2008 Vol. 23, No. 7

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Large eddy simulation of pollution formation in model annular combustor
YAN Ying-wen, ZHAO Jian-xing, ZHANG Jing-zhou, LIU Yong
2008, 23(7): 1161-1167.
Abstract PDF(1042KB) icon2178 icon406
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In three-dimensional arbitrary curvilinear coordinates,large-eddy simulation(LES) approach was employed to simulate pollution formations in the model annular combustor.The k-equation subgrid scale model was used to simulate the subgrid eddy viscosity,the eddy-break-up(EBU) combustion subgrid scale model was applied to prediction of the chemical reaction rate,the NOsubgrid scale pollutant formation model was employed to the evaluation of the rate of NOformation,and a two-step turbulent combustion subgrid scale model was applied for calculating COconcentration.Astochastic separated flow formulation was applied to prediction of instantaneous gas-liquid two-phase turbulent combustion flows.The numerical simulation results were in reasonable agreement with the experimental instantaneous velocity profiles in the primary zone,temperature and pollution concentration profiles at the outlet.It shows that the LESmethod and subgrid scale pollution formation models in this study can be used to investigate turbulent two-phase combustion and pollution formation processes in combustors.
Flow and heat transfer investigation in pre-swirl inflow rotor-stator cavity
ZENG Jun, ZHANG Jian, HUANG Kang-cai
2008, 23(7): 1168-1173.
Abstract PDF(1135KB) icon1830 icon453
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In order to investigate the flow and heat transfer in a pre-swirl rotor-stator cavity with two air inflows(central air flow and pre-swirl inflow at stator rim respectively) and two outflows(radial outflow at outer shroud and axial outflow at rotor rim respectively),a numerical study was conducted by using computational fluid dyrramics(CFD) software CFX5.7 with shear stress transport(SST) turbulence model.The computational results agree well with the test results.The results show that,rotating Reynolds number,non-dimensional flow velocities and pre-swirl ratio have different effects on the flow structure and heat transfer characteristics in the rotor-stator cavity by computing four different conditions.
Vaporization and discharge characteristics of lean premixing prevaporizing system
ZHONG Hua-gui, ZHU Tao
2008, 23(7): 1174-1181.
Abstract PDF(1476KB) icon1776 icon413
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Fuel-air mixture uniformity for two sets of lean premixing and prevaporizing system(LPP) was obtained numerically and experimentally,and the combustion characteristics of LPPwere verified with a tubular combustor.The results show that,there is a better fuel-air mixture uniformity at the exit of radial swirler premixing facilities than at axial ones.Vane number and swirl angle of a swirler,premixing distance,air velocity and fuel injection methods,etc,have remarkable effects on air-fuel mixture uniformity.When fuel-air equivalent ratio is bigger than0.5,COand NOXemissions of the LPPcombustor are significantly lower.In the event of presence of backflow at a LPPfacility exit,the flashback takes place during combustion.
Cooling air flow performance of an afterburner fuel injector with double-wall construction
YAN Bao-hua, FAN Wei-jun, YANG Mao-lin
2008, 23(7): 1182-1188.
Abstract PDF(780KB) icon1626 icon412
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The performance of cooling air flow extracted from the fan stream to a new type fuel injector with double-wall construction for afterburner was simulated experimentally,so as to provide a basis for design and cooling performance research of advanced fuel injector.The effects of mass flux and fuel injector structure on pressure coefficient were studied through experiments of eight cooling casings of fuel injector.The effects of inlet total pressure on Reynolds number of the flow in cooling casing were also obtained.An optimum,new fuel injector was selected by comparing the results of eight casings of fuel injector.The pressure coefficient of such fuel injector is 1.2,the appropriate width is 16 mm,and the Reynolds number in the same inlet conditions is the biggest.
Effect of different clapboards structure in turbine blade trailing edge complex passages on heat transfer characteristics
TAO Zhi, YUAN Xing, DING Shui-ting, XU Guo-qiang, DENG Hong-wu
2008, 23(7): 1189-1193.
Abstract PDF(807KB) icon1605 icon406
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The effect of three different dividers on the heat transfer of turbine blade trailing passage was investigated experimentally.The condensation vapor method was used in the experiment.Heat transfer and hydrodynamic drag were compared among the straight divider with hole of 2.6 mm in diameter,waved divider with hole of 3 mm in diameter on wave crest and hole of 2.2 mm in diameter on trough,and straight divider without hole.The waved divider gave better heat transfer than the straight divider with hole when the Re<20000.For the case of Re>50000,the waved divider showed worse heat transfer than the straight divider without hole.The drag of the waved divider was far less than that of the straight divider with or without hole.
Effect of relative space between mixing duct exits on the flow temperature
TANG Zheng-fu, ZHANG Jing-zhou, SHAN Yong
2008, 23(7): 1194-1197.
Abstract PDF(603KB) icon1608 icon418
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Anumerical simulation and analysis of infrared radiation field of the integrative infrared suppressor model was performed to investigate the effects of space between the model exit and curved mixing duct exit,meanwhile the temperature field of the model exit was also obtained by numerical simulation.The results show that the mixing flow temperature of the model exit will decrease 42% by extending the distances between exits,because mixing hot exhaust with rotor downwash is enhanced greatly.At the same time,the infrared radiant intensity is increased slightly between3～5μm and 8～14μm.
External heat transfer predictions of turbine cascades
ZENG Jun, QING Xiong-jie
2008, 23(7): 1198-1204.
Abstract PDF(1119KB) icon1820 icon425
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Three-dimensional Reynolds averaged Navier-Stokes(N-S) equations with Shear Stress Transport(SST) turbulence model were used to predict external heat transfer coefficients(EHTC) of turbine cascades.Atransition model was adopted to improve the accuracy.MARK-Ⅱ,VKIhigh pressure turbine stator cascade and VKIhigh pressure turbine rotor cascade were calculated.The computational results were compared with the experimental data,showing that the numerical method developed could effectively improve accuracy of external heat transfer prediction.
Numerical simulation of combustion in a wall jet combustor
MING Ping-jian, ZHANG Wen-ping, LEI Guo-dong, ZHU Ming-gang
2008, 23(7): 1205-1211.
Abstract PDF(2378KB) icon1524 icon438
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The gas-liquid two phase flow and combustion in wall jet combustor was simulated numerically using finite volume method based on unstructured grid.The gas phase flow was solved in Euler coordinate,while the droplet was described with Lagrange method.The computational domain was divided with tetrahedron.SIMPLECmethod was used for gas phase flow and Euler implicit method for droplet trajectory integration.The interaction between two phases was taken into account with full two way coupling method.Spalding evaporation model was used for droplet evaporating and eddy breakup(EBU) model for combustion.The numerical result is consistent with experimental data in literature.
Influences of axial positions of grooved casing treatment on stall margin improvement
WU Yan-hui, ZHANG Hao-guang, CHU Wu-li, DANG Chun-ning
2008, 23(7): 1212-1217.
Abstract PDF(1347KB) icon1598 icon389
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Experimental and numerical investigations were conducted to study the effects of axial positions of circumferential grooved casing treatment on compressor performance.Experiments of three different axial positions of circumferential grooved casing treatment were performed in a subsonic rotor.The experimental results show that three axial positions of groove casing treatment extend the steady operating range of the compressor at two rotating speeds.Groove with unchanged axial position has the best effect in extending the steady operating range,followed by the backward axial position moving.The calculated overall tendency for stall margin improvement fitted well with the experiment.The fundamental flow mechanism was obtained by in-depth analysis of the flow-filed at the blade tip,based on the effect of circumferential grooved casing position on the compressor performance.
Aerodynamic design of compressor blade using optimization algorithm
WANG Guang-wen, ZHOU Zheng-gui, HU Jun
2008, 23(7): 1218-1224.
Abstract PDF(1672KB) icon1635 icon465
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An automatic aerodynamic optimization system for axial compressor was constructed,which was composed of turbomachinery flow field simulations in3-D Navier-Stokes equation methods,grid automatic generations,parameterizations of blade profiles,meridional channels and stacking line and the advanced parallel genetic algorithm based on intranet.In construction of objective functions,design point adiabatic efficiency,mass flow rates,pressure ratio and non-design point mass flow rates was considered.NASArotor67 was redesigned using the optimization system,and the present method successfully obtained a design that improved adiabatic efficiency by 0.5% compared with the rotor67 while satisfying mass flow rate and pressure ratio.
Effects of inlet boundary layar on aerodynamic performance of bowed compressor cascades with large camber angle
CHEN Shao-wen, CHEN Fu, WANG Zhong-qi
2008, 23(7): 1225-1231.
Abstract PDF(2221KB) icon1526 icon456
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The annular bowed compressor cascads with large camber angle under different inlet boundary layers thicknesses were investigated experimentally and numerically under low-speed condition.The effects of bowed blade on aerodynamic performance of compressor cascade were analyzed under different inlet boundary layer thicknesses.The results show that,when the inlet boundary layer is getting thinner,the aerodynamic performance of cascades improves under most flow conditions.However,the total loss will rise sharply if bowed blade with bigger incidences is adopted in the cascade with larger camber angle when the bowed angle is bigger.
Influence of different incidences on loss in turbine cascade
SUN Da-wei, QIAO Wei-yang, XU Kai-fu, LI Wei
2008, 23(7): 1232-1239.
Abstract PDF(2951KB) icon1605 icon443
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A pressure-correction 3-Dcomputational fluid dynamics(CFD) code was used to simulate numerically the flow fluid of turbine cascade with different incidences.And three turbine loss models of off-design operating condition were analyzed and compared on the basis of the CFDnumerical simulation.The results show that the total pressure loss increases with the increase of incidence,provided that the incidence is positive;the total pressure loss decreases a little and then increases with the increase of incidence,provided that the incidence is negative.Though three turbine loss models of off-design operating condition can show the changing tendency of the total pressure loss with the change of incidence,the prediction results differ a lot.
Analysis of secondary flow structures of compressor cascade with different fences
LIU Yan-ming, ZHONG Jing-jun, WANG Bao-guo, LIU Shu-yan
2008, 23(7): 1240-1245.
Abstract PDF(793KB) icon1994 icon439
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The sketches of secondary flow structure in compressor cascade with endwall fences,blade fences and combined fences were presented.By blocking crosswise flow and spanwise flow respectively,the secondary flow status was controlled by the endwall fences and blade fences,resulting in reduced total loss of cascade.Both the cascade secondary flow characteristics with endwall fence and blade fence were embodied in the cascade flow with combined fences.Meanwhile,optimal combined fences was not the simple combination of optimal endwall fence and optimal blade fence.Amore detailed optimization process was required.While different fences improved cascade flow status,the endwall fence vortices,blade fence vortices and other vortices were formed and developed,making the vortex structure more complicated.
Analysis on the unsteady interaction between the casing treatment and the compressor
JIANG Hua-bing, LU Ya-jun, YUAN Wei, LI Qiu-shi
2008, 23(7): 1246-1252.
Abstract PDF(1298KB) icon1940 icon444
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Three arc curve slot casing treatments that differ only in the number of treatment slots were utilized to investigate the influence of unsteady interaction frequency on the performance of the compressor.The experiment results indicate that the frequency of unsteady interaction between the arc curve casing treatment and the compressor,which represents the number of casing treatment due to the relative movement between rotor blades and treatment slots,should be tuned close to the vortex shedding frequency or within the range of lock-in frequency.The influence of casing treatment on the total pressure flow fields of the compressor stator were investigated utilizing total pressure rake,the experiment results indicate that the unsteady interaction between the compressor and the casing treatment should improve the separated flow field around the compressor,and which influence the radial distribution of the total pressure rise.
Study on turbine performance at low Reynolds number
SUN Da-wei, QIAO Wei-yang, XU Kai-fu, LUO Hua-ling
2008, 23(7): 1253-1259.
Abstract PDF(1995KB) icon1760 icon454
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The Quasi-three dimensional calculation program of S2 stream surface incorporated with some different loss model is developed on the base of solving Euler equation.And the performance of 3 different sets of turbine components is calculated at different Reynolds numbers.The prediction results show that the predicted values of variations of both turbine efficiency and flow capacity with Reynolds number decreasing show smaller than that of Russia correlation,but the overall trend agrees,and the prediction results using different loss model are greatly different.
Numerical simulation of active control on tip leakage flow in axial turbine
LI Wei, QIAO Wei-yang, XU Kai-fu, LUO Hua-ling, SUN Da-wei
2008, 23(7): 1260-1265.
Abstract PDF(1259KB) icon1912 icon436
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A 3-D Reynolds-averaged Navier-Stokes equations computational fluid dynamics(CFD) code,together with pressure-correction based Reynolds stress model and wall function was used to simulate the effects of tip clearance injection active control on the tip leakage flow in a turbine rotor.The results show that the injection can have a beneficial effect on turbine rotor efficiency by selecting properly the injection hole location.The efficiency can increase nearly by 0.35 percent with the jet of combined injection hole in loose tip clearance,so does the efficiency by 0.3 percent in tight tip clearance.The number of saddle is equal to that of node in the region of injection hole in tip platform,which satisfies the singularity point total number.
Vortex structures downstream a lobed nozzle/mixer
Hui Hu, Toshio Kobayashi
2008, 23(7): 1266-1278.
Abstract PDF(2193KB) icon1292 icon449
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An experimental study was conducted to investigate the evolutions of unsteady vortex structures downstream a lobed mixer/nozzle.Anovel dual-plane stereoscopic PIVsystem was used to measure all 3-components of vorticity distributions to revealed both the large-scale streamwise vortices produced by the lobed mixer/nozzle and the Kelvin-Helmholtz vortex structures generated due to the Kelvin-Helmholtz instabilities simultaneously and quantitatively for the first time.The instantaneous and the ensemble-averaged vorticity distributions displayed quite different aspects about the evolutions of the unsteady vortex structures.While the ensemble-averaged vorticity distributions indicated the overall effect of the special geometry of the lobed nozzle/mixer on the enhanced mixing process,the instantaneous vorticity distributions elucidated many details about how the enhanced mixing process was conducted.In addition to quantitatively confirming conjectures of previous studies,further insight about the formation,evolution and interaction characteristics of the unsteady vortex structures downstream of the lobed mixer/nozzle were also uncovered quantitatively in the present study.
Inertia force of flapping wing in entomopter micro air vehicle
HU Ming-lang, WEI Rui-xuan, CUI Xiao-feng, GUO Qing
2008, 23(7): 1279-1286.
Abstract PDF(941KB) icon2156 icon498
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Inertia force and moments of flapping wing in insect flight were studied using the methods of theoretical modeling and simulation.The influence of stroke amplitude,stroke duration,mid-stroke angle of attack and flip duration on inertia force was studied by simulating the biological locomotion of insect flight.The study results show that: the magnitude of inertia force is almost equivalent to that of the aerodynamic force during the high frequency flap of small insect;the insect wing`s chord inertia is much higher than its spread inertia——higher by an order of magnitude;the influence of stroke moment of inertia is much higher than that of the flip moment of inertia,so the flip moment of inertia can be ignored;it's believed that the flap is almost symmetrical if the stroke is symmetrical and the flap is absolute symmetrical if the stroke and the flip are both symmetrical,then the inertia force can be ignored.How to design the control mechanic of insect-like flapping wing air vehicle to increase the symmetrical and eliminate the influence of inertia force was discussed at last.
Parametric analysis of an integrated airframe/propulsion module design for hypersonic vehicle
CAO De-yi, LEE Chun-Hian
2008, 23(7): 1287-1292.
Abstract PDF(794KB) icon1775 icon436
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An aerodynamic analysis model for an airframe/propulsion integrated module was established based the theory of oblique-shock,in conjunction with a quasi～-1Dengineering estimation and the method of characteristics.The viscosity effects of the module were taken into account using the method of reference temperature.Aparametric analysis was then performed using the developed model.The influences of the design parameters,including the fore-body length,the leading angle,and the width of the module upon the aerodynamic characteristics were presented.The results reveal that increasing the length of the fore-body will make the thrust and the lift,as well as the specific impulse of the module to increase first and then decrease;increasing the leading angle will increase the lift but decrease the thrust;increasing the width of the module will decrease the equivalence lift.Hence,modularized propulsion system and the trade-off among these variables must be taken into account in the configuration design of the hypersonic cruise vehicle.
Numerical simulation of the flow characteristic of tip leakage flow in a transonic axial-flow compressor at near stall condition
ZHANG Yan-feng, CHU Wu-li, LU Xin-gen
2008, 23(7): 1293-1298.
Abstract PDF(1597KB) icon1828 icon461
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Tip clearance flow and the unsteady flow phenomena of tip leakage vortex have great effect to the stall inception of axial-flow compressor.In this paper,3-Dsteady,unsteady numerical simulation of the transonic axial-flow compressor-NASArotor 37 was investigated.Compared to the numerical results and the experimental test case at peak-efficiency and near stall condition,the numerical results agreed well with experimental test data for estimation of the global performance.For the unsteady computation,Detail analyses of the flow field of the NASArotor 37 led to some preliminary conclusion: the tip leakage flow behave obviously unsteady flow phenomena.Shock-vortex induced the periodic breakdown of the tip leakage vortex.
Computation of aerodynamic drag of a fastback car in accelerating process
ZONG Ye-ling, KANG Ning
2008, 23(7): 1299-1303.
Abstract PDF(538KB) icon1775 icon491
Abstract:
Three dimensional unsteady flow field around a simplified fastback car in process of accelerating was simulated numerically with computational fluid dynamics(CFD)method.The aerodynamic drags were calculated at different speeds and different accelerations.The calculated results show that the aerodynamic drag at a certain speed and acceleration are closely related to the current speed and acceleration.Through twice linear fittings,the computational formula of aerodynamic drags was obtained.This formula could work out immediately the aerodynamic drag of the aerodynamic characteristics of a car in accelerating process at a certain speed and acceleration value.
Nonlinear dynamic analysis and experiment verification of rubbing faults of rotor-ball bearing-support-stator coupling system for aero-engine
CHEN Guo, LI Cheng-gang, WANG De-you
2008, 23(7): 1304-1311.
Abstract PDF(1659KB) icon1789 icon491
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Anew rotor-ball bearing-support-stator coupling system dynamic model including rubbing fault was established for rotor-bearing system of practical aeroengine.In the model,the stator motion,the flexible support,squeeze film damper(SFD) were considered,and the nonlinear factors of ball bearing such as the clearance of bearing,nonlinear Hertzian contract force between balls and races,and the varying compliance vibration because of periodical variety of contact position between balls and races were modeled.The numerical integral method was employed to obtain system's responses,and an aeroengine tester with stator was established to carry out rubbing fault experiment.Finally,the simulation results from rotor-ball bearing-support-stator coupling model were compared with the experiment results in order to indicate the validity of the new model.
Experimental analysis on characteristics of the system supported by magnetic bearings and magnetic damper
XIE Zhen-yu, LI Ke-lei, ZHAO Qing-quan, HUANG Pei-zhen
2008, 23(7): 1312-1317.
Abstract PDF(1283KB) icon1838 icon378
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The system was supported by two radial magnetic bearings,one axial magnetic bearing and one radial magnetic damper.The radial magnetic damper only supported the rotor with damping and with no stiffness.Influence of the control parameters on characteristics of the system was studied by experimental modal analysis and actual operation of the system.Experimental analysis of the system shows that the vibration of the rotor can be reduced effectively,when it got across the first two bending critical speeds and operated on over 16000 rotations per minute.
Efficient reformulation of3-D high-fidelity generalized method of cells
SUN Zhi-gang, GAO Xi-guang, SONG Ying-dong, HU Xu-teng
2008, 23(7): 1318-1322.
Abstract PDF(506KB) icon1782 icon447
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The efficient reformulation of 3-Dhigh-fidelity generalized method of cells had been put forward.The model was presented based on the hypothesis of periodicity in composite microstructure.In this approach,surface-averaged quantities were the primary variables which replaced the coefficient of the displacement after the mechanical equations were analyzed and answered in microscopic elements.This reduced the number of equations involved and eliminate the concept of generic cells.Numerical results based on the model agrees well with available results from experiments and theoretical analysis.
Finite element analysis of inertial load of the statically indeterminate rotor stay bearing
JIN Xiang-ming, GAO De-ping, CAI Xian-xin, GUO Xiao-jun, XIE Jun-ling
2008, 23(7): 1323-1327.
Abstract PDF(1626KB) icon1544 icon410
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Afinite element by coupling plane stress element with Fourier ring element was used in the calculation of the inertial load of the statically indeterminate rotor stay bearing.This settled two flaws in classical material mechanics,which made it difficult to establish correct deformation compatibility condition when the coupling stiffness of support and shaft bearing could not be ignored,and,bigger error in using beam theory was likely caused in the case of absence of shaft character for the rotor.At the same time,because this method transforms the complex three-dimensional question into two-dimensional question,the workload of calculation is smaller,calculating time is shorter,precision and efficiency is higher.
Investigation of acceleration factor for pre-corrosion fatigue degradation:model and analysis
HE Xiao-fan, YANG Hong-yuan, LIU Wen-ting
2008, 23(7): 1328-1333.
Abstract PDF(394KB) icon1720 icon422
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The acceleration corrosion factor(ACF) for accelerated corrosion test under service or natural exposed environment is the most important parameter in the accelerated corrosion test(ACT).The material property was degraded seriously in pre-corrosion environment,and the corrosion damage was characterized by fatigue strength.So,the acceleration factor was defined as the ratio of fatigue strength in different environments,and the expression was proposed in consideration of the degradation process of fatigue strength with corrosion time.To evaluate the fatigue property,the pre-corrosion fatigue life was assumed to follow the two-parameter Weibull distribution,the detail fatigue rating(DFR) method in pre-corrosion environment was proposed,and the relationship between the DFRand the corrosion time was expressed as an exponential function.The acceleration corrosion factor based on the DFRwas proposed by comparing the degradation process in accelerated corrosive environment and the natural exposed environment,and was proved to be a constant regardless of corrosion time.Finally,the typical ACFof LY12CZ Aluminum alloy specimen was calculated.
Investigation on the transpiration cooling of a liquid rocket nozzle
JIN Shao-shan, JIANG Pei-xue, SUN Ji-guo
2008, 23(7): 1334-1340.
Abstract PDF(2031KB) icon1645 icon474
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The SSTk-ω turbulence model was used to simulate the coupled whole field of the transpiration cooling of a Laval-nozzle of a liquid O2/H2 propellant rocket engine.The influences of porosity,variation property,compressibility,the thermal disperse effect of porous media,micro-scale flow and mass transfer were considered in the model.The influences of porosity on local blowing ratio,the wall temperature and the boundary layer thickness were analyzed and compared with the regenerative cooling.The results showed that the increase of average blowing ratio can decrease the average wall temperature with a larger proportion and for the transpiration cooling nozzle the throat is no longer the highest temperature point.The simulation results were compared with both the experimental results and the one dimension aerodynamics formula and approved to be accurate.
Study of fault diagnosis system for liquid rocket engine using multi-Agent
DENG Wei, LI Jia-wen
2008, 23(7): 1341-1345.
Abstract PDF(1208KB) icon1818 icon432
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This paper established fault detection and diagnostic system of liquid rocket engine based on multi-Agent technology,which included wavelet denoising,sensor detection,fault detection,fault diagnosis and main scheduler program.Using multithread programs,Dynamic Link Library and network programming technology,the fault detection and diagnostic had better intelligence.This paper illustrated several Agent examples of wavelet denoising and sensor detection,and demonstrated the framework of the fault detection and diagnostic system.
Feature extraction based on rough kernel Fisher discriminant analysis and its application on aeroengine fault diagnosis
HU Jin-hai, XIE Shou-sheng, WANG Cheng, LI Ying-hong, YANG Fan
2008, 23(7): 1346-1352.
Abstract PDF(1469KB) icon1756 icon485
Abstract:
A new approach based on rough kernel fisher discriminant analysis(RKFDA) was proposed for aeroengine fault feature extraction,which combined rough set and kernel Fisher discriminant analysis.Firstly,rough set was used to exclude the features irrelevant to the fault;reduce the dimension of features,remove the effect of disturbance characteristics and cut down the cost of computation.Secondly,kernel Fisher discriminant analysis was employed on the obtained subset of features to extract the nonlinear features.Finally,fault extraction and recognition experiments in aeroengine lubricating oil system were carried out to test the performance of this method.The results show that the extracted features based on the proposed method could improve the recognition for aeroengine fault,and reduce efficiently the dimension of features with strong adaptability and robustness for various classifiers.

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