1994 Vol. 9, No. 3

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METHODS FOR NONDESTRUCTIVE INSPECTION RELIABILITY AND CONTROLLING LIVES
Fu Huimin, Qian Ruoli
1994, 9(3): 227-232.
Abstract PDF(2085KB) icon1775 icon1178
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It is difficult to determine a curve of the probability of crack detection (POD) with a high confidence level,since the traditional procedures require very large sample sizes.A new method of determining the POD curves is presented.The method requires only upwards of 30 independent inspections for determining a POD curve.The formulas of one sided lower confidence limits of the POD curves and of POD/CL crack sizes are also established by means of Fisher information matrix.In order to predict and prevent mechanical failure through probabilistic damage tolerance design and analysis,the POD curves for multiple independent inspections have been studied,and a important concept of controlling lives and a method of the optimum independent inspection times are presented.This method can control the largest size of the cracks missed at inspections with high POD and confidence level,and the largest size of the missed cracks is used as the initial crack size for calculating the crack growth life of the structure in damage tolerance design.Thus the crack growth lives and inspection intervals of structures can be controlled to some extent.The method can also raise the crack detection probability and avoid the accidents caused by the missed cracks.
TWO-DIMENSIONAL FACTORS OF LIFE SCATTER AND STRENGTH REDUCTION
Fu Huimin, Xiong Junjiang
1994, 9(3): 233-236.
Abstract PDF(274KB) icon1588 icon421
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In this paper,two dimensional factors of life scatter and strength reduction are presented because of their extreme practical importance throughout life prediction and fatigue strength design.The factors can make full use of previous data and reduce the number of specimens in the present experiment.The safe life and safe strength obtained by them are more accurate than those by the traditional (one dimensional) life scatter factor and strength reduction factor.They are applicable to the complete,the incomplete and the zero failure data.
TRANSIENT CHARACTERISTICS OF A FLEXIBLE ROTOR SUPPORTED ON NONLINEAR SFD′S THROUGH BISTABLE OPERATION RANGE
Zhu Changsheng, Wang Xixuan
1994, 9(3): 237-241,330.
Abstract PDF(925KB) icon1793 icon473
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The transient characteristics of a flexible rotor supported on nonlinear squeeze film dampers (SFD′s) during passing through the resonant and bistable operation speed range with constant acceleration are studied theoretically and experimentally.It is shown that the properly designed SFD′s have not only excellent steady state performance,but also better acceleration performance.The maximum vibration amplitude of the rotor system in the acceleration process decreases gradually with increase of rotor angular acceleration,whether for the properly designed SFD′s or for the improperly designed SFD′s.The stability of multisolution in the bistable operation speed ranges depends not only on the form of bistable operation,but also on the moving process.It is impossible for the rotor system to pass through the bistable operation speed ranges with smaller amplitudes only by means of accelerating the rotor system.
CALCULATION ON FLEXIBILITY MATRIX AND MODIFICATION OF HELICAL GEARS BY FEM
Fang Zongde
1994, 9(3): 242-244,330.
Abstract PDF(569KB) icon1976 icon384
Abstract:
A computer program is worked out for modification design of helical gears by using Finite Element Method (FEM).At first the finite element mesh of gear tooth is auto generated without engagement of gears,therefore it can be divided more conveniently and uniformly.The flexibility matrixes of mesh nodes on working flanks of gears are calculated by FEM.Then,the contact lines and contact nodes on the plane of action are generated by computer according to the contact ratio of gear pair.The flexibility matrixes of contact nodes are obtained by interpolation between the mesh nodes on plane of action.Further,the deformation of shafts and bearings is added to the total flexibility matrix which is sum of the flexibility matrixes of both gears.Finally,considering minimization of transmitting error and uniformization of load density as objective functions,an optimal 3-D modification is solved by using mathematical programming technique.Moreover an experiment on modification of a helical gear pair has been done,which showed that the calculated results agreed with experimental data and the carrying behaviour of gear transmission was improved considerably.
OPTIMIZATION DESIGN OF WHOLE CONSTRUCTION OF MULTISTAGE DISK
Huang Zhijian, Hao Yanhua, Zheng Guanghua
1994, 9(3): 245-248,331.
Abstract PDF(332KB) icon1607 icon435
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The optimization design of a whole construction of multistage disk,which is of great significance in practice,is the further development of optimization design of single stage disk configuration.The ways of auto shape description,strength calculation of single stage disk with finite element method,optimization and coordination composition of multistage disk and configuration optimization of all disks,are taken to develop the software SODMROD.The calculation examples are provided.This paper also introduces the principles of shape description of disk section as well as deduction of some formulas and the formulas which are used in the deformation calculation between disk and drum.
STATE-OF-ART AND PROSPECTS OF TRANSONIC CENTRIFUGAL COMPRESSOR DEVELOPMENT
Hua Yaonan, Rao Jian, Zhang Guoqing, Li Jingping
1994, 9(3): 249-254,331.
Abstract PDF(1172KB) icon1828 icon446
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A review on the methods for predicting internal flowfield and designing aerodynamic shape of transonic centrifugal compressor is given in this paper.In general,the development of the transonic centrifugal compressor lags behind that of transonic axial compressor.However,the transonic centrifugal compressor will be widely applied to powerplant of helicopters,the turbochargers of vehicles and compressors of petroleum chemical industry etc.Thanks to an urgent need of engineering practice,it can be prophesied that transonic centrifugal compressor will make great progress within the coming several decades.At present,inviscid calculation method with a distributed loss model (or boundary layer calculation) is a main tool to predict or design the transonic centrifugal compressor.However,along with development of computer,3D Navier Stokes solver may be applied in engineering practice within the coming decade.In the inviscid calculation method,the S1 and S2 stream surface caulculation method is the most improtant method at present.When the S1 and S2 method is used,the computer memory required is smaller and the CPU time consumed is shorter than 3D Navier Stokes Solver.Of course, the S1 and S2 method is suitable only for non separated flow condition at design point.As for design methods of the transonic centrifugal compressor,it is necessary to make full use of experience of axial compressor designing.
EXPERIMENTAL INVESTIGATION ON SURFACE STATIC PRESSURE DISTRIBUTIONS IN CURVED-BLADE COMPRESSOR CASCADE
Zhong Jingjum, Su Jiexian, Wang Zhongqi, Chen Ying
1994, 9(3): 255-258,331.
Abstract PDF(293KB) icon1660 icon401
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The static pressure distributions on endwalls and blade surfaces and the corresponding outlet flow for straight、leaned and curved blades of plane axial compressor cascades at 0° incidence were measured in detail.The experimental results show that C-shape static pressure distribution can be obtained on the blade surface of the curved blades along blade height.Blade leaning and curving can eliminate piling up of low energy fluid in the blade corner,cut down the endwall losses,retard corner stalling,and improve cascade aerodynamic characteristics.
HOT-WIRE MEASUREMENT OF 3-D FLOW FIELD IN A RECTANGULAR VOLUTE
Huang Shujuan, Hu Zhiwei, Miao Yongmiao
1994, 9(3): 259-262,332.
Abstract PDF(765KB) icon1786 icon469
Abstract:
D turbulent flow fields in a rectangular volute of a small centrifugal compressor were measured with a hot wire probe at three across sections along its circumference at three different flow regimes.The space positions were adjusted with a three dimensional coordinate frame.Time average velocities and Reynolds stress tensors were calculated by means of a hot wire response equation with third order of precision.The measured results illustrated two recirculation regions near both side walls due to abrupt expansion at the inlet of the rectangular volute.The turbulent kinetic energy and Reynolds stresses in the recirculation regions were reduced as the flow rate increases and as the radius increases.In addition,asymmetry of the rectangular inlet induced the vortices at different cross sections of the volute,and made the trace of the flow as a curved spirochaeta.In consequence,the abrupt expansion and the asymmetry of the inlet must be avoided.
EXPERIMENTAL STUDY OF 3-D TURBULENT FLOW FIELD IN A 90° BEND PIPE
Shang Hong, Wang Shangjin, Xi Guang, Yuan Minjian, Kong Qingli
1994, 9(3): 263-266,332.
Abstract PDF(750KB) icon2125 icon427
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The 3 D turbulent flow field in a 90° strongly curved pipe (D=280mm,Rc/D=0.87) has been experimentally studied under different Reynolds numbers (Re=2.78×10.5～5.40×10.5) with a single slant hot wire measurement system and a five hole dynamic probe.The detailed experimental results are given,including the distributions of 3 D time averaged velocities,turbulent energy,total pressure and static pressure along the curvature direction at five different cross section.It is shown that the loss in this strongly curved pipe mainly occurs near the inner side wall,and increases rapidly near the 90° cross section due to flow separation.Static pressure distribution near the outer side wall is higher than that near the inner side wall throughout.The flow near the inner side wall accelerates from the 90° to the 30° cross section and decelerates after 30° cross section.But near the outer side wall,the tendency becomes adverse,and the pressure gradient here is much smaller than that near the inner side wall.
EXPERIMENTAL STUDY ON GASDYNAMIC PERFORMANCE OF INTAKE WITH PLENUM BYPASS
Chen Xiao, Li Lulong, Ma Rulong
1994, 9(3): 267-270,332.
Abstract PDF(337KB) icon1843 icon399
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The intake with plenum bypass is a new type subsonic intake for civil medium range aircraft.Its geometry is considered.A model of this type has been designed,which scale is 1∶2.Experiments of flow visualization,gasdynamic performance and foreign object throwing have been done.The experimental results show that its perfect gasdynamic performance and flow steadiness satisfy the requirements of aeroplane and engine.Compared to the intake with pipe by pass,this new type intake has many advantages,especially the improved ability of eliminating the foreign object,although the total pressure coefficient of this type intake slightly lessens.This type intake has extensive application in the future to the civil aviation with the strict requirements of airworthiness.
A RESTORING ANALYTIC NUMERICAL METHOD FOR SOLUTION OF VISCOUS FLOW FIELD IN TURBINE
Zhang Chiping, Feng Guotai, Cui Minggen
1994, 9(3): 271-273,333.
Abstract PDF(255KB) icon1411 icon440
Abstract:
A new restoring analytic numerical method based on application of the method of restoring nucleus is developed for solution of viscous flow field in turbine.It makes the problems of storage,speed and accuracy in calculation easy to be solved.This paper offers ideas and methodology of application the method of restoring nucleus to solving viscous flow field in turbine,as well as in curvilinear coordinate system,and demonstrates the procedure of solving flow function integral equations.Finally,a numerical experiment for the two dimensional cascade viscous flow mentioned in reference 1 by the aid of this method has been performed and the results are consistent with the data in reference.1.
NUMERICAL SIMULATION OF 3-D FIELD WITHIN A COMPRESSOR ROTOR WITH C-H GRID
Wang Licheng
1994, 9(3): 274-276,333.
Abstract PDF(246KB) icon1835 icon480
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A 3-D C-H grid generation technique and 3-D Euler governing equation are described briefly.The highly loaded transonic compressor rotor designed by ONERA is taken as a numerical example.ONERA′S numerical results and ours with H grid and C-H grid are compared respectively in respect of the pressure distributions along profiles at hub and tip of the rotor.The numerical technique presented is applied to evaluating the influence of inlet pre swirl on its downstream flow field in the rotor,in result a new numerical approach is obtained for design optimization of pre swirl distribution at compressor design stage.As numerical examples,two kinds of pre swirl distributions are examined to show its influence on Mw1 、β1 and α2 etc. distributions along radius.
EFFECT OF INTERBLADE PHASE ANGLE ON BLADE FLUTTER OF STEAM TURBINE
Zhang Yangjun, Li Kejian, Tao Deping
1994, 9(3): 277-280,333.
Abstract PDF(337KB) icon1608 icon452
Abstract:
The interblade phase angle is one of key factors to act on the aeroelastic stability of steam turbine.A two dimensional numerical deforming actuator disk method on non constant interblade phase angle along circumferential direction has been developed to predict the stall flutter of the steam turbine.The effect of the interblade phase angler on the blade flutter of the steam turbine has been studied with the help of the developed method.The results indicate that when the interblade phase angle is between -45° and +90°,the stall flutter may occur at a certain condition.
WALL TEMPERATURE CALCULATION OF A NEW MAT WALL COMBUSTOR STRUCTURE
Hei Liming, Li Zhanglin
1994, 9(3): 281-284,334.
Abstract PDF(292KB) icon1708 icon397
Abstract:
A seven heat flow model for calculating of the wall temperature of mat wall has been established,in which internal axial heat conduction of flame tube wall is considered.A numerical method for solving the model is provided,which takes into account the effect of temperature on physical parameters.Therefore,the accuracy of the wall temperature calculation is enhanced.In order to provide required parameters for calculating the wall temperature,the calculation of axial distribution of mass flow and other flow parameters in the mat wall structure have also been done.After that,the axial temperature distributions on the mat wall of a single flame tube have been calculated at design and experimental conditions,and are compared with those of the prototype with air film cooling and its experimental data.It is demonstrated that the calculated results are principally consistent with experimental data and the mat wall strueture is possessed of excellent cooling performance.In comparison with the prototype,the cooling air mass is decreased by 20%,the wall temperature is obviously lowered.Furthermore,the axial wall temperature distribution is more uniform.Therefore,this structure will prolong the life of the flame tube or raise the gas temperature before the turbine.
A METHEMATICAL MODEL OF IMPINGING JETS ATOMIZATION AT LOW WEBER NUMBER
Shi Shaoping, Zhuang Fengchen
1994, 9(3): 285-288,334.
Abstract PDF(283KB) icon1836 icon508
Abstract:
The characteristics of the spray produced by impinging jets atomization is theoretically analyzed.Depending on Weber number,two breakup regimes of sheet are considered with transition occurring at Weber numbers between 500 and 2000.In the low Weber number regime ( We ≤2000),the sheet breakup is due to Taylor cardioidal waves.While in the high Weber number regimes,the sheet disintegration is caused by growth of Kelvin-Helmholtz instability waves.The model uses an analogy with the oblique impact of a liquid jet on a wall.At Weber number less than 2000,mathematical expressions to predict the sheet thickness and shape during formation of nonviscous liquid sheet are derived from mass conservation and momentum conservation equations by reference to theoretical results and empirical correlations reported in the literature.The numerical results are in good agreement with experimental data available in the literature.Predictions of the spray droplet size and distribution formed by the disintegration of the viscous liquid sheets are also obtained by use of the mathematical formulation developed for fan spray injectors.This model can be used to estimate the size range and distribution of droplets formed by impinging jets atomization in quasi static surroundings.
AN ANALYTICAL REDUNDANCY TECHNOLOGY BASED ON A COMPONENT TRACKING FILTER
Lan Chunxian, Sun Jianguo
1994, 9(3): 289-292,335.
Abstract PDF(280KB) icon1911 icon429
Abstract:
This paper deals with an analytical redundancy technology based on a component tracking filter (CTF),which is integrated with failure detection,isolation and accommodation logic so as to improve the reliability of the engine digital control system.Its simulation tests in complete flight envelope show that the developed analytical redundancy technique enables the engine model on board to track the component performance variations correctly in the case of no sensor failure,and to detect,isolate and accommodate failures of sensors effectively without corruption when a failure occurs.
CATALYSIS OF TMO MIXTURES ON COMBUSTION PROPERTIES IN AP PROPELLANTS
Zhang Wei, Zhu Hui, Zhang Ren, Zhang Guodong
1994, 9(3): 293-297,335.
Abstract PDF(327KB) icon1932 icon424
Abstract:
The catalysis of four TMOs (CuO,Fe2O3,Co2O3 and Cr2O3) and their six TMO mixtures (mass ratio:1∶1) on the combustion properties of AP/HTPB and AP/Al/HTPB composite solid propellants was investigated systematically.The results show that the action of the TMO mixtures on burning rate of the propellants can be divided into three kinds:positive,non and negative coordination effects.The TMO mixtures with positive coordination effect can extraordinarily increase the burning rates of the propellants.The action of the TMO mixtures on the burning rate of the propellant is also depedent on the kind of the propellant.
FCG BEHAVIOR OF ALLOYS UNDER ULTRASONIC FATIGUE LOADING
Ni Jingang
1994, 9(3): 298-300,335.
Abstract PDF(259KB) icon1730 icon394
Abstract:
Fatigue crack growth (FCG) and threshold behavior of four widely used engineering alloys have been investigated at high frequency Z(f =20kHz) by means of an ultrasonic fatigue device.Specimen design has been given.Crack propagating rate da/dN was obtained between 10-9 and 10-5 mm/cycle in function of stress intensity factor △K ,which was determined by a modified analytic experimental method.For comparison,conventional FCG data ( f =2 to 50Hz) were carried out with a high stress ratio (R=0.7) applied.High frequency effect on the fracture behavior of different materials was discussed and the failure mechanism was obtained in the two different regimcs.
OPTIMIZATION OF MATERIALS YIELD LIMIT FOR RELIABILITY DESIGN
Gu Yuan, Hong Qilin, Zang Yuedun, Li Shuliang
1994, 9(3): 301-303,336.
Abstract PDF(286KB) icon1786 icon375
Abstract:

According to aeroengine structure integrity program,fracture critical components must be analysed with damage tolerance concept.Due to crack propagation produced by material defects,working defects or fatigue defects can make structure fracture.Therefore,the sufficient damage tolerance should be maintained.It is realized by selecting material correctly,controlling stress level,using the anti fracture structures and reliable inspection.In this paper,the structural reliability concept is applied to studying optimization of materials for maximum reliability under certain stress levels and crack sizes,to investigating variation influences of material strength and stress level on structure reliability.
OPTIMAL CONTROL OF STRUCTURAL DYNAMIC SYSTEM
Deng Zichen
1994, 9(3): 304-306,336.
Abstract PDF(241KB) icon1446 icon386
Abstract:
A control mathematical model of the dynamic system is established according to the differential equation obtained from the structural dynamic system.Mixed energy of time interval is defined and condensation formulas are given with the help of the variational principle.Further the substructural condensation method in structural mechanics is used for the Riccati equation solution,based on the simulation relation between computational structural mechanics and optimal control.Then,the optimal control of the dynamic system is obtained.The numerical example shows the effectiveness of this method.
A k ε k p ε p TURBULENCE MODEL FOR GAS-SOLID TWO-PHASE FLOWS AND ITS APPLICATION
Wang Yunliang, Xu Zhong, Miao Yongmiao
1994, 9(3): 307-309,336.
Abstract PDF(397KB) icon1846 icon394
Abstract:
Based on k-E two equation turbulence model of gaseous phase,the k-E-kp-Ep two phase turbulence model is presented,which includes the turbulent kinematic energy equation of particulate phase and the dissipation rate equation of that energy.The numerical computations are made for the turbulent gas solid two phase flows in two vertical straight channels.The mean velocities and turbulence intensities of gaseous phase and particulate phase,which are predicted with the presented turbulence model,are in good agreement with the experimental results.And it is concluded,that the turbulence intensity of particulate phase is often greater than that of gaseous phase.This conclusion is consistent with available LDV experimental results.Since the algebraic model of particles has no ability to describe the characteristics,the presented turbulence model is very successful in predicting the flow characteristics of turbulent gas solid two phase flows.
EXPERIMENTAL INVESTIGATION ON SWIRL CONTROL IN AN S-SHAPED DIFFUSER BY VORTEX REDUCED DEVICE
Weng Peifen, Guo Rongwei
1994, 9(3): 310-312,337.
Abstract PDF(527KB) icon1769 icon469
Abstract:
An experimental investigation on swirl control in an S duct has been completed by the aid of a so called vortex reduced device (VRD) which is made of a metallic frame and placed upwards near the throat of the diffuser.Effects of geometric sizes of the VRD and its angle of attack on the flow in the duct were investigated in a wind tunnel.The flow parameters,including wall static pressure,total pressures and 3-D velocity field at the duct exit were measured.The optimum geometry shape and size (W id =0.0595) are found.The VRD with optimized geometry can effectively reduce the swirling range and improve the average total pressure coefficient at the exit.
DEVIATION ANGLE DETERMINATION IN TRANSONIC AXIAL FLOW COMPRESSOR DESIGN
Cao Renjing, Tao Deping
1994, 9(3): 313-314,337.
Abstract PDF(509KB) icon2100 icon422
Abstract:
The deviation angle determination in transonic axial compressor design is analyzed in detail.In addition,the aerodynamic and geometrical parameters acting on deviation angle distribution are discussed.A new deviation angle calculation formula is provided and applied to redesigning of an axial compressor stage.The results show that the aerodynamic and blade design is quite satisfactory.
EXPERIMENTAL INVESTIGATION ON PERFORATED ACOUSTIC LINER IN A SINGLE TRANSONIC AXIAL COMPRESSOR INLET DUCT
Li Yunmin, Lü Yadong, Hu Zongan
1994, 9(3): 315-317,337.
Abstract PDF(238KB) icon1932 icon470
Abstract:
Some experimental results and analyses from the measurements of the sound field in a single transonic axial compressorr inlet duct with single plastic glass lining are presented.The plastic glass linings are designed and made by ourselves (two kinds of perforate rating,σ 1=2.85% and σ 2=5.85%).The experimental results are firstly obtained in China from the real sonic fields in a single transonic axial compressor at high sound pressure conditions (>150dB).The experimental results and conclusions provide some reference for the further investigation on design of the acoustic treatment assemblies in aeroengine nacells and turbomachinery duct.
ENGINE THRUST RESPONSE TO PULSED FUEL SUPPLY IN MAIN COMBUSTOR
Wang Xiaofeng, Xin Xiaowen, Dang Huaiyi
1994, 9(3): 318-320,338.
Abstract PDF(244KB) icon1470 icon398
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The mathematical model of a two spool turbojet engine with pulsed fuel supply system was established and considered in this paper.The thrust responses to pulsed fuel supply in main combustor at six flight regimes have been calculated by the use of the established model based on flight test data.The calculated results were discussed and compared with flight test data in detail.The results show that engine thrust in this case drops 77～90% in a short time.This means pulsed fuel supply system has a heavy effect on engine performance.
NUMERICAL SIMULATION ON TRANSIENT OPERATION OF TWIN-SPOOL TURBOJET ENGINES DURING PULSATORY FUEL SUPPLY
Zheng Qingxiong, Chen Fuqun
1994, 9(3): 321-323,338.
Abstract PDF(247KB) icon1665 icon480
Abstract:
Since pulsatory supply of fuel in operation of turbojet engines deteriorates both combustion and turbine efficiencies and makes them deviate from data given by characteristic maps.Moreover,it is also hard to obtain an empirical correlation for correcting the deviations of both these efficiencies.A new approach proposed in present study is to replace the two maps of combustion and turbine efficiencies by experimentally measured high pressure and low pressure shaft speed curves,which can be used as the known conditions for differential equations describing transient operation of twin spool turbojet engines.Both Euler′s method and Newton-Rapson′s iteration are used in calculation discretizing for and solving the differential equations.Based on the above mentioned approach,a transient operation of a twin spool turbojet engine during pulsatory supply of fuel has been numerically simulated.The numerical results are in good agreement with those experimental measurements.
LIQUID ROCKET ENGINE MULTI-FAILURE DETECTION USING BP NEURAL NETWORK
Huang Minchao, Zhang Yulin
1994, 9(3): 324-326,338.
Abstract PDF(252KB) icon2037 icon457
Abstract:
Based on a measurable survey pattern corresponding to a rocket engine failure pattern,the multi failure is detected by using back propagation (BP) neural network,which provides interesting means for pattern recognition and classification.The BP algorithm minimizes the mean square error between the desired and the actual output of the network.The learning algorithm is carried out with a gradient descent techniuqe.In order that the mean square error does not fall into partial minima noise,a sequence of random noises is recommended in the BP algorithm.As a test case,only the pump inefficiency and the sprayer jam in the liquid rocket engine were studied,and the failure detection simulation was given to show great advantages of the BP neural network.

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