1988 Vol. 3, No. 3

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BEVEL GEAR RESONANCE FAILURES IN CENTRAL GEARING SYSTEM OF AN AEROENGINE
Xu Ejun, Liang Shichang, Chang Chunjiang, Shen Bingyan
1988, 3(3): 193-198,279.
Abstract PDF(1264KB) icon1611 icon357
Abstract:
The resonance failures of the bevel gear in the central gearing system of an specific aeroengine have been investigated experimentally. The features of the resonance failures, the failure modes and structural dynamic characteristics are summarized, and the reasons for resonance are clarified. Some preventive measures against the failures are suggested and criteria for the dynamic strength design of this type of gear are specified.
ANALYSIS OF LATERAL VIBRATION OF A BEVEL GEAR
Van Litang, Li Qihan
1988, 3(3): 199-202,279.
Abstract PDF(443KB) icon1686 icon432
Abstract:
This paper deals with the lateral vibration characteristics of the diskshaped bevel gear including the lateral vibration modes and stress distribution, vibration excitng force at normal meshing and the conditions under which the lateral resonance occurs. The investigation shows that as vibration modes of this kind of gear are nodal diameters, the tangential tensile stress at the slot bottom of teeth will be maximum, especially at the small end of the bevel gear. Therefore, it is easy to initiate fatigue cracks there.A new theory about the conditions of lateral resonance for the disk-shaped bevel gear is presented and the experimental data are in excellent agreement with the theoretical analysis.
PHOTOELASTIC STRESS ANALYSIS OF A BEVEL GEAR
Dong Benhan, Gao Pengfei
1988, 3(3): 203-206,280.
Abstract PDF(419KB) icon2011 icon385
Abstract:
The three-dimensional photoelasticity method is used to analyze the stress distribution in the bevel gear under torsional moment and centrifugal load. The results show that the stress distributions in roots of the bevel gear are different under respective loads. According the results and the comprehensive vibration test data, it can be concluded as follows: 1. The cracks at the nothes of the bevel gear teeth are not caused by starting torque. 2. At high gearing speed the combined stresses of centrifugal load and resonance vibration at the notches are the main cause for the catastrophic failure of the bevel gear.
SIMULATINC CALCULATIONS FOR STRESS RESPONSES OF TRAVELLING WAVE RESONANCE IN BEVEL CEAR
Han Erzhong, Gou Xinhui, Yan Shiying, Zhang Rihui
1988, 3(3): 207-210,280.
Abstract PDF(417KB) icon2038 icon484
Abstract:
The formulae of travelling wave resonance in a bevel gear are derived by a simplified method. Emphasis is put on the difference of physical meanings between travelling wave resonance and forced vibration resonance. The function simulating the exciting force in bevel gear is formulated by analogy of meshing force of two straight tooth gears. And then, the stress responses of travelling wave resonances of two and three nodal diameters in the bevel gear may be calculated by FEM. It is proved that the stress response curves plotted dy computer is just the curves of travelling wave resonance of two nodal diameters mode wave motion. The calculated results coincide with the experimental data. The method provided gives more convenience to obtain stress data only by calculation rather than by complicated experimental method.
MEASUREMENT OF RESONANCE SPEEDS AND DYNAMIC FREQUENCIES OF A BEVEL GEAR
Ai Yiren, Ju Xiuting, Yu Peifu, Yan Litang, Li Qihan
1988, 3(3): 211-214,281.
Abstract PDF(410KB) icon1997 icon521
Abstract:
A simple and convenient method is proposed to measure the travelling wave resonance speeds and dynamic frequencies of bevel gear. It is based on the non-contact acoustic detection through several envelopes of engine at high level of background noise. The experimental results indicate that the method is very easy to operate and its measuring accuracy is quite high.
APPLICATION OF END-BEND BLADE FOR ENHANCING SURGE MARGIN
Cai Yunjin, Zhong Yuling, Qian Luhong
1988, 3(3): 215-218,281.
Abstract PDF(460KB) icon1779 icon376
Abstract:
The blade end-bend technique is applied to the first and second stators of the HP compressor of a twin-spool engine to ameliorate the flow on the second and third rotors. The tests of the modified engine show that its surge margin and efficiency are enhanced by 7.3 and 4.1 percent respectively, but the flow and pressure ratio vary only a little. The flight tests prove that the shutdown of the engine which occurred in flight has been eliminated, so that the engine can operate reliably and stably within the overall flight envelope, and the performances of the engine and the aircraft has been improved significantly.
APPROACH TO BLADE END-BEND MECHANISM
Huang Lixi, Wei Xinglu, Peng Zeyan
1988, 3(3): 219-222,281-282.
Abstract PDF(521KB) icon1629 icon448
Abstract:
Blade end-bend is a new technique to improve the performance of compressors. A comprehensive study of two multistage compressors has been completed with numerical calculation, theoretical analysis and experimental investigation.It is shown that the end-bend causes redistribution of the whole flowfield,and the changes of characteristics in main flow region may be a vital factor to improve the engine performance. A comparative study of several end-bend patterns shows that the character of redistribution differs for each from other. It is important to choose the end-bend pattern suitable for the specific compressor.
APPLICATION OF AN ARTIFICIAL DENSITY SCHEME OF POTENTIAL STREAM FUNCTION METHOD TO DESIGN OF AIRFOIL
Liu Bo
1988, 3(3): 223-226,282.
Abstract PDF(426KB) icon1556 icon362
Abstract:
A potential stream function method is applied to designing transonic airfoils. The flowfield is computed by solving the full potential equations with the aid of a relaxation method. An artificial density scheme has been developed to replace the type related scheme. As compared with the latter, the artificial density scheme employs an identical scheme in whole field and converges steadily. Numerical results show that this method is applicable to initial designing of compressor airfoils and provides a better approximation of the actual conditions by taking into account the effect of the axial-velocity-ratio.
UNSTEADY LOADING NOISE OF COUNTER-ROTATING PROPELLER
Sun Xioafeng, Hu Zongan, Zhou Sheng
1988, 3(3): 227-230,283.
Abstract PDF(429KB) icon1538 icon479
Abstract:
The unsteady Loading noise generated by interaction of a front rotor wake with an aft rotor in a counter-rotating(CR) propeller is analyzed and the noise radiation formulae are derived. The numerical prediction of noise of a real CR propeller are completed and compared with experimental data.It is concluded that the sound pressure level (SPL) in the axial direction of the rotor is fully determined by the component of unsteady loading noise, but in rotor plane the main contribution to SPL is the component of steady loading noise and the effect of the unsteady one is limited in the range of higher harmonics in this case.
PROPFAN DESIGN BY PRORELLER-NACELLE INTERACTION ANALYSIS
Zhu Nianguo, Chen Maozhang, Niu Daozhi
1988, 3(3): 231-234,282.
Abstract PDF(438KB) icon1608 icon356
Abstract:
A propeller-nacelle interaction analysis has been developed in this paper as a kind of lifting line analysis. It represents the blades by curved lifting lines, taking into Consideration the blade sweep and the effect of the nacelle on the propfan flowfield. The wake model assumes that the vortex filaments occur along stream surfaces. Some corrections have been made to transonic portion of the blade and large solidity cascade portion at hub. Comparison of the results of the design and analysis with those given in references show the method is feasible and effective, Aspects of its improvement are also discussed.
TWO-DIMENSIONAL SUBSONIC DIFFUSER FLOW WITH UNIFORM SHEAR VELOCITY PROFILE AT INLET
Huang Xijun, Dong Jinzhong, Fan Shixin, Shao Chengshu
1988, 3(3): 235-238,283.
Abstract PDF(427KB) icon1341 icon442
Abstract:
A prediction method has been developed for average parameters of 2-D subsonic diffuser with uniform shear velocity profile at inlet. A complete solution of all flow parameters can be obtained by interacting the zonal models and coupling them on common boundaries. The momentum integral and the entrainment equations are used for the boundary layer zone. The equations are closed by use of the improved Cole's wall-wake velocity profile. Due to different development of the boundary layers on the upper and lower walls of diffuser under conditions of the shear velocity profile in core flow, different equations are employed. Three actual diffusers are calculated by this method and experimented by authors. The predictions by this method for the streamwise distribution of pressure coefficient, velocity of core flow and the location of detachment are in good agreement with test data.
A METHOD FOR DETERMINING EXCESS AIR RATIO AND COMBUSTION EFFICIENCY WITH GAS ANALYSIS
Jiao Shujian
1988, 3(3): 239-246,284.
Abstract PDF(766KB) icon1481 icon370
Abstract:
A series of generalized formulae for determining the excess air ratio and combustion efficiency on the basis of gas analysis of combustion products for any kind of liquid, solid or gaseous fuel is provided in this paper. Due to consideration of carbon formation and fuel vapors in the combustor and on the surface of the sampling probe, this method can provide more accurate results. Of cause, a generalized computer program can be easily compiled for any kind of liquid, solid or gaseous fuel on the basis of the formulae presented.
A CHAIN REACTION MODEL FOR ALUMINUM AGGLOMERATION
Xia Younan, Li Shufen
1988, 3(3): 247-251,284.
Abstract PDF(508KB) icon1832 icon337
Abstract:
In order to describe the aluminum agglomeration process more clearly and quantitatively, a chain reaction model is proposed by analogy with the chain reaction in polymer chemistry. In this model, the agglomeration process can be divided into three steps: initiation step (breaking of oxide membrane on aluminum powder surface), propagation step (bollision of aluminum powders and agglomeration) and termination step (ignition). The formulae of aluminum agglomeration rate, mean degree of agglomeration and distribution of agglomerating powder diameters are provided. They can predict the effects of burning rate, combustion chamber pressure, AP particle size, aluminum powder size and percentage on the agglomeration degree. The trends of all predictions by the provided formulae are consistent with the experimental researches.
EFFECT OF POLUTION ON HOT-WIRE ANEMOMETER MEASUREMENT
Li Yapin
1988, 3(3): 252-252,288.
Abstract PDF(186KB) icon1360 icon356
Abstract:
EXPERIMENTAL STUDY OF ROTATING STALL IN SINGLE-STAGE AXIAL COMPRESSOR
Qiao Weiyang, Wang Zongyuan
1988, 3(3): 253-255,285.
Abstract PDF(372KB) icon1729 icon347
Abstract:
A three-hole dynamic probe is reported in this paper which can measure the unsteady flow direction, flow velocity, total and static pressures of a 2-D flow field. Three miniature pressure transducers are mounted in the prode to detect the pressure fluctuation of the unsteaey flow. The dynamic pressure signals are recorded with a digital data acquisition system controlled by an microcomputer. The flowfield in rotaing stall regime of a singl-stage axial compressor can be studied by means of this probe and the system. The distributions of the flow velocity, flow direction, the total and static pressures in the rotating stall cells have been obtained in detail.
EXPERIMENTAL INVESTIGATION OF CONVERGENT EJECTOR NOZZLE/AFTERBODY IN WIND TUNNEL
Zhang Ronghua
1988, 3(3): 256-258,285.
Abstract PDF(321KB) icon1388 icon359
Abstract:
The work is aimed at determining the overall installation performance of the convergent ejector nozzle/afterbody with or without fixed auxiliary inlet doors. The experimental mach numbers range from 0.6 to 1.2. The nozzle pressure ratio extends from 2.6 to 4.3. The corrected secondary weight flow ratio is 3.5%. The testing technique presented gives the correlation of the axial momentum tare forces of bellows with the pressure measured in the bellows. The wind tunnel test data can be revised in timely manner with the tare forces computed. The tests show that due to the effect of the tertiary flow the nozzle thrust coefficient and efficiency of the ejector nozzle with fixed auxiliary inlet doors increase by 1 to 1.6% and 1.6 to 2.8% respectively compared with one without these doors.
DYNAMIC DISTORTION IN FLOWFIELD DOWNSTREAM OF TRANSONIC SHOCK-BOUNDARY LAYER INTERACTION
He Zhongwei
1988, 3(3): 259-261,286.
Abstract PDF(378KB) icon1575 icon351
Abstract:
The dynamic diatortions in flowfield under transonic shock-turbulent boundary layer interaction of different intensity are investigated in a 2-D convergent-divergent duct.The power spectrum and probability density functions of the total pressure signals are analyzed. The control technique of this dynamic distortion is also presented.
REGULATION OF DISTORTION FLOWFIELD BY AXISYMMETRIC TURBULENCE GENERATORS
Shi Wangxing
1988, 3(3): 262-264,286.
Abstract PDF(1145KB) icon1255 icon356
Abstract:
This paper provides a regulation law for distortion flowfield by axisymmetric turbulence generators, which can meet the demands for simulating the static and dynamic inlet distortions simultaneously. The distortion flowfield is regulated by variation of throat area ratio and working pressure ratio. The experiments show that the absolute deviation of the turbulence regulated by this law is less than 0.01.
NUMERICAL STUDY OF CHARACTERISTICS OF BURNER
Zhao Jianxing, Tan Huaping
1988, 3(3): 265-267,286-287.
Abstract PDF(415KB) icon1169 icon368
Abstract:
The combustion efficiency and blowoff characteristics of burner with bluff-body flame holders are investigated with both numerical and experimental methods. The k-ε turbulence model is employed to describe the turbulent viscosity and the EBU. Arrhenius combustion model is adopted to determine the reaction rate. The radiation model of heat flux method is used to predict heat radiation flux. Because of the large variation of density in , combustion flowfield, the density-weighted average variables have been adopted in conservation equation. The com-parison of numerical results with experimental data indicates that the numerical method presented is generally feasible.
A NEW FLAME PROPAGATION TECHNIQUE FOR BARCHAN FLAME-HOLDER
Zhao Guanwu
1988, 3(3): 268-268,288.
Abstract PDF(171KB) icon1579 icon364
Abstract:
APPLICATION OF UNSTEADY FLOW REFRIGERATION TO RECORVERY OF PETROLEUM GAS
Shen Zhenhua
1988, 3(3): 269-270,287.
Abstract PDF(274KB) icon1464 icon432
Abstract:
The refrigeration principle of "thermal separator" is analyzed in light of unsteady flow dynamics and a simplified physical model is presented to improve the refrigeration efficiency. The analytical study shows that it is necessary to control the pressure ratio P4/P1 properly and to match the length of working pipes with the size and revolution speed of the unit in order to increase its efficiency. The unit may be used for recovery of petroleum gas, cold storage and central airconditioning.
A NEW APPROACH TO IMPROVEMENT OF FANS
Su Hanshou
1988, 3(3): 271-273,287.
Abstract PDF(326KB) icon1459 icon361
Abstract:
This paper presents experimental results of 3-D flowfields in the fan tip region for two actual fans. It is shown that the fan performance can be significantly improved as proplets are attached to the blade tips. The improving mechanism have been studied and can be stated as follows: The proplets retain the tip vortex and thus the tip induced loss is reduced remarkably, and the additional propulsion moment is gained because the proplets partly balance the drag moment due to profile loss in the tip section. The conclusions presented in this paper may be applied to the tip section of propeller or helicopter rotor for performance improvement.
APPLICATION OF DAMAGE RULES TO TIME-DEPENDENT FATIGUE LIFE PREDICTION
Dong Zhaoqin, Duan Zuoxiang, He Jinrui
1988, 3(3): 274-276,287-288.
Abstract PDF(414KB) icon1386 icon358
Abstract:
Linear Damage Rule (LDR) and Interaction Damage Rule (IDR) are compared and applied to Strain Range Partitioning(SRP) and Strain Energy Partitioning(AEP)methods. From the viewpoint of damage, the physical unequalities which LDR and IDR should fit are derived. With the data of materials available abroad it is verified that the scatter band and standard deviation by LDR are smaller than those by IDR. For the same damage, the predictability of SEP appears a little better than that of SRP.
STEADY-STATE UNBALANCE RESPONSES FORA MULTISPAN ROTOR
Ren Pingzhen
1988, 3(3): 277-278,288.
Abstract PDF(290KB) icon1520 icon345
Abstract:
A node transfer matrix is deduced which considers the angulau stiffness and damping in spline coupling. The steady-state unbalance responses for a rotor with several spans are obtained by using Lund method and the simplified transfer matrix method. An model rotor has also been experimented so that the damping ratio, eccentricity and deflection are measured with amplitude-frequency characteristic method. The steady-state unbalance responses have been obtained from these data. Both analytical and experimental results are in good agreement.

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