1996 Vol. 11, No. 3

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NUMERICAL ANALYSIS OF THREE-DIMENSIONAL TURBULENT FLOW IN COMPRESSOR BLADE ROW BY IMPLICIT HIGH-RESOLUTION SCHEME
Yao Jixian, Liu Qianzhi, Zhou Xinhai
1996, 11(3): 225-228,327.
Abstract PDF(287KB) icon1757 icon467
Abstract:
It is found that a three or high order accurate high-resolution scheme may be more suitable for the correct prediction of turbulent flow field characteristics in the numerical analysis of three-dimensional turbulent shocked flo w in t ransonic compressor blade row.T he conver gence of the three-dimensional turbulent f low cal culation can be remarkably sped up by using the implicit LU-SG Salgo rithm,which is unconditionally stable.A detailed comparison between numerical solutions and experimental data indicates that their agreement is quite satisfactory.
AN EXPERIMENT ON ENLARGING STEADY WORKING RANGE OF SKEWED-SWEPT ROTATING BLADES
Cai Na, Zhong Fangyuan
1996, 11(3): 229-232,327.
Abstract PDF(287KB) icon1589 icon473
Abstract:
An experimental investigation on enlarging the steady working range of skewed-swept rotating blades has been completed.Two types of fan were compared,a fan with conventional (radial) rotating blades and other with the skewed-swept blades.One comparative group was carried out on the conditions of same rotating speed and geometrical parameters but median chord of the skewed-swept rotating was increased about 20 4%,another was carried out at same peak pressure ratio and flow rate.The results of aerodynamic-aeroacoustic performance testing of the groups show not only a noise reduction about 2-4 dB(A) overall,and an increase of aerodynamic efficiency for the skewed-swept blad,but also a great enlargement of steady working range (one group about 21%,other more than 22%).On the basis of the experimental results,the mechanism of the enlargement of steady working range for skewed-swpet rotating blades was analyzed.
NUMERICAL SIMULATION OF REACTING FLOWS IN NOZZLE
Wang Jianping, Fang Dingyou
1996, 11(3): 233-236,327-328.
Abstract PDF(318KB) icon1733 icon439
Abstract:
The numerical simulation of chemically reacting flows in the nozzle is accomplished by a time-dependent technique using semiimplicit scheme.A second-order implicit difference approximation is applied to the time derivatives in governing equations and a noncentered difference approximation is explicitly employed to the spatial derivatives.The numerical instability caused by the stiffness of chemical relaxation equations is succesfully depressed by the above measure.The results obtained from numerical simulation of one-dimensional and axisymmetric nozzle flows are presented.
NAVIER-STOKES PREDICTIONS OF 2-D VECTORED NOZZLE FLOWS
Feng Jianhu
1996, 11(3): 237-240,328.
Abstract PDF(297KB) icon1998 icon397
Abstract:
In this paper,the viscous flows in the two-dimensional vectored and unvectored nozzles are numerically simulated by three-dimensional time-dependent Navier-Stokes equations in conservation forms.Finite volume discretization is used in spatial form and Runge-Kutta method in time marching direction.A new viscous terms' discretization in the frame-work of the finite volume method is used which has the advantages of less operation counts and full conservation.A modified Baldwin-Lomax algebraic turbulent model and wall function law are also adopted in the prediction.Comparision of numerical predictions with experiments shows that the Navier-Stokes code can accurately predict the flow fields in the vectored and unvectored nozzle where the flow is predominantly two-dimensional at the designed nozzle pressure ratios or above.Discrepancies between predictions and experiment are found at lower nozzle pressure ratios where separation typically occurs in a large portion of the nozzle.
EFFECTS OF GEOMETRIC PARAMETERS OF SUBMERGED DELTA VORTEX GENERATOR ON VORTEX
Zhong Yicheng, Chen Xiao
1996, 11(3): 241-244,328.
Abstract PDF(592KB) icon1880 icon434
Abstract:
The effects of the geometric variables of a submerged deltaic vortex generator on the parameters of the vortex have been experimentally studied and a type of half deltaic vortex generator has been developed.A small-size five-hole pressure probe was used to measure the velocity profiles at several transverse sections behind the vortex generators and according to the velocity profiles,the Gauss model of vortex core and quasi-Newton non-linear least square method were used to determine the parameters of single vortex such as vorticity,radius and height of the vortex core.The variation of these vortex parameters along the stream wise was analysed.In the experimental investigation the vortex parameters between the submerged deltaic vortex generator and the submerged concave vortex generator were also compared.
EFFECTS OF AUTOMATICALLY POSITIONING BLADE ON FLOW CHARACTERISTICS IN AN S-SHAPED AIR INLET
Weng Peifen
1996, 11(3): 245-248,328-329.
Abstract PDF(633KB) icon1538 icon446
Abstract:
An automatically positioning blade with a NACA 0012-series profile was placed upstream near the throat of an S-shaped diffuser and experimented to investigate the characteristics of the flow behind it.The results show that two angular positions have been found where the blade experiences no resultant aerodynamic moment,i.e. 15° and -12°.Moreover,the swirls at the duct exit have different senses of rotation when the blade is held at these two angles.The study lays the foundation for suppression of the duct swirl and its simulation.
DETERMINATION OF REVOLUTION DIFFERENCE LINE FOR TWIN-SPOOL TURBOJET ENGINE
Shang Yi, Guo Yufei
1996, 11(3): 249-252,329.
Abstract PDF(273KB) icon1732 icon400
Abstract:
The revolution difference of the low and high pressure rotors is a parameter for acceptance tests of a twin-spool turbojet engine.It indicates the relation between the reduced revolution of the high pressure rotor and the reduced turbine inlet temperature and also shows the matching between the low and high pressure rotors.In order to determine the revolution difference for a twin-spool turbojet engine it is necessary to define a standard revolution difference line for this type of engine.This paper analysis considers various possible approaches for the revolution difference line computation and suggests how to define the standard revolution difference line in practice.
STUDY ON AIRCRAFT ENGINES USED IN COAL-FIRED DIFFERENT-VELOCITY BED COMBINED CYCLE SYSTEM
Zhao Li, Xu Xiangdong, Zhu Weimin
1996, 11(3): 253-256,329.
Abstract PDF(267KB) icon1647 icon426
Abstract:
A new combined cycle system for generating electrical power from coal-Carried-heat Partial Gasification Coal-fired Combined Cycle (CGCC) is introduced by Tsinghua University,Which adopts a gas turbine modified from FT-8 aeroengine.Through analyzing the function of the gas turbine,using modeling technique,the design and off-design regimes of the gas turbine are considered comprehensively.It is proved that application of the FT-8 to CGCC system has a great advantage.
QUASIDYNAMIC ANALYSIS OF HIGHSPEED THRUST BALL BEARINGS
Luo Zhusan, Wu Linfeng, Sun Xinde, Gao Xiangqun
1996, 11(3): 257-260,329-330.
Abstract PDF(866KB) icon1652 icon524
Abstract:
A quasi-dynamic analysis of high-speed thrust ball bearings is proposed to predict the kinematic characteristics.The rolling velocity and relative sliding velocity of each point in contact zone of balls and rings in a ball bearing are determined at first.According to the elastohydrodynamic and hydrodynamic lubrication theories,the reactions between the rolling pairs and the effects of heat and oil starvation on the thickness of oil film are considered.Then the principles for setting up the basic equations of the balls,the cage and the inner ring are established for the quasi-dynamic analysis of the thrust bearings.The kinematic characteristics,the load distribution,the thickness of the oil film and the fatigue life of the ball bearings can be obtained from solution of those equations.It is shown that the rotary speeds of the cage and the balls decrease and their skiddings become serious as the thrust goes down,especially to a small value.So the minimum thrust preload for prevention of skidding of the balls on the inner race can be estimated.
INTERMITTENT AND CHAOTIC PHENOMENA IN A RUB IMPACT ROTOR SYSTEM
Chu Fulei, Feng Guanping, Zhang Zhengsong
1996, 11(3): 261-264,330.
Abstract PDF(668KB) icon2279 icon503
Abstract:
Vibration characteristics of a rub impact rotor system supported on oil film bearings were investigated.Elastic impact and the Coulomb type of frictional relationship was assumed.Rotating speed and the system damping were used as control parameters to discover routes to and out of chaos and to study various forms of periodic、quasi-periodic and chaotic vibrations.Very rich types of chaotic vibrations were found for the model discussed.Also the system motion shows two different forms of intermittent phenomena.One is the interchange between periodic and quasi-periodic vibrations.Another is between periodic and chaotic vibrations.Vibration features such as chaotic vibration,intermittent phenomena and broad-band of periodic vibration can be effectively used to diagnose the rub impact fault which often happens in a rotor system.
EXPERIMENTAL INVESTIGATION ON ROTOR VIBRATION CONTROL BY ELECTRORHEOLOGICAL DAMPER
Meng Guang, Ying Dazhang, Yao Guozhi
1996, 11(3): 265-268,330.
Abstract PDF(635KB) icon1637 icon515
Abstract:
In this paper the Electrorheological(ER) fluid and its characteristics are introduced briefly and the application of an ER damper in rotor vibration control is studied experimentally.It is found that by increasing the applied electrical field strength,the damping and stiffness of ER damper are increased, the vibration amplitude of the rotor system supported on ER damper is decreased in the sub-critical speed range and at the critical speed, and is increased in the super-critical speed range. The critical speed of the rotor system can be changed by means of the applied electrical field strength. The damping provided by the ER damper has the properties of both the Coulomb damping and the viscous damping. Experimental results show that the ER damper has obvious effect on vibration control,and features instantaneous control,little energy consumption and broad frequency range.Besides,it's structure is simple.
AN EXPERIMENTAL STUDY OF HEAT TRANSFER BY JET IMPINGEMENT ON ROUGHENED SURFACE WITH INITIAL CROSSFLOW
Zhang Dalin, Chang Haiping, Han Dong, Sheng Rongchang
1996, 11(3): 269-272,330-331.
Abstract PDF(338KB) icon1586 icon428
Abstract:
Impingement heat transfer from the rib roughened surface with two-dimensional arrays of circular jet has been investigated in comparison to the jet orifice plate.The study covered jet at Rej=5000-20000;the initial crossflow rate Gc/Gj =0-1.3;and nondimensional jet-to-surface spacing Zn=1.5,2,2.5,3.The experimental results show that the impingement heat transfer from the rib roughened surface will be improved by increasing the initial crossflow rate.The heat transfer characteristics are considerably affected by the jet-to-surfaces spacing,and there exists an optimum.The effect of relative position of jet hole to ribs on heat transfer has been observed.
EXPERIMENTAL STUDY ON ATOMIZATION CHARACTERISTICS OF PLAIN ORIFICE AT SUBATMOSPHERIC PRESSURE
Xu Puqing, Wang Jiahua
1996, 11(3): 273-276,331.
Abstract PDF(269KB) icon1717 icon526
Abstract:
The atomization characteristics of a plain orifice at subatmospheric pressure were studied by means of pulsed laser holography,and hologram images of cross-spray downstream fuel cloud field were analysed with computer image system.The results obtained show how the mean particle size and particle size space distribution vary with air velocity、ambient pressure and spray fuel pressure.The first,the air velocity is a primary factor that affacts the fuel atomization at either normal or subatmospheic pressure,the mean particle sizes monotonically increase as the air velocity decreases.The second,as the air density reduces with descending ambient pressure,aerodynamic force and turbulent fluctuation are reduced which force spray fuel sheet to breakup and drop size to fall to a critical value.As a result,the penetration is augmented,atomization is retarded,and mean drop diameter is increased,as well as fuel density space distrbution becomes non-umiform and the quality of atomization obviously deteriorates.Therefore,the ambient pressure is also important to atomization.The last,when the nozzle spary goes across the direction of air,at subatmospheric pressure spary penetration depth rises more rapidly than at atmospheric pressure as the fuel-injection pressure increases.
NUMERICAL SIMULATION OF COMBUSTION PROCESS IN LRE TEST COMBUSTION CHAMBER
Wang Zhenguo, Zhou Jin, Yan Xiaoqing, Zhuang Fengchen
1996, 11(3): 277-280,331.
Abstract PDF(278KB) icon1774 icon388
Abstract:
Two-phase turbulent reacting flow model of the internal operating processes in Liquid Rocket Engine (LRE) is set up in non-orthogonal curvilinear coordinates.By means of this model,numerical simulation of the combustion flow process in LO x/GH 2 test rocket engine has been accomplished.From the simulation,velocity patterns,contour maps of gas species concentration,temperature,pressure,Mach number,combustion efficiency,and plots of wall temperature and average radiateion temperature,and plot of spray vaporization are obtained.
LIQUID ROCKET ENGINE FAULT DIAGNOSIS BASED ON QUALITATIVE/QUANTITATIVE MODEL
Huang Weidong, Wang Kechang
1996, 11(3): 281-284,332.
Abstract PDF(556KB) icon1751 icon500
Abstract:
In order to eliminate the inherent drawbacks of qualitative fault diagnosis method,it is necessary to use quantitative information.The signed direct graph (SDG) of liquid rocket engine system lacks quantitative information.Therefore,it is improved by replacing the sign on the branches by the ratio between deviations of the effect and cause variables.The membership function of fuzzy set theory is used to integrate quantitative process knowledge into the SDG model,thus a qualitative/quantitative model is formed.After the membership function has been defined,it is easy to get the membership between the engine system and the patterns whose fault origins are known by this model,the fault of the engine system can be found according to the principle of maximum membership.This method utilizes enough available numerical resource of variables monitored in the system,it is shown by the diagnosis results that the method has a better identification and resolution capability for the fault patterns with identical qualitative features and can also identify the fault quickly.
NUMERICAL SIMULATION OF STEADY PROCESS FOR THRUST MODULATED SRM
ZHang Weihua, Guo Jian, Hou Zhongxi, Fang Dingyou, Xia Zhixun
1996, 11(3): 285-288,332.
Abstract PDF(278KB) icon1909 icon432
Abstract:
The steady process of solid rocket motor modulated by the vortex valve is investigated theoretically.The design of structural parameters for the vortex valve is considered with the method of steady analysis,and some useful conclusions are drawn.The modulation effect is much better if we have better heat-insulating situation.Reduction of the pressure exponent of the main chamber grain helps increasing the modulation effect.
A REAL TIME ON-LINE FAULT DETECTION ALGORITHM BASED ON TIME SERIES ANALYSIS FOR LIQUID ROCKET ENGINE
Wu Jianjun, Zhang Yuling, Chen Qizhi
1996, 11(3): 289-293,332-333.
Abstract PDF(441KB) icon1822 icon495
Abstract:
A real time on-line fault detection algorithm is set up and realized,which mainly employs the theory of time series analysis.A key concept for fault detection is a whiteness test on the computing residual vector over the evolution time window.A standard autocorrelation whiteness test is used,where the residuals are assumed to be white,and a 99% confidence interval threshold is adopted in the autocorrelation domain.The off-nominal test then is reduced to a thresholding technique performed on the lag terms of the residuals autocorrelation.Therefrom a fault detection scheme is designed,which includes two steps,the first is to declare an event for any model whenever the first ten lags of its residuals autocorrelation exceeding a 99% confidence interval,the second is to declare a fault condition if at least M individual ARMA models declared an event in N measured parameters ( M≤N ).Verification with a number of fire-test data of real engines shows that the algorithm is very effective and applicable for practical engineering.
APPLICATION AND LIFE RESEARCH OF POWDER METALLURGY TURBINE DISKS
Song Yingdong, Wen Weidong, Gao Deping
1996, 11(3): 294-298,333.
Abstract PDF(346KB) icon2071 icon492
Abstract:
Since powder metallurgy(PM)turbine disks hav ehigh yield strength and excellent property of resistance to fatigue and creep,they have been applied broadly in the most advanced engines at pressent in the world.As the thrust-to-weight ratio increases,the PM turbine disks will be developed in our country.At first,this paper makes a general survey of the application of the PM turbine disks.Then a review is made for the material properties,fatigue life,crack propagation,and stress analysis of PM turbine disks.Finally,so meresearch projects of the PM turbine disks fatigue life,which should be conducted in our country,are suggested.
RESEARCH ON BLADE EXCITATION FREQUENCY DURING ROTATING STALL OF AXIAL FLOW COMPRESSOR
Liu Yan, Zhu Junqiang
1996, 11(3): 299-302,333.
Abstract PDF(276KB) icon2098 icon522
Abstract:
This paper presents an investigation of blade excitation during rotating stall in a single stage axial flow compressor with various geometrical parameters,such as blade stagger and cascade solidity at the mean radius varying from 32.9 to 47.9 and from 0.583 to 1.165,respectively,and the axial distance between rotor and stator from bto 5.7b.The blade vibration was measured with strain gages on the blade.During rotating stall as the cause of blade excitation,the flow field was simultaneously deter mined by fast response dynamic pressure transducers.The rotational speed of the compressor varied from 8130 to 12500 rpm.The charact eristics of unst eady flow during rotating stall were studied in detail. The prediction criterion of the blade excitation frequency during rotating stall has been set up.The agreement between theoretical and experimental results indicates that the criterion is feasible.
INVESTIGATION OF OUTLET SECONDARY FLOWS IN CASCADES WITH END-BEND BLADES
Zhou Zhenggui, Wu Guochuan, Hu Bin
1996, 11(3): 303-305,333-334.
Abstract PDF(677KB) icon1829 icon504
Abstract:
The outlet secondary flows in compressor cascades with end-bend blades have been studied experimentally and numerically.The viscous secondary vorticity equations are applied to prediction.The experimental and predicted data of the outlet angle due to the secondary flow are presented for three cascades with end-bend blades and one with the corresponding unbended blades.The investigation shows that the change in outlet angle can be accurately predicted by the presented method.Reducing curvature of the blade rear part makes the averaged intensity of the streamline component of the outlet secondary vorticity decrease,but does not change the distance from the center of the vorticity to the end wall.
A MODEL TO CORRELATE FLOW SEPARATION WITH FLOW LOSS IN A TRANSONIC ROTOR
Zhang Yangjun, Chen Naixiang, Zhou Zhenggui, Wu Guochuan
1996, 11(3): 306-308,334,336.
Abstract PDF(293KB) icon1548 icon453
Abstract:
A model correlating flow separation with flow loss is proposed for predicting the incipient location and size of the flow separation in a transonic rotor.The flow fields of several rotors have been investigated with the model.The results show that the flow separation mainly occurs in the tip area owing to strong shock boundary interaction,and the incipient separation point is behind the shock location.The tip leakage flow vortex has a strong effect on the interaction between shock wave and boundary layer.
A PRELIMINARY INVESTIGATION ON CONTROLLING JET STRUCTURE BY HYDRODYNAMIC EXCITATION
Zhang Qingfan, Li Feng, Zhong Bo, Zhou Huihua
1996, 11(3): 309-311,334.
Abstract PDF(239KB) icon1473 icon397
Abstract:
Jets were excited by Karman Vortex Streets under three conditions of Jet Mach Number 0 206,0 361 and 0 831.Three vortex generators with different geometries were tested.Jet Velocity distributions with and without excitation were measured by stagnation presure probe.The turbulent characteristics in the jet boundary layer were detected by a single hot wire probe.It is shown that excited jet velocity decay faster than that of unexcited jet,and turbulent energy in jet boundary layer is significantly increased by votex excitation.Therefore,jet structure can be effectively controlled by hydrodynamic excitations.
A STUDY ON SUPERSONIC 6-NOZZLE EJECTOR PERFORMANCE
Wang Suofang, Li Liguo
1996, 11(3): 312-314,334-335.
Abstract PDF(1684KB) icon1829 icon509
Abstract:
The supersonic 6-nozzle ejector performance has been investigated experimentally for the given geometric dimensions.The experiment ranges over 1.98≤Pp*/Ps*≤7.46,0.971≤Tp*≤Ts*≤1.02 and Lm/Dm=0.80.The entrainment ratio x varies from 6.96 to 11.66 for the ejector with a diffuser,and its corrected value x/√Ts*/Tp* varies from 6 88 to 11.62;on the other hand,the entrainment ratio varies from 2.82 to 6.28 for the ejector without the diffuser,and its corrected value varies from 2.78 to 6.24.The experimental results show that the entrainment ratio and its corrected value decrease with the increase of Pp*/Ps* ,but the corrected momentum coefficient Km in the mixing pipe goes up.The mass flow rate coefficient μ of the primary nozzle increases slightly as the entrainment ratio goes up .The theoretical analysis has been done for the above conditions by application of aerodynamics.The comparison between the analysis and the experiment shows a good agreement.
SUBSTRUCTURE ITERATION FOR ANALYZING DYNAMIC BEHAVIOUR OF A CASING-SUPPORT-ROTOR SYSTEM
Liao Mingfu, Wei Xudong, Liu Qizhou
1996, 11(3): 315-316,335.
Abstract PDF(193KB) icon1495 icon449
Abstract:
In order to investigate the dynamic behaviour of a casing-support-rotor system,an approach associated with substructure iteration and transfer matrix is developed.With help of the approach,the dynamic response analysis of a complex rotor system is simplified and the computation time is lessened.The convergence and stability of the approach are verified with a simple model.
STUDY ON REDUCTION FACTOR OF FATIGUE STRENGTH AND DISPERSION COEFFICIENT OF LIFE IN SEAM WELDED JOINTS
Fan Yinhe
1996, 11(3): 317-319,335.
Abstract PDF(236KB) icon2095 icon617
Abstract:
The purpose of this work is to study low cycle fatigue life of engine cases.A welded test piece has been designed according to reality of cases,using material of 1Cr18Ni9Ti in order to get fatigue function survey of seam welded joints.From tests S-N curve and P-S-N curve are obtained.Then the reduetion factor of fatigue strength and dispersion coefficient of fatigue life for the seam welded joints are achieved with statistics analysis methods.Compared with a smooth test piece,the fatigue strength of the seam welded joints is obviously less than smooth test piece,but dispersion coefficient of fatigue life is better.
A BROKEN FILM CALIBRATION SYSTEM OF DYNAMIC PRESSURE MEASUREMENT
Jiang Yong
1996, 11(3): 320-322,335-336.
Abstract PDF(288KB) icon1495 icon374
Abstract:
The investigated calibration system of dynamic pressure measurement with response frequency less than 1 kHz includes two parts:a broken-film dynamic pressure signal generator and an acquisition-analysis system.Many experiment swere carried out for investigating frequency components produced by the signal generator of different lengths,which indicated that the signal generator,under first-order resonant frequency,can produce sufficient frequency components(0.5-1.5 kHz)as exciting resources.Moreover,the calibration system was used for dynamic calibration of three pressure probes of different lengths with a pressure sensor respectively.Meanwhile a particular way is adopted to obtain precise frequency response charact eristics only by measuring the pressure probe output.It is shown that the calibration system is simple,reliable,and applicable.
EFFECTS OF REINFORCED TURBULENCE ON SPRAY DISTRIBUTION AND TEMPERATURE PROFILE BEHIND AIRBLAST ATOMIZER
Zou Zhengping, Huang Xuemin, Wang Hongming
1996, 11(3): 323-326,336.
Abstract PDF(280KB) icon1652 icon454
Abstract:
The effects of turbulence intensity on liquid spray distribution and temperature profile behind airblast atomizer have been investigated.Three test model airblast atomizers with different turbulence intensity were experimented:the base line model,the one with lots of small air injection in outer swirler channel and the another with turbulence treatment on the outer swirler wall.The measurements were done by PDA (Particle Dynamic Analyser) to map out the spray and flow characteristic on cold condition,and thermocouple was used to acquire the temperature profile during combustion test.The cold tests show that the secondary atomization,spray and air mixing process can be promoted by the model with reinforced turbulence structure,and more uniform spray distribution can be achieved in the nearer downstream section.The combustion tests show that more even temperature profile and higher combustion efficiency can be obtained.It is because that turbulence fluctuation can effectively promote liquid atomization and spray transportation,and also enhance the burning rate of mixture evidently.

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