1991 Vol. 6, No. 3

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EXPERIMENTAL STUDY ON CASCADE SIMILARITY TRANSFORMATION RULES
Zhu Nianguo, Xu Liping, Chen Maozhang
1991, 6(3): 193-198,281.
Abstract PDF(397KB) icon1467 icon91
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In order to verify the similarity transformation rules in real flow situation,two sets of low speed cascades similar to the high speed NACA65 (12)10 and DCA cascades,are designed according to the similarity rules developed by the authors and tested in a two dimensional low speed cascade tunnel.The distributions of pressure coefficient on blade surfaces are measured.The results show that the measured similarity precision is of the same order of magnitude as the design simitarity precision.Therefore further improvement of the similarity precision of blade profiles can be achieved by the improvement of the design similarity precision.
THE NUMERICAL SIMULATION AND ANALYSIS OF PASSAGE VORTICES IN 3-D COMPRESSOR CASCADE
Feng Guotai, Su Jiexian, Yu Guan, Jiao Deyong
1991, 6(3): 199-202,281.
Abstract PDF(308KB) icon1430 icon82
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A simplified numerical simulation method for calculating passage vortices in a compressor cascade is presented,which can reduce computer time and save computer storage.The calculation employs the parabolized N S equiation.In order to analyze and investigate the passage vortices in the compressor cascade,the calculation has been carried out for a divergent curved channel similar to compressor cascade.It can be seen from obtained results that the passage vortices are composed of four parts,the flow behaviour near the suction surface on the both end of the straight compressor stator is deteriorated severely.For this reason the application of curved blades to the compressor is one of important means for improving the end wall flow behaviour.
APPLICATION OF TANDEM BLADES TO AN AEROENGINE
Miao Houwu, Gao jinman, Guo Jie
1991, 6(3): 203-206,281.
Abstract PDF(310KB) icon1938 icon71
Abstract:
A set of tandem blades with BC 6 profile has been designed and manufactured for a development program to modify an aeroengine.In order to demonstrate the advantages of the tandem blades,the tests have been conducted in cascade wind tunnel,at compressor test stand and on engine bed,respectively.The cascade test data show that the total pressure loss coefficient for the tandem blades is 0 0305,but it is 0 0348 for the single row of blades at the same design conditions.The range of efficient incidence angle for the tandem blades is 31 2% larger than for single row blades.As compared with the compressor of the single row blades,the tandem blades compressor test results indicate that its adiabatic efficiency is enhanced 1 3% and its surge margin is enlarged 2 8% at the design speed and the design pressure ratio.The engine tests also prove that the operation line of the aeroengine with the set of tandem blades is farther from the compressor stall line.The paper describes how to select the tandem blad parameters and how to obtain the optimum axial and tangential distances between the two rows of this tandem cascade from the test data.The paper also considers the feasibility of the tandem blades in the aeroengine to expand its range of stable operation.
ANALYTICAL METHOD FOR SUBSONIC CASCADE PROFILE
Liu Bo
1991, 6(3): 207-210,282.
Abstract PDF(634KB) icon1358 icon84
Abstract:
A method of subsonic cascade design for axial flow compressor is provided as follows.The equations of continuity and quasi irrotationality are transformed into the potential stream function coordinates.Then a Laplace equation can be deduced for an aerodynamic parameter“Q”.The boundary conditions thereby are given as the distributions of velocity coefficients on the stagnation streamlines of both suction and pressure sides of a flow channal.The flow field is obtained from the analytical solution of the Laplace equation.Subsequently the field is turned back into the physical plane by diffierentiation and integration.Then the blade profile coordinates and the geometry of the cascade result from this analysis.The method has an advantage over other inverse methods in the fact that the flow field parameter“Q”can be easily obtained from the analytical solution of the Laplace equation instead of the numerical solution of a complex diffierential equation.So the method is easy to be programmed and to save computing time.To illustrate the validity of the design method,two compressor stator blade profile with subsonic inlet Mach number were designed and compared with the method presented in ref.[3].The good agreement between the two methods show the applicability of this method.
AN EXPERIMENTAL STUDY OF 3-D FLOW IN A CASCADE
Ji Chunjun, Zhu Zhuguo, Liu Qianzhi, Zhou Xinhai
1991, 6(3): 211-215,282.
Abstract PDF(644KB) icon1397 icon85
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An experimental investigation of three dimensional flow in a cascade has been accomplished by means of flow visualization and detailed measurements,and also compared with the predictions of fully three dimensional inviscid flow calculation.The experimental measurements of the three dimensional flow in a highly cambered compressor cascade with nonplanar end wall reveal the distributions of flow parameters on blade surfaces and the whole flowfield in cascade channel.In comparison with the two dimensional cascade measurements for the same blade section,the results show that the influence of the end wall shape changing on the flow is not confined to the vicinity of end walls,and can extend to the whole field when the aspect ratio of blading is small.The comparison between the experimental data and the computational results confirms that the inviscid flow calculation can predict the major features of three dimensional flow in cascades.The flow visualization reveals the formation and development of vortex systems in the cascade passage,end wall and corner regions,which serve as a visualized information to understand the phenomena of complicated secondary flow in cascades.The experimental measurements provide a reliable basis to perfect the flow models,to investigate the mechanism of spanwise mixing in a cascade and to testify the capabilities of fully three dimensional cascade flow calculation methods.
EXPERIMEATAL INVESTIGATION OF A SMALL TWO-STAGE TRANSONIC AXIAL COMPRESSOR
Li Liangming
1991, 6(3): 216-218,286.
Abstract PDF(244KB) icon1724 icon88
Abstract:
A small dimension two stage transonic axial compressor has been designed with blade tip veloicty 436m/s and design revolution 45000r/min.Its tests has been carried out to investigate the performance of this compressor.It is shown that its performance attains or exceeds its design specifications.This paper also considers the effects of radial and axial clearances,probe blockage,step matching and measuring techniques on the performance of the compressor.
NUMERICAL STUDY OF END-WALL BOUNDARY LAYER AND BLADE FORCE DEFECT IN CASCADES
Wu Hu, Liu Songling, Chen Fuqun
1991, 6(3): 219-221,286.
Abstract PDF(259KB) icon1273 icon75
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A detail research has been completed for calculation of end wall boundary layers within an axial compressor cascade.A new calculation model for blade force defect is proposed,which is associated with development of primary flow and transverse flow.A unique feature of this method lies not only in capability to calculate the development of end wall boundary layers inside the cascade passage without any assumption about the exit of cascade,but also in ability to take into account the influecnce of its tip clearance.The calculational results of three heavily loaded cascades show that this model is superior to other existing models.
NUMERICAL STUDY OF VISCOUS FLOWS IN COMPLEX GEOMETRIES
Shi Feng, Xu Zhong, Miao Yongmiao
1991, 6(3): 222-224,288.
Abstract PDF(252KB) icon1552 icon76
Abstract:
The program SIMPLEC has been adopted to calculate the viscous flows at all Mach numbers inside a plane cascad and nozzle.In order to tread both incompressible and compressible flows,pressure is chosen as a primary dependent variable in preference to density.The effect of the pressure on the density is implicitly included in the pressure correction equation.Further,the covariant velocity components are chosen as the dependent variables in the momentum equations,which makes the pressure velocity coupling relatively easy to handle.Comparison of the calculated results with the experimental data show that the present method exibits much better stability and covergence behavior,and is applicable to a variety of the incompressible and compressible flows,ranging from subsonic to supersonic.
COORDINATION OF α、βCOEFFICIENTS WITH k COMPLEXES FOR VARYING SPECIFIC HEAT SOLUTIONS
Cui Jiya
1991, 6(3): 225-226,288.
Abstract PDF(212KB) icon1279 icon75
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Three complexes ε T,ε, ε v of k are introduced to simplify the original expressions of gasdynamic functions with k of varying specific heats and their analytical solutions,and to unite two other forms of gasdynamic functions using coefficients α of β so that the calculations and applications at higher temperatures could be more convenient.It is clarified that the effect of varying specific heats reflected through k is the essence of these functions.The different sets of formulae are also briefly compared and analysed for reference in engineering applications.
STABILITY ANALYSIS OF A RIGID ROTOR ON SFDB WITHOUT A CENTRALIZING SPRING
Zhang Jiaxin, Xue Zhongqing
1991, 6(3): 227-232,282-283.
Abstract PDF(444KB) icon1529 icon87
Abstract:
The stable nonsynchronous responses and the stability of motion of a rigid rotor supported on squeeze film damper bearings(SFDB)without a centralizing spring are studied by means of harmonic balance method.The motion of the system is approximately simulated by two coupled second order differential equations.The stable nonsynchronous response at the action point of nonlinear oil film force can be obtained from the periodic solution of the differential equations of motion.With the help of an equivalent linearized model of the oil film force,the equivalent dynamic characteristic coefficients corresponding to the determined motion of the original system are obtained.A new method to analyse the stability of the motion of the equivalent linearized system is put forward in detail according to the theory of small pertubation.It is quite interesting to point out that the derived criterion for the motion stability is simple in form and depends on the equivalent damping coefficients only.A system with 1/2 order subharmonic response is taken as an example to illustrate this method.The calculated results are compared with those of fourth order Runge Kutta method.It is shown that our method has the same accuracy of calculation,but gains an advantage in saving computing time.
DYNAMIC ANALYSIS OF CENTRIFUGAL IMPELLER
Zhang Jin, Chen Xiangjun, Wang Wenliang
1991, 6(3): 233-238,283.
Abstract PDF(447KB) icon1264 icon93
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A dynamic analysis technique is provided for rotating centrifugal impeller with guide blades and split blades.It is shown that multi component partition can be made in repetitive sector region of the centrifugal impeller.The basic repetitive sector region of the centrifugal impeller is divided into three substructures:the guide blade,the split blade and the sectoral part of the disc.The Hermite generalized mass and stiffness matrices in the reduced coordinates are derived by successful combination of Benfield mode substitution transformation with group transformation.Therefrom the natural frequencies of the bladed disc coupled system are solved and the corresponding modal shapes are obtained from further transformation.The comparison between the analytical results obtained by using this and other methods and the experimental data verifies the reliability,practicability and considerable economic benefits of the method pressented in this paper.
ESTIMATION OF HIGH TEMPERATURE CREEP PARAMETERS FOR STRUCTURAL CERAMICS
Yang Xiaoguang, Ding Jun, Xiong Changling
1991, 6(3): 239-243,283-284.
Abstract PDF(420KB) icon1364 icon80
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Power law high temperature creep parameters of structural ceramic materials are commonly deduced from load point displacement data obtained form bend tests on the assumption that tensile and compressive behaviours obey the same constitutive law.However,it is now well recognized that this premise may not always be valid because of microcracking and cavitation.Meanwhile,former methods of creep parameters estimation are not suitable,due to a demand for many CPU time.Therefore,a new optimal estimation method is proposed for the structural ceramic creep parameters.Its governing equations are derived from non coincidence of the neutral axis of a beam under bending with the cenctroids of the cross sections,and from the creep response in terms of both curvature rate and load point displacement rate as functions of the applied moment and creep parameters.Numerical solution of the governing equations is completed with golden section method.In order to obtain optimal estimation of the creep parament,a static optimal calculation program is used which turns the constrained minimum problem into an unconstrained minimum problem by penalty function.Then the problem is solved with variable matrix method that includes both DFP method and BFGS method.An example is given for a set of load point displacement data of sintered nitride silicon beam specimens crept at 900℃ and 1200℃ from three point bend tests.The results show that the conventional method overestimates or underestimates the creep rates in compression or tension,and the more accurate analysis presented here is needed.
CALCULATION OF MODAL CHARACTERISTICS FOR A PROPELLER-GEAR BOX-ENGINE COUPLE SYSTEM
Gu Zhongquan, Wang Yuanda
1991, 6(3): 244-248,284.
Abstract PDF(343KB) icon1881 icon86
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In this paper the calculation problems of modal characteristics are studied for a propeller gear box engine system considering the flapwise and lagwise flexibilities,the pitch angle of the blalde and the coupling of torsional vibration with longitudinal vibration.The experessions suitable for computer are deduced for calculation of the modal characteristics.An numerical example for a propeller gear box engine system demonstrates that the method is reasonable and feasible.
IMPROVEMENT IN SOLUTION OF EIGENVALUES WITH TRANSFER MATRIX METHOD ON COMPUTER
Li Yan
1991, 6(3): 249-250,286-287.
Abstract PDF(683KB) icon1328 icon76
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A measure is taken based on secant method and tangent method to improve the computational method of eigenvalues with transfer matrix method on computer.In the new measure the references for searching the eigenvalues are the first k th powers of the eigen determinants(where k is larger than 1 0)instead of the determinants themselves,and the searching formulas of the existing method are modified correspondingly.As the range of the references for searching the eigenvalues is reduced considerably,the phenomenon of numerical overflow is eliminated forever.
J-INTEGRAL FOR2-D VARIABLE-THICKNESS PLATE
Hong Qilin, Wang Ge
1991, 6(3): 251-253,287.
Abstract PDF(247KB) icon1781 icon81
Abstract:
The formula of a J integral presented by J.R.Rice is extended to problem of 2 D variable thickness plates.The extended J integral formula is derived in terms of the path independent.Then the integral conservation is verified by using finite element method.At last,the calculation results for some variable thickness plates made of photoelastic material are compared with their photoelastic test data,and the differences between them are less than 4%.It is proved that the extended J integral formula for the 2 D variable thickness plates is path independent and can be taken as a fracture pamarater for damage tolerance analysis.Furtheremore,this integral can be solved numerically by using 2 D general finite element programs.It is therefore of practical value for the fracture analysis of Ⅰ mode cracked plate with thickness which does not vary too mueh.
DIGITAL REAL-TIME SIMULATION OF A TWIN-SPOOL TURBOJET
Liu Shangming, Wang Xueyu, Zhu Xingjian
1991, 6(3): 254-258,286.
Abstract PDF(620KB) icon1820 icon94
Abstract:
A digital real time simulation by means of single micro computer has been developed for an actual two spool afferburning turbojet engine.In order to overcome the contradiction between the computation precision and the speed necessary to digital real time simulation technique,the characteristics of engine components have been reasonably simplified and modified and 80286 macro assembly,80287 float arithmetic parallel processing method and some programing techniques have been adopted.A non linear,large deviation digital real time simulation has been obtained.The results of this simulation are comparaed with the measured data.It is shown that its calculation accuracy and speed are suitable for the real time simulation.
DESIGN AND EXPERIMENTAL STUDY OF A COMBINED PILOT FLAMEHOLDER
Cheng Qiufang
1991, 6(3): 259-262,284.
Abstract PDF(302KB) icon1617 icon81
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The design and experimental study of a combined pilot flameholder is presented for a turbofan engine afterburner with an annular mixer.The combined pilot flameholder is composed of a main ingestion gutter ring with corrugated slots and radial finger gutters with ingestion holes.The two dimensional and double stream flow visualization tests of its reduced scale model demonstrate the flow pattern hehind the flameholder,and also reveal the reason,why the annular pilot burner can ignite and support the bypass flow flame.Its sector rig tests and engine bed tests show that the afferburners with this kind of flameholder possess enhaneed combustion efficiency,improved combustion stability and reduced pressure loss at both normal and low pressures.
EMPIRIC FORMVLAE COMBUSTOR FLOW LOSSES
Gu Mingqi
1991, 6(3): 263-266,284.
Abstract PDF(289KB) icon1691 icon81
Abstract:
Approaches to calculation of the flow losses in compoments of the combustor,such as diffuser,swirler and flame tube,and the flow losses in combustor under combustion conditions are investigated.The empiric formulae are derived from tests.They feature simplicity and sufficient accuracy and are applicable to design and redesign of combustor.The tests were conducted on the models of 4 types of diffusers,10 kinds of swirlers 7 types of flame tubes and,7 simulators of inlet flow field distortion.In comparison with the existing methods,the presented method considerably improves the calculation of the flow losses in the diffuser.For the swirler the correlation between flow resistance and the discharge coefficient and the formula for heating losses are also found out.
AN EXPERIMENTAL INVESTIGATION OF HYDROGEN-AIR SUPERSONIC COMBUSTION
Liu Ling, Zhang Zheng, Tang Ming, Liu Jinghua, Yang Lixing, Wang Juzheng
1991, 6(3): 267-270,285.
Abstract PDF(318KB) icon1901 icon82
Abstract:
The experimental results of Hydrogen fueled supersonic combustors are considered.Tests were conducted with arc heated air at inlet Mach number 2 1,total temperature 2100K,total pressure 7×10 5Pa.The axisymmetric combustor with inlet of 4 6cm inner diameter has been investigated with hydrogen injected normally or parallelly to air stream from a ring of equally spaced holes on the wall.The combustor comprised assemblies of cylindrical and diverging conical sections on which are mounted static pressure taps and thermocouples.The total pressure profiles were measured by a pressue probe rake just downstream of the combustor exit.Each fuel injection persisted about 8 seconds to obtain steady state operiating conditions.The preudo one dimensional flow analysis of supersonic combustor has been improved and employed to yield a description of the bulk processes in the supersonic combustor and to explain the characters of the measured pressure distributions.The results of a series of tests show that the combution efficiency of the transverse injection ahead of a rearward facing step is higher than behind it,and the combustion efficiency of transverse injection is higher than that of the downstream injection,and it is also evident that the total pressure loss is maximum in the case of transverse injection ahead of a rearward facing step and is minimum in the case of parallel injection.
COMBUSTION PROCESSES OF HYDROGEN IN A SUPERSONIC AIR FLOW
Yang Aikuo, Liu Ling, Wang Hongji
1991, 6(3): 271-272,287.
Abstract PDF(227KB) icon1500 icon77
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According to the implicit numerical integration method proposed by Tyson.J,an improved computer program for pseudo one dimensional flow of combustion kinetics is developed with the aid of a chemical kinectic model with 12 species and 31 reaction.Variations of temperature,prssure,Mach number and mass fraction of chemical species in a supersonic combustion model are studied in detail.The results of scramjet combustor conditions corresponding to flight Mach numbers 6,10 and 15 show that chemical reaction rates decrease at rather low temperature and pressure at a combustor inlet and there is not enough time to ignite the mixture gas in the combustor at very high Mach number,in result the performance limits of scramjet kinetic combustion occur.
CHARACTERISTICS OF DUAL SWIRLERS SPRAYER DEVICE
Chen Hong, Chin Jushan
1991, 6(3): 273-274,287.
Abstract PDF(227KB) icon1395 icon75
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The spray characteristics of dual radial swirlers mixing cup sprayer device have been investigated with the aid of Malvern laser granulometer and checked the differences of its spray characteristics from those of the pressure atomizing fuel nozzle.Two air flow proportions of the first swirler to the second one are 50%∶50% and 30%∶70%.The airflow velocity at the exit section has been designed in the range 37 to 74m/s.In the tests the fuel pressure ranges from 2 94 to 4 41×10 5Pa.The test results show that in the case of reasonable design,the sprayer device is able to provide better spray characteristics than pressure atomizing fuel nozzle.
AN INVERSE COUPLED HEAT TRANSFER METHOD FOR THERMAL CONDUCTIVITY SEMI-TRANSPARENT MATERIAL
Tan Heping, Yu Qizheng, Lallemand Michel
1991, 6(3): 275-278,285.
Abstract PDF(318KB) icon2000 icon65
Abstract:
An inverse problem method of transient combined radiative conductive heat transfer is proposed to determine the thermal conductiviity of non gray semi transfarent material is proposed on the basis of the laser impulse method for the non transparent material.The one dimensional semi transparent sample with black interfaces is submitted to an external rectangle pulsed irradiation and the temperature response occurs in the sample.There are two peaks in the temperature response of non incident surface.The thermal conductivity can be determined by this method,provided to temperature responses at the two surfaces are measured and the radiative properties of semi transparent material are known.The control volume mothod and the spectral band model are used in the numerical calculation.The divergence of radiative flux is treated as the source term of the energy equation.In the inverse problem method the golden section method is applied to searching for the optimum of the solution.The temperature response of the non irradiated surface is taken as a given condition and the temperature response of the irradiated surface as a restricted condition.Two cases are considered,i.e.the case of constant thermal conductivity and the case of thermal conductivity varying with temperature in a linear relation.The numerical simulation has been carried out.It is proved that this method is feasible.The influences of the searching region and the measurement errors are also discussed in this paper.
RESEARCH ON DISCHARGE COEFFICIENT OF COOLING HOLES ON FEEDER TUBE
Wu Dingyi, Xu Duchuen, Liu Songling, Deng Jinsong
1991, 6(3): 279-280,288.
Abstract PDF(234KB) icon1494 icon96
Abstract:
The main air flow supplied in the feeder tube is delivered to cooling holes with axis perpendicular to the main flow.This crossflow pattern exerts a significant influence on the hole discharge coefficient.The experimental investigation of the hole discharge coefficients and the measurement of static pressure distribution along the tube axis have been completed.It is shown that the discharge coefficient increases as the ratio of the orifice thickness to diameter and the velocity head ratio between orifice flow and tube flow increase.But the discharge coefficient approaches to a constant when the velocity head ratio is greater than 100.Empirical formulas have been dedueed from the experimental data.The static pressure distribution along the tube and the air flow rate allocation for the holes have been calculated by using the general air system computer program developed by author.The results ageree with the experimental data well.

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