1998 Vol. 13, No. 4

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VIBRATION CONTROL OF A NEW MOVABLE OUTER-RING SQUEEZE FILM DAMPER
Zhao Jie, Yan Litang, Zhu Zigen, Deng Jianbo
1998, 13(4): 353-356.
Abstract PDF(314KB) icon1862 icon399
Abstract:
A high efficient oil film damper,namely Movable outer Ring Squeeze Film Damper (MRSFD) is developed to meet the demands of modern gas turbine engines and other high speed rotating machinery on vibration control.By adding a flexible support outside,the outer ring of conventional Squeeze Film Damper (SFD) could be pushed under high oil forces caused by the squeezing motion of the journal.The vibration controllabilities of MRSFD and SFD are investigated and compared both theoretically and experimentally.It is proved that the nonlinear vibration characteristics such as jump phenomenon of SFD systems could be avoided under much greater unbalance level with MRSFD systems.As a novel oil film damper,MRSFD provides more effective vibration control for rotor systems and improves the unbalance loading ability of the damped supports.
STUDY ON SMA INTELLIGENT STRUCTURES FOR CRACK CONTROL
Zhang Xueren, Nie Jingxu, Du Yanliang
1998, 13(4): 357-360.
Abstract PDF(289KB) icon1531 icon466
Abstract:
The shape memory effect of Shape Memory Alloy (SMA) was used for crack active control in an intelligent component,which was made up with TiNi belts embedded in metal matrix.A linearized constitutive relation of SMA embedded in the matrix has been derived.Such a constitutive relation can be used easily in commercial finite element programs to treat the shape memory effect as the thermal effect of conventional materials.This method was applied to the numerical ananlysis of the intelligent component.Moire Interferometric tests were carried out on the component.Comparison of the calculated with test results shows that the effect of the active control is remarkable,and the computational method is feasible.
IMPACT-RUB MODEL AND CHAOTIC FEATURE OF PARTIAL RUB OF ECCENTRIC ROTOR
Liu Xiong, Li Qihan
1998, 13(4): 361-365,456.
Abstract PDF(767KB) icon2482 icon491
Abstract:
A general impact-rub model is established according to the classical impact theory.Then the suitable impact-rub model for aeroengine is found out.Two special examples of this general model are analyzed.The impact-rub dynamic equations of an eccentric and unbalanced rotor system are derived,which take the stiffness of stator into account.The equations are calculated numerically and the results are analyzed.The results reveal that the system possesses varied chaotic motions and bifurcation phenomena,besides periodic and quasi-periodic vibrations.The chaotic motions and related phenomena discovered in the impact-rub fault of the eccentric rotor system can be taken as its remarkable features and serve as symptoms to diagnose the impact-rub fault.
A SOLUTION FOR DYNAMIC RESPONSE OF SHROUDED BLADED DISC WITH COULOMB DAMPING
Li Lin
1998, 13(4): 366-370,456.
Abstract PDF(329KB) icon1704 icon389
Abstract:
The paper deals with dynamic response solution problem of shrouded bladed disc assemblies with dry friction.A hypothesis of multi-harmonic variables has been introduced into AFT method,so that its divergence problem due to alias and leakage error in iteration has been solved.This improved AFT method is independent of the harmonic number in variables of the friction number elements in the system.So it is a general method for solving dynamic response of a non-linear system.A model of cyclic two-dimensional substructure for a bladed disc has been calculated by this method,and the results have been compared with those of the direct integration method.
A COMPUTER-AIDED COMPLEX 3D PIPING SYSTEM
Fan Jiang, Ma Mei
1998, 13(4): 371-374,456.
Abstract PDF(273KB) icon1888 icon400
Abstract:
A computer-aided piping system has been researched and established for complex 3D plumbing system on aircraft engine.This system is based on the user-defined pipe object and realizes piping on aircraft engine casing with same or different geometry.The system also provides the ability of editing the pipe's property and shape and ability of interference and clearance checking.The piping object is capable of intelligent response to the change of the joint.The system can also serve as a piping system of automobile,or for petroleum and chemical field.
VIBRATION ANALYSIS OF BLADED DISC COUPLING SYSTEM WITH FRICTION DAMPING
Hu Xunfeng, Wang Qingmeng, Zhang Jin, Liu Xiaoping
1998, 13(4): 375-379,457.
Abstract PDF(331KB) icon1982 icon425
Abstract:
Nonproportional viscous damping is used to simulate the effect of frictional constraint at the shroud interfaces.The effects on the natural vibration behavior and dynamic response are investigated.The damping matrix and stiffness matrix of the interfaces in local coordinate system are presented by using the equivalent viscous damping and stiffness coefficients of the spring/friction model.The response displacements and the corresponding response stress distributions of the coupling system under three kinds of boundary conditions at shroud contact interfaces are obtained respectively by using mode superposition method.The calculation method,the basic analysis approach and the important conclusions provided in the paper may be available for reference in the designing,development and modification of turbomachinery.
A FINITE ELEMENT METHOD FOR STRUCTURE OF VISCOELASTIC MATERIALS
Yang Xiaoguang, Geng Rui
1998, 13(4): 380-385,457.
Abstract PDF(808KB) icon2294 icon404
Abstract:
On the basis of the Walker viscoelastic constitutive theory,after developing a self-adaptive time integration method for the constitutive equation,the authors implemented the Walker constitutive equation into the general-purpose non-linear finite element software ABAQUS through the user-defined subroutine UMAT,and finished benchmarks for rate dependence,cyclic,thermal recovery,non-thermal and varied loading conditions.In coded subroutine four element types were included,and the integration method has the monitor mechanism for successful integration.In the light of comparison with the results in publication,the calculated results are satisfied,and the accuracy and efficiency are acceptable.The coded subroutine can be applied to the nonlinear structure analysis of aeroengine hot sections.
NONLINEAR DAMAGE ACCUMULATION MODEL FOR TURBINE DISC SLOTS
Yang Hui, Zhang Jin, Nie Jingxu, Hou Guisang
1998, 13(4): 386-389,458.
Abstract PDF(909KB) icon1755 icon426
Abstract:
The crack initialization life and crack propagation life of turbine disc slots at high temperature under the fatigue/creep interaction are studied according to damage mechanics.The modified Chaboche's damage model of low cycle fatigue and the improved Kachanov's damage model of the creep crack propagation have been combined to establish a nonlinear damage accumulation model.A model of crack propagation under fatigue/creep interaction has been developed,based on the above mentioned model.The good agreement between the calculated results and experimental data demonstrates that the model is quite effective.Damage FEM has been developed according to damage mechanics and FEM.The method uses finite element mesh dimension to simulate damaged crack length.The criteria for the crack initialization and the crack propagation orientation are established and testified by the calculation of the fir-tree slots of a turbine disc under the two kinds of loading conditions.The effects of mesh's minimum dimension,the stress boundary condition and the displacement boundary condition of the calculation model on the crack initial life of the structure are analyzed.It is also discussed,how the calculation model scale and the peak value of trapezoid loading spectrum affect the crack propagation life of a two-dimensional structure.
EXPERIMENTAL INVESTIGATION ON TRAVELLING WAVE VIBRATION OF HIGH-SPEED ROTATING SHELL
Hong Jie, Guo Baoting, Zhu Zigen
1998, 13(4): 390-395,458.
Abstract PDF(634KB) icon1738 icon525
Abstract:
The experimental investigation on vibration characteristics of thin cylindrical shell with axial symmetry has been performed.The experimental modal analyses have been done under static condition and high-speed rotating condition for a given thin cylindrical shell by using shock vibration excitation method.The experimental results indicate that the vibration characteristics of the rotating thin cylindrical shell are different from those of rotating disk.For the former,due to the effect of Coriolis,there exist forward and backward travelling wave vibrations with different frequencies in view of rotating coordinate system and the frequency differences between two travelling waves are in a linear relationship with rotating speeds.The experimental results have a good agreement with the theoretical analysis,and it is very useful for the vibration design of a rotating cylindrical shell for turbine engine.
COMBINED FATIGUE LOAD AND LIFE CONVERSION FROM EXPERIMENTS TO SERVICE CONDITIONS
Wang Rongqiao, Nie Jingxu
1998, 13(4): 396-399,459.
Abstract PDF(275KB) icon1832 icon493
Abstract:
A contrast test investigation on the combined fatigue lives of slightly and heavily corroded turbine disc slots has been carried out at high temperature under two vibration frequencies 50 Hz and 100 Hz.In order to estimate the service life from the test life,a new two-frequency-ratio method is proposed to convert the tested combined fatigue loads and life into service ones in the field.The conversion results can be taken as criteria for discarding the corroded turbine disc.
APPLICATION OF FLEXIBLE-POROUS SQUEEZE FILM DAMPED SUPPORT TO A CORE ENGINE
Zhou Ming, Li Qihan, Zhao Fuan
1998, 13(4): 400-402,459.
Abstract PDF(326KB) icon1590 icon413
Abstract:
A porous Squeeze Film Damper (PSFD) had been developed by BUAA on the basis of the normal Squeeze Film Damper (SFD).The investigation on its application indicates that the nonlinear vibration characteristics of rotor system with SFD,such as bistable jump,nonsynchronous response and "lock up" at rotor pin-pin critical speeds under quite high unbalance level are greatly improved or avoided with the PSFD system.In conformity with the calculation and analysis of the dynamic characteristics of the rotor system in a core engine,a new flexible-porous squeeze film damped support has been designed and used in the rotor system of this core engine for adjusting its critical speeds and controlling its vibration.It is shown that the data of the engine cell tests have a good agreement with the calculation results.
STUDY ON VIBRATION DAMPING MECHANISM OF AN ELASTIC RING SQUEEZE FILM DAMPER
Zhou Ming, Li Qihai, Yan Litang
1998, 13(4): 403-407,459.
Abstract PDF(356KB) icon1700 icon397
Abstract:
The vibration reduction mechanism of the Elastic Ring Squeeze Film Damper (ERSFD) is investigated.Based on the analyses of forces and motions acting on the journal of a rotor-support system with ERSFD and generalized incompressible Reynolds Equation,the model and differential equations of the vibration reduction mechanism of an ERSFD are set up.The features of the vibration reduction for both ERSFD and SFD are considered and compared.It is found out that SFD is only the special example of ERSFD.Theoretical analysis reveals that ERSFD has a very good dynamic characteristics and can be used for both reducing vibration and retuning the frequencies (critical speeds) of the rotor-support system.
EXPERIMENTAL INVESTIGATION AND APPLICATION OF AN ELASTIC RING SQUEEZE FILM DAMPER
Zhou Min, Li Qihan, Yan Litang
1998, 13(4): 409-412,460.
Abstract PDF(330KB) icon1918 icon533
Abstract:
An experimental investigation on a model of rotor support system with Elastic Ring Squeeze Film Damper (ERSFD) was completed in the case of supplying oil for the squeeze oil film damping during rotor system operation.The dynamic characteristic experiments including vibration damping and frequency retuning characteristics of the model of rotor support system with EQSFD were conducted.It is proved true that the ERSFD possesses very good properties for both vibration damping and freqnency retuning.At last,the ERSFD has been used successfully in the rotor system of a given core aero-engine.It is indicated that the ERSFD can adjust the critical speeds of the rotor system to meet the demands of engine operation and control the vibration of whole core engine very well.
CONSTRAINT-BASED STRUCTURAL MODELING AND ANALYSIS OF AEROENGINE BLISK IN CONCURRENT ENGINEERING ENVIRONMENT
Ma Mei, Fan Xiaohua, Yang Xiaoguang
1998, 13(4): 413-417,460.
Abstract PDF(658KB) icon1651 icon398
Abstract:
A solid modeling system for aeroengine blisk in the concurrent engineering environment is developed on the platform of the integrated CAD/CAE/CAM Software-Unigraphics of network station,by using the capability for solid modeling of sophisticated components with advanced hybrid feature modeling technology and corresponding features in UG and STEP according to entity definition.A general constraint management system is established to meet the needs of multidisciplinary teams for designing the components of the engine.It coordinates the real activities of multidisciplinary teams to check all design parameters dynamically by constructing a constraint network and user defined rule-based knowledge base,and takes the follow-up operations into account in the designing stage.The data exchange between geometric model and FEA from UG to PATRAN is performed successfully.As an example,a blisk of a given turbofan engine is employed for modeling,and its static stress and modal analyses have been completed with satisfied results.So this work provides a supporting tool for application of concurrent engineering to designing the components of an aeroengine.
A CONSTRAINT MANAGEMENT SYSTEM OF AEROENGINE BLISK SUPPORTING CONCURRENT ENGINEERING
Duan Haibo, Fan Xiaohua, Ma Mei, Yang Xiaoguang
1998, 13(4): 418-420,461.
Abstract PDF(231KB) icon2297 icon398
Abstract:
In order to solve the problems caused by transition from sequential engineering to concurrent engineering in aeroengine research and development,to give the overall representation and sustain the comprehensive relationship among the multifunctional teams and the team members,the hierarchic structure of constraint network in the research and development of an engine was analysed,and a general constraint management system for supporting concurrent design has been developed.The system imitates the collaborative work of multifunctional teams and considers the needs of follow-up activities simultaneously in the design stage.As an example,a blisk constraint network of a given turbofan engine has been worked out for the blisk feature modeling system.This work provides a supporting tool for application of the concurrent engineering to the aeroengine research and development.
STUDY ON CONCURRENT ENGINEERING MODEL FOR PIPING
Chen Zhiying, Ma Mei
1998, 13(4): 421-424,461.
Abstract PDF(874KB) icon1741 icon390
Abstract:
A method,for concurrent engineering model transformation namely formark method is provided.A series designing model can be transformed into a concurrent model by the method.The mark method as a math tool can be used to transform the complex series piping model into an administrative level model.All the tasks directly related to piping can be newly marked and arranged for coordinative work according to concurrent engineering concept.Then the concurrent piping model is built.The time efficiencies of the series and the concurrent models are analyzed and compared.It is shown that the concurrent model with multi-level,in addition to CAD technology and process management,can route a new pipe system successfully for a developing engine only once.It will cut down the development time and costs.
DAMPING CHARACTERISTICS OF METAL RUBBER DAMPER ON ROOT OF CANTILEVER BEAM
Deng Jianbo, Zhu Zigen, Li Qihan, Zhao Jie
1998, 13(4): 425-427,461.
Abstract PDF(590KB) icon1743 icon491
Abstract:
An experimental investigation on application of the Metal Rubber to vibration reduction of the cantilever beam has been carried out.Therefrom the engineering application field of the Metal Rubber damping material is expanded.The parameters such as the materials of metal wire,the pressing density of the Metal Rubber and directions of the location rubber damper have been studied experimentally.The results indicate that the vibration of the cantilever beam can be greatly reduced,only if the construction parameters of the metal rubber are properly selected.
IMPACT-RUB FAULT CHARACTERISTICS AND HOLOSPECTRUM ANALYSIS OF ROTATING MACHINERY WITH IMBALANCE
Liu Xiong, Li Qihan
1998, 13(4): 428-430,462.
Abstract PDF(673KB) icon1700 icon542
Abstract:
With respect to the impact-rub dynamic equations of Jeffcott rotor only with imbalance,the characteristics of every harmonic wave in the spectrum domain are studied according to the 2-dimension holospectrum theory,and an important feature of the impact-rub is obtained.The effects of friction coefficient and rotating velocity on the precession are analysed.It is discovered that the regular forward precession resulting from unbalancing force plays a critical role when the friction coefficient is small,but as the friction coefficient is enlarged,the quasi-periodic precession or instability will appear at certain rotating velocity.
NUMERICAL METHOD FOR DETERMINING DYNAMIC STRESSES IN FLUTTER BLADES
Chen Zuoyi, Wu Xiaofeng
1998, 13(4): 431-434,462.
Abstract PDF(742KB) icon1759 icon542
Abstract:
A numerical method is presented to determine the dynamic stresses and fatigue life of a flutter blade in turbomachinery.The method contains the calculation of unsteady aerodynamic work and damping work of the vibrating blades;the conception of equilibrium amplitude;and the estimation of its fatigue life in accordance with the dynamic stresses of the vibrating blades under the equilibrium amplitude.The unsteady aerodynamic work is obtained from the calculation of 3-D unsteady N-S equations with the Oscillating Fluid Mechanics Method (OFMM) and the Parametric Polynomial Method(PPM).The maximum kinetic energy and dynamic stresses of the vibrating blades are calculated with FEM.The fatigue life of the blade is estimated with Manson-Coffin Equation.The calculated results demonstrate that the blades can operate even the unsteady aerodynamic work is positive.
A NEW METHOD FOR ESTABLISHING A STATE VARIABLE MODEL OF AEROENGINE
Feng Zhengping, Sun Jianguo, Huang Jinquan, Cai Hongwu
1998, 13(4): 435-438,463.
Abstract PDF(763KB) icon4568 icon654
Abstract:
A new method for establishing aeroengine's State Variable Model (SVM)-fitting method is proposed.The SVMs of small perturbation about steady operating points of an engine are established by fitting nonlinear dynamic simulation data of its component-level models at the points.Then the SVMs of small perturbation about steady points at ground and in flight and also the SVM of large perturbation of ground acceleration for a turbofan engine are established by this method.Dynamic simulation results show that the SVMs established by fitting method have much higher accuracy than the SVMs established by the method of bias derivative.
THEORETICAL ANALYSIS OF TEMPERATURE DISTRIBUTION ON SQUEEZE FILM DAMPER OF TURBOENGINE
Jiang Shuyun, Chen Zhaobo, Xia Songbo
1998, 13(4): 439-442,463.
Abstract PDF(327KB) icon1672 icon395
Abstract:
The oil film temperature field in the Squeeze Film Damper (SFD) was analysed by the aid of finite element method.The oil film temperature distribution was obtained from joint solution of Reynolds,energy and viscosity-temperature equations of SFD in accordance with its boundary conditions.Based on the analysis of oil film ring temperatures in SFD of a turboengine SFD,the authors put forward that the oil film temperature rises are obtained from damping in the starting stage,but mainly from heat convection from ring to oil film in the steady state.The authors also recommend the Trial-and-Error method to solve this problem.
EFFECTS OF FUEL TYPES ON PERFORMANCE OF PULSED DETONATION ENGINE
Fan Wei, Yan Chuanjan, He Liming, Jian Jian, Wang Linquan
1998, 13(4): 443-446,463.
Abstract PDF(630KB) icon1949 icon484
Abstract:
In order to design an advanced Pulsed Detonation Engine (PDE),the effects of fuel types on its performance were investigated.In the investigation,gasoline,kerosene,ethyne and hydrogen were taken as the fuel and the oxidizer is air.The PDE model was designed by authors.The performance of PDE,such as averaged thrust,specific impulse and specific fuel consumption,were calculated and analysed respectively with each type of fuel.The gasoline/air mixture was tested in PDE model to verify the calculating method.The experimental results were consistent with the calculated ones on the whole,so that the conclusion drawn from the calculated results can serve as theoretical foundation for reasonable selection of the fuel.
EFFECTS OF PHYSICAL PARAMETERS OF CIRCULAR DUCT IN SHEAR FLOW ON SOUND ATTENUATION
Lu Yadong, Hu Zongan, Cui Jiya
1998, 13(4): 447-451,464.
Abstract PDF(340KB) icon1664 icon475
Abstract:
Engineering prediction models of sound propagation in a circular duct with segmented liners in uniform flow and shear flow are established by means of the modal analysis method.The effects of the physical parameters,such as boundary layer thickness,mean flow Mach number,acoustic resistance,characteristic frequency of the facing sheet,cavity depth,and duct length on the in-duct sound attenuation have been determined for a numerical example.In addition,the test data of total sound attenuation in a duct with flow,published by other authors,have been used to verify the feasibility of the engineering prediction method provided.
RANGE EXTENSION OF ENGINE FLIGHT TEST BED WITH THROTTLE SCREEN
Wang Rugen, Shi Tingmo
1998, 13(4): 452-454,464.
Abstract PDF(306KB) icon1441 icon381
Abstract:
An approach to extending test range of the engine flight test bed by mounting a throttle screen before the tested engine is proposed.The relevant design principles of the throttle screen are given.The extended test limits by mounting a given throttle screen have been calculated.The rationality and feasibility of the approach have been proved by comparison of the calculated results with pressure loss data of an aircraft air-inlet screen.

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