1986 Vol. 1, No. 1

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INVESTIGATION ON STEADY-STATE RESPONSE OF ADUAL-ROTOR SYSTEM WITH INTER-SHAETSQUEEZE-FILM DAMPER
Yan Litang, Li Qihan
1986, 1(1): 1-6,87.
Abstract PDF(589KB) icon5680 icon1575
Abstract:
An analysis of the steady-state unbalance response of a dual-rotor gas turbine engine with a nonlinear flexible intershaft squeeze-film damper is implemented using a simplified transfer matirx method with rotating coordinates.The simplified transfer matirx method is convenient for evaluation of the critical speed and the steady-state response of the rotor system with various supports, shaft coupling, intershaft bearing, etc. The rotating coordinates are simpler than the fixed Cartesian coordinates for calculation of oil film force generated by the centralized squeeze film damper. The nonlinear characteristcs of the squeeze film damper are calculated by using iteration method.The introduction of a flexible intershaft squeeze film damper into the rotor system is effective in reducing amplitude response and bearing loading, especially at the location of the intershaft bearing and adjacent rotor bearing supports.
EXPERIMENTAL AND THEORETICAL INVESTIGATION ON AN UNCENTRALIZED SQEENE-FILM DAMPER
Feng Xinhai, Fu Caigao, Xu Shian, Li Xifan
1986, 1(1): 7-10,87-88.
Abstract PDF(590KB) icon4797 icon1647
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The squeeze-film dampers on model rotors and a real jet are studied experimentally and theoretically. It shows that it is possible to minimize the unbalance forces transmitted to the surrounding structure and the disc amplitude and to bring great potential of damper attenuation capability into full play if only the parameters of an uncentralized squeeze-film damper are chosen carefully. Generally speaking, the optimum damper design will achieve a reduction invibraton of 60% or more.A design method of uncentralized squeeze-film dampers is also recommended, which gives the bearing parameter B = 0.1 to 0.2 and the gravity parameter W = 0.05 to 0.1. The theoretical results and the experimental data have been found in good agreement.
LOW CYCLE FATIGUE LIFE TESTING RESEARCH OF AN AEROENGINE CASE
Pu Ruigang
1986, 1(1): 11-14,88.
Abstract PDF(397KB) icon5827 icon1537
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This paper presents in detail the method of low cycle fatigue life testing research on engine cases in connection with the following aspects, the determination of standard cycle load, testing samples and the design of its connection, stress testing and cycle testing under the synchronously loaded conditions at several points of a fully-sized case, the determination of approved cycle life and usage life.
MASS TRANSFER EXPERIMENTAL STUDIES ON THEFILM COOLING EFFECTIVENESS OVER THECONVEX SURFACE WITH DOUBLE-ROWDISCRETE HOLES
Yao Yongqing, Xia Bing, Ge Shaoyan, F.K.Tsou
1986, 1(1): 15-19,88-89.
Abstract PDF(514KB) icon4398 icon1430
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The distribution of film cooling effectiveness for staggered double-row discrete holes has been measured extensively over the whole area of convex surface. It has been found that whether or not the blowing ratio of first row is equal tothat of the second one, higher blowing ratio causes stronger separation of the film jet, the cooling effect is thus reduced remarkably, and the optimized value of the blowing ratio for better film cooling effectiveness is M≤0.5.Experimental results show that for convex surface the blowing ratio of first row should be smaller than that of second row in order to get better cooling results, for example Mf=0.3. The distance between cooling holes as well as the blowing ratio M should be both smaller on the convex surface.
DIMENSIONLESS PARAMETERS ON ENHANCED HEATTRANSFER IN FLUIDS BY HIGH-FREQUENCYOSCILLATIONS WITHIN PIPES
Zhao Lingde, Cao Yuzhang
1986, 1(1): 21-25,89.
Abstract PDF(420KB) icon5188 icon1491
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Enhanced heat transfer in fluids by high-frequency oscillations within a capillary bundle is a new interesting phenomenon. A new method to describe this phenomenon has been developed. Authors have obtained the same dimensionless expression by means of three different methods, experimental data analysis,dimensionless analysis of differential equations and transformation of laminar hydrodynamic theoretical expression. It shows that the ratio of the effective thermal conductivities to normal conductivities of fluids is proportional to a certain power of Prandtle number, second power of the ratio of tidal displacement to capillary radius and nearly first power of Womersley number. This dimensionless expression is convenient for calculating and experimenting.
APPLICATION OF A TWO-DIMENSIONAL LASERDOPPLER ANEMOMETER TO MEASUREMENTIN DIFFUSION FLAME
Ma Jieping, Lin Qixun, Du Qinfang, Xiao Ningfang
1986, 1(1): 27-30,90.
Abstract PDF(469KB) icon8699 icon1853
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The flow field of liquified petroleum gas (LPG) -air diffusion flame in a small scale combustion system was measured with a two-dimensional laser Doppler anemometer(LDA). In order to reduce loss of laser output the forward scatter receiving mode was employed.For this reason, the back scatter receiving optical system of two-dimensional LDA from DANTEC company was modified. The practice shows that the forward scatter receiving mode reduces the loss of laser output by a factor of 2 or more,the Doppler signals received are satisfactory.A self-made solid particle generator was used to increase data rate. Solid particles of magnesium dioxide were chosen as scattering particles. The tests verify that this approach is suitable for LDA measurement.
GROWTH OF SECONDARY FLOW LOSSES DOWNSTREAM OF A TURBINE BLADE CASCADE
Chen Lide
1986, 1(1): 31-36,90.
Abstract PDF(754KB) icon4259 icon1491
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End-wall total pressure losses downstream of a low-speed turbine cascade have been measured at several planes in order to determine the changes in secondary flow loss coefficients and the growth of the mixing loss with distance downstream.The results obtained are compared with various published secondary flow loss correlations in an attempt to explain some of the anomalies which exist at present. Some new correlations have been derived which include the important one for gross secondary loss coefficient Ysg in terms of loading and aspect ratio as well as the upstream boundary layer parameters.In the present work a small Kiel probe closely connected to a small pressure transducer was used. The probe was controled by a computer to traverse rapidly across the exit flow in order to determine the variation in pitch-averaged total pressure loss coefficient along the span and with distance downstream.
EXPERIMENTAL INVESTIGATION ON COMPRESSOR STATOR TANDEM CASCADES AT HIGH SUBSONIC SPEED
Zhuang Biaonan, Guo Bingheng
1986, 1(1): 37-40,91.
Abstract PDF(413KB) icon11351 icon1944
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The experimental results of a certain compressor stator tandem cascade (abbreviated as C-cascade) which profile is approximate to C-4, and a double circular are tandem cascade at high subsonic speed are presented in this paper. These two types of cascade were tested in a cascade wind tunnel at free stream Mach number Ma1 =0.55 to 0.75 and incidence angles I =-5 to +7.5. The experimental results are illustrated as plots of the variations of air-turning angle △β, static pressure rise coefficient cp and total pressure loss coefficient w against incidence angle I. The optimum values obtained for both tandem cascades are as follows (for Maj 0.7):C-cascade 0° 57.7°0.106 0.31double circular 0° 54° 0.136 0.35
TRANSIENT OPERATING LINE INDICATOR AND ITS APPLICATION
Wang Zongyuan, Fang Jinyan
1986, 1(1): 41-46,91-92.
Abstract PDF(564KB) icon10713 icon1898
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A special instument is presented for monitoring the transient process in a turbojet engine, which is called "transient operating line indicator". The instrument consists of analog computing circuits. It demonstrates the real-time flowrate and the pressure ratio of the engine which are calculated from the total pressure and the static pressure at the inlet and the total pressure at the exit of the compressor. By means of this instrument the transient operating line of the engine can be plotted with an x-y recorder. The description, the circuits and the performance of this instrument are given in this paper. The various transient processes of turbojet engine, such as acceleration, deceleration and surge, have been studied with this instrument.
A THEORY OF COMBUSTION EFFICIENCY COMPUTATION FOR LIQUID ROCKET ENGINE COMBUSTOR
Chen Xinhua, Zhuang Fengchen
1986, 1(1): 47-52,92.
Abstract PDF(586KB) icon4583 icon1679
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A mathematical model describing combustion in a high pressure liquid hyper-golic bipropellant(UDMH/H2O4) rocket engine combustor has been developed. In this model, the droplet evaporation process at high ambient pressure has been considered,which takes into account the droplet surface regression, the transient heating, the effects of ambient pressure on vapor-liquid equilibrium, the effects of nonideal gas behaviour, the dissociation of N2O4 and the decomposition of UDMH. The gas temperature variation has also been considered which is dependent on the local mixture ratio, the drop-size distributions and the effects of the convergent section of nozzle on the vaporization rates.Since the mechanism of the droplet secondary breakup process is different under a large flow flux,a new secondary breakup critical condition is proposed.The application of this mathematical model to different operating conditions of a specific rocket combustor is provided. The calculated results are in good agreement with experimental data. This model correlates the combustion process with the engine structure parameters, the operating parameters and the properties of the propellant. Therefore, it may be used as a guideline and a theoretical prediction for designing rocket engine combustor.
NUMERICAL SOLUTION OF A FULLY-COUPLED MODEL OF ONE-DIMENSIONAL TWO-PHASE NOZZLE FLOW
Wang Huiyu, Zhang Yuanjun
1986, 1(1): 53-58,93.
Abstract PDF(505KB) icon4052 icon1435
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A numerical method for calculating a fully-coupled model of one-dimensional two-phase nozzle flow is described in brief. Governing equations are derived. The Runge-Kutta-Gill method is adopted to solve the equations numerically. The solution for uniform acceleration of gas phase is utilized as an approximate solution for the dimensionless distance x*(=x/L) = 0 to 0.02,i.e.ug = ax*. The initial value of a is determined by a trial and error approach and then checked at the throat. The solution is continued to the throat where the conditions must be satisfied. To eliminate the singularity of the equation, a superseding variable is introduced. The computations are performed for velocity-lag as well as temperature-lag of five parsticle sizes and two ratios of particle to gas flow rates.Temperature, pressure and velocity distributions of both gas and particle along the length of the nozzle are also obtained.In addition, various modes of one-dimensional two-phase nozzle flow have also been briefly reviewed.
DIMENSIONLESS ANALYSIS OF LIQUID IMPINGINGPLANE FILM
Chen Jie
1986, 1(1): 58-96.
Abstract PDF(179KB) icon4512 icon1392
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Seven nondimensional parameters which describe the liquid phase mixing phenomenon of a pair of liquid plane impinging streams produced by two plane slot injectors are determined under specific conditions.
DOMINANT FACTOR METHOD FOR ANALYZING DYNAMIC BEHAVIOUR OF GAS TURBINE
Ni Weidou, Xu Xiangdong
1986, 1(1): 59-62,93-94.
Abstract PDF(494KB) icon9450 icon1766
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A new proposal-dominant factor method-for analyzing the dynamic behaviour of gas turbine is suggested by utilizing the results of field identification by pseudo random binary signal and combining with the theoretical analysis. The basic concept can be stated as follows.though the dynamic behaviour of gas turbine is different for each operating point,one of the parameters of the gas turbine can be selected as the dominant factor dictating its dynamic response. This parameter is the partial derivative of air flow rate Gc versus speed of the gas generator rotor n1, that is (dGc/dn1) in the compressor chart. Therefore, it isreadily to establish the simplified mathematical model of gas turbine as a nonlinear system. At first,we calculate the linear model for the design point, and then in accordance with the variation of this dominant factor the dynamic model for the other operating points can be approximately determined (for steady and unsteady regimes). The feasibility of this method is proved by experiment.
INTEGRATED DYNAMIC MODEL OF TWO-VARIABLE SUPERSONIC INLET-ENGINE COMBINATION
Yang Jianbo, Guan Yanshen
1986, 1(1): 63-68,94.
Abstract PDF(590KB) icon4018 icon1357
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An integrated dynamic model of a two-variable (normal shock position and engine speed) inlet-engine combination is formulated on the basis of the idea in author’s former paper, but the effect of engine flow feedback on the inlet during transient period is taken into consideration and the matrix fraction description method is applied to transforming frequency domain into state space domain in the model. The results of a sample digital simulation for NASA 48cm inlet-J85 engine combination show that the method of formulation is satisfactory.
DEVELOPMENT OF HIGH BY-PASS RATIO TURBOFAN ENGINES
Chen Guang
1986, 1(1): 69-75,94-95.
Abstract PDF(1229KB) icon11690 icon1916
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The development of the second and the third generations of high by-pass ratio turbofan engines,as well as the technical measures for improving the performance of engine,are summarized and reviewed in this paper. Compared with their predecessors,the second and the third generations of high by-pass ratio turbofan engines have much lower SFC,fewer parts, lower rate of performancedeterioration and superior maintainability and reliability as well as some other advantages. To achieve this,a lot of significant advanced technologies have been developed and put in practice which are presented in brief in this paper. Finally, some remarks on aeroengine development in China have been made.
A STUDY ON FATIGUE CRACK PROPAGATIONSUPERIMPOSING HIGH CYCLES ON LOW CYCLESFOR TURBINE MATERIALS
Tu Bailin, Niu kangmin, Wang Zhangan, Yan Minggao
1986, 1(1): 76-78-95.
Abstract PDF(331KB) icon4742 icon1521
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The crack propagation under combined fatigue superimposing high frequency vibration with lower amplitude on low cycles with higher amplitude and its fractographic features for GH36 alloy are studied. Experimental results show that the high cycle damage will be a main factor when the amplitude ratio of high cycle to low cycle is larger than 0.98. Then,the surface deformation just ahead of the crack tip is decreased,each wide striation consisting of a number of parallel sub-striations produced by vibration stress and the cyclic hardening are increased. In this case,assessing of the FCG rate is basically independent of the LCF damage.
EXPERIMENTAL INVESTIGATION ON HEAT TRANSFER CHARACTERISTICS FOR ARRAYS OF CIRCULAR JETS IMPINGING ON CURVILINEAR SURFACE WITH CROSSFLOW AND EJECTION HOLES
Li Liguo, Chang Haiping
1986, 1(1): 79-81,95-96.
Abstract PDF(382KB) icon3934 icon1370
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The effects of curvilinear surface with ejection holes on the internal heat transfer coefficient of arrays of impinging have been investigated for simulation of the impingement cooled turbine vanes. The experiments show that boththe curvature of the surface and the presence of the ejection holes are in favour of the heat transfer augmentation. It is noted that the internal impingement heat transfer coefficient on the suction side of the cooled blade calculated by using the correlation of that on flate plate is more or less too conservative.
APPLICATION OF THE UPWIND FACTOR METHOD TO SOLUTION OF INCOMPRESSIBLE NAVIER-STOKES EQUATIONS IN NON-ORTHOGONAL CURVILINEAR COORDINATE SYSTEM
Wang Licheng, Zhang Huimin
1986, 1(1): 82-84,96.
Abstract PDF(347KB) icon4499 icon1304
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The upwind factor method has found successful application in the finite element scheme. The purpose of this paper is to extend its application to solution of incompressible Navier-Stokes equations in non-orthogonal curvilinear coordinate system by the finite difference method. An effective velocity is introduced to keep the control equations in the computational domain as simple as in the physical domain.

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