1993 Vol. 8, No. 3

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AN EXPERIMENTAL STUDY ON BLADE NEGATIVE CURVING IN A TURBINE CASCADE WITH A LARGE TURNING ANGLE
Wang Zhongqi, Tan Chunqing, Han Wanjin, Zhou Mochun
1993, 8(3): 209-212,305.
Abstract PDF(273KB) icon1328 icon443
Abstract:
Turbine rectangular cascades with conventional straight blades and negative curved ones at obtuse angles between their pressure surfaces and both endwalls were investigated in a low speed plane cascade wind tunnel.The measuring planes with five hole micro spherical probes were arranged as 3 before,6 in and 1 after the cascades.The experimental results show that the origination and development of horseshoe vortices and passage vortices as well as the meeting of the passage vortices in the midspan region almost dominate the whole flow field of conventional straight cascade.In comparison with those of conventional straight cascade,blade negative curving improves the flows around blade leading edges near both the endwalls,and reduces the intensities and viscous dissipation losses of leading edge vortices and passage vortices.As a result,the flux capability of the cascade increases by 3 2%,the mass flux averaged overall loss coefficient is cut down by 19 1%,at the same time the good inlet condition is provided for the rotor cascade.
A COMPUTER PROGRAM FOR MERIDIONAL FLOWS IN MULTISTAGE AXIAL FLOW COMPRESSORS WITH TURBULENCE AND MULTI-EFFECTS OF 3-D FLOWS
Li Shiming, Chen Maozhang
1993, 8(3): 213-216,305.
Abstract PDF(289KB) icon1402 icon464
Abstract:
It has been shown early by the authors that the spanwise mixing is caused by turbulent diffusion and different kinds of three dimensional flow effects.This paper introduces a computer program based on this theory. A new kind of rotary enthalpy has been defined and its related equation has been derived to simplify the present problem. The details for modeling all the unknown correlation mixing terms involved in the computations and the numerical scheme have been also presented. The results obtained agree well with the experiments for five compressors. The results also show some improvement over the previous theories.
A BLADE ELEMENT METHOD FOR PREDICTING THE OFF-DESIGN PERFORMANCE OF COMPRESSORS
Tang Diyi, Wang Yongming
1993, 8(3): 217-220,306.
Abstract PDF(338KB) icon1651 icon368
Abstract:
A method for predicting the off design performance of an axial flow compressor is presented.The fundamental of the calculation is incorporation of three flow phenomena:the annulus flow,the cascade flow and the flow of annulus wall boundary layer.The calculation of the annulus flow is based on the radial equilibrium of mainstream and neglects the existence of cascades and the effects of annulus wall boundary layers,so it aims at calculating the mainstream axial velocity distribution.The calculation of the cascade flow is intended to obtain lift and drag coefficients of cascade airfoil and to calculate the incremental of total enthalpy and entropy across cascades.The calculation of the annulus wall boundary layer provides the blockage effect and the losses caused by annulus wall boundary layer.For obtaining the whole losses of the compressors,the loss models of shoke wave,blade wake and secondary flow/clearance leakage should be coupled with the above mentioned calculations.As examples,the off design performance curves of compressors have been calculated,one of them gives the effect of the annulus wall boundary layer on the compressor characteristics.Additionally,the axial development of the boundary layer momentum thickness and blockage coefficient are also given.The comparison of calculated curves with the rig test results showes that the errors will be allowable in engineering.
INVESTIGATION OF FLOWS IN A CONTROLLED DIFFUSION AIRFOLL CASCADE PASSAGE
Cheng Ronghui, Zhong Yongxing, Yun Ruqun
1993, 8(3): 221-224,306.
Abstract PDF(551KB) icon1991 icon407
Abstract:
This paper presents the flow measurement in the blade passage and downstream of a high turning controlled diffusion airfoil(CDA)cascade in details and the investigation of flow visualization on the endwall and blade surface.As a result,a thorough comprehension is obtained in respect of the flow in the blade passage especially in the endwall area,the vortex structure and of the effect of endwall boundary layer and secondary flow on the performance of the cascade.It is of great practical value in improving the flow conditions in the endwall area of a compressor and developing the second generation of the controlled diffusion airfoil.
VIBRATION CHARACTERISTICS OF ROTOR SYSTEMS WITH POROUS SQUEEZE FILM DAMPER(PSFD)SUPPORTS
Yan Litang, Zhang Shiping, Li Qihan
1993, 8(3): 225-233,306.
Abstract PDF(486KB) icon1597 icon425
Abstract:
A Porous Squeeze Film Damper(PSFD)had been developed by the authors based on the normal Squeeze Film Damper(SFD).The outer race of the PSFD is made of permeable metal material.Its permeability allows some of the oil in the clearance of the damper to seep in or out through the outer porous race for remarkable improvement of the squeeze film damping properties.In this paper,the steady state response and the transient response resulted from sudden unbalance in the case of blade loss are investigated for simple rigid rotor and a flexible Jeffcott rotor supported on concentric PSFD or SFD.The nonsynchronous response of the simple rigid rotor is analyzed.The investigations show that the nonlinear vibration characteristics with the cavitated SFD systems such as bistable jump phenomenon,nonsynchronous response and "lock up" at rotor pin pin critical speeds under much high unbalance level are greatly improved or avoided with the PSFD systems.PSFD systems could be operated efficiently at higher shaft speeds and under greater unbalance loads especially under greater sudden loading of blade loss.As a new damper based on SFD,PSFD retains all the advantages of SFD and provides more effective vibration control for the rotor systems.
VIBRATION CHRACTERISTICS OF MISTUNED DISK-BLADED
Yan Yunju, Gu Jialiu
1993, 8(3): 234-240,307.
Abstract PDF(422KB) icon1525 icon488
Abstract:
A mathematical model by Substruture Mode Synthesis Methed is provided for coupling vibration of a mistuned disk bladed.Several low order modes of each substructure are obtained by means of Experimental Modal Analysis and modifying calculation of the modes.Relying on the small perturbation of blade modal stiffiness,real mistuned disk bladed and several kinds of theoretical mistuned models are set up.Model parameters and mathematical formalas are checked by use of forced vibration experiment of a real mistuned disk bladed on vibrostand.Analytical results well reveal that the mistuning of blades is the reason why resonant response of some blade on the same stage disk is much greater than other blades.The results also show that smaller frequency difference and random mistuning distribution of blades are eligible,and also give the rational range of rotating frequencies of an engine.
PRECISE TRANSFER MATRIX FORMULAE CONSIDERING AXIAL FORCES
Li Yan
1993, 8(3): 241-244,307.
Abstract PDF(269KB) icon1894 icon343
Abstract:
Two precise transfer matrix formulae of different forms for analysis of shaft element with constant section parameters are derived which take axial forces and shearing deformation into account.Both of the formulae are applied to a practical example.The comparison between the results of the calculation and experimental data shows that the precision of the formulae is very well and that considerable axial forces do have a nonnegligible influence on dynamic properties of rotor bases system.The presented formulae not only extend the application of the transfer matrix method,but also provide a convenient approach to solving the specific engineering problems in dynamic analysis of the rotor bases system with considerable axial forces due to pre pressed coupling curves in its assemblage.
STUDY ON CONTACT STRESSES OF CYLINDRICAL GEARS ACTED BY DYNAMIC LOADS
Liu Geng, Zhu Hao, Shen Yunwen, Gao Xiangqun
1993, 8(3): 245-249,308.
Abstract PDF(373KB) icon1655 icon343
Abstract:
An approach to local finite element mesh refinement is studied for three dimensional elastic contact problems.The study shows that because of different acting loads the boundary conditions of the refinement model in contact problems are different in calculation at flexible matrices and contact stresses.On the basis of the approach,an effective method is provided for the calculation of the contact stresses of spur and helical gears during the whole engagement period.According to the position of contact lines in the action plane,the present method establishes the FE models of gears by a 3 D automatic mesh generation program.The load share ratios of gears and load distributions along the contact lines during the whole engagement period are then simultanuously calculated by using the coordinate systems of gear profile and the corresponding matrices of coordinate transformation.Furthermore,the local FE mesh refinement models of gears on a specific contact line are established and the detailed contact stress distributions of the contact line are evaluated with the use of finite element mathematical programming technique.In this case,the calculations of contact stresses on different contact lines of gears during the whole engagement period can be conveniently carried out.The contact stresses on different contact lines of a pair of aeronautical helical gears acted by dynamic and static loads of the gear system are calculated.The calculated results show,the present method and the corresponding microcomputer programs are fast and reliable in calculation as compared with those by Aeronautical Standard of China HB/Z84,2 84.
A TRANSIENT BURNING MODEL OF SOLID PROPELLANTS AND ITS APPLICATION TO LIQUID QUENCH OF ROCKET MOTOR
Yin Jinqi, Wang Kexiu, Wu Xinping
1993, 8(3): 250-254,308.
Abstract PDF(329KB) icon1716 icon392
Abstract:
A transient burning model of solid propellants is proposed,in which the distributed reactions and deep absorption of external radiation are considered in the condensed phase.The heat loss due to boiling heat transfer induced by liquid jet impinged on burning surface is taken into consideration in the energy balance equation on the buring surface.A space wise thick flame model is developed to obtain the flame heat feedback under the conditions that the decreasing of chamber pressure and gas phase temperatures is caused by liquid injection and evaporation of liquid drops in gas phase,which is described by a submodel for internal ballistics of rocket motor durning liquid quench.The model can be used to describe the transient burning behaviors of solid propellants under the influence of external disturbances,such as rapid depressurization,deradiation or liquid injection,and to obtain the critical values required for extinction of solid propellants.The results from theoretical prediction indicate that whether the transient burning comes into extinction is not only dependent on the variation rate of the external disturbance,but also on the variation amplitude of the disturbance.The critical values of liquid injection pressure drops for extinction of two kinds of aluminized ammonium perchlorate hydroxyterminated polybutadiene propellants(16%Al and 18 5%Al)were obtained by experiments.The predicted results obtained from the transient burning model are in good agreement with the experimental data.The critical value of liquid injection pressure drop increases with increasing propellant energy and chamber pressure.
DETERMINATION OF LIQUID QUANTITY REQUIRED FOR LIQUID QUENCH OF SOLID ROCKET MOTOR
Yin Jinqi, Wang Kexiu, Wu Xinping
1993, 8(3): 255-258,308.
Abstract PDF(266KB) icon1552 icon417
Abstract:
The liquid quantity required(LQR)for liquid quench of solid rocket motor was determined with the use of a theoretical model developed by the authors.LQR increases with propellant energy and decreases as the evaporation heat of liquid and the liquid pressure drop(the difference between injection pressure of liquid and chamber pressure)increase.The effects of the chamber pressure and burning rate pressure exponent of propellant on LQR merge into the effect of mass burning rate of propellant.Then LQR increases with increasing mass burning rate.The theoretical results are in good agreement with experimental data.
AN OPTIMIZATION METHOD FOR STATISTICAL ASCERTAINMENT OF THE MOST PROBABLE PEAK TEMPERATURE AT COMBUSTOR EXIT
Ding Yisheng, Lin Xiurong
1993, 8(3): 259-262,309.
Abstract PDF(276KB) icon1222 icon417
Abstract:
With a limited number of exit temperature measurements of a gas turbine combustion chamber,it is most unlikely to take a measurement just at the correct position of the real hot spot.On the other hand,numerical prediction of the hot spot temperature so far is impracticable.In this paper,on the basis of principles of statistical analysis,a very simple and effective two dimensional optimization method is employed to process the multi measured temperature data taken at an annular combustion chamber exit under a specified operating condition.As expected,an optimum fitting Weibull equation is obtained,which can meet the preset accuracy requirement of evaluation by applying least square method,and then a calculation formula is derived,which can be used to ascertain the most probable exit peak temperature value with confidence.A numerical example shows that the most probable exit peak temperature(namely the real hot spot temperature)is higher to a certain extent than the maximum value measured.Some other potential applications of this method are also metioned very briefly.
A NUMERICAL STUDY OF PARTICLE DISPERSION IN MIXING LAYER WITH RANDOM VORTEX METHOD
Xu Chenggang, Yan Chuanjun, Wan Hongji
1993, 8(3): 263-266,309.
Abstract PDF(291KB) icon1388 icon382
Abstract:
Quasi two dimensional large scale vortex structure has a dominant effect on development of plane mixing layer.Crowe used Stuart's Vortices to simulate particle dispersion in free shear flows.The results of his simulation show that the experimental observations indicating particle dispersion rates greater than the fluid dispersion rates in free shear layer could be attributed to the effect of large scale vortex structure on particle dispersion.It is the incapability of Stuart's vortices of simulating development and merging process of these large scale vortex structure,that compromises the generality of his results.In this paper,we studied the particle dispersion in the mixing layer by using the random vortex method to simulate the creation,development and merging processes and the same results as Crowe's are obtained but in a more general sense.
MEASUREMENT AND PREDICTION OF INTERNAL 2-D TURBULENT BOUNDARY LAYER SEPARATION
Yin Junfei
1993, 8(3): 267-270,309.
Abstract PDF(294KB) icon1354 icon341
Abstract:
An incompressible turbulent boundary layer separation in a two dimensional diffuser was surveyed using laser doppler velocimeter,and its time averaged velocities and turbulence quantities were obtained.The time averaged velocity profiles were compared with several empirical relationships.Prediction was made by using a quasi simultaneous viscous/inviscid interaction model and was compared with the experiment.The prediction with two empirical relationships of shape facter H 1=H 1(H) was compared.The prediction is in agreement with the experiment before the strong reversing flow.
EFFECTS OF EXTERNAL EXCITAION ON THE LEADING-EDGE SEPARATION FLOWFIELD
Xu Cheng, Zhang Shiying, Zhou Mingde
1993, 8(3): 271-274,310.
Abstract PDF(267KB) icon1690 icon391
Abstract:
This paper presents the comparison of the leading edge separation flow without and with the excitation of select frequency.A variety of excitation effects on the separation flowfield are revealed as(1)delaying separation flow or decreasing separation flow area,(2)modifying turbulence structure,intensifying turbulent activity and enhancing growth rate of separated shear layer,(3)enhancing backflow activity of local region,(4)promoting reattachment and changing separation patterns and vortex distribution,(5)weakening turbulence fluctuation of wake flow,and(6)increasing inclination of wake flow.
AN INVESTIGATION OF SWIRL FLOW FIELD IN PNEUMATIC CONVEYING DUCT
Huang Xijun, Dong Jinzhong
1993, 8(3): 275-278,310.
Abstract PDF(272KB) icon1545 icon421
Abstract:
Swirl flow field of a pneumatic conveying system is investigated experimentally.The swirling flow is imparted to the flow by the use of swirl vanes.A five hole probe is used for measuring the tangential angle of flow、axial velocity、static pressure of flow and swirl number in the flow sections of the conveying system.It is shown that the existence of central screw conveyer produces the contrary swirl flow under some of the swirl vane angle condition.The larger axial velocity is produced in the outer annular layer of flow.The maximum value of swirl number in the flow sections is agreed with the simplified theoretical relation.
ADAPTIVE ENGINE STALL MARGIN CONTROL
Sun Jianguo, Huang Jinquan
1993, 8(3): 279-282,310.
Abstract PDF(281KB) icon1812 icon381
Abstract:
This paper proposes an adaptive engine stall margin control(AESMC)for integration of flight and propulsion controls.Using the model reference adaptive control(MRAC)technique,the AESMC is to adjust exhaust nozzle area to uptrim the engine pressure ratio so that the engine stall margin remains a small constant value in all operation conditions and in full flight envelope.Benefit of the control system is to increase engine thrust and to reduce aircraft acceleration time.In order to evaluate the performance of the AESMC,a nonlinear integrated flight/propulsion model is developed.Digital simulation of the IFPC system is performed.The simulation results show that the IFPC system with the adaptive controller developed has good effectiveness for all operation conditions and for full flight envelope.For example,the thrusts of two engines are increased 16%,and aircraft acceleration time is reduced 23% at altitude 10km and Mach number from 0 65 to 0 9.
HEAT-MASS TRANSFER ANALOG OF AIR-COOLING ROTATING DISC WITH NAPHTHALENE SUBLIMATION
Cao Yuzhang, Lin Yuzhen, Feng huazhong, Xu Guoqiang, Qiu Xuguang
1993, 8(3): 283-287,311.
Abstract PDF(322KB) icon1598 icon448
Abstract:
The heat transfer characteristics of rotating disc have been investigated experimentally by means of a mass transfer analog of naphthalene sublimation.Two models are used:free rotating disc and shrouded rotor stator system.Mass transfer test results of free disc are in good agreement with experimental results of heat transfer and theoretical prediction.The test results of local Sherwood number are obtained,which are dependent on rotational Reynolds number、flow coefficient、gap ratio and shroud clearance ratio.
EFFECT OF STEAM INJECTION INTO GAS GENARATOR ON COMBUSTION EFFICIENCY AND PRESSURE LOSS
Liu Gao'en, Wang Huafang
1993, 8(3): 288-290,311.
Abstract PDF(231KB) icon1972 icon433
Abstract:
The influence of steam injection into combustor on combustion efficiency and pressure loss in the combustor is investigated.The testing was conducted with a WZ 5 gas genarator burning low BUT gaseous fuel (H uv =8172kJ/N·m 3).The steam injection was arranged in either the diffuser or the dilution zone of the combustor.The test results show that the steam injection has only a little effect on combustion efficiency and a considerable effect on pressure loss.In the case of the ratio of steam flow rate to air flow rate being 10%,the steam injection into dilution zone would cause an 12% increase in pressure loss,and even larger than that the steam injection into diffuser would cause.
FRONTALLY TAPERED SQUARED TRENCH CASING TREATMENT FOR IMPROVEMENT OF COMPRESSOR PERFORMANCE
Du Zhaohui, Liu Zhiwei
1993, 8(3): 291-293,311.
Abstract PDF(227KB) icon1542 icon388
Abstract:
A new type of frontally tapered squared trench casing treatment was designed and tested over the rotor tip in a single axial flow compressor.Variations in the rotor tip penetration into the trench and the distance of the trench front from the blade leading edge were investigated.Through the measurements of velocity and pressure,the effects of each geometric parameter upon compressor efficiency and stall margin were evaluated.An optimal configuration has been found which gives not only 0 4% improvement in efficiency but 2% in stall margin in comparison with the smooth wall baseline.The mechanism of enhancement in the efficiency and the reason for existence of optimum configuration for frontally tapered squared trench casing treatment are considered in this paper.
NUMERICAL PREDICTION OF STEADY FORCE NOISE ON A COMPRESSOR ROTOR BLADE
Chen Jiang, Ren Rugan, Sun Xiaofeng, Hu Zongan
1993, 8(3): 294-296,312.
Abstract PDF(250KB) icon1721 icon434
Abstract:
Sources of compressor noise are usually considered as multiple pure tone noise,interaction noise and broadband noise.In the paper,the noise propagation equation of steady force on the compressor rotor blade is derived.The numerical results are compared with the WP 11 compressor rotor acoustical experiment.The theoretical and experimental investigations indicate that the steady force noise on the compressor rotor blalde is an important source of the compressor noise.
1993, 8(3): 297-299.
Abstract PDF(164KB) icon1191 icon339
Abstract:
FAULT-TOLERANT CONTROL OF RECONFIGURING RULE
Wang Yinggen
1993, 8(3): 300-302,312.
Abstract PDF(226KB) icon1687 icon351
Abstract:
A new method of fault tolerant control for multiloop SOSI system is suggested.A reconfiguration control rule is applied to the neighbouring loop of any fault sensor for compensating its effect.The suggested method is able not only to maintain the stability of the system but also to keep the controlling quality to be the same as that before the fault happens.This method is suitable for both minimal and non minimal phase systems.The results of the numerical simulation show that the method is of good compensating function.
WINDAGE" FOR HIGH GEAR SYSTEMS IN AVIATION
Chen Shixuan
1993, 8(3): 303-304,312.
Abstract PDF(318KB) icon1353 icon355
Abstract:
The problems about "Windage" and churning for high speed gear systems in aviation are considered.The domestic and foreign technical projects are introduced.The structural measures for depressing and using "Windage" in high speed gear systems in aviation are presented.

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