2011 Vol. 26, No. 10

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Display Method:
WSK-SV algorithm based on scaling function of wavelet and its prediction for aerodynamic performance
WANG Bao-guo, XU Yan-ji, AN Er, SUN Tuo
2011, 26(10): 2161-2166.
Abstract PDF(958KB) icon1881 icon15
Abstract:
A new wavelet scaling kernel-support vector (WSK-SV) algorithm based on scaling function of wavelet and support vector (SV) algorithm was presented in this paper,which firstly took Daubechies and Shannon wavelet-scaling kernel function for a kind of admissible support vector kernel,respectively.WSK-SV algorithm possesses such properties as compactly supported wavelet bases,orthogonal bases,multiresolution analysis (MRA),and satisfies Mercer condition for scaling kernel function.This algorithm not only has the advantages of general support vector machine (SVM),but also has a good convergence and excellent capacity of generalization,which can improve the learning efficiency and predicting ability.Numerical experiments demonstrate that this proposed WSK-SV algorithm is feasible and effective.
Improved DES-like method for simulation of turbulent flows
WANG Hong-bo, SUN Ming-bo, WU Hai-yan, WANG Zhen-guo
2011, 26(10): 2167-2173.
Abstract PDF(1131KB) icon2200 icon13
Abstract:
A hybrid RANS/LES (Reynolds-averaged Navier-Stokes/large eddy simulation) approach based on one-equation S-A(Spalart-Allmaras) RANS model and one-equation Yoshizawa SGS(sub-grid scale) model was developed.The turbulent kinetic energy transport equation of the SGS model was transformed to an equivalent eddy viscosity transport equation,and then blended with the S-A model equation to generate a hybrid eddy viscosity transport equation,wherein both the SGS behavior and the grid-depending RANS-LES transition of DES were improved.The hybrid RANS/LES approach was then applied to simulate a supersonic,ramped cavity flow,where LES and DES were also implemented on the same mesh for comparison.It shows that the hybrid RANS/LES acts like LES in the free shear flow far away from the wall and outperforms LES and DES in the attached boundary layer.
Investigation on nacelle conversion envelope analysis method of tiltrotor aircraft
CAO Yun-yun, CHEN Ren-liang
2011, 26(10): 2174-2180.
Abstract PDF(970KB) icon2385 icon39
Abstract:
For conversion mode of tiltrotor aircraft from helicopter mode to fixed wing airplane mode,an analysis method based on the transition flight's characteristics of morphing,and speed change was established to investigate the nacelle conversion envelope.The method includes the lower speed and higher speed envelopes.A detailed analysis of the matching relationship between the rotors aerodynamic forces and wing aerodynamic forces in the conversion mode was conducted.The lower conversion boundary was restricted by wing stall and the upper conversion boundary restricted by available power limited by engines.The XV-15 tiltrotor aircraft was taken as an example to analyze the conversion envelope.The results fairly agree with the XV-15 data,showing that the calculation methodology for the nacelle conversion envelope of tiltrotor aircraft is reasonable and effective.
Influence of single square pulse injection on restart characteristics for mixed-compression inlet
YOU Jin, XIA Zhi-xun, FANG Chuan-bo, HU Jian-xin, LIU Bing
2011, 26(10): 2181-2187.
Abstract PDF(1156KB) icon1724 icon13
Abstract:
The unsteady numerical study of the mixed-compression inlet restarting flow with the single square pulse injection was performed.The results show that mass flow entering the inlet decreased and external normal shock is swallowed into lip with the joining of the injection on ramp,because of the blockage of the jet to incoming flow.As the mass flow of jet exceeds the threshold value of 5% of inlet mass flow,and the duration time of injection is less than 15ms,needing at least 0.0014kg gas for injection,the unstart flow of inlet will restart.And a high-frequency oscillation flow with 135Hz arises when the mass flow of jet is less lightly than the threshold value.The duration time for restart and total gas mass reduce with the increase of mass flow of jet because of the faster flow response when the mass flow of jet exceeds the threshold value.
Structure of low-head two-phase flow in flat nozzles during outflow of the liquid into rarefied medium
Kochenkov A G, Tonkonog V G
2011, 26(10): 2188-2192.
Abstract PDF(868KB) icon1414 icon13
Abstract:
Outcomes of experimental researches of the low-pressure adiabatic flow of the boiling liquid through two-dimensional Laval nozzles in a vacuum atmosphere were adduced. Requirements of critical conditions of flow were determined. Structural forms of a stream were investigated and their connection with crisis of flow was shown. It was established periodic non-stationary macrostructures of a stream which was stipulated by the rotational gear of origin of a vapor phase.
Optimization design of hypersonic axisymmetric inlet with controllable law of wall pressure rise
XIANG You-zhi, ZHANG Kun-yuan, WANG Lei, GAO Xiong
2011, 26(10): 2193-2199.
Abstract PDF(1018KB) icon1881 icon22
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The design method of axisymmetric wall boundary with a controllable law of wall pressure rise was investigated using the theory of rotational characteristics.With this design method, multi-objective optimization of the compression surface was carried out on the basis of surrogate models, and then a hypersonic axisymmetric inlet was designed using the optimal solutions.The inlet was investigated through numerical simulation, and was compared with the normal double-cone and triple-cone inlet.The results show that the length of new inlet is reduced by 32.5% of the radius than the double-cone inlet;under the design point, the performance of the new inlet lies between the double-cone and triple-cone inlet;under the start point, the flow capture ratio is improved by 8.24% and 12.60%, and the total pressure recovery is improved by 4.06% and 2.50% than the double-cone and triple-cone inlet, respectively.
Experimental on nonlinear vibration characteristics of high-speed rotor bearings system with compressor and turbine structure
YANG Jin-fu, CHEN Ce, LIU Yu-han, HAN Dong-jiang
2011, 26(10): 2200-2206.
Abstract PDF(1419KB) icon1899 icon12
Abstract:
Based on gas-dynamic bearings and frequency coupled modulation of rotor-bearing system,the characteristics of rotor bearing system's nonlinear vibration experimental investigations were applied to high-speed air cycle refrigerator.Furthermore,some nonlinear characteristics,for example,the motion of rotor,bearings instability and rub-impact which always happen on the flexible shaft,were analyzed.The results show that,if the design margin of safe speed is guaranteed,the steady running speed of the rotor-bearings system can be effectively increased from 40000r/min to 60000r/min above.
Method for locating rub fault of rotor-stator based on acoustic emission beamforming
HE Tian, LIU Yao-guang, CHEN Ya-nong, LIU Xian-dong
2011, 26(10): 2207-2213.
Abstract PDF(1091KB) icon2506 icon22
Abstract:
A method for locating rub fault in rotating machinery based on the beamforming of acoustic emission signals was presented.Firstly,the propagation characteristics were obtained by using plate wave theory.On the basis of these results, the feasibility of locating rotating machinery rub fault by the beamforming of acoustic emission signals was confirmed,and the acoustic emission beamforming method was presented.Then,by breaking a mechanical pencil lead on the surface of the stator,the artificial acoustic emission was implemented to verify the presented method.Finally,the present method was used to diagnose the rotor-stator rub fault on the fault experimental device,and the results were analyzed, showing that the acoustic emission beamforming method can identify rub position efficiently.
Control strategy and methods of rotor systems by an elastic support / dry friction damper
WANG Si-ji, LIAO Ming-fu
2011, 26(10): 2214-2219.
Abstract PDF(917KB) icon2029 icon21
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A proportional integral (PI) controller and continuous gain scheduling proportional integral (GSPI) controller for active control of rotor vibration were developed,according to the characteristics of elastic support/dry friction damper (ESDFD).The theoretical analyses and numerical simulation results show that it is very effective to reduce rotor vibration around the first critical speed by using these control algorithms.Moreover,the continuous GSPI controller has the advantage of giving a well-behaved rotor run-up while maintaining the efficient controlled behavior to attenuate the amplitude of vibration of the first critical speed.
Multiaxial low cycle fatigue life prediction and test verification for turbine disk
YANG Jun, LI Cheng-bin, XIE Shou-sheng
2011, 26(10): 2220-2226.
Abstract PDF(1175KB) icon2201 icon16
Abstract:
The fatigue life of a two-stage turbine disk transmission arm pin hole was predicted by the models of uniaxial,Von Mises strain and critical plane.A full-scale two-stage turbine disk was fabricated and debugged,and then tested for LCF(low cycle fatigue).The predicted life was compared with the life evaluated by fatigue test of real turbine disk,and the result shows that the predicted errors of the critical plane model are less than those of the uniaxial model and the Von Mises strain model,especially the error of SWT(Smith-Watson-Topper)model is 9.26%.
Stability analysis of parametric resonance of a crack cylindrical shell with time-varying rotating speed
XIN Jian-qiang, WANG Jian-jun
2011, 26(10): 2227-2236.
Abstract PDF(1301KB) icon1408 icon12
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A crack cylindrical shell model with time-varying rotating speed was established using the finite element method and get the system quality stiffness and damping matrix.On the basis of modal analysis,Bolotin's method was applied to explore the dynamic instability region.Examples of stability charts were worked out and the dependence of stability on various parameters,including crack length C,modal damping ratio ξ,rotating speed basic value Ω0,steady load factor α and dynamic load factor β was discussed.
Aerothermoelastic coupling dynamic model of panel flutter with time delay of heat transfer
LI Kai-lun, ZHANG Jia-zhong, ZHOU Zhen-tang
2011, 26(10): 2237-2244.
Abstract PDF(1185KB) icon1372 icon9
Abstract:
A two-dimensional infinite aerothermoelastic dynamic model of panel flutter,in which the heat transfer with time delay has been considered,was established to investigate the flutter behaviors of the panel structures of aircraft in hypersonic flow. In this study, a new model for the temperature distribution in the panel was presented considering only the finite temporal history effects,and proved mathematically for the accuracy.Then,the internal moment in the panel,which is neglected in existing model,was successfully introduced into the panel flutter model.From the numerical results,it can be seen that the aerodynamic pressure is a main driving force of the panel flutter,the internal force acts as an external pre-tightening force on two sides of the panel,and the internal moment drives vibration of the panel with small amplitude.Taking all the factors mentioned above into account,the vibration of the panel under aerothermoelastic coupling was studied in detail.It is found that the vibration becomes very complex as the Mach number is large.Finally,some kind of nonlinear dynamical behaviors were captured and analyzed by nonlinear dynamical theory.
Structure optimum design techniques for multi-web fan disk based on ANSYS
LI Lun-wei, LU Shan
2011, 26(10): 2245-2250.
Abstract PDF(855KB) icon1938 icon21
Abstract:
An optimum design model was established and main optimum design variables were chosen for fan disks based on ANSYS optimization platform.A typical fan disk structure was designed optimally by use of single-web and multi-web disk respectively.The results show that the weight of multi-web disk is much smaller than that of single-web disk, while both the deformation and strength requirements are satisfied, and the stress distribution of the former is more uniform.Generally, the multi-web has an evident advantage for the fan disk with wide rim.Moreover, multi-web fan disk is beneficial to increasing the rim's bending stiffness.
Sensibility analysis of inlet pre-swirl angle in the rotating cavity
DING Shui-ting, LI Ye, ZHANG Gong
2011, 26(10): 2251-2257.
Abstract PDF(1047KB) icon2192 icon14
Abstract:
Unidirectional FSI (fluid structure interaction) numerical method was applied to investigate the influence of the inlet pre-swirl angle on the cooling effect of the rotating cavity.And the cooling effect was evaluated by an engineering evaluation system,which includes resistance evaluation,heat transfer evaluation and stress distribution evaluation for the safety of the turbine disk.The results show that,the swirl ratio is a monotropic function of the inlet pre-swirl angle,while the inlet Reynolds number and the rotational Reynolds number are constant.The swirl ratio has a great influence on the fluid structure in the rotating cavity,which determines the heat transfer and temperature distribution of the rotating disk.Furthermore,the thermal stress of the rotating disk related to the temperature gradient could be affected.With the rise of the swirl ratio,the frictional windage of the rotating cavity increases,the heat transfer of the windward of the disk presents up-down tendency,the stress level and maximum value enlarge.Therefore,the change of the pre-swirl angle has an effect on the failure probability of the turbine disk from two aspects:material affordability and working stress.
Detailed reaction kinetic modeling of n-decane premixed combustion
ZENG Wen, LIU Jing-chen, CHEN Xiao-xiao, XIE Mao-zhao
2011, 26(10): 2258-2266.
Abstract PDF(1081KB) icon2052 icon15
Abstract:
A detailed reaction mechanism for the premixed combustion of n-decane was compiled and the process of n-decane premixed combustion was simulated.The mole fractions of the reactants,the major combustion products and the intermediate species were analyzed.At the same time,the simulation results were compared with the experimental data of the n-decane and kerosene premixed flames,respectively.The results show that the shapes of the profiles of the mole fractions of the reactants and the major combustion products in n-decane flame agree with that in kerosene flame.The simulated profiles of the mole fractions of the reactants and the major combustion products agree with the experimental data of the n-decane and kerosene flames,showing that this detailed reaction mechanism can well reflect the detailed kinetic characteristics of n-decane premixed combustion.Furthermore,through net reaction rate analysis,it's found that major paths consuming n-decane are implemented through thermal decomposition and abstraction of H and OH.
Experimental study on compressible flow in trapped vortex cavity
SONG Shuang-wen, LEI Yu-bing, YAO Shang-hong, MA Hui, HU Hao-sheng
2011, 26(10): 2267-2273.
Abstract PDF(1673KB) icon2017 icon14
Abstract:
The effect of geometry and aerodynamic factors on the flow in trapped vortex cavity was evaluated.The effect of geometry was analyzed by altering the ratio of height to length(H/L) of the cavity,injection position and main-flow inlet angle;the impact of aerodynamics was analyzed by varying main-flow and second inject flow inlet velocity.Total pressure loss was measured by total pressure probe,and the velocity field was measured by particle image velocimetry (PIV).The results reveal that:(1) When the position of the injection holes is in the bottom or the middle position,large scale vortexes can be formed in the trapped vortex cavity.A couple of opposite swirling vortexes are formed in the middle position;and only a single vortex can be formed in the bottom. (2) For the middle injection configuration, increasing the main-flow mach number and inlet angle can enhance the vortex intensity in the upside of the cavity. (3) The total pressure loss increases apparently with the growing main-flow inlet Mach number.
Calculation and experiment on minimum ignition energy at high altitude for a piston aero-engine
XU Shan-zhen, WEI Min-xiang, BAI Hong-lin
2011, 26(10): 2274-2280.
Abstract PDF(922KB) icon2427 icon13
Abstract:
A one-dimensional simulation model of a piston aero-engine was established with AVL BOOST according to the structure of the prototype engine. And the simulation model was validated by the ground performance experiment and simulation computation. A mathematical model was set up to calculate the minimum ignition energy based on thorough analysis of combustion mechanism of the engine combustible mixture. Then the minimum ignition energy at high altitude with different air-fuel ratios under stable operation condition was calculated by using AVL BOOST and MATLAB, and the minimum ignition energy MAP was provided. Experiment was conducted to validate the calculation results. The results show that the model of calculating the minimum ignition energy is correct and feasible, and also can meet the requirements of further research and performance prediction.
Numerical computation and analysis of three-dimensional wall temperature of impingement+identical flow convection+film composite cooling
WANG Mei-juan, SONG Shuang-wen, HU Hao-sheng, PENG Jian-yong
2011, 26(10): 2281-2286.
Abstract PDF(1046KB) icon1709 icon11
Abstract:
Fluid/solid conjugated heat transfer numerical computation was conducted to study impingement+identical flow convection+film composite cooling by using Fluent 6.3,and the trend of wall temperature field and the cooling effect were obtained,and then the computational results were compared with the testing results.The results indicate that the wall temperature distribution of the composite cooling is well-proportioned,and the cooling effect is better.The numerical results are in good agreement with the testing results,with their maximal relative error of 3.6%.
Numerical research on infrared radiation characteristics of two-dimension nozzle with shelter covering
WU Bo, ZHANG Jing-zhou, SHAN Yong, SHAO Wan-ren
2011, 26(10): 2287-2292.
Abstract PDF(1138KB) icon2105 icon9
Abstract:
Based on CFD/IR(computational fluid dynamics/infrared radiation) numerical calculations,the effects of shelter covering fixed at nozzle trailing edge and cooling air injected inside the shelter covering passage on infrared radiation characteristics of turbofan engine two-dimensional nozzle with aspect ratio 3.33 were investigated.The results based on the present parameters show that,ejected or forced cooling air flow through shelter covering passage enhances further mixing with plume,and suppresses plume infrared radiation in comparison with pure two-dimensional nozzle.As the cooling air massflow increases,the cooling action on nozzle trailing edge is more obvious.Utilizing nozzle ejection effectively could achieve satisfactory infrared radiation suppression.The suppression action on nozzle total infrared radiation with shelter covering is only realized in the detecting azimuth where the infrared radiation from nozzle inner walls is predominant.
Research progress and development prospects of the ram-rotor
ZHONG Jing-jun, HAN Ji-ang, YANG Ling
2011, 26(10): 2293-2301.
Abstract PDF(1419KB) icon1725 icon34
Abstract:
Based on analysis of the concept,principle and structure characteristics about the ram-rotor that adopts the technology of shock compression,the research progress both at home and abroad in this field was summarized,and technical difficulties and development prospects of the new compression system were also analyzed and discussed.
Turbulence modelling of the aerodynamic interaction of OGV wakes and diffuser flow
LI Jing-hua, Page Gary, McGuirk Jim
2011, 26(10): 2302-2312.
Abstract PDF(1233KB) icon2111 icon14
Abstract:
Different turbulence closures were used to predict the flow interaction between the wakes created by compressor outlet guide vanes (OGVs) and a downstream annular pre-diffuser. Two statistical turbulence models were tested based on the classical Reynolds-averaged Navier-Stokes (RANS) approach. Both high- Re and low- Re (Launder-Sharma) versions of the k-ε model were applied to a selected test problem for OGV wake/diffuser flows. The test problem was specifically chosen because experimentally determined inlet conditions and both profile and performance data were available to validate predictions. A preliminary study was also reported of the more advanced large eddy simulation (LES) approach. The LES sub-grid-scale (SGS) model was the basic Smagorinsky eddy viscosity assumption, with a Van-Driest damping function for improved capture of near-wall viscous behaviour. Comparison between the two RANS models showed little difference in terms of velocity contours at OGV trailing edge and diffuser exit. In terms of overall diffuser performance (static pressure recovery and total pressure loss coefficients), the high- Re model was shown to agree well with experimental data. The preliminary LES study indicates the highly unsteady character of the OGV wake flow, but requires improved treatment of inlet conditions.
Aerodynamic design and investigation of two counter-rotating fans
YANG Xiao-he, SHAN Peng
2011, 26(10): 2313-2322.
Abstract PDF(1491KB) icon1688 icon13
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The design rotating speed ratio of forward and afterward rotors was discussed based on one-dimensional analysis.The variations of pressure ratios,adiabatic efficiencies,diffusion losses and shock losses at the streamline of half-annulus-area radius against the varied design rotating speed ratios were studied.The flow fields of these two contra-stages were numerically simulated and the detailed flow physics was investigated at the design and off-design conditions.The simulations reveal that these two stages are quite well performed.For the civil engine contra-stage test fan,both rotors are conventional transonic rotors due to the low pressure ratio and low tip speed.For the military engine contra-stage fan different from the conventional transonic forward rotor,the afterward rotor is a full-span relative supersonic rotor in which both the leading edge shock and the passage shock extend from the casing to the hub.Furthermore,these two contra-stages exhibit stall margins competitive to conventional rotor-stator stages.For the civil test fan of low pressure ratio at the stall point,both the forward and afterward rotors are stall and the shocks are detached,correspondingly;for the military fan of high pressure ratio,only the afterward rotor is stall,determining the stage stall point.
PIV experiment of Reynolds stress-strain lag eddy viscosity model in axial fan
JIA Yong-xia, JIANG Nan
2011, 26(10): 2323-2329.
Abstract PDF(1096KB) icon1783 icon13
Abstract:
Time-resolved particle image velocimetry(PIV)was used to investigate the flow at suction and pressure sides of 60% span of blades,as well as the flow at the radial plane of fan outlet in a low-speed forward-swept axial fan with three blades at Reynolds number of 370000,based on the tip speed and the blade chord.The data was processed to yield the time evolution of Reynolds shear stress and averaged velocity shear strain using the phase-averaged method,and the spatial phase relationship between the both was investigated through the correlation technology.The phase lag between Reynolds shear stress and averaged velocity shear strain was found,which phenomenon widely existed in the three-dimensional non-equilibrium turbulence.So the studied Reynolds stress-strain lag eddy viscosity model could be considered as a promising closure for improving the state-of-the-art industrial computational fluid dynamics by accounting for non-equilibrium effects in comparison with a classical linear k-ε model,which is widely applied in the industry.
Full-annulus simulations on axial compressor rotor at near stall condition
LI Qing-peng, WU Yan-hui, CHU Wu-li, ZHANG Hao-guang
2011, 26(10): 2330-2338.
Abstract PDF(1637KB) icon1744 icon14
Abstract:
Full-annulus unsteady simulations were performed on a subsonic axial compressor rotor,and the detailed flow parameters at near stall condition were achieved.Ten numerical static pressure probes arranged in front of the leading edge could detect two pressure disturbances,one of which was developed into a spike wave.According to analysis of the flow field,tip secondary vortexes exist in almost all passages near the blade tip and the most violent one appears in the disturbing areas.Tip secondary vortex could force tip clearance flow to form “leading edge spilling flow” and “trailing edge back flow”.The movement of the pressure disturbance along circumference was caused by the spreading of tip secondary vortex from one passage to the next.Continuous growth of tip secondary vortex in its spreading finally led to formation of spike wave.The phenomenon that the “trailing edge back flow” goes through the inlet and spills into the adjacent passage under the blade tip can be regard as the symbol of spike emergence.
Design and experimental study on high flowrate multi-element gas-gas injector chamber
WANG Xiao-wei, GAO Yu-shan, CAI Guo-biao
2011, 26(10): 2339-2345.
Abstract PDF(1091KB) icon2084 icon20
Abstract:
To investigate the combustion characteristics of high flowrate injector in the multi-element injector chambers having interaction between the elements,based on high flowrate gas-gas injector studies in the single-element condition,a multi-element injector equipped with seven shear mixing elements was deigned,which can simulate effectively the real engine.The shear mixing element had high H2/O2 velocity ratio and tapered O2 post tip.Numerical simulation and hot-fire tests were carried out with this injector using the optimal design of the injector layout.Steady operations were obtained in all these tests,and the injector showed benign heat environments on the faceplates and cylinder walls.Combustion efficiency above 99% was gotten for this injection element in the flowrate of 3.7 times of SSME(space shuttle main engine) main injection element.
Performance characteristics of hybrid rocket motors with different grain types
ZHU Hao, CAI Guo-biao
2011, 26(10): 2346-2351.
Abstract PDF(956KB) icon2212 icon15
Abstract:
Based on the geometrical law of burning,the discipline how the burning area and burning perimeter length change with the increase of burned web thickness for different grain types was deduced.The hybrid rocket motor design model was established to convert the design process to mathematical model.Then a genetic arithmetic was used to optimize the design of hybrid rocket motor with different grain types.Through comparison and analysis of the optimal results,the study of hybrid rocket motor performance characteristics and the mechanism with different grain types were implemented,and the difference between the hybrid rocket motor and solid rocket motor in internal ballistic performance was pointed out.
Design and experimental research of a gas oxygen / propane small thrust engine
LI Jun-hai, ZENG Peng, YU Nan-jia, CAI Guo-biao
2011, 26(10): 2352-2357.
Abstract PDF(1111KB) icon1904 icon19
Abstract:
A kind of small thrust engine,using gas oxygen and propane as the propellants,was designed in tune with the development of new generation small thrust engine that features non-toxicity,non-pollution,high performance and low cost.With platelet injectors,electrical spark ignition was implemented using the gap between different injectors.The film cooling injectors were used for cooling the body of the engine.An experimental system was designed and a series of experiments were conducted.The results show that the experimental system scheme is reasonable.The ignition of the engine is reliable and the combustion is stable,showing good effect of thermal protection.The experimental system and small thrust engine work well,indicating they are excellent fundamental platforms for the future investigation.
Vacuum experiment study on a N2O monopropellant micro-thruster
HAN Yue, LI Mao, FANG Jie, SUN Wei, CAI Guo-biao
2011, 26(10): 2358-2363.
Abstract PDF(943KB) icon1673 icon12
Abstract:
Impulse measurement scheme for a nitrous oxide (N2O) monopropellant micro-thruster was presented.The experiment results were used to fit the relationship between the steady thrust and the pressure.Dynamic pressure was utilized to calculate the thrust and impulse.Two different micro-thrusters with catalytic bed of φ 8mm×35mm and φ 10mm×25mm were fabricated and experimented.The influence of the mass flow on the specific impulse performance was studied.The relationship between the steady thrust and the pressure in different mass flow rates was obtained.Experiment strategy and analysis result can provide some reference for accurate control of the micro-thruster impulse.
Method of dual-redundant control law design for aero-engine
JIANG Cai-hong
2011, 26(10): 2364-2370.
Abstract PDF(880KB) icon1618 icon11
Abstract:
A concept of dual-redundant control law design for aero-engine was proposed and a method of utilizing dual-redundant control law for the control sensors signal fault processing policy was derived in the paper.The technique and principles of the backup control law design were built and applied to the dual-redundant control law design and research of one high performance turbofan engine.The study result indicates that the dual-redundant control law can be made undisturbed conversion and control loop reconfiguration,so that mission reliability of engine is improved.The means may have application in all kinds of engine which is equipped with digital electronic control system.
Performance seeking control of turbo shaft engine with variable inlet guide vanes
ZHOU Jian-bo, SHI Rui-jun, ZHANG Qiu-gui, FAN Si-qi, SUN Jian-guo
2011, 26(10): 2371-2375.
Abstract PDF(893KB) icon1981 icon18
Abstract:
A mathematical model of turbo shaft engine with variable inlet guide vanes was established according to the theory of variable specific heat.Numerical simulations had been conducted on the mathematical model.The performance seeking control(PCS) modes of variable geometry turbo shaft engine had been investigated.Simulation results show that the engine model works well with higher accuracy and the PSC control modes can significantly improve the performance of turbo shaft engine.
Gas-path fault diagnosis for aero-engine based on variable weighted least-squares
LU Feng, HUANG Jin-quan, KONG Xiang-tian
2011, 26(10): 2376-2381.
Abstract PDF(875KB) icon1950 icon12
Abstract:
A method of variable weighted least-squares was presented to solve the problem of large deviation in aero-engine gas-path fault diagnosis.Weighted least-squares was adopted and improved by correcting the weight coefficient matrix depending on the initial diagnosis result.Simulation on a turbofan engine shows that this method can provide meaningful and verified diagnosis of severe fault with more believable results.
Thermal tribology analysis of spiral bevel gears in EHD lubrication
WANG Yan-zhong, ZHOU Yuan-zi, CHEN Cong-hui, GUO Mei, ZHAO Xing-fu
2011, 26(10): 2382-2387.
Abstract PDF(1037KB) icon1888 icon16
Abstract:
The thermal elastohydrodynamic (EHD) analysis of lubrication was applied to investigate the friction factor of spiral bevel gears in helicopter's main transmission system.The calculation was based on the simultaneous solution of the Reynolds,energy and elasticity equations,including variations of lubricant viscosity and density in relation to pressure and temperature.The real contact load and velocities of sliding and entrainment between meshing tooth surfaces were treated based on loaded tooth contact analysis (LTCA) of spiral bevel gears.A thermal finite element analysis based on one-tooth sector model developed by real tooth profile was actualized,with calculated heat flow rate generated by sliding friction as thermal load and heat convection coefficients of all exposed surfaces as thermal boundary conditions.The tooth temperature field in steady state and flash temperature of contact location in transient state over several revolutions were investigated.The obtained results were reported and discussed.The comparison with analytical and experimental results from references and gear bench test was given in the end.
Grinding wheel dressing method for inner helical gear form grinding based on numerical simulation
SU Jian-xin, DENG Xiao-zhong, REN Xiao-zhong, XU Kai
2011, 26(10): 2388-2393.
Abstract PDF(1009KB) icon2239 icon17
Abstract:
In view of grinding interference produced in the process of inner helical gear form grinding,the grinding wheel dressing method for the inner helical gear form grinding was studied.On the basis of establishing the mathematical model of inner helical gear form grinding,the conditional equations sets conforming to the contact points between grinding wheel and tooth space were obtained by means of circle cutting,and then the wheel profile was found through solving the equations by using Newton iteration.The practical profile of wheel simulated by numerical method was compared with the theoretical involute tooth to inspect whether the gear grinding causes interference,and whether the radius of grinding wheel and its installation angle are correct.Wheel dressing and simulating analysis software was prepared based on Visual C++ 6.0 ,which can be used to select the grinding wheel radius and installation angle,and output the computer numerical control (CNC) program for dressing form grinding wheel.The practical inner helical gear grinding test and inspection results show that the dressing method is correct and the dressing software is feasible.
Research on singularities of base worm thread surface for hobbing or grinding face gear
GAO Jin-zhong, ZHU Ru-peng, LI Zheng-min-qing
2011, 26(10): 2394-2400.
Abstract PDF(1058KB) icon2149 icon10
Abstract:
In order to produce face gear by a hob or grinding worm,a base worm used for hob or grinding worm was designed.In the investigation,a coordinate was established to describe the enveloping process of the worm,the equations describing the worm thread surface were presented,and the three-dimensional (3-D)entity of base worm was created by Catia.The derivation and avoidance of singularities of base worm thread surface was analyzed.A numerical example was given to calculated singularity point.The influence of the base worm radius,the module of shaper,the teeth number and the pressure angle on the singularity point were analyzed,respectively.

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