1989 Vol. 4, No. 1

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Display Method:
A NEW ADJUSTING SCHEME OF MULTI-POINT EXCITING PURE MDDE
Yi Liyan, Zhang Yison
1989, 4(1): 2-6,88.
Abstract PDF(436KB) icon1847 icon41
Abstract:
A new technique of multi-point exciting for modal testing is discussed. In consideration of the trouble of phase shift in some experimental instruments, a new scheme is proposed to assign multi-point exciting forces and a practical method is provided to discern the modal parameters in pure modes. Calculations and experiments demonstrate that the new technique is applicable to the multi-point exciting experiments for general structures.
ON EVALUATION OF AIRCRAFT PROPULSION SYSTEM PERFORMANCE
Tao Zengyuan, Xu Qishan, Chen Xiaoxiong
1989, 4(1): 7-10,87.
Abstract PDF(403KB) icon1495 icon72
Abstract:
In order to meet the requirements of performance evaluation for an aircraft propulsion system, the paper elaborates on how to implement the procedures, contents and methods specified in National Military Standarts and other concerned problems. The paper can serve as a reference in designing, developing and testing an aircraft or an aeroengine and as one of the main arguments for checking and accepting the aircraft propulsion system performance in aircraft qualification flight tests.
PERFORMANCE ANALYSIS OF A PROPULSION SYSTEM
Zhang Jing
1989, 4(1): 11-16,87.
Abstract PDF(485KB) icon1616 icon46
Abstract:
Performance analysis programs of a propulsion system are established and recommended as tools for estimating installation penalties. The performance parameters such as inlet capture area, inlet pressure recovery, inlet drag, nozzle gross thrust coefficient, nozzle/afterbody drag, installed thrust and specific fuel consumption can be obtained on condition that the uninstalled engine performance is matched with the inlet/nozzle internal and external performances. The influences of design parameters and operation conditions on the propulsion performance are also discussed. Finally, an aircraft/propulsion system integrated program has been worked out which can optimize the engine cycle parameters. The numerical results obtained show that the installation penalties are 20% to 30% at the identical flight conditions and throttling settings. Therefore it is very important to reduce the installation penal-tiesand to reach the optimal integrated propulsion performance.
ADJUSTMENT OF RATIO OF ROTATION SPEED DIFFERENCE IN A TWIN-SPOOL TURBOJET ENGINE
Wu Zizhong, Shang Yi
1989, 4(1): 17-20,88.
Abstract PDF(373KB) icon1846 icon73
Abstract:
Analyzing the concept and the function of the ratio of rotation speed difference in a twin-spool turbojet engine indicates that the ratio has an effect on the surge margins of the high and low pressure compressors and the match between the speed of high pressure compressor and the inlet gas temperature. It is proposed how to adjust the ratio of rotation speed difference reasonably. The results of the adjustments made by us are shown in good agreement with the trial run data. In addition, the effects of the ratio on the thrust, specific fuel consumption, speed of high pressure compressor and turbine inlet gas temperature are also considered.
NEW GASDYNAMICS FUNCTIONS WITH VARIABLE SPECIFIC HEAT TAKING MACH NUMBER AS INDEPENDENT VARIABLE
Peng Ying, Fan Zuomi
1989, 4(1): 21-24,88.
Abstract PDF(343KB) icon1645 icon46
Abstract:
The new gasdynamics functions with variable specific heat proposed in this paper take Mach number as independent variable. The four existing methods, namely the thermodynamics method, two kinds of conventional gasdynamics functions with variable specific heat and another kind of new gasdynamics functions with variable specific heat are compared with the presented method in solving thermo dynamic processes with variable specific heat. It is shown that the proposed new method is the most convenient.
A STUDY ON GH169 CRACK PROPAGATION UNDER CREEP-FATIGUE INTERACTION
Yan Li, Jiang Wenglong, Zhou Hongfan
1989, 4(1): 25-29,89.
Abstract PDF(1370KB) icon1288 icon33
Abstract:
As a new technique of crack detection at high temperatures, Reversing DC Electric Potential Method is used to study the crack propagation behaviours of aeroengine turbine disk material GH169 under creep-fatigue interaction at 650 C and at different hold-times. The fracture surfaces has examined with a scanning electron microscope. The experimental results indicate that the life prediction model by hyperbolic sine function is superior to the life prediction model by Paris formulation in correlativity with experimental data and predictability at the crack initiation propagation. Moreover, the former model is more convenient in application. It has been found that the crack propagation ratio obtained in the case of gradually increasing loading is smaller than that resulted from one-time loading.
INVESTIGATION ON SIMULATION OF FOREIGN OBJECT IMPACT DAMAGE TO COMPRESSOR BLADE
Sun Zhende, Lu Qixin
1989, 4(1): 30-32,92.
Abstract PDF(1901KB) icon1420 icon40
Abstract:
An experimental method for simulation of foreign object impact damage to a compressor blade is investigated. The impact damage mechanism is analyzed by the aid of a scanning electron microscope. A reasonable experimental method is proposed by comparing the bullet damage witb the pendulum impact damage.
EXPERIMENTAL RESEARCH ON 3D TURBULENT GAS-PARTICLE FLOWS IN A COMBUSTOR OF CO-FLOW JET WITH LARGE VELOCITY DIFFERENCE
Li Rongxian, Zhao Huiquan, Huang Xiaoqing, Yin Taiqing, Pan Min. Zhou Lixing, Zhou Lixing
1989, 4(1): 33-36,89-90.
Abstract PDF(393KB) icon1730 icon41
Abstract:
The time-averaged and root-mean-square fluctuation velocities of gas and particle phases and particle mass flux distributions have been measured by a 2-dimen-sional laser Doppler velocimeter combined with a sampling probe in a combustor of co-flow jets with large velocity difference. The results show large velocity slip between gas and particle phases. The gas-phase flow has astrong reverse flow in the near-axial region, while particles keep their forward motion almost everywhere, even in the strongly reverse flow region. The particle mass flux distributions measured have their maximum values in the near-axial reverse flow region. Presence of high-velocity jets remarkably enhances particle mixing. All these facts reveal the mechanism of flame stabilization and combustion intensification in the combustor of co-flow jets with large velocity difference. The four peaks of gas turbulence intensity observed in experiments demonstrate that the turbulence is caused by large velocity gradient resulted from sudden expansion and high velocity jets.Particle turbulence intensity has the similar behaviour as gas one,but the former is not always smaller than the latter. This means that the classical Hinze-Tchen's theory of particle following gas motion must be reexamined.
A STUDY ON EXIT RADIAL TEMPERATURE PROFILE OF 2D EXPERIMENTAL COMBUSTOR
Li Jibao, Jing Rushan
1989, 4(1): 37-40,90.
Abstract PDF(375KB) icon2027 icon64
Abstract:
The exit radial temperature profiles formed by four configurations of dilution hole design have been studied experimentally on a two-dimensional experimental combustor. According to the results the effect of different configurations of dilution hole design on combustor exit radial temperature profile shows certain regularity. A semi-empirical and semi-analytical model has been developed for predicting the exit temperature profile of gas turbine combustor.The model can predict the effect of change in dilution zone design or combustion operating conditions on the variation of combustor exit radial temperature profile based on exit temperatures meas-sured before change. The comparison of the predictions with the measurements shows excellent agreement. The model provides a quantitative design tool for adjustment of temperature profile of gas turbine combustor.
ANALYSIS AND CALCULATION OF VAPOR PUMP CHARACTERISTICS
Gu Min
1989, 4(1): 41-44,91.
Abstract PDF(345KB) icon1674 icon61
Abstract:
A calculation method of hydraulic losses in a vapor pump is proposed with reference to calculation method for high-speed centrifugal pumps. The pressure distribution in the collectors is determined by means of segmentation of flow together with pipe line, therefrom the radial force, pressure head and vapor core variation are found. Some numerical examples are also persented. The method can be applied either to estimation of the characteristics of a new pump in its preliminary design or to approximate evaluation of existing pumps.
EXPERIMENTAL RESEARCH ON A BIPROPELLANT THROTTLING LIQUID ROCKET ENGINE WITH CONTROLLABLE INJECTOR AND THROTTLING CAVITATING VENTURI
Gao Hanru, chen Qizhi, Yang Loping
1989, 4(1): 45-49,91.
Abstract PDF(442KB) icon1916 icon61
Abstract:
A bipropellant throttling liquid rocket engine with controllable injector and throttling cavitating venturi has been designed,tested and analyzed.In result the relationships of pressure, pressure recovery coefficient of venturi, stroke of injector pintle, propellant flow rate and mixture ratio, combustion efficiency, specific impulse, thrust, stability and response time to control voltage signal are obtained and the corresponding plots and data are also presented.
DETERMINATION OF MASS FLUX FOR IGNITRON
Zhang weihua, Dai Xuheng
1989, 4(1): 50-54,91.
Abstract PDF(388KB) icon1495 icon48
Abstract:
An one-dimensional two-phase flow model is put forward for ignitron in solid propellant rocket,and its governing equations are derived. The gas pressure,tempera-ture,density and particle velocity in the ignitron are obtained from solution of the equations by finite difference method. A experimental apparatus has been set up to testify the calculations. From analyzing the results of the calculations and experiments the following conclusions are drawn. First, consistency of the flux calculated with the flux measured proves feasibility of the present calculation method;Second, the particle size and charge of igniter have significant effects on pressure in the ignitron; Third, the gas pressure,temperature and density in the burned area change very little, but the gas and particle velocities vary a lot; Last, the acceleration of flame spreading which comes from the calculations is testified in the experiments.
EXPERIMENTAL RESEARCH ON PLANAR CASCADE ENTIRE CHARACTERISTIC
Fun Qi, Zhang Huimin
1989, 4(1): 55-58,91-92.
Abstract PDF(409KB) icon1536 icon47
Abstract:
The concept of planar cascade entire characteristicis first introduced, which comprises forward and reversed flow characteristics. A single-row and a tandem planar cascades with equivalent geometrical parameters are investigated experimentally. Their forward and reversed flow characteristics are obtained separately from measurements of their wakes. The variation laws and relationship of these characteristics are analyzed.In our test conditions,the cascade with better forward flow characteristic has worse reversed one.
A COMPUTATION METHOD FOR A CONFINED JET IN SUDDEN EXPANSION DUCT
Bao Guohua, Jiang Zhenxin
1989, 4(1): 59-60,92.
Abstract PDF(202KB) icon1622 icon39
Abstract:
A confined turbulent flow in a sudden expansion duct is computed by a numerical method of time-averaged Navier-Stokes equations with k-e model. The pressure and velocity are obtained by using Newton's method and sparse matrix techniques. The numerical examples show that the computation results are in satisfactory agrefement with the experimental data.
A METHOD FOR CONFIGURATION OF ANNULAR DIFFUSER
Li Changlin
1989, 4(1): 61-62,92.
Abstract PDF(190KB) icon1701 icon61
Abstract:
A new method for calculation of annular diffuser configuration is offered, which takes pressure loss and perpendicularity of air-through section to the center airflow-line into consideration. When there exists large declination of center flow-lines at inlet and exit,this method is more reasonable than the conventional one which ignores these two factors.
VARIATION OF CRITICAL SPEED OF A ROTOR-BEARING SYSTEM WITH SLIGHT RELOCATION OF BEARING
Li Yan, Yin Zeyong
1989, 4(1): 63-64,93.
Abstract PDF(211KB) icon1207 icon45
Abstract:
A formula has been derived for calculating the variation of critical speeds of a rotor-bearing system with slight change of bearing position. The folmula can determine which bearing should change position and in which direction it should move so that the desired critical speeds of the system could be reached. The formula has been applied to rearanging the bearings of a certain aeroengine so successfully that its critical speeds are farther away from the working speed range than before.
APPLICATION OF MICROCOMPUTER TO AUTOMATIZING FATIGUE TESTING
Yang Daman, Zhuang Zhongliang, Lu Qixin
1989, 4(1): 65-66,93.
Abstract PDF(237KB) icon1258 icon41
Abstract:
This paper describes how a microcomputer is applied to a blade fatigue testing system. Automatic checking and controling of blade fatigue testing in the system are implemented with the aid of a nest-form of assembly language and high-level language. The system can also be used for fatigue testing of fuel or oil tubes.
EXPERIMENTAL INVESTIGATION OF SUDDEN IMBALANCE RESPONSE ON A FLEXIBLE ROTOR SYSTEM WITH SQUEEZE-FILM DAMPER
Fu Caigao, Li Xifan
1989, 4(1): 67-69,93.
Abstract PDF(1103KB) icon1795 icon48
Abstract:
An experimental method is used to investigate suddenly applied imbalance responses of a flexible rotor with an uncentralized squeeze-film damper. The results show that the unstable transient process in this system is very short, and only after a few cycles the system recovers to steady state on new vibration level. The squeeze-film damper system has a limited capability of sudden subjection to the imbalance load. The limits depend mainly on the oil-film clearances of the damper. This work will be helpful for selecting squeeze-film parameters and experimental method of suddenly applied imbalance.
RESEARCH ON TEMPERATURE PROFILE FACTOR AT EXIT IN AN ANNULAR COMBUSTOR
Zhang Baocheng
1989, 4(1): 70-72,94.
Abstract PDF(260KB) icon2021 icon75
Abstract:
The visualized statistics of the temperature profile factors (PF) at exits in an annular combustor and its sectors have been made. The results indicate that the number of heads in a sector has significant effect on PF. The empirical formulae for calculating all-ring combustor PF have been obtained from fitting of statistical data. The relative errors between the calculations with these formulae and the measurements in tests are less than0.045.
ON ATOMIZING MECHANISM IN ATOMIZING CHANNEL
Liu Zhigang, wang Jiahua
1989, 4(1): 73-75,94.
Abstract PDF(284KB) icon1562 icon58
Abstract:
The atomizing process in atomizing channel has been investigated by means of pulse laser. The results show that most of atomizing spray comes from the unstable atomization of fuel film on the front edge of the channel. The recirculation znoe of the channel impels the fuel film to turn over from the inside to outside of the channel. The width of the fuel film and recirculation zone of the channel have also been measured. An empirical expression for fuel fiim width has been deduced.
STUDY ON FUEL SPRAY CHARACTERISTICS IN HEATED AIR STREAM.
Yang Guixiang, Jing Rushan
1989, 4(1): 76-78,94.
Abstract PDF(296KB) icon1916 icon41
Abstract:
Based on studying interdependence of spray characteristics and evaporation history of fuel sprays and on measuring the spray characteristics by light scattering in heated air stream,authors conducted an experimental and analytical research on variation of spray characteristics of vaporizing kerozine sprays in a straight cylindrical vaporizer with heated air stream. The fuel was injected co-axially from a plane orifice air blast atomizer upstream of the vaporizer. Both the experimental and analytical results show that within the present parameter range, the spray Sauter Mean Diameter and drop size distribution parameter increase with downstream vaporization distance.
COMPUTATION OF DYNAMIC PROCESS WITH LARGE DISTURBANCE FOR SPLIT-SHAFT GAS TURBINE
Lu Zehua, Ye Bosheng
1989, 4(1): 79-81,95.
Abstract PDF(259KB) icon1706 icon43
Abstract:
Taking Spey core engine used in a gas-stream combined cycle as an example, this paper deals with computation of dynamic process with large disturbance for split-shaft gas turbine with a variable-coefficient divisional small-disturbance for linearization method.
OPTIMIZING DESIGN FOR TURBOENGINE DIGITAL SPEED CONTROLLER
Yang Shengfa
1989, 4(1): 82-84,95.
Abstract PDF(268KB) icon1818 icon63
Abstract:
A method for optimizing characteristics of digital speed controller of a turbo-engine is presented. A dynamic model of this system has been developed. According the chosen quadratic property criterion,six characteristic quantities of the digital controller are optimized by system simulation in a digital computer. As JT15D-4 turbofan is taken for example, its digital speed controller system optimized by the present method is obviously better than the original hydromechanical system.
STUDY ON EXCHANGE OPERATION BETWEEN TWO MICROCOMPUTERS IN AEROENGINE DIGITAL CONTROL
Xu Qihua, Wu Qihua
1989, 4(1): 85-86,95.
Abstract PDF(221KB) icon1610 icon46
Abstract:
Communication and trouble-selfdetection of microcomputers in dual-computer system of aeroengine digital control are considered,and exchange operation between two microcomputers is discussed emphatically .The simulation tests of the exchange operation in dual-computer engine speed control system have been performed. The results of the tests are satisfactory.
1989, 4(1): 96-96.
Abstract PDF(101KB) icon1331 icon36
Abstract:
A DISSIPATION-DISPERSION TURBULENCE THEORY AND ITS MODIFIED k-ε MODEL
Gao Ge
1989, 4(1): 97-104.
Abstract PDF(713KB) icon1569 icon39
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Based on the perturbation equation of the Navier-Stokes equation and the instability analysis of strongly nonlinear flow, a set of new control equations is presented featuring the interaction between dissipation and dispersion of turbulence. Three extra terms representing respectively the effects of extra strains, rotation and dispersion on the turbulent stresses introduced into the momentum equation. The defects of the original k-e modelart removed mainly by introducing new soerce terms. This modified k-i model has advantages of simplicity, self-consistency and clarity of physics It is able to handle complex flows and provides new perspectives for looking at a diversity cf turbulence probiems, such as intermuttency, coherent structvires, amsotropy , turbulent energy inversion and the cut-off of turbulence spectra.

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