1988 Vol. 3, No. 1

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1988, 3(1): 2-2.
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INSTABILITY ANALYSIS OF STRONG NONLINEARITY OF TURBULENT FLOW
Gao Ge
1988, 3(1): 3-8,87.
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In order to analyse the instability of turbulent flow from the viewpoint of fractal dynamics, an arbitrary curve with discrete disturbance wave is chosen as the element of fractal structures of turbulence. Meanwhile, a quantized scale and coordinate method is adopted to handle the strongly nonlinear phenomena of flows despite their complex structures and large amplitudes of disturbance. Two of the main difficulties for the complexity of turbulence,i.e. nonlinearity and discreteness, have been approximately solved by the above-mentioned means. The bifurcated solution leading to transition and turbulence is meaningful, which embraces all the effects of nonlinearity and discreteness, including shearing, stretching, rotation, dispersion, pressure-strain interaction and memory. Therefore, the result should deepen our comprehension of turbulence.
A SYSTEM OF DATA ACQUISITON AND PROCESSING IN AEROENGINE
Han Wenqing, Li Longqiang, Huang Zhiqing
1988, 3(1): 9-12,87-88.
Abstract PDF(509KB) icon1817 icon367
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A comprehensive system of data acquisition and processing in aeroengine testing is described which can acquire and process all parameters including dynamic ones. Its advanced hardware and program compiled with PL/M language enhance its maximum acquisition speed to more than 5000 times per second. The thermocouple regression equations are obtained by polynomial fitting in sections with changing weight and applied to linearization of temperature measurement. The self-made sca-nivalve controlled by microcomputer is used for steady multipoint pressure measurement, and the technique of real time calibration is also adopted to guarantee high accuracy of the measurement. The self-made frequency channel is capable of turning frequency into analog or digital signal in real time and its response time makes up only one period of the signal measured.The practice of employing this system in aeroengine testing shows that its hardware and software are reliable and easy to operate. The time of the whole processingreduces from half a day manually to merely several minutes. The test run time is also saved up to about 20%, but the average measurement accuracy increases from 0.8% to 0.3%.
EXPERIMENTAL INVESTIGATION OF THE INFLUENCE OF DIFFUSER SHELL SHAPES ON PERFORMANCE OF DUMP DIFFUSERS IN COMBUSTOR
Hua Guangshi, Wang Weibin, Tang Ming, Chen Binglu
1988, 3(1): 13-17,88.
Abstract PDF(545KB) icon1934 icon441
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The overall performance of a two-dimensional symmetric straight-walled dump diffuser in combustor is investigated experimentally. The test model consists of a straight-walled pre-diffuser with fixed diffuser wall angle(2 = 12°) ,a semicircular head flame tube without holes, two throttles for varying flow split ratio(S)between upper and lower channels surrounding the flame tube, add eight different diffuser shells, The experiments were carried out under the conditions of Main =0.277 and S = l, and for each of the eight shells, the dump gap (D) was changed 4 times. The main purpose of the tests is to study the influence of the different shell shapes and dump gaps on the overall performance of the dump diffusers.The results show that their influence on the loss of total pressure of the diffuser is strong and the maximum loss occurs when the front wall of the shell is located in the pre-diffuser outlet section. However, the change of shell shapes has only small influence on optimal dump gap (for minimum loss of total pressure). In all the test cases, the optimal dump gaps are within D = 40mm and D = 50mm. The experiments also indicate that under certain operating conditions there exist low pressure areas around the head of the flame tube, The external static pressure in these areas can be lower than the pressure in the flame tube. Therefore, any holes in the areas should be placed with great care to avoid reversed flow.
STUDY OF PERFORMANCE OF ROTATING STALL IN BLADE ROW
Liu Zhiwei, Zhu Junjiang, Wang Zhunsheng
1988, 3(1): 18-22,88-89.
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The experimental performances of rotating stall in the blade row of altered geometric parameters are analyzed by use of the flow model and the method providedin Ref.(1). The tendencies that the performances of rotating stall vary with the stagger angles and the solidities are observed. All of blockage ratio, the performance loss and the hysteresis in stall rise with the increase of the stagger angles and the solidities. Both blockage ratio and performance loss in stall for a stage are larger than those for an isolated rotor,but the hysteresis effect of the stage is weakened due to the presence of the stator. The flow model with the active cell structure is discussed and evaluated on the basis of analyzing experimental data. The results show that the features of the active cell model should involve two atpects: (l)the mass interchange between the stall flow region and the unstall one as well as between the stall cells from the outlet to the inlet of the blade row; ( 2 ) the momentum interchange in the tangential direction of the rotor between the fluid in the stall cell and the rotor.
A COMPUTATIONAL METHOD OF EXCITING FORCES GENERATED BY NOZZLE WAKES ON TURBINE BLADES
Liu Ling, Meng Qingji
1988, 3(1): 23-26,89.
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A computational method has been developed to solve the problem of two-dimensional compressible unsteady flow passing through a rotating blade row of turbine. This work aims at determining the exciting forces generated by nozzle wakes on the blades. The numerical results obtained show that the distribution of the exciting forces is different from that of the nozzle wakes.
AN ANALYSTS SYSTEM FOR TRANSONIC FLOW IN CASCADE
Ji Chunjun, Zhou Xinhai
1988, 3(1): 27-30,89-90.
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A Practical analysis system for predicting inviscid blade-to-blade flow and coupled inviscid-boundary layer flow in transonic cascade is presented in this paper. Generally, an analysis system should be as convenient and inexpensive as possible in use. For this purpose, a faster and simpler algorithm using central difference scheme is developed. The difference method adopts a relaxed linear interpolation technique in the y direction combined with the "opposed-difference scheme"proposed by Denton in the quasi-streamline direction. This makes it possible for the algorithm to obtain accurate flow parameters on the blade surface with less mesh points.We found that the scheme can be stable in any case if the relaxation coefficient is greater than one. For calculation of boundary layers over blade surfaces,an integral method which can treat turbulent separating flows is studied. The coupling method of inviscid flow with boundary layer flow is also given in this paper. Several computed results of transonic flows in cascades show good agreement with experimental data. It is anticipated that this analysis system will provide a useful tool for engineering design.
INVESTIGATION ON STEADY-STATE RESPONSE OF A ROTOR-SUPPORT SYSTEM WITH TWO SQUEEZE-FILM DAMPERS
Li Xifan, Fu Caigao
1988, 3(1): 31-34,90.
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The rotor investigated is supported on two major ball bearings with squeeze-film dampers in the absence of the centralizing retaining springs. The coefficients of the film forces are linearized by using dynamical performances of the damper in the fixed coordinate system (four oil-film stiffness and four oil-film damping coefficients). The steady-state unbalance responses of an asymmtrical flexile rotor system has been easily determined by means of transfer matrix and linear iterative methods. Generally speaking, for the rotor system with nonlinear squeeze-film dampers, the optimum damper design with suitable unbalance level of the rotor, i.e. the mass eccentricity e = 0.01cm, will achieve the effect of vibration depression. The calculations show that the effect of vibration depression with two squeeze-film dampers is better than that with one. This conclusion has also been proved by the measured vibration data of a jet engine.
PHOTOTHERMOELASTIC EXPERIMENTAL INVESTIGATION OF TURBINE DISK
Dong Benhan, Wang Ju
1988, 3(1): 35-38,90-91.
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This paper deals with three aspects of photothermoelastic study of the steady thermal stress field on the turbine disk.First of all,the test methods and techniques are investigated. It is necessary to select a suitable model material which will not change mechanical and optical properties within the range of test temperature. In this experiment the epoxy resin is adopted. Then, it is imperative to determine measuring and recording methods oftemperature and to research heating and controlling techniques of temperature field.In this case, the surface of outer edge of the disk is wrapped with heating tapewhich is a polyester film coated by carbon. The temperatures of the model are measured with thermocouples EA2 embedded in the surface or indepth of the model, and are autocontrolled.Secondly, the photothermoelastic experiment and theoretical calculation of aplane disk have been carried out. Both results of experiment and calculation are ingood agreement. It is proved that the methods and techniques proposed can be usefulfor practice.Thirdly, the photothermoelasticity model test of a turbine disk has been completed. The data of the test can be used as a reference for turbine disk design.
OPTIMUM DESIGN FOR PROFILE CONTOUR OF TURBINE DISK
Lin Xiurong
1988, 3(1): 39-42,91.
Abstract PDF(444KB) icon1105 icon376
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A combined optimization method for searching the minimum disk weight and the best disk profile contour is provided which uses the random-walk method and the random-try method alternately. The whole disk profile contour can be linearized by linear segments,and thus the disk can be treated as a series of trapezoid-section ringlets. A subroutine for automatical generation of calculation sections is deveon loped. Taking the disk weight as objective function,the geometric parameters and the axial thickness of the ringlets as design variables, and the five stress criteria as constrains, we applied the combined optimization method to a practical disk and obtained a feasible point within 5-7 minutes on an IBM-PC. After one hour calculation the disk weight has been reduced 12.22%. It is proved that this method increases convergence rate obviously.
HIGH- AND LOW-CYCLE COMBINED FATIGUE AND ITS TEST TECHNIQUE
Liang Guowei
1988, 3(1): 43-46,91-92.
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A simple combined fatigue test facility is introduced, which produces and controls high- and low-frequency combined load spectra by means of a closed circuit consisting of a microcomputer and a hydraulic servo unit. The minor-cycle frequency attains 100Hz with a force amplitude of about 500kg,but higher frequency(say, 400-500Hz) may be attained if a better servo unit be available.About 50 specimens of aluminum alloy LY12-CZ have been tested and the results show that both the minor-cycle frequency and force amplitude have a detri-mental effect on crack initiation life.A ratchetting phenomenon appeared as the minor-cycle frequency was lowered to l0Hz. It is probably a "deformation failure" in this case.
A STUDY ON IGNITION OF SOLID PROPELLANT BY C02 LASER
Ji Qiuying, Li Lu, Zhao Yuanxin
1988, 3(1): 47-50,92.
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Experimental research and theoretical analysis have been carried out by means of a C02 laser as the radiation source to heat the test samples at atmospheric pressure and temperature. The ignition delay of each of the test isamples was measured as a function of radiation intensity. According to the experimental observation and theoretical analysis,a comprehensive model of ignition for composite solid pro-pellant is established which tikes into account the effects of the gas-phase reaction, the oxilizer release, the hetergeneous reaction and the polymer fuel pyrolysis in the depth of the propellant. The results of theoretical analysis come to quite a good agreement with the corresponding experimental data. Both experimental and computational results show that the ignition delay decreases with increasing radiant heat flux. The minimum and the optimum values of heat flux appear to exist. The criterion of ignition is deduced.
AN OPTIMIZATION DESIGN OF ENERGY CHARACTERISTICS OF COMPOSITE SOLID PROPFLLANTS
Tian Deyn, Yang Bin
1988, 3(1): 51-54,92.
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The free energy minimization technique is adopted for calculation of theoretical rocket performance under equilibrium flow conditions. According to optimization theory, the direct search method is employed in combination with a computer program. A composite solid propellant ingredient is chosen for maximum specific impulse and maximum characteristic velocity. The numerical results obtained agree fairly well with the results obtained by graphical method for determining the optimum composition of solid propellant systems.
A DYNAMICAL MATHEMATICAL MODEL AND DIGITAL SIMULATION FOR ANTI-SURGE CONTROL SYSTEM OF A TURBOFAN ENGINE
He Huizhu
1988, 3(1): 55-58,93.
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An anti-surge control system of a certain turbofan engine is taken as an object,the dynamical mathematical model of this system has been developed and the simulation has been done on a digital computer. In the first step of the simulation the linear system is studied and the dynamical performances are calculated under four conditions,thereby the main influencing parameters of the dynamical performances are obtained. In the second step,the effects of nonlinearities of the dead-region and the backlash on the dynamical performances are studied. The digital simulation results indicate that the effects of two nonlinearities on the performances are opposite. The former enhances the relative stability of the system, but the latter reduces that. Both effects appear not to be in agreement with the superposition principle. Finally, the ways of improving the quality of the system are presented based on the results of the calculations.
A MATHEMATICAL MODEL OF TRANSITION CURVE OF VANE PUMP
Song Laisheng
1988, 3(1): 59-62,93.
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For purpose of the computer-aided design and computer-aided manufacture of the transition curve of the dual-purpose vane pump cam ring,a mathematical model of the transition curve is proposed instead of the commonly-used transition contour equation in polar coordinates. The characteristics of different contours can be analyzed, compared and evaluated by means of the mathematical model. The model is advantageous to compiling a generally applicable computer program and favourable for optimum design of the transition contour.
OPTIMAL CONTROL OF A MARINE GAS TURBINE PROPULSION SYSTEM
Ni Weidou, Lu Siqing
1988, 3(1): 63-66,94.
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A design method of"Linear Quadratic Output PI Feedback Control" is proposed in this paper. Amarine gas turbine propulsion system controller has been designed by use of this method. The controller not only has the advantages of the PI controller in classical control theory, but also those of the state-variable feedback in modern control theory. The simulation of this controller gives satisfactory results.
A CONTOUR LINE PLOTTING SYSTEM W|TH POLAR COORDINATES FOR AEROENGINE INLET FLOW FIELD
Wang Zhanxian
1988, 3(1): 67-69,94.
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Three interpolating surface algorithms, i.e. bilinear, biquadratic and circular spline function radial parabolic algorithms,are provided in this programming system. The last of them is considered to be the most ideal one for interpolating surface because it has high accuracy,truly expresses the distorted flow field,and overcomes the unsmoothed joints of the biquadratic algorithm. In order to determine the intersection points between contour and network,rectangular grids of polar coordinates instead of rectangular coordinates are used. In result, many advantages for engine inlet flow field plotting can thus be achieved. This programming system can save computer time and reduce costs.
IDENTIFICATION OF HIGH FREQUENCY SIGNAL UNDER LOW SAMPLING RATIO
Zhang Yisong, Yi Liyan
1988, 3(1): 70-72,94-95.
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Considering that the highest resolving frequncy in dynamic data is restricted by sampling ratio,a new method is proposed to identify the high frequency signal from three low-ratio sampling spectra. The complicated case of vibration measurement ofrotary blades is investigated with error analysis and illustratrated by a numerical example.
DYNAMIC FLEXIBILITY COEFFICIENT MATRIX AND ITS MEASUREMENT FOR AEROENGINE SUPPORTING SYSTEM
Li Zhiwei, Yang Shenji
1988, 3(1): 73-75,95.
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This paper deals with the concept of the dynamic flexibility coefficient matrix and the measuremnt of the coefficients. As an example, the method of the coefficient measurement and the results of the coefficient matrix calculation are given for the supporting system of a twin-spool jet engine. The method and results will be useful for practice.
EQUIVALENT TEST OF PLUNGER FUEL PUMP
Zou Pixian, Xue Jianhua, He Xiude
1988, 3(1): 76-78,95.
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The equivalent test presented in this paper is a technique developed to accelerate the life test. It is achieved by increasing the testing load whereas reducing the test time to make the sample product being tested have approximately the same degree of damage as compared with the main failure mode. The epuivalent formula for this purpose has been deduced from analysis and calculation,and the equivalent test specifications can be thus compiled on the basis of the epuivalent formula.
MEASUREMENT OF RESIDENCE TIME DISTRIBUTION FUNCTIONS OF FUEL IN COMBUSTOR
Lu Xinli, Chen Jie
1988, 3(1): 79-80,95.
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An experimental epuipment for measuring the residence time distribution functions of fuel in combustor has been made, based on the absorption of radiation from a line source at 253.7nm generated by mercury vapour. The residence time distribution functions of fuel both in a main conbustor and a model afterburner under cool conditions have been measured by means of this equipment and have been analyzed.
3D-Computaional Mesh Generation around a Propeller by Elliptic Differential Equation System
Makoto KOBAYAKAWA, Ichiro HATANO
1988, 3(1): 81-86.
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In this paper, an analytic method is applied for the generation of 3D mesh system in order for Navier-Stokes equations around ATP (Propfan). One of the advantages of this method is that mesh lines have strong differentiability. The differential equation used is Poisson type and the right hand side is called control function, and this is able to control the degree of mesh line clustering. Here, the form of control function was contrived to cluster near the solid surfaces. By this method, several mesh lines are laid in the boundary layer above the blade surfaces.
INFORMATON ROR FOEIGN CONTRIBUTORS
1988, 3(1): 96-96.
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General Requirements: Send all manuscripts with covering letter to Wang Zhenhua, Director, Editorial Departmemt, JOURNAL OF AEROSPACE POWER, 37 Xue Yuan Road, Beijing 100083, China. The covering letter should include the author's full name, institution or company affiliation, official title and address. For a Japanese author, it is preferable to write his name in Japanese with Chinese characters too. Signed assurance must be given that the manuscript or its equivalent has not been submitted for publication elsewhere.

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