1997 Vol. 12, No. 2

  Previous Issue | Next Issue 
Display Method:
SHAPE OPTIMIZATION FOR CONTACT PROBLEMS WITH BOUNDARY ELEMENT METHOD
Shen Xiuli, Wen Weidong, Gao Deping
1997, 12(2): 113-116,215.
Abstract PDF(295KB) icon1553 icon439
Abstract:
An analytical method of shape optimization is put forward for two-dimensional elastic contact problems with boundary element method.Choice of the design variables and a method of shape description,as well as determination of target function and restrain conditions in two-dimensional elastic contact problems are considered.The numerical examples are carried out on the sensitivity and shape optimaization.Furthermore,the shape optimization analysis of the the fir-tree tenon/mortise in an aeroengine is carried out.
AN EXACT SOLUTION FOR FREE VIBRATION OF TOROIDAL THIN SHELL
Li Lin
1997, 12(2): 117-121,215.
Abstract PDF(893KB) icon1372 icon498
Abstract:
A new exact solution is developed which enables to determine the free vibration characteristics of toroidal thin shell with homogeneous boundary conditions.But the solution requires numerical evaluation of an eight order complex determinant to find its eigenvalues.The results are exact in the same sense as the numerical solution of the transcendental frequency equation for a beam yields an exact solution of its vibration frequency.The eigenvalues of cylindrical shell with the boundary conditions corresponding to simple-simple support(SS),clamped-free support(CF)and clamped-simple support(CS)have been calculated and their dependences on the slenderness of the shell have been found out yet.The results are compared with those obtained by other investigators using different methods and experiments.
NUMERICAL ANALYSIS OF BLADE TRANSIENT RESPONSES TO BIRD IMPACT UNDER CENTRIFUGAL LOADINGS
Chen Wei, Song Yingdong, Yin Jing, Gao Deping
1997, 12(2): 122-124,215-216.
Abstract PDF(178KB) icon1731 icon627
Abstract:
The integrative rigidity and the local rigidity of blades are enhanced by their centrifugal loading,so that when a flying bird impacts on the aeroengine blades under their rotating states,the responses of the blades are different from those under the static states.The nonlinear transient responses of the blades to the bird impact under the different centrifugal loadings are analyzed by using the finite element method.The results show that the centrifugal loadings have a significant effect on the local and integrative deformations of the blades as well as the character of the responses.
DAMAGE MECHANICS DESCRIPTION OF DUCTILE CRACK GROWTH
Zhou Baizhuo, Schomburg Uwe, Nie Jingxu, Yang Shijie, Zhang Xiaoxia
1997, 12(2): 125-128,216.
Abstract PDF(298KB) icon1751 icon420
Abstract:
Damage models of material failure by microvoid nucleation and growth to coalescence are described.Approximate constitutive relations are used,to model both the nucleation and growth of the microvoids.The Crack growth has been numerically analyzed,based on damage medel of finite element method and compared with the experiments of compact tension specimen successfully.
RESEARCH ON VIBRATION CHARACTERISTICS OF A CRACKED BLADE
Xu Kejun, Liu Qizhou
1997, 12(2): 129-132,216.
Abstract PDF(285KB) icon1784 icon400
Abstract:
A method for calculating vibration characteristics of a cracked blade has been developed by using a transfer matrix analysis.The effects of the crack on stiffness at the crack location is equivalent to the flexibility of an elastic hinge.A cantilever beam with rectangular cross-section with a transverse crack extending uniformly along its width is taken as an example.The influence of parameters,such as depth,position of crack,on natural frequencies of blade oscillation is discussed.It is found that the natural frequencies of the rotating cracked blade increase as the crack moves from the root to the tip of the blade and decrease as the exent of the crack increases oscillation and the crack in the beam has substantial effects on the natural frequencies as rotational speed increases.The nonlinear vibration characteristics(frequency spectrum)of the cracked blade are analyzed theoretically by using square function to simulate crack open and closure.It is shown that nonlinear vibration characteristics become obvious as the extent of the crack increases.The experimental research on vibration characteristics of cracked blade has been carried out with rectangular cross-section cantilever beam as a specimen.The experimental results verify the analysis of the theoretical method.Finally,a suggestion is offered on an on-line diagnostic system of blade crack.
CALCULATION OF THERMAL RATE IN ANALYZING THERMAL STRESSES
Zhang Jiazhong, Xia Songbo, Zhang Ying
1997, 12(2): 133-135,217.
Abstract PDF(613KB) icon1771 icon477
Abstract:
The real-time monitoring of rotor life comsumption makes urgent demands on exact real-time calculation of the thermal rate in analyzing thermal stresses.In order to eliminate the data fluctuation in temperature sampling and meet the demands of real-time calculation,the zone linear regression is adapted to accomplish the data filtering of thermal rate curves instead nonlinear regression,and the time subdomains are so divided,that the later one covers as much as possible the data of former one except first sampling data.As a result,a recurrence formula of the regression has been worked out.The exactness of the formula has been verified by numerical simulation.The convergence and filtering efficiency of the method are very well.
RESEARCH ON BENDING FATIGUE LIFE PREDICTION METHOD OF AIRCRAFT GEARS
Xu Yingqiang, He Dawei, Qian Guanliang
1997, 12(2): 136-138,217.
Abstract PDF(673KB) icon1280 icon528
Abstract:
The limitations of the conventional bending fatigue life prediction method for aircraft gears are investigated and the applicability of local stress-strain approach to the gear bending fatigue life analysis is researched.Some valuable conclusions have been drawn from comparison between the computational results and experimental data.
EFFECTIVENESS OF AN ADVANCED HYBRID SQUEEZE FILM DAMPER ON NONSYNCHRONOUS RESPONSE SUPPRESSION
Zhu Changsheng
1997, 12(2): 139-142,217.
Abstract PDF(781KB) icon1617 icon381
Abstract:
The effectiveness of an advanced Hybrid Squeeze Film Damper(HSFD)without the retainer springs on suppressing the nonsynchronous response of the rotor system was studied theoretically.A flexible rotor supported on the orifice-compensated HSFD is taken as an example.It is shown that the HSFD is able not only to improve obviously the highly nonlinear behaviours of the conventional squeeze film dampers,but also to enhance its capability of nonsynchronous response suppression greatly.
A RING-LIKE METAL RUBBER DAMPER
Wang Xin, Zhu Zigen
1997, 12(2): 143-145,217-218.
Abstract PDF(897KB) icon1715 icon453
Abstract:
A new kind of rotor damper,Ring-like Metal Rubber Damper(RMRD),has been invented.Its application to a rotor rig shows that RMRD has excellent damping property and linear characteristics.RMRD has better damping effects and can withstand larger unbalanced load than Squeezed Film Damper.As a kind of dry-friction damper,RMRD can work under very high or low temperature for a long period of time.It is especially suitable for High Pressure Liquid Hydrogen(Oxygen) Pumps of rocket engines working under very low temperature.
AN INVESTIGATION ON IGNITION PERFORMANCE OF A CATALYTIC IGNITER AT HIGH ALTITUDE
Dong Kang, He Xiaoming, Han Qixiang, Tan Haoyuan
1997, 12(2): 146-148,218.
Abstract PDF(305KB) icon1641 icon498
Abstract:
An experimental investigation on performance of a catalytic igniter made of platinum/rhodium catalyst has been conducted in a turbofan engine afterburner.Its ignition delay was measured under the conditions:the static pressure of 0 04-0 115 MPa;the inlet total temperature of 673-773 K;the velocity at the lip of igniter cone λ =0 20-0 36.The investigation simulates the operation of the engine's afterburner when aircraft flies at an altitude of 18000 m and the Mach numer of 1 0.The experiments on performance of the igniter for igniting of 1100 runs at normal pressure were also conducted to verify the longevity of the catalytic igniter.
ANN-BASED OBSERVER FAILURE DETECTION
Zhang Xuefeng, Wang Yonggen
1997, 12(2): 149-151,218.
Abstract PDF(237KB) icon1701 icon497
Abstract:
An Artificial Neural Network(ANN)-based observer failure detection method is presented,which uses ANN's self-learning ability instead of analytical computation of the obsever design to get the redundancy relationship of the system.In order to deal with the failure detection of model uncertainty system,the failure detection of the control system sensor of a given aeroengine has been simulated with the presented method.The simulation shows that this method not only has the advantage of the observer failure detection method,but also has no need for the precise model of system.It is useful to the failure detection of the model uncertainty system.
ANN-BASED MMAF FAILURE DETECTION
Wang Yonggen, Zhang Xuefeng
1997, 12(2): 152-154,218-219.
Abstract PDF(283KB) icon1809 icon465
Abstract:
Artificial neural network(ANN)and Multiple Model Adaptive Filter(MMAF)are combined in a new failure detection method-ANN-based MMAF,which uses ANN's self-learning ability instead of analytical computation of the filter design.Numerical simulations of an areoengine have been performed to detect the sensor failure of the control system.The results show that this method not only can detect the failure of the system with an uncertain model,but also has self-learning ability for the unknown failure pattern.
MULTIPLE-SECTOR PARALLEL COMPRESSOR MODEL FOR FLOW FIELD CALCULATION UNDER DISTORTION
Song Wenyan, Li Ming, Fan Feida
1997, 12(2): 155-158,219.
Abstract PDF(272KB) icon1837 icon575
Abstract:
This paper describes in some detail the method for computing an axial-flow compressor flow field under distortion.Based on the multiple-sector parallel compressor model and stream line curvature method,the stage distributions of the parametres of distorted flow field,such as total pressure,total temperature,static pressure,static temperature,air velocity and swirl angle,are obtained by solving the radial-equilibrium equation,then the details of compressor flow field under the given inlet distortion can be reached.As an example the flow field computation for a single stage compressor has been completed under the inlet circumferential distortion.The results demonstrate the practical value of the method.
AN EXPERIMENTAL OBSERVATION ON STALL OSCILLATION AT LOW FLOWRATE IN A CENTRIFUGAL IMPELLER Dai Ji and Chen Jingyi
Dai Ji, Chen Jingyi
1997, 12(2): 159-162,219.
Abstract PDF(273KB) icon1607 icon361
Abstract:
An experiment was conducted to investigate the self-excited flow oscillation in a centrifugal fan impeller.The unsteady dynamic pressures were measured around the periphery of the impeller outlet with 8 high-response transducers.The experimental observation shows the existence of a lower frequency,nonrotating oscillation in the low flowrate conditions.The measurements also indicate that the oscillation is unstable at a short duration and at a local position,and the peripheral distribution of oscillation strength is non-uniform.The analysis shows that there may be some relationship between the self excited flow oscillation and rotating stall,especially during inception behavior of rotating stall.
EFFECTS OF SOLIDITY ON CHARACTERISTICS OF COMPRESSOR CASCADE WITH CURVED-BLADE
Zhong Jingjun, Wang Wei, Su Jiexian, Wang Zhongqi
1997, 12(2): 163-166,219-220.
Abstract PDF(758KB) icon1971 icon432
Abstract:
The relationship between solidity and the characteristics of compressor cascades with curved blades is investigated. The experimental results show that with the increase of cascade solidity,the cascade loss increases at most incidences.The minimum loss incidence of the straight and positive curved blade cascade takes place at positive incidences,while the negative curved blade cascade appears at negative incidence.In order to reduce the loss, the solidity for the positive curved blade should be less than that of the straight blade.In the case of the same solidity,the secondary loss can be reduced and good incidence characteristics can be obtained with the negative curved blade,compared with the straight blade cascades.
THREE-DIMENSIONAL FLOW FIELD INSIDE A COMPRESSOR ROTOR TIP REGION
Ma Hongwei, Jiang Haokang
1997, 12(2): 167-171,220.
Abstract PDF(967KB) icon1585 icon509
Abstract:
An experimental study of the three-dimensional flow field inside the tip region of a low-speed,large-scale axial-flow compressor rotor has been completed.With the help of a rotating four-coordinate probe traverse mechanism,the measurements were conducted with a five-hole conical probe in both design condition and near stall condition.The results indicate that the tip leakage vortex plays a decisive role in the tip region flow in the design condition,leading to substantial flow loss and blockage in the passage.In near stall condition,flow separation occurs on the blade suction surface while radial migration of the boundary layer on the suction surface is strong,which makes more low-energy fluid accumulate at the corner between the casing annual wall and the suction surface.A corner vortex is induced by the tip leakage flow, and the low-energy fluid migrates to the pressure side due to the effect of the leakage vortex.Strong flow mixing among the corner vortex,the leakage vortex,the boundary layer on the casing wall and the main flow occurs at median part of the passage,which leads to substantial deficiencies of relative total pressure and relative velocity.
SWEEP FINITE ELEMENT SOLVER FOR 3-D VISCOUS COMPRESSIBLE FLOW IN RECTANGULAR NOZZLE
Zhao Guiping, Shen Huili
1997, 12(2): 172-174,220.
Abstract PDF(260KB) icon1897 icon457
Abstract:
A numerical anlysis method of three-dimensional compressible viscous flow has been developed for a rectangular exhaust nozzle in which the shape of the circular-to-rectangular duct changes abruptly and its flowfield is very complex.Therefore,the sweep finite element method proposed by the second author in 1983 is employed since the governing equations are directly used to establish the element equation.In this paper,a hexahedral element of 27 nodes is adopted for spacial discretization,and applied to a C-D nozzle flowfield and several transition duct and nozzle flow fields.The results are in good agreement with the experimental data,and indicate the effectiveness and accuracy of the method.
EXPERIMENTAL STUDY ON PIN FIN ARRAY FLOW FIELD
Su Hongzhen, Liu Songling, Chen Fuqun, Xu Duchun
1997, 12(2): 175-179,220-221.
Abstract PDF(382KB) icon1644 icon445
Abstract:
An experimental study was performed to investigate the staggered pin fin array flow field in the specially constructed small wind tunnel.The experimental result gives the detailed distributions of the flow field parameters.The analysis reveals that the velocity distribution on the odd measuring plane is different from that on the even measuring plane.Channel vortex can be observed on the odd measuring plane,and horseshoe vortex is caughted on the even measuring plane.
A MAW UPWIND SCHEME FOR 3-D CONVECTION TERM
Wang Xu, Yan Chuanjun
1997, 12(2): 180-182,221.
Abstract PDF(262KB) icon1739 icon473
Abstract:
A new mass-weighted(MAW)upwind interpolation scheme,the control-volume finite-element method,is adopted for three dimensional convection term based on tetrahedral element,and its subcontrol volumes and surfaces on each element are symmetrical.This feature not only guarantees the positive coefficients in the discretization equation,but also is easy to be fulfilled in the computer program.The scheme has been applied successfully to some three dimensional convection-diffusion problems and some three dimensional viscous,incompressible fluid flow problems.
A SURVEY ON APPLICATION OF TBC FOR AEROENGINE HOT SECTIONS
Yang Xiaoguang, Gen Rui, Xiong Changbin
1997, 12(2): 183-188,221.
Abstract PDF(803KB) icon1804 icon519
Abstract:
This paper gives a detailed survey about application of Thermal Barrier Coating(TBC)technology to aeroengines.First of all,thermal barrier coating system and coating technology are examined to identify the state of art of the coating technique,then characteristics of Plasma Spray Coating are compared with those of Electric Beam-Physic Vapor Deposition Coating.Meanwhile,the coating failure mechanism,coating interface strength and life prediction method are also surveyed.According to the thermal barrier coating researches at home and abroad,the authors offer some suggestions to promote the Chinese thermal barrier coating research and application.
MECHANICAL BEHAVIORS OF TBC IN AEROENGINE HOT SECTION
Xiong Changbing, Yang Xiaoguang
1997, 12(2): 189-193,221-222.
Abstract PDF(949KB) icon1796 icon492
Abstract:
A systematical study on the mechanical behaviors of Thermal Barrier Coating(TBC),the thermal compatibility of TBC with basic material of turbine blade,and the interface residual stress caused by various TBC materials.The change of the blade working temperature leads to crack,separation and scars between TBC and substrate,that results in TBC failure,so the blade cannot work normally.It is discovered from the experiments that addition of trace elements Zr-Y-Nb-AL in the thermal barrier coating as the interface coherent layer enhances the combination strength between TBC and substrate significantly,increases the thermal burst resistance,improves the surface smoothness.The operating temperature of the blades with TBC is enhanced up to 200℃-300℃ higher than that of the blades without TBC.The thermal barrier coating not only can be applied to turbine blade,but also has a significant effect on the surface protection of the combustor and jet exhaust nozzle of aeroengine.
A MODEL EQUATION FOR SIMULATING FLOW-FIELD IN MULTIROW AXIAL TURBOMACHINES
Ji Lucheng, Guo Enmin, Meng Qinguo, Zhou Sheng
1997, 12(2): 194-196,222.
Abstract PDF(263KB) icon1271 icon455
Abstract:
In order to simulate the flow-field in multirow turbomachines,a model equation,named Time-averaged Effect Navier-Stokes equation,(hereafter referred to as TENS equation)has been firstly deduced.This TENS equation was obtained from ensemble average and time average processes in succession.As distinguished from Renolds-averaged N-S equation,the TENS equation has time-averaged stresses and time-averaged energy source terms to consider the zero order unsteady effect.As a result,it gives a better engineering method to transmit parameters across the interface of neighbour blade rows.
A NUMERICAL METHOD FOR PREDICTING TURBINE PROFILE LOSS
Yu Qing, Yang Hong
1997, 12(2): 197-200,222.
Abstract PDF(292KB) icon1821 icon560
Abstract:
A new numerical method for predicting the profile loss of turbine blades in subsonic and supersonic flows is presented.The profile loss consists of two parts:friction loss in the boundary layer on pressure and suction surfaces and mixing loss due to the interaction between wake and mainstream.A time-marching finite-volume Euler solver is used for mainstream calculation while a finite-difference computation for the boundary layer.A local C-grad correction is used in mainstream calculation and a full implicit difference scheme is applied to the boundary layer calculation.On the basis of mass,momentum and energy consrvation laws,the mixing loss is obtained between cascade exit and the far uniform downstream and compared with several experimental data.It is shown that this numerical method can make quite precise prediction of turbine blade profile loss.
EFFECTS OF DISTURBANCE WAVES ON ROTATING STALL STABILITY OF AXIAL COMPRESSOR
Cao Renjing, Zhou Sheng
1997, 12(2): 201-202,223.
Abstract PDF(216KB) icon1774 icon466
Abstract:
A 2-D rotating stall stability model considering the inlet and outlet flow angles and unsteady loss of axial flow compressor was proposed,for which numerical analysis has been conducted.The calculated results show that the disturbance waves at the upstream of compressor have influence on the rotating stall stability.The configuration of the compressor produces a strong impact on the propagation speed of the distrubance waves.
AN INVESTIGATION ON FLOW BEHAVIOUR IN AN S-SHAPED DUCT
Ma Handong, Wang Yiyun
1997, 12(2): 203-205,223.
Abstract PDF(774KB) icon1980 icon427
Abstract:
A new efficient finite-difference scheme for solving turbulence k-ε equations-Turbulence U-scheme has been developed.This method was combined with the solver of Navier-Stokes discreted by a modified Beam-Warming scheme to investigate three-dimensional turbulent internal flow in S-shaped duct.Many numerical experiments and practical applications show that this method provides detailed flow field and parameters for engineering design.As a special example,a numerical simulation has been completed for an S-shaped duct including separation,secondary flow,vortices etc.The comparison of its results with the flow patterns in the circular section s-shaped duct shows a good agreement in essence.
IDENTIFICATION OF GEAR TRANSMISSION SYSTEM WITH A ROTOR ON DYNAMIC NATURAL CHARACTERISTIC
Shao Renping, Shen Yunwen, Liu Geng, Xu Min
1997, 12(2): 206-208,223.
Abstract PDF(241KB) icon1571 icon456
Abstract:
A gear transmission system with a helicopter rotor was experimentally investigated and on-line identified during its operation,and the results were compared with its theoretical analysis.It is found that the gear transmission system with a rotor differs from other gear transmission system by such natural characteristics,that its dynamic characteristics change with it's rotational speed.It's changing law has also been obtained,which provides basis for the dynamic modeling analysis and the dynamic design of the system and an effective analytical approach of the gear transmission system.
FAILURE DETECTION ISOLATION AND ACCOMODATION OF SENSORS FOR ENGINE CONTROL SYSTEM
Yang Weihua, Sheng Wen, Sun Jianguo
1997, 12(2): 209-211,224.
Abstract PDF(304KB) icon1781 icon485
Abstract:
A method of failure detection,isolation and accomodation for engine sensors is presented.The method is based on engine component level nonlinear model and extended Kalman filter to obtain optimal estimation values of failed sensors and calculation references of the engine model.This makes engine model adapt to the actual engine perfectly and provides analytical redundancy for the failed sensors.In this case,the reliability of the engine control system is enhanced greatly.A numerical digital simulation of a given turboshaft engine has been accomplished.The results prove the effectiveness and practicability of the present method.
AN EXPERIMENTAL STUDY ON A LOBED NOZZLE OF AN INFRARED SUPPRESSION SYSTEM
Zhang Jingzhou, Li Ligao, Gao Chao, He Wenbing
1997, 12(2): 212-214,224.
Abstract PDF(293KB) icon10356 icon1663
Abstract:
An experimental study on the lobed nozzle of an infrared suppression system has been carried out at the low-speed wind tunnel with the electrical heater.The total temperature distribution at mixing flow exit and the temperature distribution on mixing duct and sheltering sheath were measured under different mass flow ratios of secondary stream to primary stream and differeat distances of the mixing duct from the sheltering sheath.The results show that ambient air mixing plays a dual role for reducing the exhaust temperature and mixing duct temperature.Sheltering from the hot wall makes the sheltering sheath temperature close to ambient temperature in case of the sheltering distance greater than 20 mm.Simultaneously,the plume irradiance and total radiation intensity for a typical lobed nozzle of an infrared suppression system were also measured to evaluate the infrared suppression effect.The data indicate that it does significantly reduce infrared radiation signature.

Copyright © 《Journal of Aerospace Power》 All Rights Reserved.

Supported by: Beijing Renhe Information Technology Co., Ltd.