan-zhi
2014, 29(1): 42-50. doi: 10.13224/j.cnki.jasp.2014.01.006
Abstract PDF(2139KB) icon1760 icon1107
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The thrust characteristics and infrared radiation characteristics in the waveband of 3-5μm of 2-D ejector nozzle with long/short shrouds in the high-flying unmanned aerial vehicle(UAV) were studied.The thrust characteristics and infrared radiation characteristics of 2-D ejector nozzle under the conditions of high-altitude and ground state were compared.The system of the exhaust jet, UAV flow field and temperature field were calculated with commercial software Fluent, and the infrared radiation characteristics were calculated with an infrared analysis software(NUAA-IR) developed independently.The results show that the 2-D ejector nozzle can still improve thrust characteristic under the condition of high-altitude,but the thrust characteristic is a little weaker than that under ground condition.The effect of infrared radiation suppression of 2-D ejector nozzle used by UAV is obvious in most of the detection directions,with the largest decreasing amplitude of 90%.The trend of infrared radiation suppression of these two types of 2-D ejector nozzles in the direction of UAV's tail is different from that under ground condition;the infrared radiation of the 2-D ejector nozzle with short shroud is greater than that with long shroud,and the largest increasing amplitude is 7%.
Effects of helicopter rotor downwash air flow on exhaust plume flow
REN Li-feng, ZHANG Jing-zhou, SHAN Yong
2014, 29(1): 51-58. doi: 10.13224/j.cnki.jasp.2014.01.007
Abstract PDF(3121KB) icon1585 icon1103
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The exhaust plume flow characteristics subjecting to the action of helicopter rotor downwash air flow were investigated based on CFD numerical calculations.And the effects of rotor downwash air flow velocity and exhaust direction on the exhaust plume flow and pumping capacity of the exhaust system were analyzed.Results show that:exhaust plume yields flow strong downward deflection to the rear fuselage,as well as deflection to the rotor rotational direction;under the action of rotor downwash air flow,these deflections are especially obvious under higher rotor downwash air flow;when the exhaust is ejected upwards,the exhaust plume flow could come into collision with rear fuselage; pumping capacity of the exhaust system is weakened slightly and pumping coefficient decreases approximately 0.01;while the exhaust is ejected obliquely or laterally,the exhaust plume flow do not come into collision with rear fuselage; pumping capacities of the exhaust system are somewhat enhanced and pumping coefficient increases maximally 0.12.
Vortex cooling performance in internal cooling channel of turbine blade trailing edge
XU Hong-yan, ZHANG Jing-zhou, TAN Xiao-ming
2014, 29(1): 59-66. doi: 10.13224/j.cnki.jasp.2014.01.008
Abstract PDF(2575KB) icon1773 icon1124
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Three different kinds of vortex cooling configurations were designed and applied to the simplified blade trailing edge. The cooling air flow was injected into the vortex cavities from jet orifices located at the middle of the vortex cavity, staggered side of the vortex cavity and the inline side of the vortex cavity, respectively. A comparison with the common cooling channel fitted with bumps and pin fins was made by numerical simulation. The mechanism and effect of enhanced heat transfer were analyzed. Results show that the configuration of vortex flow cavity and the arrangement of cooling air inflow have important influences on the vortex cooling performances. The vortex cooling configurations with the cooling air injected to one side of the vortex cavity causes significant vortex flows not only in the streamwise plane but also in the spanwise plane, which enhances the convection heat transfer. The vortex cooling configuration can enhance heat transfer in comparison with the bumps and pin fins, with the average Nusselt number increasing 6.8%-22.9%. However, the flow resistance also increases. The vortex cooling configuration with the jet orifices located at the staggered side of the vortex cavity enhances heat transfer capacity greatly, and the configuration with the jet orifices located at the inline side of the vortex cavity, of which the comprehensive coefficient of convection heat transfer is 4.2% higher than that of the bumps and pin fins, achieves the best comprehensive performance.
Fault diagnosis method of rolling bearing based on dual-tree complex wavelet packet transform and SVM
XU Yong-gang, MENG Zhi-peng, LU Ming
2014, 29(1): 67-73. doi: 10.13224/j.cnki.jasp.2014.01.009
Abstract PDF(1813KB) icon2029 icon1092
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For the problem of non-stationary signals of rolling bearing and the difficulty to get a large number of typical fault samples in practice, a fault diagnosis method was proposed based on dual-tree complex wavelet packet transform and support vector machine (SVM). Firstly, the non-stationary fault vibration signal was decomposed into several different frequency band components through dual-tree complex wavelet packet transform; secondly, normalization processing was made from the energy of each component. Finally, the energy characteristics parameters of each frequency band component were taken as input of the SVM to identify the fault type of rolling bearing. The analog signals of experiments, containing normal condition of the rolling bearing, crack fault of bearing outer ring, crack fault of bearing inner ring and pitting fault of bearing rolling element, were analyzed and the fault recognition rate reaches 99.5%. The proposed method can identify the working state and fault type of rolling bearing accurately and effectively, as compared with the method of combining traditional wavelet packet transform with SVM.
Investigation on high cycle fatigue-low cycle fatigue life of alloy material
LIU Hong-bin, HUANG Wei-na, CHEN Wei
2014, 29(1): 74-80. doi: 10.13224/j.cnki.jasp.2014.01.010
Abstract PDF(1719KB) icon1616 icon977
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The effects of high cycle fatigue-low fatigue life(HCF-LCF) on titanium alloy (TC4 and TC11) were researched experimentally with foreign object damage (FOD) simulation through pendulum method and air-gas gun method and the features of these two different damage notches were analyzed and compared. Fatigue tests on nondestructive and destructive specimens were further conducted to analyze and compare the effects of FOD on the titanium alloy fatigue life.The conclusions show that:pendulum impact test method simulation lacks of representativeness, while air-gas gun projectile method simulation is much closer to the truth; FOD leads to severe decline of HCF-LCF life of titanium alloy, and air-gas gun projectile method simulation decreases the titanium alloy fatigue life from 105 to 104 order of magnitude.
Parametric sensitivity for coupling vibration characteristics of bladed disk
WANG Pei-yi, LI Lin
2014, 29(1): 81-90. doi: 10.13224/j.cnki.jasp.2014.01.011
Abstract PDF(2372KB) icon1561 icon1100
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Based on parametric modeling and solution of bladed disk, the parametric sensitivity for coupling vibration characteristics of bladed disk were studied, of which the frequency veering and modal localization caused by random mistuning of structure parameters were mainly focused on. The study on coupling vibration characteristics of frequency veering of bladed disk uncovers that the loci of the gap of frequency veering is a bowl-style-curve while the inter-sector stiffness or bladed stiffness varies within a certain range. And the study on localization vibration characteristics finds that there exists a quasi-saddle-surface while the amplification factor is related to inter-sector stiffness and mistuning strength. The latter reveals that the existence of threshold of amplification factor against mistuning strength depends on the strength of inter-sector stiffness. It is also found that a proper choice of inter-sector stiffness and mistuning strength in saddle could lead to a suppression of amplification factor of 37.5%.
Research on vibration problem of integral mistuned bladed disk assemblies at home and abroad
BAI Bin, BAI Guang-chen, TONG Xiao-chen, XU Zhe, LI Xiao-ying
2014, 29(1): 91-103. doi: 10.13224/j.cnki.jasp.2014.01.012
Abstract PDF(1284KB) icon1596 icon1421
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Mistuned integral bladed disk assemblies,including the mode,the vibration transmission localization and the localization factors,were elaborated.Besides,the modeling and solving methods of mistuned bladed disk assemblies were discussed.The mainly related hot topics,the latest research methods and their achievements in recent 10 years,were reviewed and investigated in detail,including:nonlinearity,flutter,sensitivity,pneumatic and structure coupling,mistuning identification and prediction,mistuning optimization,intentionally mistuning,multi-stage and multi-component disks coupling,Coriolis forces,reliability and robustness etc.Finally,potential topics for future research work were proposed,for instance,building a more effective and applicative model with higher precision,verifying theoretical simulation with the test method,impact on multi-stage and multi-component integral bladed disk assemblies of pneumatic and structure coupling as well as the shroud tip and friction coupling,the principle of Coriolis forces,insensitivity and robustness to the mistuning of bladed disk assemblies and so on.
Research on fretting fatigue life of dovetail joints
SHI Wei, WEN Wei-dong, CUI Hai-tao
2014, 29(1): 104-110. doi: 10.13224/j.cnki.jasp.2014.01.013
Abstract PDF(1352KB) icon1750 icon940
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The fretting fatigue contact problem of dovetail joints between blade and disk in aero-engine was simplified due to geometric characteristic of the contact area. The stress, strain and displacement between these two contact bodies were obtained through the finite element method for numerical simulation of the simplified model. A fretting damage parameter was introduced and the research on the fretting fatigue life prediction model was carried out, based on the critical plane theory and fretting damage mechanism. The results confirm the validity of the life prediction model by comparing the estimated fretting fatigue life with the experimental life of TC11 and dovetail joints. And the errors are within 2 times of dispersion band.
Buckling load computation of spherical-cone diaphragms based on Kriging metamodel
ZHOU Suan, QIANG Hong-fu, WANG Xue-ren, WANG Guang, ZHOU Zhi-qing
2014, 29(1): 111-117. doi: 10.13224/j.cnki.jasp.2014.01.014
Abstract PDF(1249KB) icon1493 icon898
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Regarding typical structural characteristics of radius and thickness of diaphragms,height and angle of cone section,a method was built to compute the buckling load of diaphragms based on Kriging metamodel.The Kriging metamodel was validated by typical samples.Research results show that:for the Kriging metamodel based on Cubic correlation function,the error percentage to compute buckling loads at untried inputs is less than 5%,more suitable for computing the buckling loads of spherical-cone diaphragms than that based on Gauss correlation function;the metamodel could precisely compute buckling loads at untried inputs,without need of modeling and simulation by finite element method;the metamodel could compute parameter values of typical structural characteristics according to a set buckling load,and also could be used as bound function or object function for structural optimization design of spherical-cone diaphragms.
Control strategy of active magnetic bearing system based on variable bias current control
LONG Ya-wen, XIE Zhen-yu, XU Xin, WANG Xiao, ZHOU Hong-kai
2014, 29(1): 118-124. doi: 10.13224/j.cnki.jasp.2014.01.015
Abstract PDF(1622KB) icon1618 icon924
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The experiment setup of five degree-of-freedom active magnetic bearing (AMB) system was built up. The working principle of variable bias current control was presented. H∞ control strategy was adopted for the digital controller design. Weight functions were selected according to the vibration amplitudes of the rotor operating at the natural frequency of the system. The signal of the rotation speed was introduced into the digital controller. The dynamic performance of the system with variable bias current was investigated, and also compared with the result of the system with fixed bias current. The results show the variable bias current control will not deteriorate dynamic performance of the system and it reduces the total currents of AMBs more than 25%.
Numerical simulation of stall inception in single-stage axial-flow compressor
WU Yan-hui, WANG Xiao, LANG Fang-yu, WU Jun-feng
2014, 29(1): 125-132. doi: 10.13224/j.cnki.jasp.2014.01.016
Abstract PDF(2562KB) icon1609 icon985
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Based on the investigation results involving pre-stall behavior in subsonic single-stage axial-flow compressor test rig under isolated-rotor environment, whole-passage simulations were further carried out to investigate the stall inception process under single-stage environment. The monitoring results from the numerical probes indicate that the local breakdown of flow-field of single-stage axial-flow compressor is initiated at rotor tip region during stall inception process. The simulation results were validated by available experimental data. Detailed instantaneous flow-field analysis demonstrates that the type of pre-stall wave is "multi-cell" disturbance under single-stage environment in contrast to "spike" disturbance under isolated-rotor environment, implying that the presence of stator alters the pattern of near-tip circumferential loading distribution. However, the flow mechanism for the emergence of "multi-cell" disturbance is still represented by the formation and movement of tip secondary vortex.
Numerical and experimental investigation on highly loaded aspirated compressor cascade
LIU Bo, LI Zhi-peng, ZHAO Peng-cheng, CAO Zhi-yuan
2014, 29(1): 133-139. doi: 10.13224/j.cnki.jasp.2014.01.017
Abstract PDF(1549KB) icon1538 icon1069
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Numerical calculation and experiment were conducted on suction of boundary layer whose separation was induced merely by strong adverse pressure gradient without passage shock.The research was performed for a highly loaded aspirated compressor cascade with large turning angle.Numerical simulation was conducted using MISES which was used for simulating the flow field of quasi-3-D cascade.After deciding the suction position,wind tunnel experiment was conducted.The results show that,loss coefficient is reduced remarkably after suction,and for the boundary layer whose separation is induced merely by strong adverse pressure gradient,the best position for suction lies in where separation has already happened but not fully developed;the suction position can be decided according to the separation in design condition;the suction mass flow required in practice is less than that in calculation; in the numerical calculation,the concrete suction model needs further improvement and correction,in order to make the simulation more accurate.
Performance calculation of compressor based on object-oriented method
ZHENG Hong-tao, PAN Fu-min, YANG Ren
2014, 29(1): 140-145. doi: 10.13224/j.cnki.jasp.2014.01.018
Abstract PDF(1210KB) icon1588 icon990
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A characteristic prediction method was proposed and variable specific heat calculation was applied to the performance analysis and programming of compressor based on object-oriented theory.Also,a method named particle swarm optimization(PSO) based on back propagation (BP) neural network was presented by combining the global optimization ability of the PSO with the local optimization ability of the BP neural network,and the prediction error and fitting error were analyzed.The fitting error is mostly within 0.5% while the highest prediction error is within 0.8%;and both the fitting accuracy and prediction accuracy could meet the requirements.Variable specific heat calculation method was applied to the compressor performance calculation,and object-oriented method was used to build the compressor performance computing program.Compared with several working condition points of the compressor,the output parameter errors are less than 1.12%.Therefore,the characteristic prediction method and performance mathematical model are suitable for compressor performance calculation,and the compressor calculation procedure is also suitable for gas turbine performance calculation.
Correlative analysis of performance experimental data of axial flow fans/compressors based on statistical characteristic
XIANG Hong-hui, HOU Min-jie, LIU Zhi-gang
2014, 29(1): 146-152. doi: 10.13224/j.cnki.jasp.2014.01.019
Abstract PDF(1554KB) icon1549 icon1084
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Using correlative statistical study idea, performance experimental data of 14 units of domestic axial flow fans and compressors were collected. Two kinds of basic attributes were presented to describe aerodynamic performances of fan and compressor based on analysis and identification of shape structure of off-design characteristic curves of high mass flow fan and high pressure ratio compressor. In an attempt to build a number of non-dimensional physical parameters, the quantitative correlative relationship between shift degree under variable speed and operating range under constant speed of characteristics of fans and compressors was explored in the statistical level. The results show that offset degree of non-design rotating speed characteristic lines and operating range of effective mass flow of fans are greater than that of high pressure ratio compressors, and the relative pressure ratio, relative mass flow, relative mass flow-speed ratio and relative work-speed ratio on peak efficiency line of fans and compressors exhibit obvious statistical regularity. The uniform correlative analysis of performance experimental data can be conducted by means of some empirical mathematical models presented.
Influence of discretization of turbulence equation diffusion terms on flow field compuation of a radial impeller
XIAO Jun, ZHAO Yuan-yang, WANG Le
2014, 29(1): 153-160. doi: 10.13224/j.cnki.jasp.2014.01.020
Abstract PDF(2242KB) icon1471 icon886
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By discretizing convective terms with the HLLC scheme in the relative rotating coordinate system, a finite volume analysis code based on multi-block structured grids was developed independently, in order to numerically solve the internal flow fields of turbomachineries. The flow simulations of an unshrouded radial impeller and a shrouded backswept impeller were carried out respectively. The surface pressure at various blade heights calculated by the code and commercial software agrees well with the relative difference smaller than 1%, which verifies the accuracy of the algorithm. As for the diffusion terms of turbulence equations, full discretization and part discretization by neglecting cross-derivative terms were used respectively. Through comparisons of turbulence viscosity contour, aerodynamic force and moment, it indicates that neglecting cross-derivative terms exerts little impact of less than 1% on the results when the grid orthogonality is not too bad, and thus the calculation quantity of turbulence equations can be reduced obviously.
Experiment of effect of micro injection on compressor stability
LI Liang, HU Jun, WANG Zhi-qiang, TU Bao-feng, LAI An-qing
2014, 29(1): 161-168. doi: 10.13224/j.cnki.jasp.2014.01.021
Abstract PDF(2268KB) icon1486 icon898
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Experiment study was carried out on the low speed two-stage axial compressor about various injection arrangement and injection parameters, and the reason why the micro injection enhanced the compressor stability was explored. The results indicate:under the precondition that injection is equally distributed circumferentially and injectors aren't less than 4,the key influential factor to the compressor stable margin improvement is the outlet momentum of every injector.The mechanism of micro injection improvement stability is to suppress modal wave in the frequency and pressure amplitude,and closer to the injection means more modal wave is suppressed.Once injection can't suppress modal wave,the compressor enters into the stall condition.
Analysis of a turboshaft engine starting failure
CAI Jian-bing, LI Jian-hua, ZHONG Jian-ping, WANG Xu, LONG Ji-ping
2014, 29(1): 169-174. doi: 10.13224/j.cnki.jasp.2014.01.022
Abstract PDF(1446KB) icon1510 icon1052
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The test data of an engine outfield starting failure were analyzed.Also,the temperature field during startup was measured and the low oil pressure spray test of fuel jet nozzle was conducted.Finally the fuel jet nozzle carbon deposits were validated to decrease the fuel nozzle spray cone angle and deteriorate the quality of fuel spray,affecting the reliability of the cross ignition directly in engine starting and yielding a great impact on engine starting performance.The parts test results show that the insert depth of swirler has no effect on swirler outlet spray.The utilization results of engine simulation outfiled show that when the engine is operated for a long time under low state of power not greater than 30%,the centrifugal-type fuel jet nozzle is prone to carbon deposits.
Optimization of aero-engine nozzle control schedule under the maximum dry thrust condition based on installation performance
XIE Ye-ping, SHANG Shou-tang, LI Jian-rong, SHI Lei
2014, 29(1): 175-180. doi: 10.13224/j.cnki.jasp.2014.01.023
Abstract PDF(1637KB) icon1685 icon1170
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A zooming technology was implemented by combining aero-engine zero dimensional performance code and computational fluid dynamics (CFD) software for simulating two-dimensional nozzle inner/outer flow.The research was conducted based on Matlab with the incorporation of MS-DOS command and CFD operational log.To optimize the cruise performance of aircraft propulsion system and aircraft afterbody drag,the control schedule of aero-engine nozzle throat area and exit area was investigated.The results show that the installed thrust of aero-engine is improved over 1% in the flight condition of high Mach number only by optimizing the schedule of nozzle exit area,while maintaining the stability margin of aero-engine.
Design of turbo diffuser for TBCC inlet based on characteristics of turbo mode
ZHANG Hua-jun, LIU Xing-guo, GUO Rong-wei, XIE Lü-rong
2014, 29(1): 181-191. doi: 10.13224/j.cnki.jasp.2014.01.024
Abstract PDF(2739KB) icon2019 icon963
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Turbo diffuser for over/under type TBCC (turbine based combined cycle engine) inlet was designed with extended center line under different flow section area variation laws and blend radius variation laws. The influence of design parameters on the turbo diffuser and its aerodynamic characteristics in turbo mode were investigated by numerical simulation. High speed wind tunnel experiments were carried out to validate the numerical simulation method. Results indicate that turbo diffuser obtains high total pressure recovery coefficient and low total pressure distortion index at outlet when the ordinate of center line control point is within 1.50-2.25 and the ratio of constant area section length of turbo diffuser to exit radius is within 0.3-0.7. Both the flow section area and blend radius variation laws in a "first quick,then slow" manner contribute to a low total pressure distortion index at outlet of turbo diffuser. With the increase of flight Mach number, mass flow coefficients of both inlet and turbo diffuser firstly decrease until reaching its lowest point at flight Mach number of 0.9, then increase subsequently. Total pressure recovery coefficient at outlet of turbo diffuser firstly increase then decrease and the peak comes around at flight Mach number of 0.7. The total pressure distortion index at outlet of turbo diffuser is less than 0.5 for turbo mode and it satisfies the requirements of turbo engine for the flow quality at the entrance section.
Optimization design of shroud configuration of transporter based on surrogate model
MA Yang, WANG Dan-dan, YANG Tao, FENG Zhi-wei, ZHANG Qing-bin
2014, 29(1): 192-198. doi: 10.13224/j.cnki.jasp.2014.01.025
Abstract PDF(1608KB) icon1528 icon928
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Transporters with different shroud configurations were chosen, and aerodynamic characteristics were analyzed. Kriging surrogate model was introduced and established with aerodynamic characteristic parameters. The surrogate model with adequate analysis precision was used to replace CFD analysis in optimization process.Single-objective optimization with the minimum resistance coefficient and the maximum longitudinal pressure center coefficient of transporter and multi-objective optimization considering these two objects were implemented under the conditions of Mach number of 3,angle-of-attack of 3 degrees and flight altitude of 8km.The optimization results indicate that the conflict exists between two objects. To take account of decreasing the resistance and enhancing the longitudinal stability, multi-objective optimization is necessary and the method based on surrogate model is efficient and credible.Optimization design obtains desired configuration of transporter,where the resistance coefficient is decreased by 1.95%,and the longitudinal pressure center coefficient is increased by 5.93%.
Nonlinear mathematical model of regenerative cycle microturbine
DUAN Jian-dong, ZHAO Ke, WU Feng-jiang, SUN Li, WANG Yao-qiang
2014, 29(1): 199-206. doi: 10.13224/j.cnki.jasp.2014.01.026
Abstract PDF(1635KB) icon1541 icon1012
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Nonlinear dynamic model of regenerative cycle microturbine was established and considering versatility,the static model was built by using analytical generic characteristics of compressor,recuperator and turbine under the off-design conditions.The general mathematical model was instantiated according to the specific design parameters; the determination method of analytical characteristic coefficients was given and the computer simulation iteration order was achieved.Results show that there is small difference between the static characteristic simulation results and the actual reference data of Capstone C30,so better consistency with actual reference data can be gotten according to regulating coefficients of analytical generic characteristic formulae using more detailed specific design parameters.The best operation mode with constant turbine input temperature is adopted,with the dynamic time about 100s from empty load to full load;in the same time the metal wall average temperature of recuperator drops from 750K of empty load to 670K of full load.
Analysis on dynamic characteristics of cage in high-speed cylindrical roller bearing
DENG Si-er, GU Jin-fang, CUI Yong-cun, SUN Chao-yang
2014, 29(1): 207-215. doi: 10.13224/j.cnki.jasp.2014.01.027
Abstract PDF(2655KB) icon2520 icon1178
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Dynamic differential equation of a high-speed cylindrical roller bearing was established.Fine integral method and predict-correct Adams-Bashforth-Moulton multi-step method were used to solve the dynamic differential equations of high-speed cylindrical roller bearing.Then the dynamic characteristics of cage were analyzed and discussed.The result shows:it's unlikely to keep stable rotation of cage when the ratio of pocket clearance to guiding clearance becomes too large;when one of the rings is fixed, the other is working and the cage guided by the rotating ring has lower slip ratio;it is helpful for stable mass center motion of cage when the cage is guided by outer ring; when the bearing is co-rotating and its outer ring's speed is larger than its inner ring's speed, the cage is guided by outer ring, and the cage has lower slip ratio;when the bearing is counter-rotating and its inner ring's speed is smaller,mass center trajectory of cage becomes irregular;the value of cage slip ratio becomes negative when the cage is guided by outer ring.
Dynamic performance tests of bump-type gas foil journal bearing-rotor system in start-up and shut-down procedures
XU Fang-cheng, LIU Zhan-sheng, MA Rui-xian, HUANG Fei-lin
2014, 29(1): 216-224. doi: 10.13224/j.cnki.jasp.2014.01.028
Abstract PDF(2583KB) icon1640 icon956
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In order to study the dynamic performance of bearing-rotor system supported by bump-type gas foil journal bearing, a test bed was designed for bump-type gas foil journal bearing. A rotor of 0.458kg including turbine was supported by two bump-type gas foil journal bearings and multi-leaf thrust gas foil bearing, and the speed was more than 80000r/min. The experimental results show that bump-type gas foil journal bearings can offer high-speed operation stability after rotor lift-off, and the vibration displacement amplitude at bearing support is less than 20μm. The rotor lift-off speed in start-up procedure is higher than that in shut-down procedure due to asymmetric drive of turbine.
Compound fault diagnosis method for gearbox based on morphological component analysis and order tracking
CHEN Xiang-min, YU De-jie*, LI Rong
2014, 29(1): 225-232. doi: 10.13224/j.cnki.jasp.2014.01.029
Abstract PDF(2009KB) icon1950 icon1050
Abstract:
In view of the problem of extracting fault characteristics from rotating speed changing gearbox with compound faults, a compound fault diagnosis method for gearbox based on morphological component analysis(MCA) and order tracking was proposed. According to the morphological diversity of the fault signals of gear and rolling bearing, the vibration signals of gearbox with compound fault could be decomposed into the harmonic component containing the fault information of gear, the impulse component containing the fault information of rolling bearing and the random noise component by using MCA. And according to the measured rotating speed,the harmonic component and the impulse component were then analyzed respectively by the envelope order analysis, and the compound fault diagnosis was carried out based on the envelope order spectra. Simulation and application examples indicate that the proposed method can effectively separate the fault characteristic signals of gear and rolling bearing under changing rotating speed,and it is superior to traditional envelope order spectrum method according to the effect of fault characteristic extraction.
Mission reliability simulation modeling of space TT&C system based on DSPN
YANG Xiao-song, WU Xiao-yue
2014, 29(1): 233-240. doi: 10.13224/j.cnki.jasp.2014.01.030
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Abstract:
A general methodology for mission reliability modeling and analysis of space TT&C system using DSPN was proposed to evaluate the TT&C scenarios.By dividing the time sequences of TT&C mission profile and taking into consideration of the complex situations which were difficult to be dealt with by other modeling methods such as phase dependency of TT&C units,reparability of the system and different time intervals for various TT&C units,the mission reliability of TT&C system was modeled by "component-system logic-phase " three levels of Petri nets (PN) that could interact with each other.After simulating the DSPN model,the quantitative assessment mission reliability of TT&C system for given TT&C scenario can be obtained.The case study reveals that the simulation results have a good convergence with the increase of simulation numbers,and the errors are controlled with one percent compared with the analytical result of Markov analytic method.

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