2011 Vol. 26, No. 3

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Parameters optimizing for a turbofan engine cleaning system using flow field simulation
JIANG Ke-yi, SHEN Wei, LI Ben-wei, LIU Hai-feng, MA Li
2011, 26(3): 481-488.
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An initial cleaning project was presented,including cleaning types,frequency and its design parameters for a turbofan engine.Using flow field simulation technique,the initial cleaning project was validated and its designing parameters were optimized.All these works show that:detergents injection will not affect this engine fan's stability at detergents-to-air ratios less than 3% by mass;the larger nozzle spraying angle means better droplets cover of the fan in the radial direction at equivalent other system parameters;flow field simulation of compressor can not confirm the effectiveness of the nozzle fluid pressure and detergents-to-air ratios to cleaning efficiency.
Comparison research on performance and size of micro axial turbine and radial turbine
XIA Chen, HUANG Guo-ping, QIU Jian
2011, 26(3): 489-497.
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The selection of an axial turbine or a radial turbine is a key problem for advanced micro-turbine engine with larger mass flow rate and power.A comparative research was completed to determine the suitable turbine form.For a micro-turbine engine of 12 centimeters diameter,one-dimension estimative model of axial turbine was established,and the output characteristic of axial turbine was analyzed.A micro axial turbine was designed,and the differences of power,efficiency,size and mass between the axial turbine and radial turbine were compared.The results indicate that:axial turbine has more compact size and lighter mass,but radial turbine has larger power.For an advanced micro-turbine engine,when the total pressure ratio of the compressor exceeds 4,a two-stage scheme is required for the axial turbine to provide enough power output,rather than one-stage for radial turbine.The comparison between two-stage axial turbine and one-stage radial turbine indicates that,radial turbine-stage has smaller size and mass when the flow rate is less than 500g/s,and the total pressure ratio is 4~6,and the engine has a high thrust-mass ratio.So when a high pressure ratio is required but the power output of one-stage radial turbine isn't exceeded,the radial turbine has more advantages.
SysML-based safety analysis of thrust reverser
YIN Shu-yue, YANG Yun, MIAO Xue-wen, ZHAO Ting-di
2011, 26(3): 498-504.
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System modeling language (SysML),a system engineering modeling tool,was employed to model operational scenario of thrust reverser according to SysML,and the case diagram model and sequence diagram model of thrust reverser were developed.Based on operational scenario model,hazard and operability (HAZOP) analysis technology was applied to analyze operational scenario hazards,and hazard conditions of thrust reverser in operation could be achieved by this method.Moreover,the corresponding safety requirements can be derived.The result of SysML-based safety analysis of thrust reverser shows that,integrating SysML and HAZOP is a more effective safety analysis method than traditional system safety analysis.
Overview of recycling-rescaling method for inflow boundary conditions of LES and DNS of compressible wall bounded turbulent flows
LIU Wei-dong, CHEN Ti, SUN Ming-bo, FAN Xiao-qiang, LIANG Jian-han
2011, 26(3): 505-511.
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The inflow turbulent fluctuating boundary conditions play a key role in large eddy or direct numerical simulations of many turbulent problems.This paper introduced a method — recycling-rescaling method for inflow fluctuation generation of compressible wall bounded turbulent flows.The theory foundation and deduction of the method were given in the paper.Several recycling-rescaling methods were introduced and some key points in the implementation were indicated.Applications were summarized and limitations were discussed.This paper can be a reference for further investigation in LES (large eddy simulation) and DNS (direct numerical simulation) of turbulent flow and combustion problems.
Numerical simulation of sound radiation from moving bodies based on immersed boundary method
LIANG An, ZHONG Guo-hua, SUN Xiao-feng
2011, 26(3): 512-517.
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To simplify the grid generation procedure in aeroacoustic problem simulation and develop a computational scheme suitable for moving complex geometries,a strategy of guaranteeing the impermeable boundary condition based on the immersed boundary(IB) method was proposed in the paper.Simulations of sound radiation from moving bodies were performed with relatively simple motion.Satisfactory comparison was conducted between present computational data and theoretical solutions,verifying the feasibility of the present method.
Investigation on hypersonic inward turning inlets with controlled pressure gradient
NAN Xiang-jun, ZHANG Kun-yuan, JIN Zhi-guang, SUN Bo
2011, 26(3): 518-523.
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Axisymmetric basic flowfields with controlled pressure gradient used for hypersonic inward turning inlets were investigated using the rotational method of characteristics.In combination with streamline tracing technique,a circular inward turning inlet with the law of constant pressure gradient was designed and numerically simulated.Results show that the inward turning inlet could maintain the same law of pressure rise as its basic flowfield.Through study of the three laws of wall pressure rise,pressure gradient increase,steadiness and decrease,it's found the inlet with the first law of pressure rise has the maximum compression efficiency,and the inlet with the third law of pressure rise has the lowest compression efficiency.In addition,we can get good internal and external compression assignment by adjusting the law of pressure rise,contributing to make this type of inlet operate well over a large wide range of Mach number.
Low-diffusion preconditioning scheme for numerical simulation of low-speed flows
CAO Ning, WU Song-ping
2011, 26(3): 524-529.
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A low-diffusion preconditioning Roe scheme was proposed by using an adjustable parameter in preconditioning Roe scheme to control the numerical dissipation and the adjustable parameter value rules. The low-diffusion preconditioning Roe scheme reflected the real physical dissipation in the extremely low-speed zone. In the region similar to the inflow speed, low-diffusion preconditioning Roe scheme could ensure the stability of the flow field. The low Mach/low Reynolds number steady solutions of viscous flow passing a circular cylinder and the low Mach/high Reynolds number steady solutions of viscous flow passing NACA0012 were satisfied. Numerical results show the efficiency of the new scheme to simulate low Mach number flows.Numerical experiments show that the numerical dissipation of the scheme has a notable effect on low-speed flow numerical simulation with preconditioning method.
Nonlinear acoustic dissipation mechanism of a slit resonator
DAI Xi-wen, JING Xiao-dong, SUN Xiao-feng
2011, 26(3): 530-536.
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To simulate the vortex/sound interaction phenomenon at a slit with high sound pressure level and calculate the acoustic impedance of the slit,a discrete vortex model was set up.By combining the discrete vortex model with a one-dimensional sound propagation model,the acoustic impedance and the absorption coefficient of the slit resonator were calculated.The numerical results reveal that the acoustic properties of the slit are dominated by the vortex shedding and the evolution of the vortex sheet;the absorption coefficient of the resonator increases with the increase of the sound pressure level;the frequency of the incident sound has significant influence on the absorption coefficient of the resonator.The present results agree well with the previous direct numerical simulation (DNS) results.
Whole flight envelop corrected equilibrium manifold modeling for a turbofan engine
LI Shu-qing, ZHANG Sheng-xiu, HU Wei-hong
2011, 26(3): 537-542.
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Based on the aero-engine resemble theory and the nonlinear system equilibrium manifold theory,a corrected equilibrium manifold modeling method for aero-engine's simulation in whole flight envelop was put forward.First,according to the corrected variables,by extending the concept of equilibrium manifold,corrected equilibrium manifold was presented.Then,a two-dimension schedule variable was defined though compressor rotor's corrected speed and Mach number,and was used to fit the corrected equilibrium manifold.Next,following the modeling frame of nonlinear system equilibrium manifold theory,a whole flight envelop corrected equilibrium manifold model for a turbofan engine was presented.Last,some simulation about this turbofan engine's dynamic response at different situations were shown,and were accordant with the corresponding result of this turbofan engine's component nonlinear model.In all,this model in this paper exhibites well about applicability,precision and real-time simulation for a turbofan engine.
Experimental study of the discharge coefficient of film outflow varying with the internal cooling channel’s height
MAO Jun-kui, HU Bo, SU Yun-liang, GUO Wen
2011, 26(3): 543-550.
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According to the heat transfer enhancement with vortex,experiments were performed to investigate the discharge coefficient of film outflow in narrow confined space,which the ratio of the internal cooling channel height to the diameter of film cooling hole (h/d) was smaller than 1.In experiments,the rules of discharge coefficient Cd varying with the film cooling hole Reynolds number (4800~26000),blowing rate M(0.36~2.74),dimensionless of film cooling channel height h/d(0.33~2.0)were studied in detail,and the similarity criteria for discharge coefficients varying with these parameters were concluded.The experimental results show that the film cooling hole discharge coefficient increase with the film cooling hole Reynolds number when the main flow Reynolds number is constant.In the constant film cooling hole Reynolds number cases,Cd increase with the blowing rate M rising especially when M is smaller than 1.It is also found in experiments that the Cd decrease with dimensionless of film cooling channel height h/d increasing,especially in the cases which the film cooling hole Reynolds number is larger than 9500.
Numerical study of the flow characteristics and excitation parameters for the sparkjet actuator
SHAN Yong, ZHANG Jing-zhou, TAN Xiao-ming
2011, 26(3): 551-557.
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The way of using the source term in energy equation to simulate the input energy of actuator was reasonably compared with the experimental data for the sparkjet actuator.The processing of energy deposition,discharge and recovery of actuator was obtained.The instance energy input can produce the condition of high pressure and temperature in the actuator,inducing the formation of synthetic jet.Under the periodic action,the velocity of synthetic jet on the nozzle is stabilized on a non-sinusoidal law after three periodic times.The characteristic of short discharge time and long recovery time is different from the piezoelectric synthetic jet.The vortices pair at the downstream of nozzle with high intensity has an ability to roll environment air.While the input energy and actuator volume remain unchanged,the velocity at nozzle is enhanced firstly and then decreased with the increase of the excitation frequency.The recovery stage time is shortened with the increase of excitation frequency.So,the choice of excitation frequency is considered in view of the temperature resistance of actuator.
Experiments of leakage effects of rub-grooves on straight-through labyrinth seals
JI Guo-jian, JI Hong-hu, WANG Zheng-wei
2011, 26(3): 558-562.
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Based on early studies,a straight-through labyrinth seal was developed,which has a bush with a rub-groove machined opposite the teeth cavity.The rub-groove manufactured on the smooth bush opposite to the tooth cavity destroys the continuity of the wall jet boundary layer,which lead to the jet flow change it direction and greatly improve sealing effect.The experimental studies show that it has a better sealing effect.The leakage coefficient of labyrinth seal with the rectangle rub-grooves is decreased 15% and the parallelogram rub-grooves 30%.Little windward angle of rub-grooves leads to jet deflection and big leeward angle of rub-grooves is beneficial to increase the resistance of the jet and also leads to jet deflection.
Numerical simulation of enhanced heat transfer in tubes using methane steam reforming
MAO Zhi-fang, JIANG Pei-xue, LIU Feng
2011, 26(3): 563-569.
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Convectional heat transfer with methane steam reforming was investigated in catalyst films on the walls of a tube.The study analyzed the effect of catalytic activity,film thickness,inlet gas flowrate,pressure,temperature and concentration on reaction and heat transfer.The results show that the heat transfer is efficiently enhanced by the endothermic reaction in the catalyst films,and the wall temperature is reduced.Increased catalytic activity and film thickness increase the reaction heat and reduce the wall temperature.However,the effect of the film thickness becomes less significant as the thickness reaches a certain value.As the inlet flowrate increases,the conversion rate and the ratio of reaction heat decrease.As the inlet pressure increases,the reaction heat decreases and the wall temperature increases.As the inlet temperature increases,the wall temperature near the inlet increases,but this effect is very small on the wall temperatures downstream.There is an optimal inlet concentration,which corresponds to the lowest wall temperature and the highest hydrogen fraction at the outlet.
Comparative study on the numerical computation of convective heat transfer over rough surfaces
YANG Sheng-hua, LIN Gui-ping, SONG Xin
2011, 26(3): 570-575.
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To compute the convective heat transfer coefficient in the ice shape simulation process,three different methods that take wall roughness into account were presented,namely,the traditional integral boundary layer (IBL) method,a method based on k-ε turbulence model plus standard wall function (k-ε method) and a method based on extension of the Spalart-Allmaras turbulence model (S-A method).The convective heat transfer coefficients were calculated for a 15cm diameter cylinder with an equivalent sand grain roughness height of 1.35mm under Reynolds numbers of 8.8×105,2.8×105 and 4.8×104 respectively.Comparisons show that IBL and S-A method have the same trends.Near the stagnation point,the predicted results show laminar features,and coincide with experimental data.Both methods overpredict the heat transfer in the following turbulent region,but S-A method agrees better with the experiment.The k-ε method overpredicts the heat transfer near stagnation region.
Investigation of mode transition in a dual mode supersonic combustor with hydrogen fuel
LIU Hao, SONG Wen-yan, WANG Dian
2011, 26(3): 576-581.
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To investigate the mode transition in the dual mode combustor,using the method of computational fluid dynamics(CFD),numerical simulation of hydrogen-fueled combustor flow field was conducted at different equivalence ratios,flying Mach numbers and fuel injection modes.The simulation results are found to agree well with the experimental data.Results show that increase of equivalence ratio and reduction of flying Mach number along with two-sides injection make the combustor tend to work in sub-combustion mode.
Pressure drop characteristics of supercritical aviation kerosene in U-turn tube
HUANG Wen, DENG Hong-wu, XU Guo-qiang, ZHU Kun
2011, 26(3): 582-587.
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The flowing characteristics of aviation kerosene at supercritical pressure flowing through a U-turn tube were investigated.The pressure and temperature were analyzed to evaluate their effectiveness on the pressure drop.The results indicate that,when the temperature of the fuel at the outlet is below the critical temperature,the pressure drop does not change with the increase of the temperature of the fuel,but increases with the rising pressure;when it is above the critical temperature,the pressure drop increases with the increasing temperature,and decreases with the increasing of pressure.The slope of pressure drop with temperature increases near the pseudo-critical temperature.Furthermore,a relation-formal was proposed to predict the pressure drop when hydrocarbon fuel flowed through a U-turn tube at supercritical pressure.
Approximate model-based optimum design for wall temperature of floatwall
GUO Jia-liang, WEN Wei-dong, CUI Hai-tao, GAO Jian-hui
2011, 26(3): 588-592.
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In order to realize better cooling effect for the floatwall structure,optimization study about the floatwall's wall temperature was performed;approximate model and genetic algorithm were combined;and the optimization method was developed and applied to the floatwall's wall temperature optimum design under a certain aerodynamic parameter.The results show that,the average temperature of the floatwall decreases by 2.4%.At the same time,according to the approximate model constructed,this paper analyzed the wall temperature's changing rules of the geometric parameters,and gained the changing rules of the aperture and the pitch of impact.The results show that:under the size constraints and aerodynamic parameters selected in this article,the cooling effect gets better with the enlargement of the film hole diameter,or with the reduction of the impaction hole diameter and the reduction of the pitch of impact.
Macro and micro scale coupled constitutive model based on virtual displacement principle
GAO Xi-guang, SONG Ying-dong, SUN Zhi-gang
2011, 26(3): 593-602.
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A novel constitutive model was developed for composite by combining the theory of macro and micro scale coupled constitutive model and the virtual displacement principle.The displacement within the subcell was expanded in terms of the global strains and the fluctuating displacements.Then the virtual displacement principle was used to construct the basic equations of the model.The periodic boundary conditions were employed to solve the basic equations.Finally the relation between global stress increment and global strain increment was deduced.Both the accuracy and efficiency of the new model were verified numerically by comparing with finite volume directe average method(FVDAM).The global elastic modulo and transverse elastic-plastic stress-strain responses were also predicted by the new model.The results show that predictions of the model are in good agreement with transformation equations and experiment.
Incipient fault detection for aero-engine rotor based on frequency compression of stochastic resonance
WANG Guo-fu, ZHANG Hai-ru, ZHANG Fa-quan, YE Jin-cai
2011, 26(3): 603-610.
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A frequency compression based on stochastic resonance (SR) for detecting incipient fault weak signal was presented because of the benefits of SR for detecting weak signals.The frequency limitation of SR was eliminated by introducing frequency compression.The incipient fault signal was detected from heavy noise under the condition of adiabatic approximation.Theoretical analysis and experiment results show that:to deal with the unknown incipient fault signals mixed with heavy noise,the mixed signal is compressed continuously to achieve a suitable frequency and then input to SR system.According to the change of resonance spectral peak value,the unknown incipient fault frequency can be obtained from heavy noise by inverse transform algorithm.Compared with traditional methods,the computing speed is increased by four magnitudes.The target signal is detected under -50dB.
Sequential inspection method for long-storage-products based on storage degradation mechanism
FENG Jing
2011, 26(3): 611-616.
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In order to specify the optimal inspection way for long-storage-products,such as engine,under storage reliability requirement,the sequential inspection method based on storage degradation mechanism was proposed.The storage degradation mechanism covers the aging of non-repairable components and degradation of repairable components despite of the inspection and maintenance.The storage reliability model for Weibull products and its parameters estimation methods with least square errors were proposed.Sequential inspection time was confirmed based on storage reliability request and virtual storage life.At last,a simulation example was given to illustrate the validity of the method.
Investigation on residual stress of plasma sprayed thermal barrier coatings based on moire interferometry and hole drilling method
QI Hong-yu, LIU Jin-long, YANG Xiao-guang, WANG Jing-ke
2011, 26(3): 617-621.
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Moire interferometry technique and hole drilling method were applied to study the residual stress of DZ125 in thermal barrier coatings (TBCs).The residual deformation,residual strain,and residual stress were obtained experimentally and computationally.The results show that moire interferometry combined with hole drilling method has the advantage of full field measurement and high sensitivity in measuring residual stress of TBCs.It has positive significance to study residual stress of TBCs using optical measurement method.
Momentum wheel Wiener process degradation modeling and life prediction
LI Hai-tao, JIN Guang, ZHOU Jing-lun, ZHOU Zhong-bao, WU Chun-hua
2011, 26(3): 622-627.
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For the problem that there is no failure data to use in momentum wheel's life prediction, a model of the degradation of momentum wheel' bear temperature was established using Wiener process with drift.At the same time,considering of the uncertainty which was made by the process technics and manufacturing error, the drift and the diffusion parameters were described as stochastic variables,and the bias correction estimate was obtained using bootstrap method.And then, the sample path was simulated based on the established model.At last, the life prediction and residual life prediction were performed at the uncertain failure threshold.The model provides a method for the degradation modeling and life prediction of momentum wheel,and the theory and method can be generalized for the degradation modeling and life prediction of some similar high reliability and long life products.
Experimental study of particle damping for a two-dimensional vibrating structure
TANG Wei, WANG Yan-rong, WANG Zhou-cheng, Bhatti Riaz Ahmad
2011, 26(3): 628-634.
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By use of a non-contact laser vibrometer,experiments were made on an L-shaped beam with a cavity attached to the free end,so as to investigate the damping properties of particle damping for a two-dimensional vibrating structure under different cavity sizes.The experimental results show that: (1)the nonlinear particle damping,which is at least one order of magnitude higher than the intrinsic material damping of metals,can significantly suppress the vibration of structures. (2)The features of two-dimensional particle damping are almost the same in each direction;with the increasing of dimensionless acceleration amplitude,particle damping firstly increases and then decreases,meaning that there is a critical dimensionless acceleration amplitude causing the highest damping. (3)Particle damping as well as the critical dimensionless acceleration amplitude corresponding to the damping peak increases with the cavity sizes.The experimental results could provide a reliable basis for numerical simulation of particle damping in two-dimensions.
Method of lifetime and reliability of some helicopter's main reducer
XUE Xiang-zhen, LI Yu-xi, WANG San-min
2011, 26(3): 635-641.
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The reliability of the main reducer drive system was acquired by dealing with the original load date of a typical mission profile of the helicopter,the load spectrum was changed into the stress spectrum of all gears using three-dimensional finite element analysis;the fatigue life of all gears at each load stage was calculated with Goodman formula and materials P-S-N curves,the life date was analyzed using Minitab.It's concluded that the contact fatigue life of gears is subject to Weibull distribution with two parameters,thus working out the reliability of each transmission part according to the reliability function of Weibull distribution and based on series-to-parallel reliability model of the system.Then,this thesis can provide a method for determining life and reliability of complex drive systems.
Analysis of inlet pre-swirl influence on aerodynamic performance in highly loaded transonic fan
ZHAO Bin, LIU Bao-jie
2011, 26(3): 642-648.
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Numerical simulation was conducted to explore the inlet pre-swirl design methodology and its influence on aerodynamic performance for highly loaded inlet stage fan rotor at full speeds,as well as the typical part speeds characteristic with optimum inlet pre-swirl distribution.The fan rotor was designed to produce a total pressure ratio of 2.55 and loading coefficient of 0.42 at a tip speed of 480m/s.The result indicates that conventional rotor has capability of achieving this loading level,but inlet guide vane is necessary in design.The adoption of positive pre-swirl and low reaction degree increases the tip performance effectively,negative pre-swirl is required at hub for stator based on conventional design method;rotor with aforementioned pre-swirl design has favorable performance at typical part speeds.
Analysis of characteristic and mechanism of pipe diffuser for a highly loaded centrifugal compressor
WANG Yi, ZHAO Sheng-feng, LU Xin-gen, ZHU Jun-qiang
2011, 26(3): 649-655.
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Pipe diffuser was designed for a highly loaded centrifugal compressor in this paper.Parametric studies on the throat area of pipe diffuser were completed through numerical simulation.And detailed analyses of the flow visualization in the compressor have exposed the different radial diffuser blade flow topologies between channel diffuser and pipe diffuser.Furthermore,this paper made some preliminary conclusions as for the design criteria of pipe diffuser throat and the flow physics involved in the stall margin improvements afforded by the use of pipe diffuser.
Influence of suction-side winglet length on tip leakage flow in compressor cascade
HAN Shao-bing, ZHONG Jing-jun, YAN Hong-ming
2011, 26(3): 656-661.
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The numerical simulation was performed to investigate the influence of the suction-side winglet with different lengthes on the tip leakage flow in compressor cascade.The simulation results show that the suction-side winglets can improve the tip clearance flow condition.It is found that the winglet is most effective to weaken the intensity of the leakage vortices if their length is the same with that of the blade tip.With increasing clearance and stronger intensity leakage flow,the winglet's effect is gradually decreased.
Effects of loading distribution on a vaned diffuser
CAO Si, LIU Bao-jie
2011, 26(3): 662-669.
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The effects of loading distribution on a vaned diffuser of a highly loaded centrifugal compressor were numerically investigated by NUMECA.Three kinds of loading distributions, i.e. :forward loading,backward loading and hub/tip loading,were discussed.Their effects on the vaned diffuser and the flow mechanism were analyzed.It is demonstrated that the vaned diffuser with hub/tip loading could achieve the best performance.
Aero-engine health monitoring method based on joint entropy of symbolic series
SHI Yong-sheng, JIANG Ying, SONG Yun-xue
2011, 26(3): 670-674.
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Information entropy theory was introduced into this paper for aero-engine health monitoring in combination with symbolized multiple parameters time series.The joint entropy of symbolic series,which depicts the disorder degree of aero-engine performance parameters,was used to analyze aero-engine health condition and evolutive trend.Experiments of two data sets were done,and the results show that the method described in the healthy evolution of aero-engine coincides with the actual situation.The method can reflect the health condition and also can be applied in aero-engine health monitoring.
Chaos arithmetic for civil aero-engine forecasting
SONG Yun-xue, PENG Peng, SHI Yong-sheng
2011, 26(3): 675-679.
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Firstly,using Haar wavelet and DB16 wavelet,the original exhaust gas temperature data series were denoised.Further analysis on the denoised data series indicates the existence of a chaos feature.Then,by using chaos theory,chaotic forecasting arithmetic was established to forecast the exhaust gas temperature data series.Finally,by testing the stable level of data series and comparing the series with the red line,the condition of aero-engine was defined.The proposed arithmetic was verified through some types of aircraft aero-engine exhaust gas temperature data series obtained from actual flight,and then compared with adding-weight one-rank local-region arithmetic and auto-regressive and moving average (ARMA) arithmetic.The result shows that the proposed arithmetic has a better forecasting accuracy.It can be used as a supporting model in the decision-making of aero-engine fault forecasting.
Torque feed-forward control of engine / helicopter system based on support vector regression
SUN Li-guo, SUN Jian-guo, ZHANG Hai-bo, CHEN Guo-qiang
2011, 26(3): 680-686.
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Turbo-shaft engine's controller design based on the compensation from disturbance was mainly studied in this article.A torque prediction model design scheme was proposed based on recursive reduced least squares support vector regression(RR-LSSVR)algorithm and model prediction procedure.Firstly,reduced least squares support vector regression was utilized to train the dynamic estimation nonparametric model of torque by using the handling input and flight state variables as training data.Then,a prediction procedure was arranged to obtain the torque information in advance.After that,the turbo-shaft engine's compensator was implemented using the former predicted torque information.In order to take full advantage of the disturbance signal and its dynamic information,the proportional-differential form was adopted in the compensator design.Finally,simulation of integrated helicopter/turbo-shaft engine system shows that the control scheme has better dynamic disturbance rejection ability than traditional system,it can decrease the droop of power turbine's speed more than 10%.
General simulation on modularization of liquid rocket engine
ZHANG Li-hui, LI Wei, DUAN Na
2011, 26(3): 687-691.
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Based on the development of large liquid rocket engines,a universal system organization capability approach was presented according to the thought of modularization modeling and the requirements of general simulation.Mathematical model in the module was stored in the form of code text;and the operator could add models or expand block library from the operator interface.This paper described the approach of realizing such software architecture.In Microsoft Visual Studio 6.0 platform,C++ language was utilized to develop the simulation software and implement visual modeling based on MFC(Microsoft Foundation Classes) document view architecture,and finally a particular transient simulation of liquid propellant rocket engine was fulfilled.By comparing the results with the test run curve,the feasibility and correctness by adopting the simulation method was verified primarily.The researchers can carry out expediently dynamic process simulation in other liquid rocket engines.
Research on flow visualization of coaxial gas-gas injector mixing flowfield
JIN Ping, DU Zheng-gang, YANG Li-jun, CAI Guo-biao
2011, 26(3): 692-697.
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To pursue the proper design criteria for gas-gas injector,the flow visualization technology with particle image velocimetry(PIV) system was adopted to investigate the mixing mechanism.The coaxial shear and swirl configurations were selected.The results show that the momentum ratio of oxygen to hydrogen prevails in the mixing process of coaxial shear injector,while the swirl numbers dominate the mixing part of coaxial swirl injector.Good mixing was gained at high momentum ratio and high swirl numbers.For the designer,the combination of high annular pressure drop and low center pressure drop is recommended for the coaxial shear injector,and the combination of low annular pressure drop and proper recess length of center post recommended for swirl injector.
Abnormal recognition algorithm based on manifold learning for turbopump mass data
XIA Lu-rui, HU Niao-qing, QIN Guo-jun
2011, 26(3): 698-703.
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To extract the information from turbopump mass data and analyze its health condition,the paper presented a mass data abnormal recognition algorithm based on manifold learning.The algorithm reconstructed turbopump vibration data in high-dimensional space.Then,the diffusion map method was used to directly learn the high-dimensional data and extract intrinsic low-dimensional manifold feature in data set.The abnormal condition in turbopump mass data was discerned visually.The validation results of simulation and test data demonstrate the feasibility and effectiveness of the presented algorithm.The algorithm conquers the shortcoming of the traditional methods that are insufficient for nonlinear problems,and gives a new solution of turbopump post-test health analysis.
Analysis on support reaction of asymmetric gear based on friction between teeth
LI Xiu-lian, WANG Gui-cheng, ZHU Fu-xian, ZHOU Jin-yu, HE Qing
2011, 26(3): 704-710.
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The calculation equation of the gear supports reaction was deduced under the action of sliding friction between teeth,by fully analyzing the forces exerted on the driving gear of reducing-speed asymmetric spur gear drive system with double pressure angles in the single and double gears meshing range.And,the evaluation indexes of gear supports reaction fluctuation in the condition of the random interteeth load were presented.Simulation indicates that the friction between teeth is one of influential factors to the gear supports reaction fluctuation,and the effective measures to decrease the fluctuation range of gear supports reaction include:improve the precision of gear face,lubricate reasonably,decrease the pressure angle and increase the gear number.
Analysis of reliability sensitivity for gear engagement based on response surface methods
LI Chang, HAN Xing
2011, 26(3): 711-715.
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Rules of variation of contact stress in gear engagement were obtained by means of dynamic simulation in ANSYS after the three-dimensional parameterize finite element model was created.Based on the effects of original manufacturing errors,rotational speed and load on gear drive,expanded response surface method was adapted in multiple stochastic virtual test of the meshing gear to compute the reliability;and reliability sensitivity of each parameter was given in quantitative probability,providing a theoretical base for fatigue strength calculation and dynamic optimum design of the drive gear mechanism.The effects of different parameters’ original manufacturing error on gear contact stress were got.
Quantitative detection approach for transmission system of helicopter based on physical model and gray relational analysis
CHENG Zhe, HU Niao-qing, QIN Guo-jun
2011, 26(3): 716-720.
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Abstract:
An approach to detect the damage quantitatively in rotary machine was presented based on physical model and gray theory.For the purpose of detecting sun-gear tooth-chipped damage in 2K-H planetary gear sets,physics-based models for damage system with multi-stage severity were established,and then simulation data of damage system was obtained.Then,feature vector of simulation data extracted and computed was used as standard damage mode.Relational analysis in grey theory was carried out between standard damage mode and the feature vector of signal,and also checked.The quantitative detection result for damage was achieved from relational grade computed before.Tooth-chipped seeded tests were carried out and used to validate the approach.It is proved that the approach presented above is effective to detect the sun-gear tooth-chipped damage,and its potential profit in other rotary mechanical equipments will be researched in the future.

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