1987 Vol. 2, No. 2

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EXPERIMENTAL RESULTS OF AEROELASTIC INSTABILITY OF AN AXIAL COMPRESSOR
Feng Yucheng, Hu Zongan, Zhao Xiuhua, Wang Yuwei
1987, 2(2): 97-100,183.
Abstract PDF(484KB) icon1782 icon405
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This paper describes the initial experimental results of aeroelastic instability of BF-1 rotors on a transonic axial compressor facility at BIAA. Designing of BF-1 rotors depends upon the principle that the total damping is equal to zero at the point near the stall flutter boundary. The experimental results show that the design principle of BF-1 rotors is correct. Two rotors, BF-1-1 and BF-l-2,have been run from 8000 rpm to 16500 rpm. Several flow-induced vibration phenomena such as stalling flutter,wake-induced vibration, stall vibration of the blades,have been observed in experiments. In addition,a loud monotonous screaming has been heard during the stalling flutter onset. A primary theoretical analysis of this special sound is discussed. This paper also presents the experimental results of effects of the blade tip clearance and the airfoil shape on the stall flutter boundary. By comparison of the empirical methods to predict the stall flutter onset with the experimental results,it is believed that these prediction methods are acceptable.
NUMERICAL SOLUTION OF TWO-DIMENSIONAL INCOMPRESSIBLE VISCOUS FLOWS IN CASCADES
Wang Licheng, Zhang Huiming, Yang Chongying
1987, 2(2): 101-104,183-184.
Abstract PDF(492KB) icon1523 icon373
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This paper aims at developing an incompressible N-S equation solver for two -dimensional compressor cascade flows with massive separation for engineering applications. A staggered grid system different from that of SIMPLE method is proposed to make discretization and implementation of boundary conditions very simple and to reduce the computational efforts needed for a two- or three-dimensional problem nearly to the efforts for one-dimensional one. To ensure the numerical stability of convection-diffusion equations,a so-called upwind factor method is devised, which is robust and accurate. To deal with the determination of the pressure field an algebraic pressure correction expression is derived to simplify the numerical scheme further.To verify the scheme four different compressor cascades are taken as examples for numerical experiments. The incident angle varies from -13 to +11. The numericalresults of the deviation angle and separation point are compared with the corresponding physical experimental data in good agreements.
COMPARISON OF THREE EXPERIMENTAL METHODS FOR TRANSONIC TURBINE CASCADES
Yang Xuezhen
1987, 2(2): 105-108,184.
Abstract PDF(450KB) icon1743 icon392
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Three typical transonis turbine cascades have been designed for this purpose and tested with the aid of three different methods(two-dimensional cascade wind tunnel test, wind tunnel test with sector of annular cascade,and hydraulic analogy). The results of these three methods are compared under the condition of geometry similarity. They are also compared with numerical solutions of the Finite Area Time Marching calculation. The strong and weak points and reliability of these methods are evaluated preliminarily.
EXPERIMENTAL INVESTIGATION OF A DOUBLE CIRCULAR ARC CASCADE WITH 73° CAMBER
Cheng Gang
1987, 2(2): 109-112,184.
Abstract PDF(427KB) icon1723 icon379
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A double circular arc (DCA) cascade with 73° camber has been tested, and accordingto the test results its critical Mach number, optimum incidence, deviation angle,pressure distributions on airfoil surfaces,pressure losses and incidence angle range are analysed. This cascade is also compared with a supercritical airfoil cascade.The results indicate that the DCA cascades with such large camber still can achieve good aerodynamic performances(large turning,high velocity,low loss and wide incidence angle range)and coincide well with the general princples of DCA cascades provided that the cascade parameters are chosen correctly and distribution of passage area is reasonable.
INVESTIGATION OF SUPERSONIC MULTIPLE CIRCULAR ARC (MCA) AIRFOIL CASCADE OF AXIAL-FLOW COMPRESSOR
Zha Gecheng, Yan Ruqun
1987, 2(2): 113-116,184-185.
Abstract PDF(1135KB) icon2092 icon531
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A computational method of characteristics initial-value line in the rotational supersonic cascade flow field with detached shock waves is presented. With the solution of complete Euler flow equations by shock fitting method, a MCA cascadesupersonic inlet flow field containing detached waves is computed. The calculateddetached shock waves before the cascade and the pressure distribution in the supersonic region are satisfactory. From the calculated results of the flow field, the relation between the Mach number and the unique incidence, which meets the design requirements can also be obtained.In our investigation ,the loss-computational method of the supersonic cascade is also firstly presented, which correlates the computation of supersonic flow field with the wake method of subsonic profile. This method can determine the shock loss and the subsonic profile loss separately. Agreement between the calculatedand the measured total loss is quite good.
EQUIVALENT LINEARIZATION OF A NONLINEAR ELEMENT WITH RESPECT TO SUBHARMONIC MOTIONS
Chen Songqi, Xu Jiankang
1987, 2(2): 117-120,185.
Abstract PDF(421KB) icon1653 icon486
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This paper presents a linearization technique for nonlinear force by the methodof harmonic balance. The element which produces nonlinear force is incorporatedinto the multidegree-of-freedom system, the steady-state motions at the element have components that are non-synchronous with the external harmonic force exerted on the system. The equivalent force component is supposed to pe composedof two parts. The first part is the sum of an average force ,a linar spring force and a linear damping force just as in the case of linearization with respectto harmonic motions. The second part is the sum of the equivalent external harmonic forces having frequencies like those present in the non-synchronous motioncomponents at the element. The unknown parameters that characterize the equivalent force may be expressed analytically by the original nonlinear force and the assumed steady-state motion at the element, and may be evaluated by an iterativeprocedure. The technique is illustrated and tested for the sub-harmonic whirling of an unbalanced rigid rotor incorporating squeeze-film damper,without centralizing spring. The obtained results agree well with those from the full transientsolutions when using the Runge-Kutta method. But if the linearization technique is used,the computation time may be significantly reduced.
INVESTIGATION ON THE NON-SYNCHRONOUS RESPONSES OF FLEXIBLE ROTOR——UNCENTRALIZED SQUEEZE FILM DAMPER BEARINGS SYSTEM
Meng Guang, Xue Zhongqing, Zhu Changsheng, Feng Xinhai
1987, 2(2): 121-125,186.
Abstract PDF(507KB) icon1556 icon415
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The characteristics of the non-synchronous response of a flexible rotor---uncentralized squeez film damper bearings system are investigated theoretically and experimentally. In the result it is found that.1. In case of unsuitable selection of system parameters, the system responsesvary with the increase in speed ratio from harmonic to 1/2 subharmonic, then harmonic response follows again and is succeeded by the sub-harmonic responsesof 1/3, 1/4,1/5,1/6, ...... consecutively. In some cases, the procession of the whole non-synchronous orbit is observed. The non-synchronous responses can be suppressed by choosing suitable system parameters.2. Medium value of bearing parameter B should be chosen,too big or too small value of B may cause non-synchronous and instable responses. 0.15
CALCULATION OF TURBINE DISK VIBRATION CHARACTERISTICS
Zhu Zhigen
1987, 2(2): 126-130,186-187.
Abstract PDF(539KB) icon1187 icon387
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The vibration of turbine disk is analysed using thin plate and Mindlin thick plate theory. The displacement function in circumferential direction can be representedby means of Fourier Series,so that the two-dimensional problem becomes one-dimensional.Based on the governing equations of plate the equivalent one order differen- tial equation sets can be derived. The frequency equation can be obtained using numerical integration method, such as Runge-Kutta method, under certain boundaryconditions, Muller method to solve the resonant frequency of disk is also employed.The calculation results agree better with experimental data than the results of the finite element method. Moreover, the computer program can be significantlysimplified and the computer time can be considerably reduced.
RESEARCH ON OVERLOAD TO STOP CRACKING FOR USED COMPRESSOR BLADES
Hou Jingyong
1987, 2(2): 131-135,187.
Abstract PDF(2529KB) icon1478 icon407
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In order to increase the service life of compressor blades, the effects of overload on fatigue crack formation life in the stainless steel compressor blades which have served for 840 hours and have had some damage on its surface have been investigated. The results show that the residual fatigue life of blades increases with the increasing overload ratio m, and when the overload ratio m≥1.6, the residual life of blades is obviously increased. But when m< 1.48, the effects of overload on blade life is not pronounced.
TRANSONIC VIBRATION INDUCED BY MISMATCHING BETWEEN ENGINE AND THRUST NOZZLE
Lun Yjyun
1987, 2(2): 137-140,187-188.
Abstract PDF(594KB) icon1541 icon389
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The transonic vibration occured in the flight tests of some combat aircraft at H=3000-4000m and Ma=0.82-0.96 is analyzed in this paper. For nozzle pressure ratio of about 2.9-4.6,the vibration frequency ranged from 8 to 12Hz. Some measures were taken to discover the vibration source, such as eliminating the clearance of the aircraft structure,blocking air inlet apertures in the tail sectionof the aircraft,streamline tracing with power and strapping, and model testingin wind tunnel,but all of them failed.On the basis of extensive investigation and calculations,it was decided to make simulation test of the ejector nozzles with increased secondary flow rate or with the nozzle shroud apertured for third flow. Finally it was found out that the transonic vibration was induced by mismatching of engine with thrust nozzle. "Long skirt", "short skirt"and tail shroud with the apertures cotrolled by spring loaded differential pressure valves were tested in the flight tests. During 18 flights,the number of the differential pressure valves increased from 10 to 16,in consequence the vibration reduced to 0.1g or below,and the aircraft passed smoothly through the transonic range.
TECHNIQUE OF THRUST TERMINATION WITH REVERSAL NOZZLE FOR SOLID ROCKET MOTORS
Huang Jianding
1987, 2(2): 141-146,188.
Abstract PDF(582KB) icon1705 icon393
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This paper presents a discussion of the calculation approach to the pressure decay in the motor chamber and thrust transient,as a result of the blowing-out plug of reversal nozzles during the thrust termination process of the solid rocket motor. The delay time in the blowing-out process and correction to the exhaust coefficient Cw under the chamber pressure less than 2500 kPa is considered in the calculation of pressure decay. The transient thrust is calculated by use of the variation of thrust coefficient both in main nozzle and reversal nozzle with the chamber pressure. The tailoff impulse is calculated with integration. A comparison of theoretical calculation with testing results shows that the corrected theoretical calculation approach agrees well with the testing results.
MODELING CALCULATIONS FOR AP/AI/HTPB COMPOSITE SOLID PROPELLANT COMBUSTION
Zhao Yin, Tian Deyu, Jiang Yu
1987, 2(2): 147-152,188-189.
Abstract PDF(667KB) icon1790 icon415
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Based on some new concepts about the description of chemical kinetics of solid propellant combustion,such as dr/dt,the change of temperature with time, to represent the rate of reaction, we propose a comprehensive model describing the combustion of AP/HTPB composite solid propellant. A large number of detailedcalculations have been performed and compared with the experimental data. The calculations with relative error less than 10% make up 77%. The modeling calculations are conducted for the solid propellant containing Al ingredient and the effects of the Al additive amount and the Al particle size on the burning rate and pressure exponent are investigated. Data calculated by this method are found to be accurate to less than 10% for 90% of the results and in good agree- ment with those of the experiments. It is shown that this technique meets the requirements for quantitative estimation.
ANALYSIS OF HEAT TRANSFER OF FLUIDS OSCILLATING WITHIN PIPES
Zhu Gujun, Zhao Lingde, Cao Yuzhang
1987, 2(2): 153-158,189.
Abstract PDF(519KB) icon1516 icon402
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Heat transfer can be enhanced when fluid oscillates axially within pipes. A numerical analysis is given using the finite difference method. The relationship derived from differential equations and unambiguous conditions is written in theform ofwhere ae- the effective thermal diffusivity ,a-the thermal diffusivity, AS-the tidal displacement of oscillation ,R-the radius and L-the length of the pipe. The results obtained show that ae/a is independent of L/R as L>>ΔS and proportional to the square of AS/R, and its value increases with an increase in Wom or Pr. The numerical solution is in good agreement with the data of experiments.
EXPERINENTAL INVESTIGATION ON FLOW PERFORMANCE OF TANDEM BLADE CASCADES WITH DOUBLE CIRCULAR ARC PROFILES
Zhuang Biaonan, Wu Guochuan, Guo Bingheng
1987, 2(2): 159-161,189.
Abstract PDF(321KB) icon1987 icon407
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Wind tunnel experiments have been made with 24 types of tandem blade cascadeswith different geometrical parameters. Under the conditions that the inlet Mach number is 0.3 and the Reynolds number is 2.7 x 105,the main flow characteristicsof tandem cascades have been obtained, and the operation ranges of main geometrical parameters under optimum conditions have been found.
SUPERSONIC AND TRANSONIC AERODYNAMIC CHARACTERISTICS OF SB301 TWO-DIMENSIONAL CASCADE WIND TUNNEL
Jiang Zhengli, Ma Jinxian
1987, 2(2): 162-164,189-190.
Abstract PDF(1800KB) icon2010 icon393
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SB301 wind tunnel was designed to test two-dimensional cascades of compres- sor in subsonic,transonic and supersonic flow. The wind tunnel has been equipped with advanced instrumentation and enables to accomplish a wide range of experimentation. It is first successful one for testing the two-dimensional cascades of compressor in transonic and supersonic flow in China by now. It provides a new test rig for research and development of aeroengines with high performances.
COMPUTER-AIDED EXPERIMENTAL INVESTIGATION OF AXIAL-FLOW COMPRESSORS
Zhu Nianguo, Chen Maozhang
1987, 2(2): 165-166,190.
Abstract PDF(281KB) icon1410 icon395
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An approach has been developed to evaluate some important aerodynamic parameterssuch as air-flow angle, blockage factor and loss coefficient, at immeasurablesurfaces. It can be used for two cases of measurement of multi-stage, axial-flow compressors. In order to testify this approach, several examples have been calculated and the results show that this approach provides reliable data for further performance improvement.
AN EXPERIMENTAL STUDY ON THERMAL STRESS IN CYLINDRICAL CASE
Shang Weijun, Zhang Weixin
1987, 2(2): 167-169,190.
Abstract PDF(328KB) icon1357 icon486
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This paper describes temperature and thermal stress distributions as well as measuring technique and method to generate these two parameters. The temperaturedistributions are produced by iodine-wolfram lamps and measured by thermocouples.The temperature fields which are steady and symmetrical have both axial and radial temperature gradients. The experimental curve has been fitted with the aid of the least square method in form of algebraical polynomials. Under such temperature distributions,the measurements of thermal stresses in cylindrical case with fixed ends were carried out by mid-temperature strain gauge,and the profiles of thermal stresses versus the case axial distance were obtained.In addition,thermal stresses were calculated numerically employing the finite element method, SAP-5 program. The calculated results are compared with the test data satifactorily.
AN EXPERIMENTAL INVESTIGATION OF FORCED SURGE BY WATER INJECTION IN A TWIN-SPOOL TURBOJET ENGINE
Zhang Ju, Wu Yuegeng, Yun Qisheng
1987, 2(2): 170-172,191.
Abstract PDF(362KB) icon1805 icon406
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An experimental investigation of forced surge by water injection in a twin-spoolturbojet engine has been performed on the ground thrust bed. It is demonstratedthat water injection into the main combustion chamber coupled with the flow area scale-down of both turbine nozzle and jet nozzle is satisfactory for the test. An optimum scale-down percentage of both areas was found from a large number of tests.During such combined forced surge process, the engine operating condition can approach the surging boundary accurately along the line of the corrected constantrotation speed. Hence,exact stable operating margin as well as stable operatingboundary for the compressor can be obtained.
A DATA AQUISITION AND PROCESSING SYSTEM FOR SMALL WIND TUNNEL TESTING
Jiang Zhi, Tang Zhiming, Ning Huang
1987, 2(2): 173-175,191.
Abstract PDF(319KB) icon1499 icon388
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This paper presents a data aquisition and processing system designed and adapted to small wind tunnels for testing simulation models. For convenience and efficiency a remote control subsystem is especially designed for communication between the computer and the testing site. The relevant data aquisition and processingsoftware package has been composed. Actual operation of this system shows that its performance is satisfactory. This system can process a data collection of 5x50 messages in 10 different conditions in only a few minutes.
EFFECTS OF FLAMEHOLDER GEOMETRY ON PENETRATION AND MAXIMUM CONCENTRATION LINE OF FUEL SPRAY
Gu Shanjian, Yang Maolin, Wu Jipin
1987, 2(2): 176-178,191-192.
Abstract PDF(371KB) icon1621 icon483
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The penetration and the maximum concentration line of fuel spray are very important for designing afterburner. The effects of airstream velocity, pressure drop across the orifice of fuel ejector and diameter of fuel ejector on the penetrationand the maximum concentration lion of fuel spray have been studied. When the flameholder is mounted in the test section, both the direction of flow and the magnitude of velocity vary consequently. It is necessary to consider the contribution of these factors to the fuel distribution. Therefore the effects of vertex angle and position of the flameholder on the penetration and maximum concentration line of fuel spray are further investigated experimentally. The expirical formulas are obtained from the test results.
NUMERICAL RESEARCH OF TURBULENT FLOWS IN A CYLINDRICAL COMBUSTOR
Zhao Jianxing
1987, 2(2): 179-181,192.
Abstract PDF(417KB) icon1637 icon488
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A two-dimensional transient finite difference technique has developed to predict recirculation zones behind bluff body f lameholder in a cylindrical combustor. For turbulent flow simulation,the two-equation k-e turbulent model has been comprised in a simple computer program. The governing equations consist of continuityequation,momentum equation, turbulent kinetic energy equation and turbulentkinetic energy dissipation rate equation. The calculations show that the dimensionlesslength L/d of recirculation zones and the maximum mass flow rate Mr/Mo increase with the flameholder cone angle a. The results are infair agreement with experimental data. Therefore,the transient time-marching method employedin this paper is quite simple and reasonable.

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