1997 Vol. 12, No. 4

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RECUPERATION OF TURBOFAN ENGINE AND ITS THERMODYNAMIC ANALYSIS
Cai Ruixian, Zhang Shizheng, Wang Xu
1997, 12(4): 337-340.
Abstract PDF(292KB) icon1756 icon402
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A novel method for modifying a turbofan aeroengine into a land-base turboshaft engine was proposed by late Prof.C.H.Wu.In this case,the exhaust of hot core flow is used to recuperate the bypass flow,therefore,it is not necessary to redesign the low pressure compressor (fan) and the low pressure turbine.A comprehensive thermodynamic analysis is given to study the applicable range and results of this proposal.It is found that such modification is suitable for the turbofan engines with bypass ratio approximately equal to 1.The optimum total pressure ratio for efficiency is rather low and approximate to the optimum pressure ratio of pure gas turbine for specific output.The obtainable system efficiency and power can be higher than the conventional modification method (cutting the top of fan blade) for about 10% relatively.
AN EXPERIMENTAL STUDY ON SPRAYS OF A LIQUID JET IN A CROSS AIR STREAM
Xu Hang, Guo Zhihui, Bian Shouhua
1997, 12(4): 341-344.
Abstract PDF(295KB) icon1852 icon372
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The atomization character istics of a liquid jet injected into a high velocity cross air stream have been studied experimentally. The distributions of SMD, velocity and concentration of liquid droplets were measured with two dimensional PDA. The main conclusions have been drawn from the expermental investigation as follows:(1)In all measured sections along the direction of injection, the SMD and the velocity component perpendicular to air stream decrease, whereas the velocity component parallel to air stream increase. (2)Along the traverse direction, SMD in periphery of spray is larger than that in its center. (3) Droplet penet ration increases with an increase in diameter of droplet. Crescent concentration of droplets with identical diameter can be observed due to the interaction between liquid jet and the cross air stream.
A TWO-PHASE AFTERBURNER COMBUSTION MODEL
Zhu Zuojin, Chen Yiliang, Zhang Xiaochun
1997, 12(4): 345-349.
Abstract PDF(384KB) icon1645 icon460
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According to the fundamental concept of two-fluids,the governing equations for description of gas-droplets turbulent combustion in an afterburner of jet engine have been formulated,in which the important injection effect of the droplets in afterburner has been taken into detailed consideration.The Farve average method has been employed to represent the effects of turbulent combustion in the afterburner.The multiple time scale turbulent k-ε model proposed by Kim is applied to calculating the eddy viscosity of the turbulenct field.The heat flux radiation model has been taken to consider the effect of radiation at high temperature,the simple one step chemical reaction model is used to approximate the combustion of kerosene.The chemical reaction rate is assumed to be controlled by eddy break up process,and the reaction rate is modified by premixed reaction model in Arrhenius form.The application of SIMPLE algorithm indicates that the present twofluid model can calculate the two-phase turbulent combustion in the jet engine afterburner and obtain reasonable results.
NUMERICAL SIMULATION OF COMBUSTOR FLOWS
Xu Hang, Huang Yang
1997, 12(4): 350-352.
Abstract PDF(696KB) icon1895 icon369
Abstract:
A method has been developed for calculation of three-dimensional flows in aeroengine combustor including diffuser and flametube,inner and outer annuluses.The 3D body-fitting grid has been generated to deal with the complex geometry of the combustor.The non-staged grid scheme and k-ε turbulence model has been adopted.The mass flowing thought primary holes,dilution holes and film cooling holes has been calculated.The calculated results are consistent reasonably with the experimental measurements.
AEROENGINE TEST AUTOMATION OF ADAPTIVE CONTROL WITH RESTRAINTS
Fan Ding, Li Runzhi
1997, 12(4): 353-356.
Abstract PDF(827KB) icon1904 icon468
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An automatic control system of aeroengine test has been designed,based on the method of model reference adaptive control with restraints.According to its simulation results,this method has good adaptability when the controlled member contains non-linear elements or the controller member varies in a large range.The simulation results also show that ,the controlled system still has satisfactory performance index by regulating the controller's parameters,even if the restraints are out of limits.
ADAPTIVE PREDICTIVE PI CONTROL BASED ON NEURAL NETWORKS FOR ELECTROHYDRAULIC FORCE SERVO SYSTEM
He Yubin, Yan Guirong, Zhang Zhidong, Xu Jianxue
1997, 12(4): 357-361.
Abstract PDF(808KB) icon1762 icon485
Abstract:
An adaptive predictive PI controllor based on neural networks for electrohydraulic servo system is presented with respect to its complex nonlinearities and uncertainties.The method can be realized by a parallel structure which is composed of a real-time controller for real-time control operation,a predictive controller for regulation of control parameters and a supervising mechanism to determine whether or not the realtime controller is replaced by the predictive controller according to the variations of control performance. Thus, the real-time controller can be adjusted independently of the real operation of the controlled system by introducing neural networks as predictive model and predictive controller.It avoids the difficulty of the real-time control in control methods based on neural networks,thus makes the on-line learning control of complex systems possible.The learning ability of neural networks enables the predictive model to be modified on-line to simulate the behavior of the controlled system, and makes the predictive controller adjustable adaptively to variation of the system dynamical properties.Simulation results demonstrates its satisfactory control performance and it has been applied to a electrohydraulic servo structural testing system with success.
BIAS ESTIMATION RESEARCH OF FAULT DETECTION IN LIQUID ROCKET ENGINE
Huang Minchao, Chen Qizhi
1997, 12(4): 362-366.
Abstract PDF(436KB) icon1700 icon470
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Two accumulative error indices are defined as the discernment signals of the fault detection in a liquid propellant rocket engine.The biases of the fault detection are selected by way of the interval estimations of the discernment signals,and the operation conditions of the rocket engine are monitored on the basis of the biases derived from the interval estimations.Moreover,the maximum optimal questions of the fault isolation thresholds are considered with the aid of the probability density function for the discernment signals of the fault isolation.The data analysis of the test firings in a large turbo-pump fed liquid rocket engine demostrates that the estimation techniques of confidence interval can improve fault detection time compared to the current engine redline monitoring system.In the detection of anomalous test firings,both of the accumulative error indices correctly detected all faults.In the detection of normal ones,no false alarms were indicated by the first accumulative error index,while only one false alarm was indicated by the second accumulative error index.
APPLICATION OF ADAPTIVE VARIABLE NEURAL NETWORK TO AEROENGINE FAILURE DIAGNOSIS
Xie Shousheng, Fan Siqi
1997, 12(4): 367-370.
Abstract PDF(740KB) icon1707 icon470
Abstract:

A new adaptive variable neural network is developed according to the inner product feature of sample space.This method does not need to iterate learning.It features that its self-learning velocity is fast,accuracy is high,and it is able to change self-structure on work according to producing new sample.It has been applied to a type of aeroengine start system,its accuracy of failure diagnosis is prior to the original one,and the maintenance work is cut down.Moveover it has capability for real-time failure diagnosis,which opens up bright prospect for its propagation.
NEAR DEADBEAT CONTROL OF AN AEROENGINE SPEED SIMULATION SYSTEM
Sheng Wanxing, Dai Ruwei, Wang Sun'an, Shi Weixiang
1997, 12(4): 371-373.
Abstract PDF(552KB) icon1887 icon417
Abstract:
The near deadbeat control design was applied to an aeroengine speed simulation system for flight handling simulation.High power demand of the aeroengine speed simulation system can be met by adopting a type of electrohydraulic pump controlled motor system.But the desired dynamic properties are difficultly obtained under the condition of large step imput amplitude.According to the idea of deadbeat control,a method of quasi-deadbeat control design is proposed to overcome the difficulty.The experiments testified the effectiveness of the presented design.
NUMERICAL SIMULATION OF TWO-DIMENSIONAL FLOWFIELD IN PARTICLE SEPARATOR
Hou Lingyun, Yan Chuanjun
1997, 12(4): 374-376.
Abstract PDF(369KB) icon1629 icon464
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The numerical simulation of the two-dimensional,viscous and axisymmetric flowfield and various diameter particle trajectories in a inertial Inlet Particle Separator(IPS)has been completed.Forthe complex boundaries,a grid system of the non-orthogonal body-fitted coordinates is generated,which is ideally suitable to this case;For the split flow,multiply connected regions are transferred to simple connected region.A SIMPLEC agorithm for the full Navier-Stokes solver in generalized curvilinear coordinates is applied to calculate the viscous flow in the IPS.At last,the particle trajectories in the above viscous flowfield and separator efficiency are obtained.Good agreement between the experimental data and predicted results indicates that the presented procedure and its program contribute to development and design of future high perfomance inlet particle separator.
AN IMPROVEMENT OF k-ω TURBULENT MODEL
Shen Huili, Zheng Xiaoqing, Liu Feng
1997, 12(4): 377-380.
Abstract PDF(297KB) icon1746 icon391
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The k-ω turbulence model for predicting turbulence transition at a local Reynolds number lower than that observed in experiments.Wilcox suggested an approach to predict transition through modifying the viscosity in the ω equation with five more closure coefficients,but the approach maded the model too complicated.Here we introduce only one simple parameter to improve the model.An inequality is proposed to set a lower limit for the specific dissipation.In order to make the Navier-Stokes equations and k-ω equations strongly coupled,a staggered finite volume scheme for discretizing the N-S equations and the k-ω model equations has been developed.The algorithm was tested for a flat plate flow.Computational results shows that the present improvement of the k-ω turbulence model to control the transition position is effective.
NUMERICAL SIMULATION OF NORMAL SHOCK WAVE/TURBULENT BOUNDARY LAYER INTERACTION WITH PASSIVE CAVITY
Liang Dewang, R. Bohning
1997, 12(4): 381-384.
Abstract PDF(343KB) icon1759 icon383
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A full Navier-Stokes procedure,coupling with a Baldwin/Lomax turbulence model,is used to study the normal shock wave/turbulent boundary layer interaction with passive cavity.In addition,the ventilation velocity profile on the porous plate is calculated by a empirical model formulated from experiments.The total pressure and total temperature boundary conditions for inflow are given due to the existancc of sonic section in the channel flow and the static pressure boundary condition for out flow is given as well.The comparison between numerical and experimental results shows that the presented procedure can predict the shape of the shock,the mach number in front of the shock,the pressure ratio on the wall and position of the shock quite well.
PERFORMANCE PREDICTION OF BOWED VANE AXIAL-FLOW TURBINES
Yu Qing
1997, 12(4): 385-388.
Abstract PDF(281KB) icon1822 icon461
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A method for the performance prediction of axial-flow turbines with bowed and conventional vanes is presented,which uses flow function as control equation on S2 surface. Profile loss is calculated by numerical method on several S1 flow surfaces. Secondary loss and tip-leadage loss are empirically estimated with pitch-wide average losses along the cascade blades.The effect of the blade bowed angle on the secondary loss is taken into account.The comparison of the predicted results with experimental data confirms the feasibility of the method.
MEASUREMENT AND DETERMINATION OF AEROENGINE THRUST
Du Heling
1997, 12(4): 389-392.
Abstract PDF(763KB) icon1971 icon464
Abstract:
It is difficult to measure the flight thrust of Aeroengine directly.It is determined now by calculation with mathmatical relationships of the flight thrust to the physical quantities which can be measured directly.According to the definition and the expression of the thrust,as well as the conditions derived from them,a method of aeroengine thrust determination and its program are provided on the basis of engine part tests,model tests,engine ground test,altitude-simutation tests,and flight tests.At the same time,the important function of the altitude-simulation facility is also analyzed in respect of correct flight thrust determination.
VALIDATION TESTS WITH A SCALE-MODEL FOR SURFACE SOUND PRESSURE PREDICTION OF PROPELLER AIRCRAFT
Wang Tongqing
1997, 12(4): 393-396.
Abstract PDF(339KB) icon1328 icon463
Abstract:
An experimental research with a propeller aircraft scale model has been completed to obtain reasonably comprehensive data for validating its improved sound field model.Instead of the tests in anechoic windtunnel as abroad,the scale-model tests was accomplished in outdoor conditions.In the predicton of propeller noise in free field with the improved sound field model,the load data on the propeller blade surface were obtained from calculation of inverse problem.The measured results of sound pressure on the scale-model have been compared with that predicted by the improved sound field model in a reasonable agreement.
COMPARISON BETWEEN TWO KINDS OF CONVENTIONAL LABYRINTH
Wu Dingyi
1997, 12(4): 397-400.
Abstract PDF(641KB) icon1796 icon479
Abstract:
Straight-through and stepped labyrinths are often used in aircraft engine.According to large amounts of experimental data,the empirical formulas of mass flow factor for these two kinds of labyrinth have been provided which are superior to their theoretical formulas due to various corrections.The seal characteristics of the two kinds of labyrinth were compared and analyzed in detail so that their featuers and reasonable conditions of their application were found out.Finally,the new empirical formulas for calculating their critical pressure ratio were derived too.
MULTISECTION LINERS FOR NOISE REDUCTION OF COUNTER-ROTATING FAN
Shi Wei
1997, 12(4): 401-403.
Abstract PDF(631KB) icon1720 icon364
Abstract:
It has been found that multisection liners not only attenuate the sound waves in ducts,but also to suppress sound wave thorugh the wave reflection at impedance discontinuities.As a consequence,the maximum noise reduction in a duct of given length can be realized by designing each section liner and different combination.In the present investigation,different combinations of multisection liners have been designed to suppress the discrete noises generated by a counter-rotating fan.The experimental results testified that,the noise was reduced by 9 dB in far field under the conditon of 60 cm liner length.
DIGITAL SIMULATION ON TOOTH CUTTING AND MESHING OF SPIRAL BEVEL GEARS
Wang Sanmin, Ji Minggang
1997, 12(4): 404-406.
Abstract PDF(665KB) icon1845 icon458
Abstract:
The conventional methods for determining the tooth geometry and tooth contact of spiral bevel gears are based on differential geometries of rigid body movement,and consequently make description of tooth surface and analysis of tooth contact behavior very complicated.In this paper,the authors work out a digital simulation method for tooth cutting and meshing of spiral bevel gears.A numerical model of tooth surfaces is set up by digital simulation of tooth cutting.The analysis of tooth contact behavior is completed with the numerical model of tooth surfaces.Solution of the meshing equation v·n=0 in conventional methods is replaced by minimizing the normal distance between points on the tooth surfaces in our method.The results of digital simulation for the spiral bevel gears used in a Chinese aeroengine show that the presented method describes the tooth shape and tooth contact characteristics more conveniently and efficiently,and can determine optimal cutting adjustment parameters for obtaining spiral bevel gears with good contact quality.
FRETTING FATIGUE OF DOVETAIL JOINT UNDER COMBINED CYCLIC LOADING
Xu Qi, Pan Shengcai
1997, 12(4): 407-409.
Abstract PDF(245KB) icon1734 icon370
Abstract:
The state-of-art in research on fretting fatigue of dovetail joint in aircraft engine at home and abroad was sized up.Stress analysis of dovetail joint part was carried out.Experimental equipment was desiged and set up.A number of tentative experiments was conducted.It is confirmed that the experimental technique and equipment can offer a great deal of data for designing.
PRESSURE AND AVERAGED THRUST OF A PULSED DETONATION ENGINE MODEL
Fan Wei, Yan Chuanjun, He Liming, Wang Linquan, Lie Hengren
1997, 12(4): 410-412.
Abstract PDF(618KB) icon2100 icon461
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A mode of Pulsed Detonation Engine (PDE) has been made.Its pressure and averaged thrust were analysed and calculated according to detonation wave theory,and then were measured with two sensors in testing of the PDE model.The comparison of the calculated results with the measured data shows that the PDE model can produce the pulsed detonation wave and thrust.
EFFECTS OF FILM COOLING ON INTERNAL HEAT TRANSFER COEFFICIENTS OF BLADES
Tao Zhi, Cai Yi
1997, 12(4): 413-415.
Abstract PDF(886KB) icon1853 icon394
Abstract:
Effects of film cooling on the internal heat transfer coefficients of turbine blades were investigated numerically and the key factors have been found out as the film cooling hole distance ratio and the inlet Reynolds number.The local heat transfer coefficient variations were discussed both for the pressure and the suction sides of blades.Numerical results showed that,for the pressure side the internal heat transfer coefficient was much enhanced and could be doubled,as compared with the no-hole passages at the same range.Heat transfer coefficient for the suction side,however,was decreased due to film cooling.
DEVELOPMENT OF FAILURE DIAGNOSIS TECHNIQUESIN ENGINE DIGITAL CONTROL SYSTEMS
Huang Xianghua, Sun Jianguo
1997, 12(4): 416-418.
Abstract PDF(243KB) icon1987 icon461
Abstract:
This paper surveys the development of sensor failure diagnosis in engine digital control systems.First,the early research works on techniques of sensor failure detection and isolation are reviewed.The main disadvantage of model-based methods is high sensitivity to modeling errors which are inevitable because of the complexity of the aircraft engine.Then,the paper considers the necessity of robust failure diagnosis and its development.In view of the fact that the neural networks have been successively applied to control realm and possess themselves of tremendous potentials,the neural-network-based failure diagnosis is recommended as a promising approach in the engine digital control systems.
INFLUENCE OF TEMPERATURE RATIO ON PENETRATION DEPTH OF 2D CONFINED CROSS FLOW
Wang Weidong, Guo Zengyuan
1997, 12(4): 419-421.
Abstract PDF(323KB) icon1951 icon383
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The influence of temperature ratio on the penetration depth of two-dimensional confined cross flow is investigated numerically.It is found that the temperature ratio of jet to main flow was an important parameter independent of momentum ratio.This phenomena can be explained in terms of the concept of "thermal drag".A cold jet injected perpendicularly into a confined hot air flow is heated and accelerated as the momentum ratio is given.The thermally induced pressure drop is converted into the momentum increase and consequently increases the penetration depth.On the contrary,a hot jet injected perpendicularly into a confined cold air flow for the given mometum ratio decreases its own momentum due to cooling by the mainflow.As a consequence,its penetration depth also is cut down.
FINITE ELEMENT STRESS ANALYSIS OF POWDER METALLURGY TURBINE DISC
Song Yingdong, Chen Wei, Wen Weidong, Gao Deping
1997, 12(4): 422-424.
Abstract PDF(289KB) icon2287 icon544
Abstract:
A stress analysis of a Powder Metallurgy (PM) turbine disc was accomplished by finite element method.First,the calculation boundary was determined according to the linkage mode of the rotor,then its elastic,thermoelastic and thermal stress analyses were made.The results show that the deformation of the PM disc is elastic at maximum rotational speed.As the rotational speed exceeds the maximum by 22%,the deformation of disc remains elastic except in the core.The inhomogeneous temperature field has a strong effect on the stress distribution of the disc.
APPLICATION OF DOMAIN DECOMPOSITION METHOD TO PREDICTION OF TURBULENT FLOW FIELDS
Zhang Chuhua, Liu Zhengxian, Gu Chuangang, Miao Yongmiao
1997, 12(4): 425-428.
Abstract PDF(309KB) icon1520 icon425
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The Domain Decomposition Method (DDM) is applied to calculation of turbulent flow fields.A general DDM-1 scheme SI,ω is developed for turbulence equations with treatment of variables in overlapped domains.It features that the whole computational domain is decomposed into several subdomains according to the flow properties and the different decomposed domains employ corresponding physical models.A prediction of turbulent flow fields in a sudden pipe expansion was made and compared with the experimental data.It was shown that the scheme can predict the reattachment point,mean axial velocity and turbulence kinetic energy more accurately than the methods using a single model in entire domain.
THRUST CHARATERISTICS OF EXHAUST EJECTOR SYSTEMS WITH LOBED NOZZLES TESTED AT COLD HIGH SPEED CONDITIONS
Li Li, Wu Shousheng
1997, 12(4): 429-432.
Abstract PDF(661KB) icon1524 icon471
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A set of thrust charateristics (thrust with nozzle pressure)of a round covergent nozzle、five lobed nozzles and lobed nozzle-mixing tube combinations with and without difffusers have been obtained from the experimental investigation at cold high speed conditions (nozzle pressure=0.15～0.5 MPa) Test results show that the lobed nozzles of the exhaust ejector systems at high speed conditions also have superior application prospects,provided their designs consider the impact of high speed flow,in especial,the aerodynamic charateristics of supersonic exhaust flow.

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