1993 Vol. 8, No. 4

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AN FEM FOR NEARLY-INCOMPRESSIBLE VISCOELASTICITY AND ITS APPLICATION IN PROPELLANT GRAIN STRESS ANALYSIS
Wang Yuanyou, Wang Xinhua, Hu Yafei
1993, 8(4): 313-317,415.
Abstract PDF(334KB) icon2092 icon435
Abstract:
Since solid propellant exhibit nearly-incompressible material behaviour,the displacement formulation of the finite element method is unable to give acceptable solution to mechanical problems of these materials.This paper introduces a new constitutive relation based on Herrmann variational theorem for incompressible and nearly-incompressible viscoelasticity.The corresponding finite element formulation is presented here and a computer program VFAPINP is developed for solution to plane problems.The results show that the approach and the computer program are valid for stress analysis of viscoelastic materials with all admissible values of Poisson′s ratio and particularly for the propellant grain stress analysis.
THREE-DIMENSIONAL FLOW FIELD INSIDE COMPRESSOR ROTOR TIP REGION AT NEAR STALL CONDITION
Ma Hongwei, Jiang Haokang, Li Yuchun
1993, 8(4): 318-322,415.
Abstract PDF(303KB) icon1564 icon486
Abstract:
The three-dimensional flow field inside the tip region of a low speed large-scale axial-flow compressor rotor at near stall condition was measured with the help of a five-hole conical probe drived by a rotating four-coordinate probe traverse mechanism.Results indicate that,radial migration of boundary layer of blade suction surface is strong,which induces a vortex nearby,flow separation appears on the blade suction surface,a blade scraping vortex exists in the corner of the blade pressure surface,strong mixing occurs between boundary layers of the pressure surface and the suction surface at median part of the rotor passage,which leads to substantial deficits of total pressure and axial velocity.All of these forms a complicated flow field in the rotor tip region.
EXPERIMENTAL STUDY ON ENGINE PERFORMANCE AND INTERNAL FLOW FIELD UNDER INLET DISTORTION
Li Wenlan, Huang Zhitao, Hu Zhengfeng
1993, 8(4): 323-327,415.
Abstract PDF(304KB) icon1740 icon434
Abstract:
A turbojet engine has been tested under the conditions of a series of screen-induced inflow distortion.Its compressor interstage flow field (static pressure,total pressure and total temperature),inlet distortion transmission,temperature field at turbine outlet and bed-tested engine performance were measured.The measurements indicate that:the inlet total and static pressure distortions are attenuated through the stages,the inlet total pressure distortion induces total temperature distortion at the compressor outlet,the inlet pressure distortion reduces the engine thrust and increases its specific fuel consumption.The tested data reveal also that there exists probably a correlation between temperature distributions at turbine outlet and compressor outlet.
RESEARCH ON FUNCTION OF 8-SHAPED VORTEX IN OSCILLATORY PROPULSION
Wu Jing, Gao Ge
1993, 8(4): 328-332,416.
Abstract PDF(304KB) icon1364 icon396
Abstract:
A wave-vortex principle of oscillating propulsion is presented,which is based upon the observation and experimental study of fish′s oscillating propulsion.The theoretical analysis shows,that the occurence and interaction of 8-shaped vortex is the reason for creation of thrust.The experiments accomplished with oscillating stiff blades give a strong heuristic evidence.It is that the discovered 8-shaped vortex possesses behaviour of energy storage.This new principle is of great significance for analysing fish′s swimming and designing high efficiency propeller.
PREDICTION OF PROPELLER PRESSURE DISTRIBUTION AND PERFORMANCE BY LIFTING SURFACE THEORY
Chen Zemin, Pan Jieyan
1993, 8(4): 333-336,416.
Abstract PDF(267KB) icon1953 icon533
Abstract:
A numerical method is presented for prediction of propeller performance and pressure distribution on blade surface according to lifting surface theory.The lifting surface model consists of two layers of constant strength quadrilateral vortex-ring elements covering both surfaces of the blades.The velocity jump across vortex sheet is included in the computation of the pressure distribution.The effect of blade drag has been included in the calculation of propeller performance.Numerical results agree well with experimental data for the considered two propellers.
A TURBULENCE MODEL FOR FILM COOLING RECOVERY REGION
Jiang Tao, Liu Songling, Zhu Huiren
1993, 8(4): 337-340,416.
Abstract PDF(284KB) icon1617 icon360
Abstract:
It is observed that the normal k-ε turbulence model,which is very popular in computational fluid dynamics,is inapplicable to predicting the film cooling recovery region flow successfully.The reason might be the fact that the profiles of flow parameters are significantly different from those in normal boundary layer due to the blowing and the distance needed for flow returning to the normal boundary layer is too large.A new turbulence model based on Lam-Bremhorst low Reynolds number k-ε turbulence model has been proposed for prediction of the film cooling recovery region.It was found that the constant c μ and c 1 in the original model should be modified to be functions of coordinates x and y,and the low Reynolds number functions f μ,f 1 and f 2 should be varied with x and y too.The modified expressions feature that they should be approaching to nonblowing boundary layer when the distance from initial section becomes large enough.Three numerical examples demonstrate the advantages of this new model over the original one for the blowing ratio ranging from 0 4 to 1 0.
EXPERIMENTAL INVESTIGATION OF AN END-MODIFIED COMPRESSOR CASCADE
Wu Gouhua, Peng Zeyan, Yan Ming, Ren Liyin
1993, 8(4): 341-344,417.
Abstract PDF(329KB) icon1794 icon378
Abstract:
A compressor end-modified cascade and its original cascade are compared experimentally to study the three-dimensional flow characteristics at the exit plane of the cascade.The results show that the modification of the end part at the trailing edge of the original blade (which is different from end-bend)would effectively improve the exit air angle spanwise distribution and meet the need of the inlet air angle of next row blades,on condition that the total pressure lose coefficient does not change or decrease.The test results also indicate that although the camber angle of the blades in the end part decreases due to the modification,the paseage-mass-averaged value of the camber angle changes few.Otherwise,the air flow through the cascade is the same to the original or even better.This technique has been successfully applied to improving both stall margin and efficiency of axial multistage compressors and to depressing the unsteady pressure disturbance.
A NEW METHOD FOR SOLVING LOCAL FLOW NEAR LEADING OR TRAILING EDGE OF AN AIRFOIL
Liu Gaolian, He Hong
1993, 8(4): 345-348,417.
Abstract PDF(278KB) icon1370 icon377
Abstract:
a new algorithm coupled with the variational finite element method (FEM) is presented for solving the local flow near the leading or trailing edge of an airfoil or cascade.The solution of the local flow is considered as a combination of two parts.One of them is the approximate analytical solution of the flow near the stagnation point,it absorbs the greatly changing part in the original solution and makes the rest a more smooth distribution with better analytical nature which can be computed more accurately.Taking advantage of the variational principles,it is possible to locate the stagnation point more precisely and automatically.The numerical results show that the method described is effective to solve the subsonic flow accurately,especially in conditions with non-zero angle of attack.The theory can be coupled with the variational difference method as well as the variational FEM.
3-D ANALYSIS OF CIRCUMFERENTIAL GROOVED CASING TREATMENT
Du Zhaohui, Liu Zhiwei
1993, 8(4): 349-352,417.
Abstract PDF(273KB) icon1911 icon436
Abstract:
The 3-D incompressible steady time-averaged N-S equation,continuity equation and k-ε turbulence model equations are applied to calculating the flowfield in the cascade passage with circumferential grooved casing treatment.The mechanism of extending stability of the circumferential grooved casing treatment is elaborated by means of a 3-D viscous numerical simulation.It is revealed that a pressure difference between suction side and pressure side induces a strong gas flow which is absorbed in the pressure side and poured out from the suction side.This flow can blow off the low energy boundary layer efficiently to retard the stall emergence.The physical model and the flow pattern of the flowfields affected by inductive velocities are described.This is a new approach to analysis and design of the compressor casing treatment.
A BIFURCATION PHENOMENON IN COMBUSTOR WITH A NON-SLOT CONICAL SWIRLER
Jiao Shujian, Lee Jin, Liu Jing, Chen Liru
1993, 8(4): 353-357,418.
Abstract PDF(850KB) icon1494 icon412
Abstract:
A bifurcation phenomenon was discovered by experiments in a gas turbine combustor with a non-slat conical swirler.With different kind of perturbation,two different flow patterns may be found in the liner of this gas tubine combustor separately.The characteristics of these two flow patterns are quite different as described in great detail in this paper.In addition,a brief analysis of the causes for initiation of this phenomenon was made on the basis of the experiments.Therefrom it is shown,that this phenomenon will cause flame periodical fluctuation.
AN EXPERIMENTAL STUDY ON FLUID FRICTION AND HEAT TRANSFER IN COMPLEX NONCIRCULAR PASSAGES
Chang Haiping, Huang Taiping, Yang Yansheng
1993, 8(4): 358-362,418.
Abstract PDF(317KB) icon1641 icon432
Abstract:
Due to the effect of centrifugal force in an operating turbine,the passage between the tenon of blade root and the mortise of the disk is formed as complex noncircular flow passage.The characteristics of flow friction and heat transfer in this kind of noncircular passages are investigated experimentally.It is discovered that the "multiple flow states" occur in the noncircular passages and some special features exist in the flow friction and heat transfer characteristics.The criteria of the flow friction and heat transfer are obtained for this case.
LOADING MODELS FOR BIRD IMPACTING ON BLADES
Yin Jing, Gao Deping, Fan Erning
1993, 8(4): 363-367,418.
Abstract PDF(311KB) icon1592 icon378
Abstract:
In order to predict the blade response to bird impact,it is neccesary to establish the bird impact loading models at the first.For this purpose,the following research work has been completed:(1)Analyzing the physical process of the bird impact according to the theory of high-speed stroke dynamics,(2)accomplishing the loading experiments of the bird impact,and (3)studying the effect of the various factors of the bird impact loading on the blade response by means of computer numerical simulation.Based on the synthesis of the above research results,some methods and principles for the bird impact loading models are obtained.They are the method of determining the impulse and loading duration,the method for selecting the force-time function and the principles of determining the spatial factors of the loading including the load types,the loading location and the spatial distribution of the loads.These methods and principles are applicable to establishing the bird impact loading models.
REAL-TIME SIMULATION OF A TWO-SPOOL TURBOJET BY PARALLEL PROCESSING
Zeng Qinfu, Zhang Yong, Guan Yanshen
1993, 8(4): 368-370,418.
Abstract PDF(233KB) icon1400 icon467
Abstract:
A real-time simulator of a two-spool turbojet is introduced,which is implemented with a parallel-processor/microcomputer system.A PC286 microcomputer is used as the host computer,and four TMS32020 digital signal processors are chosen as processing units of the parallel system.The A/D and D/A boards serve as the interfaces of the hardware-in-the-loop simulation of the engine control system.For the parallel processing,it is necessary to partition the aerothermodynamic model of the two-spool turbojet.The elements of Jacobian matrix of Newton-Raphson′s iterative method are calculated parallelly in the 4 processing units.The whole real-time simulation was carried out under the control of the simulation support software,which guaranteed synchronous operation and communication between different processing units,A/D,D/A,the display,and the storage.The real-time engine simulator has been applied to the hardware-in-the-loop simulation for an engine digital control system.The simulation frame cycle time is 29 6 milliseconds.
APPLICATION OF FUZZY CONTROL THEORY TO DESIGNING AN ADAPTIVE DEVICE
Luo Enke, Wu Qihua
1993, 8(4): 371-374,419.
Abstract PDF(266KB) icon1325 icon427
Abstract:
A new design approach is proposed according to fuzzy control theory.It has been applied to designing the proportional and integral adaptive control device for a speed digital adaptive control system of a two-spool turbojet.Two methods (phase-plane method and membership degree method) have been used in this design.The digital simulation of the whole system has been completed.Its results demonstrate that this new approach brings the advantages of the proportional,integral and fuzzy controls into full play.It simplifies the control algorithm and enhances the control accuracy.Finally,this new design approach is suitable for nonlinear and high-order controlled object,which is lacking precision mathematical model.
AN EXPERT SYSTEM FOR AEROENGINE OIL MONITORING
Zhong Rongbin, Ma Mei
1993, 8(4): 375-378,419.
Abstract PDF(790KB) icon1290 icon364
Abstract:
Since oil monitoring is an effective diagnostic method in aeroengine troubleshooting,an expert system OSTM is developed,which means"Oil System Troubleshooting Master".Its goal is to help maintenance personnel to analyze the complex information acquired from the oil monitoring.This software is implemented in Turbo Prolog language and customized for use in portable personal computers.An exhaustive back-chain inference algorithm is adopted.The rule ignition superiority is determined by rule sequence in the knowledge base.Hence,common faults can be picked out at first.An explanation mechanism is included as well.Further,a menu query interface is programmed for quick manipulation of particular faults.For this purpose,the fault symptoms are classified according to their respective diagnostic domains.Moreover,knowledge acquisition and knowledge base management modules have been created.Until now,the diagnostic knowledge is mainly adopted from aircraft maintenance manual.
PATTERN RECOGNITION OF EXTREME LOAD DISTRIBUTIONS
Cheng Dejing, Sun Zhenyi
1993, 8(4): 379-382,419.
Abstract PDF(270KB) icon1625 icon366
Abstract:
the largest prototypes of extreme load coefficient for a variety of flights have been obtained from pretreating extreme load data of flight tests and field surveys.Different mathematical patterns of distribution,such as Normal Distribution、Weibull Distribution、Pearsun Distribution、Rayleigh Distribution and Gumber Distribution,are applied to calculation,from which are derived both probability density function and probability distrbution function in each of these patterns.By means of recognition algorithm of Fuzzy Mathematics,approximation grades of the different patterns to the prototypes are determined.Then a reliable distribution regularity of the extreme load coefficients is provided for strength and reliability analyses of the aeroengine.
FINITE ELEMENT ANALYSIS AND EXPERIMENTS ON CREEP OF MULTIHOLED PLATE DZ-22
Yue Yanfang, Rao Shouqi
1993, 8(4): 383-386,420.
Abstract PDF(287KB) icon1545 icon431
Abstract:
Experiments on tension creep behavior of the ortho-anisotropic material DZ-22 have been performed at 750℃,850℃ and 900℃.This material is applied to directionally-solidified air-cooled turbine blade.A constitutive equation of the creep is formlated by fitting with the experimental data.The equation shows three stages of the creep behavior.Effectiveness of the FEM analysis for the creep behavior of the ortho-anisotropic material is proved by the experimental results.Then,in consideration of the features of the air-cooled blade,a simplified FEM is presented for analysis of the creep of a multiholed component and is proved by the creep experiments with densely multiholed plate specimens.
TRANSIENT BEHAVIOUR OF CRACKED ROTOR THROUGH PARAMETRIC RESONANCE RANGE
Zhu Xiaomei, Gao Jianmin, Guo Yi
1993, 8(4): 387-389,420.
Abstract PDF(246KB) icon1714 icon464
Abstract:
In order to diagnose the existence of a crack in rotating machinery,the transient vibration of a cracked rotor through parametric resonance range is investigated.By means of primary harmonic transformation,the normal motion equation of the cracked rotor is transformed into a new differential one.From direct solution of this equation,the amplitude of primary harmonic vibration can be obtained under nonstationary or stationary excitation.In respective consideration of ideal and nonideal sources of energy,it is found that:(1)Whether the source of energy is ideal or not,the largest amplitude of transient vibration near 2ω c/3 and 2ω c (Parametric resonance range) of the rotor with crack is bigger than that without crack (where ω c is the critical speed of the rotor without crack).And the deeper the crack,the larger the amplitude in the case of the ratio of crack depth to shaft diameter less than 0 4.(2)When the source of energy is ideal,the larger the acceleration,the less the largest amplitude of transient vibration through parametric resonance ranges of the cracked rotor.Because parametric resonance is the exclusive characteristic of cracked rotor according to the authors′ previous work,the authors believe that the transient vibration behaviors near 2ω c/3 and 2ω c may be a basis of diagnosing cracks on a shaft of rotating machinery.
A NEW METHOD FOR EXTENDING VECTOR EQUATIONS OF VISCOUS FLOW IN TURBINE IN CURVILINEAR COORDINATES
Zhang Chiping, Feng Guotai, Wang Zunzheng
1993, 8(4): 390-392,420.
Abstract PDF(249KB) icon1765 icon418
Abstract:
A new idea is suggested to extend the viscous vector equations in non-orthogonal curvilinear coordinates.In the expansion equation obtained with the help of this new method,the number of terms is greatly decreased,so that it is easy to apply to engineering calculation.Meanwhile the expanded forms of compressible and incompressible equations are also presented and a generalized expression is given.Finally,by the aid of this new method,the numerical calculations have been carried out for 2-dimensional compressible viscous cascade flow and 3-dimensional compressible viscous cascade flow.It is shown that the new expansion equation is of great value to engineering practice.
STUDY ON EXISTENCE AND UNIQUENESS OF SIMILARITY TRANSFORMATION IN CASCADE
Zhu Niangou, Xu Liping
1993, 8(4): 393-395,421.
Abstract PDF(239KB) icon1315 icon428
Abstract:
Based on the similarity theory and two-dimensional potential equation,the existence of similarity transformation in a cascade at different inlet Mach numbers has been considered.It has been shown that only for linearized two-dimensional flows there exists an exact similarity.In the case of full disturbance,only approximate similarity can be found.The uniqueness of similarity transformation in accordance with inlet Mach number has been also considered.The conclusion provides some theoretical basis for similarity transformation.
MISMATCH ANALYSIS BETWEEN COMPRESSOR STAGES
Miao Houwu, Liu Jianhua
1993, 8(4): 396-398,421.
Abstract PDF(242KB) icon1611 icon427
Abstract:
A new three-stage compressor has been made by scaling up a two-stage transonic compressor and adding a third stage in order to enhance its mass flow and pressure ratio.Its tests show that serious flow mismatch exists between second stage and third stage.Factors for the flow mismatch are found out as effect of scaling up coefficient on flow block factor,variation of its rotor blade airfoil section stagger angles due to centrifugal force and the unsteady effect for supersonic blading with low aspect ratio.Owing to above mentioned three factors,the flow capaility of third stage is increased by 6 3%.Tip-cut of the third stage demonstrates that the flow-path-area of the third stage is reduced to 93 7% and modified three-stage compressor has good flow match between the second stage and third stage, as a result its surge margin is enhanced by 5 8%.
EXPERIMENTAL INVESTIGATION OF A SINGLE-SIDE SLOPE-SLOTTED ATOMIZER
Qu Benquan
1993, 8(4): 399-402,421.
Abstract PDF(275KB) icon1671 icon355
Abstract:
A single-side slope-slotted atomizer has been constructed for single-side atomization.The experimental investigation has been carried out on flow pattern and flow resistance of this atomizer.The feature of its low total pressure loss is testified.The information on its atomization field has been collected,from which its atomization characteristics of single-side atomizing field and its fuel atomization density distribution are obtained.It is shown,that this atomizer is one of better atomizers for an afterburner of turbofan aeroengine.
NEURAL NETWORK APPROACH TO LIQUID ROCKET ENGINE HEALTH MONITORING
Huang Minchao, Feng Xin, Zhang Yulin
1993, 8(4): 403-405,421.
Abstract PDF(243KB) icon1663 icon372
Abstract:
An ART2 (Adaptive Resonance Theory) neural network was trained to detect failures in a liquid rocket engine (LRE) from noisy normal steady-state sensor data.Power spectra of successive windows of individual sensor data were presented to an ART2 neural network to learn.The trained network was then tested to verify its effectiveness of failure detection and failure onset detection.Sensor data were collected from ground tests RS61 of the variable thrust LRE.The test results show that detected by the neural network corresponds with that the failure onset determined by experts from their post-test analyses.
INTEGRATION OF DESIGN AND MANUFACTURE OF CENTRIFUGAL COMPRESSORS
Jiu Jianfeng, Cao Xiaojin
1993, 8(4): 406-408,422.
Abstract PDF(235KB) icon1802 icon453
Abstract:
A system for integrating design and manufacture of centrifugal compressor by CAD/CAM is established which includes blade design,machining coordinates transformation,blade profilling in arbitrary section,checking coordinate calculation.Especially,a set of design and calculation methods is provided for manufacturing turbomachines by four-axis numerically controlled machining center.The integration system can be used on microcomputer.The system has been applied successfully to designing and machining centrifugal compressors in a factory.It is proven that the system is practical,flexible,reliable and it can cut down the time of design and manufacture with high quality.
FLOW DISTORTION MONITORING IN AN S-SHAPED INTAKE
Weng Peifen, Guo Rongwei
1993, 8(4): 409-411,422.
Abstract PDF(233KB) icon1835 icon364
Abstract:
A series of experiments were made in an S-shaped air intake at high incidence.The observations show that larger the incidence,the more distorted the flow field.And further,there is a certain relation between high incidence,swirling flow,total pressure field and position angle φ of the flow with the lowest total pressure coefficient C p.The position angle φ is given as a better detective parameter which can monitor the distorted velocity and pressure field.
STUDY ON ATOMIZATION CHARACTERISTIC OF AIR ASSISTED ATOMIZER
Gu Shanjian, Huang Yong, Yang Maolin, Chen Hongbo, Liang Xueping, Zhang Yingnian
1993, 8(4): 412-414,422.
Abstract PDF(226KB) icon1643 icon393
Abstract:
The atomization characteristics of a new type air assisted atomizer have been investigated for heavy oil with Engler viscosity more than 20,and compared with "Y" type atomizer commonly used in industry.A standard diffraction based sizing system (i.e.Malvern) is applied to this investigation .The results reveal the influences of the air pressure,fuel pressure,and air/fuel ratio on the atomization characteristics,the influence of the fuel pressure on the spray angle,and demonstate the fuel atomization superiority of this new-type atomizer over the "Y" type atomizer in atomization.

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