1998 Vol. 13, No. 2

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ACOUSTIC CONTROL OF SEPARATED FLOW OVER A 2-DIMENSIONAL AIRFOIL AT DISTURBED INCOMING FLOW
Zhong Fangyuan, Dong Guoping, Luo Cishen
1998, 13(2): 113-117.
Abstract PDF(355KB) icon2528 icon463
Abstract:
The effects of disturbed incoming flow on the acoustic control of separated flow over a 2-dimensional low speed airfoil under high incidence have been investigated experimentally,including the benefits of acoustic excitation,the influence of parameters of exciting sound,and the variation of flow parameters in the boundary layer.The testing results indicate that,the flow velocity fluctuation of Large Scale Organized Structure Vorticity (LSOSV) v l and the benefit of turbulence intensity in the boundary layer u ' a/U ∞,the benefit of lift coeffecient,induced by exciting sound,will rapidly decrease along with the increase of turbulence intensity in the incoming flow.But the effective threshold value of sound pressure level will still enlarge gradually.It is also shown that,because of the rapid attenuation of oscillating velocity amplitude △ U ∞/U ∞ along the flow direction at natural flow field without exciting sound,the oscillating incoming flow has no effect on the benefits of acoustic excitation for the low speed 2-dimensional airfoil by and large.
ANALYSIS OF ENERGY LOSSES FROM STATIC PRESSURE DISTRIBUTIONS ON BLADE SURFACES IN CURVED CASCADES
Wu Jiquan, Wu Guochuan, Zhong Jingjun, Su Jiexian, Wang Zhongqi
1998, 13(2): 118-122,216.
Abstract PDF(411KB) icon1909 icon466
Abstract:
The exit flow field and the static pressure on the blade surface for three sets of different cascades were measured at four incidences of -5°,0°,5° and 10° respectively in a low-speed cascade wind tunnel.The three sets were a conventional straight cascade,a positive curved one and a negative curved one.The static pressure distributions on blade surfaces and the energy loss distribution in the exit flow fields have been obtained.The purpose of this paper is to find out the energy loss mechanism of the curved blade cascades from the static pressure distribution on the blade surface,and to study performance of compressor cascades at different incidences.
APPLICATION OF BALDWIN-LOMAX TURBULENCE MODEL IN ROTOR/STATOR INTERACTION
Wu Xianhong, Chen Maozhang
1998, 13(2): 123-127,216.
Abstract PDF(870KB) icon1884 icon504
Abstract:
The Lagrangian vortex method is applied to direct description of the unsteady flow due to rotor-stator interaction in turbomachinery by tracing the trajectory of vortices.The Baldwin-Lomax turbulence model adapted for wakes overcomes the short comes of other numerical methods,that they cannot continuously monitor the moving wake centerlines and give the computed viscosity in the outer region much higher than in the boundary regions.The agreement between the computational and experimental results is generally good,which shows that the present method is feasible.The result also show that the development of wakes and other vortices can be correctly predicted with the help of the presented turbulence model.So this method can be used as a new tool for analyzing unsteady flow and complicated phenomena in turbomachinery.
TWO-DIMENSIONAL NUMERICAL SIMULATION OF UNSTEADY-ROTOR/STATOR INTERACTION
Wu Xianhong, Chen Maozhang
1998, 13(2): 128-132,216.
Abstract PDF(769KB) icon1708 icon478
Abstract:
A disturbance vortex method for simulating unsteady rotor/stator interaction in turbomachinery is presented in this paper.The algorithm takes the result from time-averaged,steady solution as input,which can give an initial description of the unsteady disturbance flow field.To calculate the unsteady response to these disturbances,the Lagrangian vortex method is used to capture the convective process of the disturbance vortex.The deterministic vortex scheme is adopted to approximate the viscous diffusion process.The numerical simulation result of two-dimensional,viscous flow for a high loading transonic compressor with a pitch ratio of 1 74 shows that the method has an excellent ability for convergence and a fast convergent speed.The chopping,migrating process of rotor wake and other vortices,the influence of unsteadiness on incidence and decaying characteristic of the unsteady pressure first harmonic amplitude are included in this paper.
MECHANISM INVESTIGATION ON CASING TREATMENT FOR RESTRAINING ROTATING STALL BY MEANS OF WAVELET TRANSFORM
Zhang Yong, Wang Guanghua, Lu Yajun
1998, 13(2): 133-138,217.
Abstract PDF(347KB) icon1510 icon465
Abstract:
Wavelet transform,as a tool for signal analysis,is applied to analysis of compressor rotating stall signals.With the Morlet wavelet transform,the time-evolution of the unsteady signals during the stall inception and the local behavior in the casing treatment plenum are investigated.By comparison with structure characteristics of the coherent waves in the casing without treatment,it is shown that the casing treatment do has different influences on pressure impulse signals.A mechanism for restraining perturbations of stall inception via casing treatment is proposed.
NUMERICAL PREDICTION OF SECONDARY FLOW LOSS IN A TURBINE CASCADE BY USING TVD SCHEME TO SOLVE N-S EQUATIONS
Chang Jianzhong, Feng Zhenping, Li Guojun, Shen Zuda
1998, 13(2): 139-143,217.
Abstract PDF(803KB) icon2074 icon402
Abstract:
Harten's TVD scheme and Baldwin-Lomax turbulence model are applied to solving 3D N-S Equations for simulation of emergence and development of secondary flow and its loss in a rectilinear turbine cascade at a-8° incidence.The computation simulates successfully the vortex structure of the secondary flow and its loss distribution in the cascade passage.The predicted pitch averaged cascade distribution along blade height is consistent with the experimental data well.The mechanism of secondary flow loss emergence and development is revealed.It is found out that the incoming endwall boundary layer,the horse shoe vortex and its induced separation,and the shear motion of the horse shoe vortex with that of passage vortex are the major sources of the loss production,and the cascade boundary layer development and the passage vortex play an important role in the cascade loss development and redistribution.As a result,the numerical technique developed by the authors has a high accuracy and resolution,and can be adopted in the engineering application.
NUMERICAL SIMULATION OF THREE DIMENSIONAL SHOCK WAVE-BOUNDARY LAYER-SEPERATED FLOW INTERACTIONS
Han Zhenxue, Fang Ren, Liu Zhijian
1998, 13(2): 144-148,218.
Abstract PDF(351KB) icon1771 icon459
Abstract:
Three dimensional turbulent flows with strong shock wave-boundary layer-seperated flow interactions are numerically simulated.Time-dependent compressible Navier-Stokes equations in conjunction with Baldwin-Lomax turbulence model are discrete with finite volume method and LUSGS time marching scheme to get the steady flowfields.Inviscid flux and viscous flux on the control volume surfaces are calculated with Van Leer flux vector splitting scheme and central difference scheme separatelly.The numerical methods are valid for 3D transonic flow through a diffuser.The computational results are in a good agreement well with the experimental data of Mach number before the shock wave,separation and reattachment positions.
CALCULATION OF FLOWFIELDS WITH MULTI-UNSTRUCTURED GRIDS
Han Zhenxue, Fang Ren, Liu Zhijian
1998, 13(2): 149-152,218.
Abstract PDF(387KB) icon1781 icon472
Abstract:
Two dimensional transonic flows are simulated by solving Euler equations with finite volume method numerically.Multi-Unstructured grid technique is used to accelerate the three-stages time marching convergence.Multi-Unstructured grid generation technique and interpolation method are investigated.As an example,2D transonic flows around NACA0012 airfoil are calculated with the present method.
ANALYSIS OF CONTROL SCHEDULES FOR HIGH THRUST-WEIGHT RATIO TURBOFAN ENGINE
Zhu Zhili, Li Dong
1998, 13(2): 153-156,219.
Abstract PDF(669KB) icon1676 icon535
Abstract:
It is important to design a suitable control schedule for aircraft engine in order to exploit its full performance potentiality and to enhance its reliability.Comparison and analysis of uninstalled performance of engine with different control schedules are carried out in this paper.The result indicates that the control schedules for the modern high thrust-weight ratio turbofan are superior significantly to the traditional control schedules of engine in enhancement performance at high speed and improvement of the working conditions of the hot section components.
NUMERICAL FLOW SIMULATION OF INLET VALVE BOX OF TURBINE
Li Siqi, Zhang Di, Du Zhanbo, Sun Bi
1998, 13(2): 157-160,219.
Abstract PDF(315KB) icon1567 icon382
Abstract:
A computational fluid dyanmics code is used to simulate the flow in a test inlet valve box of turbine.The work sets two major goals:to acquire a comprehensive understanding of the complex three-dimensional flowfields in the valve box at representative operating conditions and to find out an effective tool to optimize performance at the given operating conditions.In order to improve the convergence and precision of the calculation,the numerical algorithm employs Body-fitted Coordinate (BDC) grids,the SIMPLEST method,the standard k-ε turbulence model,wall function method and the porosity method.In the results,the calculated flow pattern in the valve box and the loss coefficients of the valves appeared are in an improved agreement with the measured data.The tested values of the total pressure diverge from the numerical results,but their trends are about the same.
AN ASSESSMENT METHOD FOR BLADE VIBRATION RELIABILITY
Ou Yangde, Kong Ruilian, Song Zhaohong
1998, 13(2): 161-164,219.
Abstract PDF(688KB) icon1894 icon442
Abstract:
A method is presented to assess the vibration reliability for blade design.The method based on Campbell diagram and the concept of PFTA (Probability Fault Tree Analysis) is used to improve conventional assessment methods,and aims at developing an effective method for resonance identification and assessment of the characteristics of blade resonance system,which consists of multiple resonant interception on the Campbell diagram at or near the operating speed.Much information will be obtained from this PFTA analysis,and it is useful for designer to improve the vibration characteristics of a given blade in design and in elimination of failure blade yielded from vibration fatigue.
NONSYNCHRONOUS MOTION AND JUMP PHENOMENON OF ROTOR-FLUID FILM BEARING SYSTEM WITH SQUEEZE FILM DAMPER
Zhang Jiazhong, Xu Qingyu, Zheng Tiesheng
1998, 13(2): 165-168,220.
Abstract PDF(713KB) icon1748 icon490
Abstract:
The dynamical behaviors of a flexible rotor-fluid film bearing system with squeeze film damper are investigated.Owing to the nonlinearity of the film forces, there are many complex phenomena in the system,such as:jump,nonsynchronous motion etc.As the parameters are varied,the system can undergo a series of bifurcations.It is found that the secondary Hopf bifurcation,a series of period-doubling bifurcation and the saddle-node bifurcation result in quasi-periodic motion,subharmonic adoption motion and jump phenomenon respectively.The results of this study show that the introduction of squeeze film dampers in this system may lead to undesirable nonsynchronous vibrations.
AN ITERATIVE PRECISE INTEGRATION METHOD FOR CALCULATION OF TRANSIENT RESPONSE IN ROTOR-BEARING SYSTEM
Jiang Peilin, Yu Lie
1998, 13(2): 169-172,220.
Abstract PDF(302KB) icon1822 icon388
Abstract:
An iterative precise integration method is proposed to calculate the transient response of rotor-bearing systems.The state transfer matrices are calculated with the precise integration method and the precise solutions of homogeneous equations can be obtained.Therefore an implicit integration procedure is given in the light of the characteristics of oil film forces.The matrices and vectors are partitioned and the dimension of the nonlinear equations is reduced greatly.The integration method presented is unconditionally stable and can assure high precision and efficiency.
VIBRATION FEATURES FROM RUBBING BETWEEN ROTOR AND CASING FOR A DUAL-SHAFT AEROENGINE
Yan Litang, Wang Deyou
1998, 13(2): 173-176,220.
Abstract PDF(790KB) icon1978 icon500
Abstract:
The vibration features from rubbing between rotor and casing for single-shaft gas turbine engine are well known and have been studied by many researchers.The dual-shaft engine has two shafts with different frequences in the engine system.An improved model and calculation method are provided,based on the mathematical models derived by the former researcher on rubbing of rotor and stator.The vibration characteristics for some types of rubbing for the dual-shaft engine are analyzed and discussed.The theoretical results are consistent with data measured on a dual-shaft aircraft engine.
STRESS ANALYSIS OF TRAPEZOID TOOTH BELT WITH FEM
Wu Cong, Wang Yong, Ding Weiping, Wang Buying
1998, 13(2): 177-179,221.
Abstract PDF(583KB) icon1620 icon381
Abstract:
The geometric nonlinearity of synchronous trapezoid tooth belt is taken as the point of departure.A nonlinearity finite element solution of the synchronous belt is provided on the basis of elastic linear finite element method to solve two-dimensional stress distribution problem.The level stress distribution for a tooth of the synchronous belt is researched with help of this method.Finally,for an example,a maximum stress point and stress distributions of a synchronous belt tooth have been found out and compared with its elastic linear solution.
NUMERICAL PREDICTION OF COLD FLOW FIELD BEHIND EBMC FLAMEHOLDER
Yue Lianjie, Yang Maolin, Huang Yong, Xu Hang
1998, 13(2): 180-184,221.
Abstract PDF(751KB) icon1640 icon510
Abstract:
A numerical prediction of the cold flowfield behind a novel flameholder-Edge Blowing Mixture Curtain (EBMC) in two-Dimension duct was completed by using a modified k-ε model and SIMPLER method.The influence of the airflow parameters and the flameholder geometrical parameters on the recirculation zone was also studied. The prediction provides basis for designing the novel flameholder and studying its combustion performance.
EXPERIMENTAL INVESTIGATION ON EBMC FLAMEHOLDER
Yang Maolin, Quan Zhong, Bai Xingyan, Yue Lianjie, Zhang Pinjie
1998, 13(2): 185-188,221.
Abstract PDF(708KB) icon1725 icon482
Abstract:
A novel flameholder is presented,as named Edge Blowing Mixture Curtain (EBMC) flameholder.It has a streamline form head,small base width,with air and fuel mixture flowing from the slots at it's edges into the main flow.It has small cold pressure loss without reheat and variable blowing on reheat so as to enlarge recirculation zone and improve combustion performance.An experimental investigation of this flameholder was carried out,and its pressure loss、lean flame blowoff range and combustion efficiency were researched.It seems that the EBMC flameholder is superior to the conventional V-type one.
NUMERICAL MODELING OF TURBULENT FLOW AND HEAT TRANSFER IN A PIN-FINNED CONVERGENT PASSAGE OF GAS TURBINE GUIDING VANE
Liu Dong, Gu Weizao, Liu Wenyan, Deng Huayu
1998, 13(2): 189-194,222.
Abstract PDF(561KB) icon2275 icon433
Abstract:
A numerical model of cooling air flow and heat transfer in a pin-finned convergent passage of gas turbine guiding vane was set up,which employed a turbulent k-ε model,a 3D Body Fitted Coordinates (BFC),the SIMPLEST Algorithm and the whole field solving method of convection-conduction conjugate heat transfer problem,taking the interlinks among the flow field,pressure field,the temperature field,the property variation and the effects of compressibility and 3D heat conduction inside a guiding vane shell into consideration.The computation results are in a good agreement with experimental data.
RESEARCH ON EFFECT OF CHEMICAL-EQUILIBRIUM ON THERMODYNAMIC CYCLE PERFORMANCE OF GAS TURBINE ENGINES
Tu Qiuye, Wang Zhanxue, Wang Shu, Tang Diyi
1998, 13(2): 195-198,222.
Abstract PDF(288KB) icon1534 icon390
Abstract:
A quickly convergent algorithm to solve the chemical equilibrium equations is adopted and new subroutines are developed to serve as interfaces between the high temperature components routines and the chemical equilibrium routines.The effect of chemical equilibrium on each individual component is also given quantitatively and the mechanism is analyzed.Finally,an engine performance with considering the chemical equilibrium is compared with one without considering the chemical equilibrium.
NUMERICAL SIMULATION OF FLOW FIELD IN AN AIR PARTICLE SEPARATOR
Lin Guohua, Yuan Xiugan, Yang Yansheng
1998, 13(2): 199-202,223.
Abstract PDF(312KB) icon1521 icon448
Abstract:
A general differential equation in oblique curvilinear coordinates has been established according to the tensor analysis and has been used to simulate the 3-D flowfield in a particle separator.Computational grid are set up with the body-fitted coordinates and a k-ε turbulence model is adopted in computation.Special fluid phenomena in a helicoidal pipe have been simulated.The particle trajectory model has also been established and has been used to analyze the performance of the vortex tube.The results are in good agreement with the experiment.
NUMERICAL ANALYSIS OF COMPRESSOR CASCADE FLOW WITH NOVEL TURBULENCE MODELS
Li Ling, Lu Yajun
1998, 13(2): 203-205,223.
Abstract PDF(255KB) icon1746 icon368
Abstract:
An explicit N-S solver has been written at the option of one of three turbulence models:Standard K-ε model is an implicit K-ε model coupled with the explicit N-S solver in a novel way which takes account of multiple time scales by adding an extra term to the dissipation equation,and turbulence model based on RNG method which takes account of unbalance effect by adding an extra term to the dissipation equation.The code has been applied to numerical analysis of the flow in the compressor cascade.Three solutions obtained with the three correspondent turbulence models are compared with the experimental results by Flot,R and Papalion,K.It is shown that the results with later two turbulence models become closer to the experimental results.
A CALCULATION OF CROSS-SECTIONAL STIFFNESS OF COMPOSITE HELICOPTER BLADE
Xiang Jinwu, Zhang Xiaogu, Zhao Xiang
1998, 13(2): 206-208,224.
Abstract PDF(699KB) icon2245 icon464
Abstract:
An approach is presented for calculation of composite helicopter blade cross-sectional stiffnesses with finite element method on the basis of the two-dimensional linear model.The warping effect and deformation characteristics are incorporated in the formulation.As a result,a software was been developed,which consists of 3 nodes,4 nodes,6 nodes,8 nodes elements.The effectiveness of the program has been verified by means of comparison with NABSA's analytical results.
APPLICATION OF TWO-VARIABLE SELF-STUNING FUZZY CONTROL BASED ON FUZZY REASONING WITH FOUR INPUTS IN AEROENGINE CONTROL
Fang Zhongxiang, Li Huacong, Wu Qihua, Zhang Jiazhen, Chen Fuqun
1998, 13(2): 209-211,224.
Abstract PDF(243KB) icon1653 icon484
Abstract:
Self-stuning technicalization was introduced into the fuzzy control algorithm based on the fuzzy-reasoning with four inputs.A new two-variable self-stuning fuzzy control algorithm was synthesized based on the fuzzy-reasoning with four inputs.Then a two-variables self-stuning fuzzy controller with four inputs has been designed.The research focuses on the algorithms and the property of this controller,as well as its application in aeroengine control by computer simulation.The results show that this method is feasible for the aeroengine control system.
EXPERIMENTAL RESEARCH OF REVERSE FLOW IN AXIAL-FLOW COMPRESSOR
Li Jun, Zhu Junqiang, Liu Hong, Liu Zhiwei
1998, 13(2): 212-214,224.
Abstract PDF(299KB) icon1657 icon497
Abstract:
The experiments of reverse flow in a single-stage axial-flow compressor were completed.The parameters,such as velocities,static and total pressure,incidence and deviation,were measured at three sections:the inlet section of rotor,the section between rotor and stator,the outlet of stator.The pressures and temperatures of the flow are measured with a steady acquisition system.The experimental results show that,uniform flow parameters are obtained at the outlet section of stator,but the parameters in the inlet section of rotor vary obviously at the radial direction.The incidences of the reverse flow are very large,so there exists a great loss.Therefore,the temeprature rises as the gas flow through the compressor reversely.

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