2010 Vol. 25, No. 1

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Thermal design method of temperature control for regenerative cooling panel
XIA Xin-lin, AI Qing
2010, 25(1): 1-5.
Abstract PDF(1541KB) icon1725 icon523
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By analyzing characteristics and influential factors of heat transfer in regenerative cooling channel,a thermal design method of cooling panel based on restriction of operating temperature of materials was presented.In this design method,the structure of each channel was separately designed in the cooling panel,so that heat transfer characteristic of cooling channel could change with varying channel positions.By combining finite volume method,empirical relations of heat convection and Monte Carlo method,the cooling effect of regenerative cooling panel was investigated.The results show that the cooling panel can be geared for non-uniform heat flux distribution and operating temperature restriction of structure material.This design method can also ensure thermal reliability of structure.
Flow and heat transfer characteristics in a periodical changeable cross-section micro-channel heat sink
XIA Guo-dong, XU Zhi-bo, QI Jing-zhi
2010, 25(1): 6-10.
Abstract PDF(1516KB) icon1703 icon469
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This paper conducted an experimental investigation on flow and heat transfer characteristics associated with the forced flow of de-ionized water in a periodical changeable cross-section micro-channel(PCMC) heat sink.The friction factor,Nusselt number,average temperature of heating film and thermal resistance of heat sink under different pump power were obtained.In comparison with traditional micro-channels with constant cross-section,the periodical changeable cross-section micro-channels could produce higher heat transfer coefficients and friction factors.
Experimental study of the flow structures of the concave surface with inclined impingement in limited space
MAO Jun-kui, MIU Guo-jun, LIU Zhen-xiong
2010, 25(1): 11-17.
Abstract PDF(1009KB) icon1666 icon444
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Smoke wire flow visualization was used to investigate the characteristics of the flow structures of a round jet inclined impingement on the concave surface in limited space.Reynolds number of impingement,inclined jet angle,the ratio of the jet distance to the diameter of the jet hole and the relative curvature(the ratio of the diameter of jet hole to the diameter of concave surface) were changed to study the rules of flow structures varying with these parameters.At the same time,the developing and disappearing phenomena of the induced vortex were analyzed.All the experimental results show that,around the stagnation region,it can form swirl structure and generate vortex because of inclined jet and curvature of target concave.The central angle of the impingement fluid separated from the target surface became larger with the increase of jet Reynolds.And the separating angle also increased with the increasing ratio of the jet distance to the diameter of the jet hole,while the range of induced vortex became smaller.It was also found in experiments that,because of the influence of the inclined impingement’s angle,it is easier to generate vortex at the left of the stagnation region where the relative jet angle is smaller.
Improvement of an engine lubricating oil heat diffusion system
CHEN Wei-jian, ZHANG Da-lin, MENG Fan-xin
2010, 25(1): 18-22.
Abstract PDF(784KB) icon1618 icon449
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Improvement scheme of an engine lubricating oil heat diffusion system was provided to solve oil over-temperature problem on the ground.Impacts of mixing cavity area,length,diffuser and nozzle type in original ejector system on ejector performance were investigated experimentally.The results indicate that the combination of small cross section area,long mixing cavity,diffuser and supersonic nozzles can considerably improve the ejector system performance.The test and installation validation prove that the improved lubricating oil heat diffusion system can meet the engine heat requirement.
Experimental study on outlet temperature field for combustor of heavy-duty gas turbine
LIU Kai, ZHANG Bao-cheng, CAI Jiu-ju, MA Hong-an
2010, 25(1): 23-27.
Abstract PDF(1446KB) icon1651 icon462
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Experimental study on combustor temperature field of heavy-duty gas turbine(E) was finished on high-pressure test system.Experimental results indicate that: circular temperature distribution coefficient of combustor is 0.2538,and radial temperature distribution coefficient is 0.1312,all of which do not meet the design requirements.Through adjustment of mix-holes size and layout of chamber,and increase of the penetration depth and intensity of mixing,the circular temperature distribution coefficient decreased to 0.2164,radial temperature distribution coefficient decreased to 0.0897,approaching the design target.The results have important significance for the experiment of similar combustors.
Effects of dynamic load on the heat transfer characteristics of two-phase pipe boiling flow
YAO Qiu-ping, SONG Bao-yin, ZHAO Mei
2010, 25(1): 28-34.
Abstract PDF(1170KB) icon1585 icon469
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An experimental investigation was performed comparatively to obtain the flow and heat transfer characteristics of single-phase water flow and two-phase pipe boiling water flow under dynamic load in present work.By analyzing the effective heat,flow pattern,fluid resistance and heat transfer coefficient of the experimental data,the effects of dynamic load on the flow and heat transfer characteristics of single phase water and two-phase boiling water flow were investigated.The results show that the dynamic load significantly influences the flow characteristic and boiling heat transfer of the two-phase pipe flow.It will enhance the fluid resistance and heat dissipation toward the ambient environment,and also reduce the heat transfer capability of the two-phase boiling flow.The impact mixing flow caused by the dynamic load breaks the uniform and varying properties of the wall temperatures,so the greater the dynamic load,the lower the wall inner bottom temperature,and the higher the wall inner top temperature occurs in a certain extent.
Comparison of characteristics of ramjet with cavity-based flameholder and V-gutter flameholder
LI Qing, PAN Yu, TAN Jian-guo, WANG Zhen-guo
2010, 25(1): 35-40.
Abstract PDF(1595KB) icon1691 icon521
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Experimental research and numerical simulation were carried out in order to study the characteristics of cavity-based flameholder and V-gutter flameholder in liquid hydrocarbon fuel ramjet.The results suggest that flameholder based on cavity could be ignited by high-energy spark igniter or hydrogen pilot flame,but flameholder based on V-gutter could only be ignited by hydrogen pilot flame.Also,the fuel injection mode was closely related to the flame holding mode.Central injection was applied to V-gutter and wall or near-wall injection applied to cavity.The combustion of ramjet with cavity was organized in the near-wall area but that of V-gutter organized in the central area,making it helpful to the mixing of the unburned and the burned.The combustion efficiencies of cavity and V-gutter were very close to each other,but the pressure loss of V-gutter was a little higher.
Hybrid RANS/LES simulation of mass exchange characteristics of cavity for supersonic combustion
WANG Hong-bo, SUN Ming-bo, WU Hai-yan, WANG Zhen-guo
2010, 25(1): 41-46.
Abstract PDF(704KB) icon2053 icon456
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Mass exchange characteristics of cavities for scramjet applications under supersonic cold and combustion flow were investigated.The hybrid RANS/LES(Reynolds-averaged Navier-Stokes/large-eddy simulation) approach was used to simulate numerically unsteady state flowfields.The influences of the cavity parameters and the combustion on the mass exchange characteristics were investigated systemically.The mass exchange process in the reactive flow was described for the first time by using atom-tracking method.The hybrid RANS/LES data suggest that longer cavities have a longer residence time both in cold and combustion flow.The aft wall angle has a significant influence on the residence time just in the cold flow.For the same cavity,residence time reduces obviously in the combustion flow as compared with that in the cold flow.
Numerical investigation of the effect of thermo physical properties on the performance of heat storage system
WU Bin, XING Yu-ming, RUI Shou-zhen
2010, 25(1): 47-52.
Abstract PDF(1467KB) icon1815 icon441
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Two-dimensional mathematical model of latent heat storage performance was presented for heat storage system in consideration of the conduction of container wall,and only the process of phase change heat transfer was considered by conduction.The decoupled method computational model was used to analyze the phase change process of phase change material(PCM).Numerical calculation and comparison of the melting process of PCM were conducted for various types of container materials.The results show that thermo physical properties of thermal conductivity,specific heat and density of the container material have very important effects on the melting of PCM.Furthermore,numerical calculation and comparison of the melting process of PCM were conducted for different values of initial temperature and boundary wall temperature.The conclusion provides guidelines for latent heat storage system thermal performance and design optimization.
Pressure measurements on a static disk with high positioned inflow and radial outflow under rotor-stator system
QUAN Yong-kai, SUN Ji-ning, LUO Xiang
2010, 25(1): 53-57.
Abstract PDF(907KB) icon1705 icon516
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The pressure distribution of a static disk and relative rotational speed in the rotor-stator cavity were experimentally investigated.Results show that the static pressure increases with the radial accretion within 0.6 radius range,and the lowest value of pressure appears at the ejection hole and then increases sharply to the moderate stage along the radial direction.The pressure upon the static disk increases with the augmentation of flow rate,and decreases with the increase of rotational Reynolds number.A steady rotational core can be formed when the value of rotational Reynolds number is less than 2.6×106 and the mass flow rate less than 4.50×104.In addition,the variations of mass flow rate and rotational Reynolds number have little influences on the relative rotational speed.
Numerical simulations of upstream wake-tip leakage vortex interactions in turbine rotor
ZOU Zheng-ping, QI Lei, LI Wei, LIU Huo-xing
2010, 25(1): 58-66.
Abstract PDF(2272KB) icon1578 icon441
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The internal flow of turbomachinery is intrinsically unsteady,so the research on the unsteady interactions in the tip region of turbine rotor is key to improve the performance of low aspect/high loading turbine.The upstream wake-tip leakage vortex interactions in a turbine rotor were simulated by a 3-D unsteady viscous solver.The flow diagrams of steady,time-averaged and transient results were analyzed.The results indicate that the unsteady interactions between the upstream wake and the rotor tip regions have changed the spatio-temporal evolution of the tip leakage vortex and the passage vortex,consequently leading to loss change.The tip leakage vortices and the passage vortices are separated into periodic perturbation counterrotating vortices.These counterrotating vortices move downstream along the tip leakage vortex path.
Experimental study of the mechanism of improving stall margin of low speed axial-flow compressor with micro-injection under rotating inlet distortion
ZHANG Jing-xuan, LUO Ma, NIE Chao-qun, LIN Feng, CHEN Jing-yi
2010, 25(1): 67-71.
Abstract PDF(1308KB) icon1691 icon488
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An experimental investigation was carried out in the paper to clarify the flow mechanism of how micro-injection improves the stall margin of a low speed axial-flow compressor under rotating inlet distortion.The results show that,in distorted sectors,the tip leakage flow is pushed forward to the leading edge;as the mass flow rate is decreased,tip leakage flow would spill out of the blade passage and trigger the rotating stall.Micro-injection can inhibit the formation of distortion disturbances and then delay the occurrence of rotating stall.
Study on turbine aerodynamics design of small turbofan engines
ZHANG Wei-hao, ZOU Zheng-ping, LIU Huo-xing, LI Wei
2010, 25(1): 72-79.
Abstract PDF(1812KB) icon1902 icon622
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The characteristics of the flow through the small turbine components were analyzed in detail based on the mission and operating conditions.It was shown that the effect of boundary layer and secondary flow,including passage vortex,trailing vortex and tip clearance flow,etc,was remarkable.This was determined by the small-scale and high rotating-speed as the basic features of small turbine.By investigating the aerodynamic design ideas and concrete methods of small turbine component,a new turbine for a small turbofan engine with the thrust of 1000daN was designed.The results of 3-D viscous numerical simulation show that,the turbine meets the design requirements with high efficiency.
Improvement on S-A model for compressor flow based on turbulence transport nature
WANG Dan-hua, LU Li-peng, LI Qiu-shi
2010, 25(1): 80-86.
Abstract PDF(1331KB) icon1635 icon470
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In off-design conditions the corner separation can become severe thus lead to strong non-equilibrium turbulent state.To correctly simulate the flow field the transport process of non-equilibrium trubulence must be predicted reasonable.Based on the analysis of turbulence transport nature at different operating conditions in compressor corner separation flows,a modification method on the relationship between the production and dissipation of turbulence viscosity to improve the simulation ability of Spalart-Allmaras(S-A) model at off-design condition in compressor flow was proposed and studied by numerical simulation.It shows that comparing with experimental data and academic analysis the modified S-A model could give out more reasonable and correct predictions than conventional S-A model.
Numerical simulation method for stochastic fluctuation of inlet total pressure
WANG Zhi-qiang, HU Jun, LI Liang, JIANG Da-zhi, ZHAO Yun-sheng
2010, 25(1): 87-91.
Abstract PDF(1547KB) icon1597 icon483
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In order to simulate the influence of the dynamic inlet total pressure distortion on the stability of the aero-engine,the stochastic fluctuation of the pressure should be first simulated.The inlet total pressure stochastic fluctuation process was simulated on the base of the normal school and auto correlation characteristic of the inlet total pressure stochastic fluctuation,and the influence of the integral time constant,time-step and time-length on the inlet total pressure stochastic fluctuation process was analyzed.The results show that the shorter time-step and longer time-length can obtain better simulate result,but the integral time constant does not affect the simulate result.
Numerical simulation of active suppression of rotating stall in axial compression systems
YU Lan-lan, HU Jun, TU Bao-feng, WANG Zhi-qiang
2010, 25(1): 92-101.
Abstract PDF(2778KB) icon1920 icon477
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A theoretical model was proposed to analyze the transient behavior of suppression of rotating stall in axial compression systems through an additional disturbance.The influences of system parameters on the suppression effectiveness and the interaction between rotating stall and surge have been discussed.The analysis of the influence of system parameters shows that,the effectiveness decreases with the increase of B and the number of stages or stage loading of the compressor.The onset flow rate of pure one-dimensional surge depends on the value of B and axisymmetric compressor characteristic,except for the slope of the compressor characteristic.When surge is initiated by rotating stall,it is possible to inhibit the occurrence of surge by suppressing rotating stall in a compression system.
Predictions of dynamic damping coefficients of basic finner based on CFD
TAO Yang, FAN Zhao-lin, ZHAO Zhong-liang
2010, 25(1): 102-106.
Abstract PDF(1736KB) icon1842 icon579
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A method of predicting pitch and roll damping derivatives of missile geometries with fins using an unsteady RANS(Reynolds-averaged Navier-Stokes) solver was presented.A three-dimensional structured RANS solver based on arbitrary Lagrangian-Eulerian(ALE) formulation with a dynamically deforming mesh algorithm was used and validated by the wind tunnel and ballistic range data available in the literature.Roll and pitch damping derivatives were calculated from load history of the unsteady flow around the model.A standard research configuration,known as the basic finner,was studied under forced pitching and rolling conditions.Pitching and rolling motions with oscillation were analyzed at supersonic Mach numbers ranging from 1.5 to 2.5.Predicted results show good agreement with the available wind tunnel data.
Analysis of flight stability and rear flow field of the cargo projectile
LI Jian-ping, BAI Chun-hua
2010, 25(1): 107-113.
Abstract PDF(1151KB) icon1258 icon489
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Flight stability and rear flow fields of the cargo projectile were studied by simulation test and numerical computation.The cargo projectile can fly stably and the results of simulation test agree well with numerical computation.In addition,the rear pressure distribution was also obtained by numerical computation,showing that there are eddy-current zones at the bomb rear,which will increase with the flight speed.
Performance analysis and parameters optimization of fly-like aircraft
HU Ming-lang, WEI Rui-xuan, SONG Min, LI Xia, GUO Qing, LIU Yue
2010, 25(1): 114-122.
Abstract PDF(3221KB) icon1698 icon472
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With revised quasi-steady aerodynamic estimation and energy exhaustion methods,the fabric and kinematics parameters of fly-like aircraft were optimized.Firstly,the aerodynamic and energy exhaustion of several example fly-like aircrafts was computed with revised quasi-steady aerodynamic.And then,the minimal energy exhaustion of different flight states and longest flight time together with its optimal kinematics parameters was counted with number inserting approach.The result is as follows: 1) Fly-like aerodynamic structure is more preferable to aircraft with size of several centimeters and millimeters,but its capacity is not superior to routine structure when its wingspan is more than 3.75 centimeters.2) The optimal kinematics parameters of fly-like aircraft are: the rotation is symmetric and its duration of flip is 0.2T～0.25T;acceleration and deceleration duration of stroke is 0.15T～0.2T;mid-stroke angle of attack is 25～30 degrees;the stroke amplitude should be greater when possible,and only when current frequency couldn’t render adequate lifting force can the stroke amplitude be advisably reduced for augmenting the frequency.
Shear-modified sub-grid model and its applications to turbulent channel flow
XIAO Hong-lin, LUO Ji-sheng
2010, 25(1): 123-128.
Abstract PDF(933KB) icon1657 icon487
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This paper presented a sub-grid model called shear-modified eddy viscosity model,which modifies eddy viscosity coefficient with use of strong shear near the wall.This model can make eddy viscosity coefficient satisfy the wall modification automatically.Thus,the eddy viscosity approaches to zero in the proximity of the wall in the case of zero eddy viscosity coefficient in the place without fluctuation.Numerical simulation was performed in the situation of blow-suction,no blow-suction,low Reynolds number and high Reynolds number.The result is consistent with the direct numerical simulation(DNS) by comparison.
Research on selection of measurement parameters of engine fault diagnosis based on primary factor model
SUN Xiang-feng, CHEN Yu-chun, HU Fu
2010, 25(1): 129-135.
Abstract PDF(1083KB) icon1749 icon528
Abstract:
The selection of measurement parameters of engine air path fault diagnosis was researched in this paper based on the primary factor model and prediction error sum of squares(PRESS) principle.Through plenty of computing results,a method was established for fault diagnosis of one spool turbofan engine by selecting six measurement parameters,namely,corrected mass flow of fan,outlet total pressure of fan,outlet total temperature of compressor,outlet total pressure of compressor,outlet total temperature of low-pressure turbine and fuel mass low.This can also obtain satisfactory diagnosis results while the results can also be applied to other forms of aero engines.It is indicated that the reasonable type and quantity selection of measurement parameters not only guarantees the diagnosis,but also cuts down the cost.The method is of some engineering value.
FEM/BEM combined model for prediction of sound propagation and radiation of a duct inlet
REN Zhi-wen, HOU Wei, DU Lin, JING Xiao-dong
2010, 25(1): 136-141.
Abstract PDF(1958KB) icon1848 icon577
Abstract:
A finite element/boundary element combined method has been developed for the duct acoustic problem,using finite element method(FEM) to solve the acoustic transmission of inner acoustic field inside the duct,while employing boundary element method(BEM) to construct the artificial boundary condition for the far field radiation computation.The FEM and BEM were matched by the impedance continuity condition at the interface between the computational domains,and the combined numerical code was solved by a fast iteration algorithm.The validation of the model was first carried out by comparing the present results with the Levine-Schwinger solution for the sound radiation of a cylindrical pipe opening.Furthermore,the present model was used to simulate the sound propagation and radiation phenomenon for a simplified duct configuration of an aero-engine nacelle without flow.Finally,an analysis of the acoustic liner effect on the far field sound radiation was conducted based on the simulation results.
Regression analysis method for type-Ⅰcensored data
FU Hui-min, YUE Xiao-rui
2010, 25(1): 142-147.
Abstract PDF(1703KB) icon2147 icon464
Abstract:
Regression analysis method for type-Ⅰ censored data was presented.The regression equation for type-Ⅰ censored data was established.The best unbiased integral estimators of the regression coefficients and the standard deviation,the point estimators and confidence intervals of percentiles were given.The regression analysis methods for type-Ⅰ censored data from extreme distribution,Weibull distribution,normal distribution and location-scale distribution were discussed in detail.As the experimental information at the censoring time and the cross information among test data in different states were fully exploited,the presented method could reach a high precision.The method provides a feasible and effective approach to life prediction and reliability estimation of products when the test time or expense are limited.
Method of predicted fatigue life of aero-engine’s principal shaft
LU Shan, CHEN Qian, CHEN Jun
2010, 25(1): 148-151.
Abstract PDF(1313KB) icon2330 icon528
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Based on EDG-3 SPEY MK202 stressing standards,a main method was presented to study the fatigue life of aero-engine’s principal shaft.In this paper,EGD-3 was used to predict the fatigue life of a turbine runner shaft.So,two methods were used to work out the stress concentration coefficient,one was looking up datum and the other was computed on the basis of finite element method(FEM);whilst the method of stress correction coefficient was used to estimate the low cycle life of shaft,then compared with the nominal stress method.The result shows that it is feasible to estimate the low circle fatigue life of principal shaft using the method of stress correction coefficient;and the result agrees well with that of EGD-3 using the stress concentration coefficient on the basis of FEM under the low cycle load.
Bayesian analysis for the power law process based on Markov Chain Monte Carlo
WANG Yan-ping, LU Zhen-zhou, ZHAO Xin-pan
2010, 25(1): 152-159.
Abstract PDF(3228KB) icon1541 icon468
Abstract:
Based on Markov Chain Monte Carlo(MCMC) technique,a simple sampling approach for Bayesian analysis of a power law process was presented under various reasonable noninformative priors.The Bayesian approach provides a unified methodology for both time and failure truncated data.Markov Chain Monte Carlo samples for the power law process are easily obtained from the presented approach.Based on these MCMC samples,not only the posterior distributions of some parameter functions of the power law process are given directly,but also the methodologies for single-sample and two-sample prediction are given easily.The results from an engineering numerical example illustrate the feasibility,rationality and validity of the presented approach.The proposed approach has a certain degree of superiority,thus providing an alternative method for the reliability growth analysis of small-sized samples.
Mistuning characteristics analysis of mistuned bladed disk assemblies
LIAO Hai-tao, WANG Jian-jun, LI Qi-han
2010, 25(1): 160-168.
Abstract PDF(1280KB) icon2039 icon507
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The problem of determining the worst mistuning pattern and robust maximum mistuned forced response of turbine engine bladed disks was presented and solved as an optimization problem.Maximum resonant amplitudes searched across all degrees of a mistuned bladed disk and across all excitation frequencies in a given range were combined into an objective function.Individual blade mistuning was controlled by varying mistuning parameters.This approach was exemplified by a lumped-parametric model with two-degree-of-freedom per blade disk sector.Results of the optimum search of the worst-case mistuning patterns for the lumped parameter model were analyzed,showing that maximum blade forced response in a mistuned bladed disk was associated with mistuning jump,causing strong localization of the vibration response in a particular blade.Detailed two-degree-of-freedom per blade disk model was also used for calculation of the maximum forced resonant response of mistuned assemblies and for determination of its sensitivity coefficients with respect to mistuning variation.Studies have shown that there is not a threshold of frequency mistuning beyond which the maximum forced response levels off,or even drops,as the degree of mistuning is increased with the tendency of the forced response amplification factor.
General-structural design study of a micro turbojet engine
CHEN Wei, DU Fa-rong, DING Shui-ting, LI Yun-qing
2010, 25(1): 169-174.
Abstract PDF(996KB) icon1847 icon726
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The work is referred to the general-structural design method and process of a micro turbojet engine with thrust of 245N.The main subsystems design were introduced respectively including rotor system,flame chamber and lubrication-cooling system,plus the structural problems and corresponding solving methods met in ground operation.The design process was achieved by combing finite element method(FEM) and experiments,and the experimental results indicated that this engine satisfied the design requirements.These design experiences are valuable references for series design of micro turbojet engines.
Research on optimal operator of blade edge detection from computed tomography images based on computational theory
SUN Jing-jing, YANG Min, LIU Jing-hua
2010, 25(1): 175-179.
Abstract PDF(1741KB) icon1310 icon412
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Based on the mathematical model and computational edge detection theory of Canny,an optimal operator for edge detection in computed tomography image processing was proposed in order to resolve the accuracy and efficiency problem in blade edge detection from computed tomography images.The quantitative analysis and simulation of standard images verify that,the performance of the optimal operator is better than the conventional operators in the signal-to-noise ratio(SNR),location and multi-response.The performance of the optimal operator is also verified by the practical computed tomography images.It is found that the edges of blade detected by the optimal operator are smoother,the noise points and false edges are less.
Basic parameters analysis of first stage engine system for heavy lift vehicle
LI Xiang-ning, LIU Yu
2010, 25(1): 180-186.
Abstract PDF(1828KB) icon1544 icon572
Abstract:
Two proposals of manned lunar-landing propulsion system were discussed.The structure and basic parameters of propulsion system for existed heavy lift launch vehicles were analyzed.The structure and task requirements were proposed to meet the manned lunar-landing demand.Considering the performance,economics,technical difficulties,working reliability,a scheme of the first stage engine system for heavy lift launch vehicle was proposed.A heavy lift vehicle(HLV) system and a HLV series were estableshed,and their payload capability was calculated.Based on integrative analysis,the lunar launch vehicle is suggested to be 3 stage with 4 boosters,and two 50t liquid oxygen/liquid hydrogen are used for the third stage,while liquid oxygen/kerosene stage combustion cycle engines about 5000kN are used for all other stages.
Simulation of radiant heat flux of rocket engine exhaust plume on lunar detector
SHI Liang-chen, ZHU Ding-qiang, XU Xu, CAI Guo-biao
2010, 25(1): 187-192.
Abstract PDF(2161KB) icon1827 icon453
Abstract:
It’s necessary to solve radiative transfer equation(RTE) of gaseous mediums when simulating the radiation of rocket engine exhaust plume.In the calculation model,spectral parameters of gaseous constituents were given based on single line group(SLG) band model;and RTE was settled by the use of discrete transfer method(DTM).Radiant heat flux emitted by exhaust plume was then achieved through integral wavelength.The program was then validated by applying to high temperature carbon dioxide gas with geometry of cylinder.Finally,radiant heat flux on different parts and instruments,which was emitted by main and attitude control engines,was calculated according to flow field of plume.The results of heat flux provide a reference for integrated design of the detector.
Application of Kriging model to reliability analysis of solid rocket motor grain
LIU Ji-tao, LIU Fei, ZHANG Wei-hua
2010, 25(1): 193-197.
Abstract PDF(1671KB) icon1943 icon423
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The structure reliability of solid rocket motor grain was analyzed based on Kriging method.Firstly,Lating hypercube sampling was used to get sampling data of random variables.Secondly,the grain structure was analyzed using finite element method with sampling data.At last,a response surface of octahedron shear stress was estimated using Kriging model.And,the reliability of grain was estimated in combination with failure criterion.To evaluate the applicability of the Kriging method,Monte Carlo simulation was employed to compare with it.The approximate results of reliability qualify the performance of the method.
Effect of backpressure on the film thickness inside liquid swirl injector
CHEN Xiao-dong, LIU Yu, YANG Vigor
2010, 25(1): 198-202.
Abstract PDF(634KB) icon1700 icon486
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The film thicknesses of liquid swirl injector under different backpressures were studied theoretically and numerically.A loss coefficient model including friction effect on liquid/gas interface was established based on classical theory.It shows that the theoretical model is not sufficient to show variations of film thickness under different backpressures.The numerical simulations were conducted with a swirl axi-symmetric model to solve Navier-Stokes equations coupled VOF(volume of fluid) equation on an adapted grid,showing that the decreased mean velocity in the transition region near liquid/gas interfaces in liquid film is a contributing factor to the increase of the film thickness.
Fault diagnosis system based on knowledge pushing
YANG Si-feng, WANG Qi, LIU Lu
2010, 25(1): 203-207.
Abstract PDF(760KB) icon1722 icon435
Abstract:
Fault diagnosis system based on knowledge has been analyzed.To deal with the disadvantages that the fault diagnosis system can not transfer initiatively the knowledge to the decision-maker at opportune moment,a dataflow-driven architecture framework of fault diagnosis system based on knowledge management and knowledge pushing was proposed.Its primary hierarchy,organized and managed mode of knowledge was analyzed,and the dataflow-driven active pushing manner for knowledge was studied.The control mode of knowledge active pushing was founded,and the dataflow-driven integration prototype system based on knowledge management was developed.Finally,taking the fault diagnosis of liquid rocket engine test stand,for example,the fault diagnosis system based on knowledge pushing was conducted,and the latter experiment has shown the effectiveness of the method.
Dual engine control strategy for an unmanned helicopter
SHENG Shou-zhao, WANG Dao-bo, JIANG Bin, ZHAO Chao
2010, 25(1): 208-212.
Abstract PDF(1968KB) icon1703 icon487
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This paper discussed the dual engine control strategy for an unmanned helicopter.The parallel control for two engines to keep their output power consistent was presented,and the method of improving the stability of the helicopter rotor speed was discussed by using the higher rotation speed of two engines instead of the helicopter rotor speed as feedback signal.Furthermore,the test measurement and computation methods of the feed-forward compensation control quantity of collective and flight speed were given,showing two major factors affecting the stability of helicopter rotor speed.On this basis,two engines’ cylinder temperature difference was used to differentially compensate the two engine control quantity,so that the two engines output power and the driven system was further improved,and the helicopter torsion was enormously reduced.Finally,its feasibility and effectiveness were verified through hitching tests on the ground and flight tests.
Real-time simulation model for a turbofan engine based on nonlinear system equilibrium manifold theory
HU Wei-hong, LI Shu-qing, SUN Jian-guo
2010, 25(1): 213-217.
Abstract PDF(1844KB) icon1612 icon419
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Based on the nonlinear system equilibrium manifold theory,a simplified real-time simulation model for a turbofan engine was developed.According to the engine test data,an engine model,which could represent the states space equation between the engine corrected-states and the corrected fuel and corrected rotate speed,was presented.And a set of simulating result was accordant with the engine test result.In all,the work in this paper shows well trait about applicability,precision and real-time simulation of this real-time simulation model for a turbofan engine.And this model is very suit to the early research for the control systems of the aero-engine.
Fault diagnosis based on underdetermined blind source separation using potential energy function
ZHANG Yun, LI Ben-wei, WANG Yong-hua
2010, 25(1): 218-223.
Abstract PDF(1859KB) icon1621 icon446
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This paper studied underdetermined blind source separation(UBSS),i.e.the number of mixtures is smaller than that of sources.A blind sparse source separation algorithm based on potential energy function was proposed to estimate both mixing matrix and the number of sources.In the algorithm,the problem of finding mixture signals’ linear clustering was transformed to that of finding the accumulative potential energy function’s local maximum by constructing potential energy function.The algorithm avoided the disadvantage of k-means clustering algorithm that the number of sources in UBSS should be given in advance.The advantage of the proposed algorithm was verified from simulation signals.Based on the assumption that the signal was sparse in frequency domain,the algorithm was applied to underdetermined blind separation of rolling bearing vibration fault signals.The results show the fault signals are separated effectively.
Tooth surface design and manufacture for arcuate tooth trace face-gear
FANG Zong-de, CAO Xue-mei, SHEN Yun-bo
2010, 25(1): 224-227.
Abstract PDF(975KB) icon1807 icon488
Abstract:
A new type of face-gear drive with intersected axes of rotation formed by an arcuate tooth trace face-gear and an arcuate tooth trace cylindrical pinion was proposed,which has better meshing performance than the helical and spur involute face-gear drives.An arcuate tooth trace spiral bevel face-gear drive used for transformation of rotation between intersected axes that was consisted of a spiral bevel face-gear and an arcuate tooth trace cylindrical pinion.By applying space engagement theory,the author developed the cutting principle,mathematical model of design and machining for arcuate tooth trace face-gear.The equations of tooth surface of arcuate tooth trace face-gear was deduced and a 3-D model of FEM(finite element method) was established for further analysis.Based on the analysis of the machining method,it is convenient to generating the tooth surface of arcuate tooth trace face-gear by using the common Gleason cutter head with the general multi-axle numerical control machine tool.
Performance optimization for finger seal based on fuzzy Nash equilibrium game
ZHANG Yan-chao, CHEN Guo-ding, SHEN Xiao-long
2010, 25(1): 228-233.
Abstract PDF(723KB) icon1469 icon411
Abstract:
For the purpose of multi-objective optimization of finger seal with different preference requirements in engineering application,the fuzzy comprehensive evaluation was introduced into Nash equilibrium game,and performance optimization model with uncertain payoff of finger seal was built.By using the presented model,the performance multi-objective optimization problems with uncertain preference requirement for finger seal were researched.As compared with exiting methods,the results show that the presented method can not only effectively reflect the different response requirements of optimization objectives,but also significantly reduce the decision-making difficulty of multi-objective optimization for finger seal performances.Furthermore,the finger seal structure obtained through presented multi-objective method has good performances.
Gear fault diagnosis based on wavelet and neural network
LI Yong-long, SHAO Ren-ping, XUE Teng
2010, 25(1): 234-240.
Abstract PDF(1177KB) icon1902 icon458
Abstract:
By measuring experimentally the vibration signals of the gear system at different rotating speeds for different faults,the testing signals were obtained.The feature signals of system were analyzed using wavelet de-noising by threshold in different running conditions.Using discrete wavelet transform(DWT),the signals can be decomposed into eight detail components and an approximated component.After reconstruction of each level,their energy distributions were computed in order to extract the feature of the fault signals,these features were used for fault recognition using a neural network.The neural network was researched and analyzed.The results of using wavelet-neural network and neural network were also compared.Based on the research,it indicates that the feature of the denoised signal is superior to the original one.When dealing with various situations,such as the crack at the gear root,the crack at the gear’s reference circle and the wear abrasion fault of tooth surface,the performance rates are over 95%.The proposed method can be effectively used in engineering diagnosis of different faults of gear system.

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