1999 Vol. 14, No. 2

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DSMC PARALLEL NUMERICAL SIMULATION ON VACUUM PLUME
Cai Guobiao, Liu Shijian, Wang Huiyu, Zhuang Fenggan
1999, 14(2): 113-118,215.
Abstract PDF(684KB) icon1814 icon452
Abstract:
The DSMC (Direct Simulation Monto-Carlo) computer code of a small nozzle vacuum plume was reformed.The computation showed that parallel computing could greatly accelerate computation,shorten computing time and enlarge computing scale.The parallel computation results accorded well with the sequential computation results.An example of DSMC parallel computation was also completed successfully for a vacuum plume and the computation results agreed well with theoretical analysis.The sequential computation won't be able to cope with this task.
A PIV STUDY OF NEAR WAKE FLOW OF AIRFOIL PART Ⅰ-KINEMATIC CHARACTERISTICS
Wang Guanghua, Liu Baojie, Liu Tao, Gao Ge
1999, 14(2): 119-124,215.
Abstract PDF(419KB) icon2133 icon418
Abstract:
Detailed 2D velocity fields obtained from on-line PIV (Particle Image Velocimetry) measurements in a low speed wind tunnel are used to investigate flow structures in the turbulent near wake flow of a NACA0012 airfoil.The Reynolds number on chord length is 2.39×105,the angles of attack are 0° and 4°.The experimental results indicate that the turbulent near wake flow is dominated by the dynamic and kinematic characteristics of vortices at relatively high Reynolds number.According to the flow structures identified from instantaneous velocity fields,the vortex street is created at the airfoil tail region.Structures in the vortex developing region (within 0.5 chord length) are similar to those for the Karman vortex street and structures in the vortex break-up and dissipation region (between 0.5 and 1.0 chord length) change from organized to non-organized.The results also show that the boundary layer of the airfoil affects the structures in the near wake flow.The fields of mean velocity,turbulence intensity,strain rate and correlation coefficients of EMBED Equation are also obtained.
PIV STUDY OF AIRFOIL NEAR WAKE FLOW PARTⅡ DYNAMIC MECHANISM
Liu Baojie, Wang Guanghua, Gao Ge
1999, 14(2): 125-130,216.
Abstract PDF(1437KB) icon1805 icon356
Abstract:
Detailed 2D velocity and vorticity fields were measured to investigate the turbulent near wake flow of NACA0012 airfoil with on-line cross-correlation PIV in a low-speed wind tunnel.The Reynolds number on chord length is 2.39×105,the angles of attack are 0° and 4°.The experimental results indicate that ordered vortex streets exist in the turbulent near wake,the vortex streets created at the airfoil trailing edge region will fully develop and finally break up downstream,and the ordered wake flow turns into disordered.The near wake flow is dominated by the kinetic characteristics and dynamic mechanism of vortices.As the second part of the investigation,the paper mainly discusses the formation of the vortex streets,the dynamic mechanism of the near wake,and the fluid instability of the vortex and vortex streets.
FEM CALCULATION AND EXPERIMENTAL STUDY OF THE 3-D FLOW IN VANE DIFFUSER
Liu Xiaomin, Xi Guang, Wang Shangjin
1999, 14(2): 131-134,216.
Abstract PDF(620KB) icon1538 icon465
Abstract:
The viscous incompressible turbulent flow in a vane diffuser was analyzed numerically by using penalty finite element method,based on Galerkin variational finite-element method.During discreting the controlled equations in arbitrary curvilinear coordinates,the consistent formulation of penalty pressure matrix was chosen,and conjected with the streamline upwind Petrov-Galerkin weighed residual formulation to modify the weight function.In reference to the experience of the finite difference method,the streamline upwind term only along the flow direction was controlled by the upwinding parameters.This approach ensured the stability the solution of the pressure.Numerical results of the turbulent flow in the vane diffuser were satisfactorily consistent with the experimental measurements and indicated that the spurious pressure was eliminated while the false diffusion of other terms was simultaneously minimized.
A NUMERICAL SIMULATION OF 3D VISCID STEADY FLOW IN A TURBINE STAGE
Yuan Ning, Wang Songtao, Zhang Zhenjia, Wang Zhongqi, Feng Guotai
1999, 14(2): 135-138,216-217.
Abstract PDF(732KB) icon1585 icon370
Abstract:
A 3D numerical methodology is presented for simulating blade rows in a turbine stage by solving 3D time-dependent compressible Navier-Stockes equations.This numerical method is based on Godnov's finite volume scheme with third-order-accuracy and TVD property.Baldwin-Lomax algebraic turbulence model is employed to simulate largely separated flow.The principal assumptions are made as follows:the flow is steady between stator and rotor and these rows can communicate via inter-row mixing plane.These reformative "mixing planes" introduce circumferential averaging of flow properties but preserve general radial variations.The circumferential disequilibrium in the same row is assured by using non-reflecting extrapolated boundary condition.In view of wide working temperature range in turbine stage,varying specific heat is applied in this method.The calculation instability resulted from inter-row mixing treatment is improved remarkably by using Riemann solver and lax gene in the case of small inter-row gap.The application of this method is illustrated for an axial high-pressure turbine stage in an areoengine.The results show that this method not only is available but also reveals flow phenomenon in rows very well.
COUPLING OPTIMIZATION CALCULATION FOR AEROENGINE PERFORMANCE
Wang Xun, Zhang Shizheng, Cai Ruixian, Du Heling, Guo Xin
1999, 14(2): 139-142,217.
Abstract PDF(660KB) icon1844 icon399
Abstract:
Coupling-Optimization Algorithm is comprised of coupling methods used in SPEY aeroengines and optimization method.This new method can be used to simulate the engine performance accurately on the basis of very limited engine test results even if its component characteristics are unknown.In addition,the component characteristics can also be inferred in the same time.This method has been used to simulate the performance of a turbofan engine and to infer its unknown component characteristics.The comparison of the results with the engine test data confirms the feasibility of the proposed method.
AN EXTENDABLE OBJECT MODEL FOR GAS TURBINE SIMULATION
Xie Zhiwu, Su Ming, Weng Shilie
1999, 14(2): 143-147,217-218.
Abstract PDF(754KB) icon2076 icon483
Abstract:
A generalized gas turbine simulation software must be not only capable of extending to new engine components and configuration,but also able to shift among different simulation algorithms.For this purpose the object-oriented analysis and design method is applied and the Unified Modeling Language (UML) is used.Different computational tasks of simulation are categorized and summarized into a 3-layer generalization:component calculation,gas path calculation,and system state calculation.Based on this generalization,a class framework is proposed and a Node-Connector-Component model is presented and analyzed.New components,gas path algorithms,and numerical integration methods can be extended from the appropriate base classes in the framework. New engine configuration can be realized by connecting nodes in different components.A 3-shaft gas turbine engine's dynamic performance is simulated using an innovative gas path calculation method,the plenum algorithm.The extendability of the model is fully verified.
INVESTIGATION OF HEAT TRANSFER IN LABYRINTH SEALS
Zhang Li, Liu Songling, You Shaokun, Xu Duchun
1999, 14(2): 148-152,218.
Abstract PDF(664KB) icon1593 icon358
Abstract:
Heat transfer coefficients around labyrinth are the necessary boundary conditions and important parameters for the thermal analysis of construction in aircraft engines.Heat transfer experiments for straight-through conventional labyrinth,straight-through slant labyrinth and stepped conventional labyrinth are conducted under the conditions of different Reynolds numbers and gap widths.Effects of geometric and flow parameters on the heat transfer are considered physically.For the convenience of practical application,the relations are derived from the experimental data.
LOCAL HEAT TRANSFER AND FLOW CHARACTERISTICS OF A ROTATING CAVITY WITH AN AXIAL FRINGE INLET AND A RADIAL OUTLET
Ding Shuiting, Tao Zhi, Xu Guoqiang, Qiu Xuguang
1999, 14(2): 153-156,218.
Abstract PDF(290KB) icon1698 icon383
Abstract:
A turbine cooling configuration of an aero-engine was simplified into a rotating cavity with an axial fringe inlet and a radial outlet.The influences of rotating Reynolds number,cooling air Reynolds number and Grashoff number on the local heat transfer and flow characteristics were investigated experimentally.The results indicated that the local heat transfer coefficient on the edge of main disk rapidly increases with the increase of cooling air Reynolds number and rotating Reynolds number.The local heat transfer coefficient becomes negative near the center of the disk.The flow friction coefficient increases with the increase of the cooling air Reynolds number and decreases with the rotating Reynolds number.
AN EXPERIMENTAL STUDY ON OVERALL COOLING EFFECTIVENESS OF INCLINED MULTIHOLE PLATES
Li Bin, Hu Zhengyi, Lin Yuzheng, Liu Gaoen
1999, 14(2): 157-160,218-219.
Abstract PDF(340KB) icon1710 icon507
Abstract:
The overall cooling effectiveness of the inclined multihole plates was investigated through approximate simulation experiments.The plates had five different geometry configurations.The experimental results indicated that the convective heat transfer coefficient in the cooling hole,the adiabatic film effectiveness and geometrical configuration were the critical factors for the overall cooling effectiveness.The investigation plays an important role in designing the inclined multihole wall and selecting the geometry of these cooling configuration.
EXPERIMENTAL STUDY ON FILM COOLING ON A SUCTION SURFACE OF A PLANE TURBINE CASCADE
Chen Fu, Song Yangping, Wang Zhongqi
1999, 14(2): 161-165,219.
Abstract PDF(837KB) icon1822 icon357
Abstract:
The flow field structure of a film cooled turbine for a typical design with four rows of cooling holes on the suction surface has been investigated in a plane cascade rig by the aid of flow visualization techniques and pneumatic probe measurement.The experimental results showed that a little vortex in opposite direction of rotation emerged as the passage vortex existed at the root of suction surface.The vortex was induced mainly by mixing between mainstream and injecting air,and resulted from formation of kidney-shaped vortex.The injected air was essentially absent in a triangular region extending from near the region of peak curvature on the blade to its trailing edge,and the separation line of the passage vortex was skewed toward the end wall.A very complex three-dimensional flow occurred in the downstream of the jet exit,and remained near the blade surface at the exit of the cascade.The kidney-shaped vortex was kept near the blade surface,and mixed with the wake at the exit of the cascade.
HOPF BIFURCATION OF A ROTOR-SLIDING BEARING SYSTEM
Yuan Xiaoyang, Zhu Jun
1999, 14(2): 166-170,219-220.
Abstract PDF(380KB) icon1905 icon456
Abstract:
A new numeric-analytical method for Hopf bifurcation of a rotor-bearing system is presented according to the Hopf bifurcation theory and Floquet stability theory.The method comprises a modified shooting method for calculating periodic solutions,a calculation method for determining the stability of the solutions,and a prediction correction procedure for tracing the solutions,etc.The software package realized with these techniques was used for efficient and accurate study of Hopf bifurcation behaviors of rotor-sliding bearing systems.The results show that there exists an unstable subcritical limit cycle for small E s ,the journal center eccentricity ratio at a critical instability.A stable supercritical limit cycle exists for large E s .When supercritical bifurcation occurs,limit cycle appears as soon as the rotor speed exceeds its threshold value,and the limit cycle does not become unstable until the rotor speed surpasses the threshold speed a lot.When subcritical bifurcation occurs,the behavior of rotor is more complicated.In addition to existence of an unstable limit cycle below the threshold speed,there are large-amplitude stable limit cycles both above and below the threshold speed.That explains why jump phenomena and hysteresis in the amplitude may occur in a rotor-sliding bearing system.
VIBRATION CONTROL OF ROTOR ELECTRO-RHEOLOGICAL SYSTEM BASED ON FUZZY LOGICAL SYSTEM
Qu Wenzhong, Yao Guozhi, Qiu Yang
1999, 14(2): 171-174,220.
Abstract PDF(1166KB) icon1827 icon394
Abstract:
Electro-rheological(ER) fluids have extensive application in the field of vibration control as a kind of intelligent materials.It is very difficult to develop a conventional control system due to the nonlinearity of the ER effect in regard to electric field strength,temperature or shear rate.An adaptive fuzzy control system is composed of a structural identification system and a controller system,and introduced for the ER damper-rotor vibration system due to the function approximator property of fuzzy logical system.A numerical study indicates the validity of the adaptive algorithm and the effective suppresion of the rotor vibration.
A ROTATIONAL SYMMETRY FINITE ELEMENT MODEL OF GAS TURBINE ROTOR IN CHARACTERISTICS ANALYSIS
Zhou Chuanyue, Wen Xueyou, Liu Xueyi, Zou Jingxiang
1999, 14(2): 175-178,220.
Abstract PDF(567KB) icon1805 icon469
Abstract:
A rotational symmetry finite element model is provided to calculate gas turbine shaft critical speeds and unbalance response analysis.A Fourier series representation allows the three-dimensional shaft geometry to be modeled in a basic section by using three-dimensional element.Unlike a beam element model,a solid element representation allows the actual rotor geometry to be modeled.A matrix reduction technique is used to reduce the degrees of freedom.An engineering example of marine gas turbine rotor is applied to the verification of the provided model.
FINITE ELEMENT ANALYSIS AND EXPERIMENTAL MEASUREMENT OF STIFFNESS OF HOOP
Yin Zeyong, Chen Yanong
1999, 14(2): 179-182,221.
Abstract PDF(614KB) icon2177 icon485
Abstract:
It is important to determine the stiffness coefficients of the hoops precisely for the vibration analysis of a pipeline system.For this purpose the finite element models for calculating the stiffness coefficients of the hoops are established in accordance with the structural features of the various hoops used in aeroengine pipeline systems.The stiffness coefficients of a grounded hoop for single pipe and a hung hoop for double pipes are obtained by the finite element analysis.In addition,the stiffness coefficients of a typical hung hoop for double pipes are measured by using the established experimental method.The comparison between the calculational and experimental results of the hoop shows that the provided method is feasible in the engineering practice of vibration analysis for a pipe line system.
AN ANALYSIS OF A GAS LUBRICATED COMPLIANT MULTILEAF JOURNAL BEARING
Chen Yuanxian, Yang Yansheng
1999, 14(2): 183-186,221.
Abstract PDF(1501KB) icon1524 icon419
Abstract:
A performance analysis model of the gas lubricated compliant multileaf journal bearing of the high-speed rotor for air cycle machine of aircraft environmental control system has been established.In the analysis,the differential method is used to solve the compressible Reynolds equation,which governs the airflow in the journal bearing.The solution is coupled with the load deflection equations of the leaves to obtain such information as minimum film thickness, the stiffness coefficients,and the equivalent damping coefficients.The graphical solutions are provided for a range of relevant geometric and operational parameters.The journal bearing has good stability in all range of eccentricity ratios and all possible operating speeds.
EXPERIMENTAL STUDY OF A GAS LUBRICATED COMPLIANT MULTILEAF JOURNAL BEARING
Chen Yuanxian, Qian Chuanqu
1999, 14(2): 187-190,221-222.
Abstract PDF(608KB) icon1587 icon427
Abstract:
The gas lubricated compliant multileaf journal bearing of the high-speed rotor for air cycle machine of aircraft environmental control system was investigated experimentally.In the earlier work,an analysis model was developed to predict the performance of the air lubricated compliant multileaf journal bearing.In the experiments,the load deflection tests revealed the elastohydrodynamics of the compliant leaves;the starting torque tests found out the frictional influence between leaves and journal;the air cycle machine operational tests demonstrate the dynamic characteristics of the journal bearing.All of the experimental results show that the journal bearing can run steadily in wide operating range,and it has excellent static and dynamic performance.It is insensitive to environmental conditions.
MULTIVARIABLE CONTROL FOR AEROENGINE WITH 3-LAYER NEURAL NETWORKS
Huang Jinquan, Chai Hongwu, Sun Jianguo
1999, 14(2): 191-194,222.
Abstract PDF(262KB) icon1609 icon413
Abstract:
A multivariable neural network adaptive control is provided for a turbofan engine.The nonlinear system is compensated dynamically by a 3-layer neural network.An on-line weight-tuning algorithm with simplified Hebbian rule and e-modification is worked out to guarantee tracking performance as well as bounded weights without off-line training.The precise model of the engine is not necessary for design of control system.The multivariable control system has satisfactory performance for the full flight envelope with good adaptation and robustness. Simulation results show satisfactory dynamic and static performance within the whole flight envelope and good effectiveness of reducing interaction in the multivariable system with significant coupling.
DESIGN OF AEROENGINE LQG/LTR CONTROLLER ACCORDING TO PERFORMANCE TARGET
Tao Tao, Yan Wenbo
1999, 14(2): 195-198,222.
Abstract PDF(274KB) icon2196 icon355
Abstract:
When LQG/LTR methodology is applied to control system design,it is not easy to choose proper covariance matrices for Kalman filter design for good dynamic performance and robustness of the control system.The methodology is based on the idea that if the control system is decoupled,the target close loop transfer functions of each channel can be presented according to the demands of dynamic performance.After the recovery procedure is finished,the system performance must approximate the target.With the methodology provided for designing the Kalman filter,the Kalman filter gain matrix can be calculated directly in accordance with the performance targets and state space matrices of the plant so that it is unnecessary to solve the Riccati equation.The simulations show that dynamic performance of the control system designed by using this methodology meets the design target,and its robustness is good.
A NEW VARIABLE STRUCTURE ADAPTIVE CONTROL SCHEME AND ITS APPLICATIONS
Guo Yingqing, Xu Demin, Fan Siqi
1999, 14(2): 199-201,222-223.
Abstract PDF(663KB) icon1582 icon431
Abstract:
A new variable structure adaptive control scheme is proposed.The scheme consists of conventional model reference adaptive control and sliding mode control.The adaptive control based on plant's normalized model can match reference model exactly at the design point.The sliding mode control copes with bounded parameter variations and unmodeled dynamics.Signal synthesis is used as adaptive law instead of the conventional integral law.Through introducing linear zone to sliding mode,the chattering phenomenon is eliminated to a great extent.In comparison with conventional adaptive control,the scheme needs only the plant's input-output mesurements,and has superiority in fine convergence,strong robustness to parameter variation and unmodeled dynamics.The simulation results indicate that this scheme is applicable to aero-engine control.
DESIGN OF AERO-ENGINE CONTROLLER WITH QUADRATIC STABILITY AND DISTURBANCE-RESTRAINING PERFORMANCE
Tao Tao, Yan Wenbo
1999, 14(2): 202-204,223.
Abstract PDF(231KB) icon1551 icon359
Abstract:
A methodology is presented to design aeroengine output dynamic feedback controller.When the state and output matrices of a control system are perturbed,the controller designed in this way can lead the system to be quadratic stable.When disturbances are equal to zero,the system will be of quadratic disturbance-restraining performance when the perturbation of the matrices does not exist.The problem is simplified into a standard output dynamic feedback control problem on the basis of two theorems about quadratic stability and disturbance-restraining performance.From the two theorems,an augmented plant is derived.With the augmented plant,the controller is designed by using control theory.For an example,the flight envelope of the engine is divided into 12 subregions,and in each subregion the simulation under different flying conditions is given.It is shown that the dynamic performance of the control system meets the design target and the robustness of stability is good.
AN EXPERIMENTAL INVESTIGATION OF FILM COOLING EFFECTIVENESS ON LEADING EDGE OF TURBINE BLADE
Zhu Huiren, Xu Duchun, Guo Tao, Liu Songlin
1999, 14(2): 205-208,223-224.
Abstract PDF(701KB) icon1824 icon351
Abstract:
Film cooling effectiveness of hole-rows on leading edge of turbine blade has been studied experimentally.The model is a blunt body with a half-cylinder leading edge and two flat side-walls.Six rows of round holes were ungradationally located at and from stagnation on the half-cylinder leading edge.The holes in each row were spaced three hole-diameters apart at angles to the surface spanwise and streamwise respectively.The length of hole is of four hole-diameters.Spanwise and streamwise distributions of film cooling effectiveness in the leading edge and on the flat side-wall were measured in the range of mainstream Reynolds number (based on leading edge diameter) from 42000 to 127000 and blowing ratio (average secondary to mainstream mass flux ratio) from 0.8 to 2.0.The results indicate that the film cooling effectiveness decreases with increasing blowing ratio but does not depend too much on the mainstream Reynolds number.The secondary flow locus is depedent on blowing ratio but also does not depend on mainstream Reynolds number too much.
HIGH-ORDER INTERPOLATION SCHEME OF CVFEM
Wang Xue, Gu Chuangang
1999, 14(2): 209-211,224.
Abstract PDF(257KB) icon1828 icon368
Abstract:
Even though all upwind schemes of Control-Volume Finite-Element Method (CVFEM) enhance the accuracy for simulation of advection-dominated fluid flows,but lead to severe false diffusion for flows oblique or skew to the axis direction.A high-order polynomial interpolation scheme is proposed,based on the locally skewed upwind scheme and an upwind neighbor element of the interpolated element.The numerical tests of lid-driven cavity flow in three different geometric fields for Re =1000,and with 41×41 uniform grids,proved that the proposed high-order scheme can almost achieve the bench-mark solutions that previous researchers obtained with much more refined grids.
AEROELASTIC OPTIMIZATION OF A HELICOPTER ROTOR WITH SINGLE-CELL COMPOSITE BLADES FOR VIBRATION REDUCTION
Xiang Jinwu, Zhang Xiaogu
1999, 14(2): 212-214,224.
Abstract PDF(642KB) icon2019 icon440
Abstract:
An unsteady aerodynamic environment and highly flexible rotating blades lead to harmonic loadings on the rotor so as to cause high vibration in the helicopter.An optimization is carried out for a four-bladed,soft in-plane hingeless rotor consisting of a single-cell composite box-beam spar for helicopter vibration reduction.The design variables are the ply angles of the box-beam walls;the objective function is of the vibration hub loads.Constraints are imposed on blade rotating frequencies and aeroelastic stability.As compared to the initial design,the optimum solution results in a 20-70% reduction of the 4/rev hub loads.

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