1997 Vol. 12, No. 3

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CALCULATION AND ANALYSIS OF FATIGUE CRACK GROWTH UNDER ULTRASONIC FATIGUE LOADING
Ni Jingang, Zhang Xueren
1997, 12(3): 225-229,327.
Abstract PDF(955KB) icon1806 icon493
Abstract:
Stress and modal analyses of an ultrasonic vibration system,consisting of a notched specimen and one or two amplifying horns have been performed by using 3D finite element calculation.The stress intensity factors in ultrasonic fatigue crack propagation are evaluated by means of displacement and energy approaches.The particular advantages as well as limitations of the two approaches are briefly discussed.Two types of ultrasonic fatiuge loading with different stress ratio are exerted on the specimen respectively.The comparison between these two approaches comes to the conclusion that the energy approach is more accurate.It has wide range of practicality in engineering.
FATIGUE RELIABILITY ANALYSISUNDER VARIABLE AMPLITUDE
Ni Kan, Zhang Shengkun, Gao Zentong
1997, 12(3): 230-234,327.
Abstract PDF(355KB) icon1475 icon372
Abstract:
First of all,randomness of fatigue loading,fatigue life and fatigue strength are classified into three types of random-constant amplitude,random-variable amplitude and random-stochastic time history,respectively.Then,according to Miner's two-dimensional Probabilistic Rule,a new reliability-based prediction procedure of fatigue life is established for the structural component subjected to one-dimensional and two-dimensional cyclic loadings of variable amplitude or stochastic time history.Meanwhile,the probability distribution of α in Statistical Miner Rule is derived.The verification of the obtained results by means of variable amplitude experiment at data of fatigue life shows that the new prediction procedure is very accurate.In the end,an example is presented in detail,which indicates that this new procedure is of simplicity and of feasibility in engineering application.
VIBRATION CHARACTERISTICS ANALYSIS FOR A SHROUDED TURBINE BLADE WITH AIR-COOLING HOLES
Ou Yangde, Kong Ruilian, Song Zhaohong, Yu shengzhong, Xiao Bo
1997, 12(3): 235-238,328.
Abstract PDF(290KB) icon1713 icon499
Abstract:
A finite element model has been established for analyzing vibration characteristics of a shrouded turbine blade with air-cooling holes.The effects of uniform and nonuniform temperature distribution,holes and constraint conditons of the shrouds on the vibration characteristics are considered.According to the resonant fatigue-damage life theory,the optimum clearance between neighboring shrouds is determined to increase the service life.The results of the analysis show that the air-cooling holes have less,but the constraint conditions and temperature distributions have significant effect on natural frequencies of the blades.
A SIMPLE METHOD FOR CALCULATION OF RESIDUAL STRESS IN THERMAL BARRIER COATING
Yang Xiaoguang, Gen Rui, Xiong Changbing
1997, 12(3): 239-242,328.
Abstract PDF(292KB) icon2067 icon418
Abstract:
The residual stresses are always emerged in plasma sprayed coatings due to their spray method.The accurate calculation of the residual stresses is important for strength evaluation and thermal fatigue prediction of the coatings,as well as for controlling and evaluating the spraying process.First of all,a main process causing residual stress is identified by analyzing plasma spray process and simplified into a model.The residual stresses in the coated part is resulted from the difference in thermal expansivities of the various materials involved.According to the above mentioned,authors bring forward a simple method for calculating residual stresses,which can be easily used with finite element method.Finally,as a demonstration,cylinder-type specimens are chosen to calculate residual stresses with FEM under various calculating conditions.
A NUMERICAL ANALYSIS OF THERMAL BENDING DEFORMATION AND ITS INFLUENCE ON ROTOR
Lu Shan, Zhao Ming, Ren Pingzhen, Qi Xianping
1997, 12(3): 243-246,328-329.
Abstract PDF(343KB) icon2128 icon384
Abstract:
Thermal bending deformation and its influence on an aeroengine's rotor are analyzed numerically,and some useful results for engineering are obtained.On the basis of axial symmetrical static temperture field of engine's rotor,its axial non-symmetrical temperture field is formed by the aid of thermal bending test data,three-dimension thermal elastic FEM is used to calculate the thermal bending deformation,and transfer matrix method is employed to calculate thermal bending vibration response.These methods are verified by thermal bending tests.In general,this numerical method is simple and applicable to the thermal bending analyses and investigation of its influence on aircraft engine.
TOOTH CONTACT ANALYSIS OF MODIFIED HELICAL GEARS
Fang Zongde
1997, 12(3): 247-250,329.
Abstract PDF(691KB) icon1854 icon443
Abstract:
An approach for calculating tooth working-surface contact and tooth edge contact of modified helical gears is proposed.The generation of tooth surface and Tooth Contact Analysis(TCA)of the modified helical gears under various errors can be simulated on computer by the aid of this approach.Then,the tooth modification by changing tooth profile of rack-cutter and by CNC machine is considered.As an example,TCA on pair of modified helical gears is completed by using above metioned approach,and the improvement for contact under errors is shown.This method can be used for modification of helical gears.
LOADED TOOTH CONTACT ANALYSIS OF MODIFIED HELICAL GEARS
Fang Zongde
1997, 12(3): 251-254,329.
Abstract PDF(681KB) icon1639 icon371
Abstract:
A simulation approach for loaded tooth contact analysis is presented.Deformation of the tooth,deflection of the supporting system,backlash between the teeth,gaps on points except temporary contact point,manufacturing and assembling errors are considered.In this procedure,the accurate geometry resulted from TCA is foundation of whole calculation,and the flexibility factor matrix by using finite element method is adopted.Besides,the non-linear contact analysis between multi-pairs of teeth can be done only through the mechanical and geometrical analyses of single-pair of teeth.
RESONANCE INTERFERENCE ANALYSIS AND RELIABILITY ASSESSMENT FOR A FAILED TURBINE BLADE
Ou Yangde, Fu Xiaoping, Song Zhaohong
1997, 12(3): 255-257,329-330.
Abstract PDF(290KB) icon1939 icon451
Abstract:
A series of analyses for blades of second turbine in a given aeroengine have been accomplished such as vibration analysis,resonance analysis,modal stress analysis,and statistical analysis for the blade nature frequencies obtained in field and mass-production.The failures of the blades have been investigated by the synthesis of the obtained results and a resonance interference analysis.In result,the failure sources have been found out and some measures have been proposed for elimination of the failure modes.
FLOW VISUALIZATIONS OF FLOW FIELD IN ENDWALL REGION OF A COMPRESSOR CASCADE
Ma Hongwei, Jiang Haokang
1997, 12(3): 258-262,330.
Abstract PDF(330KB) icon1620 icon434
Abstract:
This paper describes flow visualizations of the flow field in the endwall region of a compressor cascade. Within the cascade passage without radial clearance,it was found that many low-energy fluids exit in the corner between the suction surface and the endwall, and some vorticities of the corner vortex come from the leading edge horse shoe vortex.Tangential migration of the pressure-side horse-shoe vortex leads to flow mixing among the endwall boundary layer, suction surface boundary layer and the horse-shoe vortex.Small radial clearance leads to a weak leakage vortex that is far away from the suction surface,while large radial clearance leads to a strong one closer to the suction surface.The corner vortex is not obvious due to blowing of the leakage flow.In the endwall region, reaction among the vortexes and the boundary layers result in much more flow mixing and unsteadiness.
EFFECTS OF BLADE CURVING ON CLEARANCE FLOW LOSSES
Huang Hongyan, Han Wanjing, Wang Zhongqi
1997, 12(3): 263-267,330.
Abstract PDF(424KB) icon1659 icon398
Abstract:
Detailed experimental investigations of the flows in the cascades of conventional straight blades and positively curved ones,both with 2.3% tip clearance,were carried out in a low speed wind tunnel.The measuring planes were arranged as 4 before,11 in 4 after the cascades and 1 in the middle of the tip clearance.Flows inside the clearance were searched in great detail with a micro five-hole pitot tube of 1mm head size and another of 5 mm head size in the passage.The quite detailed information about the tip leakage flows and the flows in the cascades has been obtained,such as flow vectors,pressure and loss distributions throughout the clearance and in the passage.In comparison with the conventional straight blades,positive blade curving decreases the flow vectors within the tip clearance and also reduces the strength of the leakage vortex.As a result,the mass flux crossing the tip clearance decreased,the interaction between leakage vortex and passage vortex in the curved cascade also decreased.Thereby,the total flow losses downstream of the curved blade have been cut down by 8%.
3D TURBULENT FLOW AT COMPRESSOR ROTOR EXITUNDER DIFFERENT FLOW CONDITIONS
Ma Hongwei, Jiang Haokang
1997, 12(3): 268-272,331.
Abstract PDF(370KB) icon1562 icon436
Abstract:
Detailed measurements of three-dimensional turbulent flow field at the exit of an axial flow single-stage compressor rotor were made under different conditions.The flow structures were surveyed with both hot-wire probe and high frequency pressure probe.Under the design condition,substantial blockage,loss and turbulence mainly emerge in the tip mid-passage,in the wake and the corner between the suction surface and the hub,and the tip leakage vortex exists in the mid-passage at the exit.When the mass flow reduces,the flow becomes more turbulent.As a result,flow mixing is more,and the leakage vortex is far away from the suction surface,that leads to more substantial blockage,loss and turbulence in the tip region.Under the near stall condition,the radial migration of the blade suction surface boundary layer and the tangential migration of the endwall flow play a more important role in the flow field of the passage.
APPLICATION OF LIFTING SURFACE METHOD TO RAM AIR TURBINE PERFORMANCE CALCULATION
Zhang Jianfeng, Liu Siyong
1997, 12(3): 273-275,331.
Abstract PDF(259KB) icon1733 icon554
Abstract:
The modern propeller lifting surface method has been applied to calculating the performance of Ram Air Turbine,and a single layer vortex model is adapted to the blade,the wake is modeled to rigid cylinder wake coincided with Goldstein hypothesis.A numerical calculation for a model of Ram Air Turbine shows a good agreement of the coefficient of wind power utilization with its experimental data at both small and large loading.The distributions of induced velocities and circulation are reasonable.
A LIMITED DOMAIN SEARCHING METHOD FOR SOLUTION OF NONLINEAR MATHEMATICAL MODEL FOR TURBOFAN ENGINE
Li Songling, Sun Jianguo, Li Jianming, Tang Shijian
1997, 12(3): 276-278,331-332.
Abstract PDF(289KB) icon2270 icon475
Abstract:
An algorithm is developed based on the N-R(Newton-Raphson) iteration method to solve the nonlinear mathematical model of turbofan engine.It enhances the ability to search for the nonlinear equation solutions within a limited domain,which is dcsignated around the initial guess of solution and covers the genuine solution.Three iteration factors defined in this algorithm can be automatically readjusted by programming.Accordingly,the least times of iteration and corresponding optimum iteration factors can be found out from the program.
NUMERICAL PREDICTION OF TWO-DIMENSIONAL TRANSONIC TURBULENT FLOW IN A DIFFUSER
Han Zhenxue, Fang Ren, Zhong Zhibin
1997, 12(3): 279-282,332.
Abstract PDF(306KB) icon1798 icon384
Abstract:
Two-dimensional transonic flow in a diffuser is numerically invesgated by solving 2D time-dependent Reynolds-averaged compressible Navier-Stockes equations.The numerical method is based on Van-Leer's flux splitting cell-centered finite volume scheme.Baldwin-Lomax algebraic turbulence model and Johnson-King non-equilibrium turbulence model are tested to simulate largely separated flow.Comparison of the computational results with corresponding experimental data shows that the predicted wall static pressure distributions and shock strength by both two turbulence models agree well with the experimental data,but Johnson-King model does better than Baldwin-Lomax model in the prediction of separation reattachment point.
3D VISCOUS FLOW COMPUTATION WITH ARBITRARY LAGRANGIAN-EULERIAN METHOD
Zheng Qun, Liu Shunlong
1997, 12(3): 283-286,332.
Abstract PDF(710KB) icon2017 icon547
Abstract:
Arbitrary Lagrangian-Eulerian schemes are deduced for computation of three dimensional viscous flow in rotating impeller channel.The convection effect is simulated by the pseudo-moving of grids.Viscous sub-cycle time step and Lagrangian sub-cycle time step are adopted to accelerate convergence.The upwind scheme is improved into part-donated scheme to diminish diffusion. Flowrate restriction is used to control dissipitive truncation error.A short wave damp is introduced to reduce the computational corrugation.Sub-Grid-Scale(SGS) turbulent model is adopted to simulate turbulent flow.Eckardt's experimental results on centrifugal impeller have verified effectiveness of the method.
OPTIMIZATIONAL DESIGN FOR TRANSONIC TURBINE CASCADE
Li Jun, Feng Zhenping, Shen Zuda, Chang Jianzhong
1997, 12(3): 287-290,332-333.
Abstract PDF(752KB) icon1703 icon388
Abstract:
A design method of aerodynamic optimization is presented for transonic turbine cascades.The method couples Genetic Algorithms (GAs) to a inviscid flow field Euler solver and the boundary layer calculation.The objective function of the transonic turbine cascade is the minimum of loss factor.The multinomial coefficients of blade geometry are taken as design variables.RA cascade and Beizhong cascade have been used as the examples of optimizational design.It is shown that the aerodynamic performance of the transonic turbine cascades has been improved greatly with little variation of the work and the strength.
EXPERIMENTAL INVESTIGATION ON MASS-HEAT TRANSFER OF SHROUDED ROTOR-STATOR SYSTEM
Chen Jian, Xu Guoqiang, Cao Yuzhang
1997, 12(3): 291-294,333.
Abstract PDF(784KB) icon1612 icon377
Abstract:
According to the theory of analogy between heat transfer and mass transfer,the mass transfer technique is applied to a shrouded rotor-stator system for experimental,investigation on its heat transfer.An experimental model is set up:The cooling air is blown axially from the front edge of the stator,and the naphthalene(C10H8) sublimation technique is employed to obtain both local and average mass-transfer coefficients for the rotor surface coated by naphthalene.The heat transfer characteristics of the shrouded rotor-stator system are investigated using the mass transfer analog technique.The emphasis is put on analyzing the effects of the following parameters on the transfer characteristics:The ratio of axial gaps Gs 、 the ratio of axial clearance Gc 、the rotational Reynolds number Reθ and flow coefficient Cw .Correlations are obtained experimentally,conclusions are drawn for the test conditions as follows:1.The average mass transfer coefficient increases with increase of the flow coefficient Cw and the rotational Reynolds number Reθ ;2.The average mass transfer coefficient decreases with increase of the ratio of axial gap Gs and the ratio of axial clearance Gc ;3.The peak of local mass transfer coefficient radically moves out with reference to impingement point.
SPRAY CHARACTERISTICS OF A NEW AIR-ASSISTED ATOMIZER
Xu Hang, Guo Zhihui, Gu Shanjian
1997, 12(3): 295-298,333-334.
Abstract PDF(324KB) icon1963 icon414
Abstract:
The spray characteristics of a new air-assisted atomizer was investigated experimentally.Annular and central swirling air jets smash the fuel jet and make it spray.The radial distributions of the mean and fluctuating velocities of the air flow and drops,the drop size and the concentration were measured at several axial stations with 2D PDA.Two atomizers with different mixing chamber were tested to investigate the effect of the central swirling air jet on the spray structure.The radial distributions of the mean velocity show that a lower axial velocity region and a solid rotation body exist at the center of the spray.The radial profile of drop volume flux peaks drifts off the centerline,indicating a hollow cone spray.The results show that high turbulence occurs at the central region and the region where the central swirling jet intersects the annular jet.The radial position of maximum mean axial velocity moves outwards with increasing strength of swirling.The atomization performance of the atomizer with lower swirling strength is better than that of the atomizer with higher swirling strength near the atomizer exit,but downstream the both atomizers possess same atomization performance.
NUMERICAL SIMULATION FOR MATCHING DIFFUSER WITH LINER IN A SMALL DIRECT-FLOW COMBUSTOR
Li Gaiqi, Yan Chuanjun
1997, 12(3): 299-302,334.
Abstract PDF(360KB) icon2185 icon521
Abstract:
Numerical simulation was carried out for inside and outside flowfields of the liner in a small direct-flow combustor with special structural arrangement,numerical tests of combustor performance were performed for matching of different diffusers with the liner.The program employs two-equations(K-ε model)to describe turbulent characteristics.The combustion following vaporization was simulated by a two-step chemical reaction eombustion model.Arrhenius-EBU model was used to determine the reaction rate,and the air flow mass distribution was taken as a bridge to link the inside and outside flowfields of the liner.The calculated results indicated that two strong recirculation zones emerged when air flowed into combustor annular cavity from prediffuser,the inside and outside flowfields were very unsymmetrical.The inclination of the predliffuser was an important geometrical parameter for the combustor performance.
A STUDY ON EFFECTS OF ENVIRONMENTAL FACTORS ON ALUMINUM OXIDE PARTICLE SIZES
Zhang Wei, Cao Taiyue, Wang Ningfei, Zhang Weihu, Zhu Hui
1997, 12(3): 303-305,334.
Abstract PDF(576KB) icon1634 icon489
Abstract:
On the basis of diffusional combustion model of metal combustion and heterogeneous nucleation mechanism,the average particle sizes of the product Al2O3in aluminum combustion were calculated.The results show that the temperatures on the combustion surface and on the metal surface increase with enhancing pressure,and the average particle size of the condensed product decreases as pressure increases.The effect of the pressure on the parameters is larger than that of the temperatures.
CALCULATION OF 3D CASCADE FLOW WITH N-S EQUATION
Ji Lucheng, Zhou Sheng
1997, 12(3): 306-308,334-335.
Abstract PDF(305KB) icon1977 icon376
Abstract:
A cell-centered finite volume method was developed to solve Renolds-averaged Navier-Stokes equation with Jameson`s Runge-Kutta scheme.In its programming special attention was paid to the addition of artificial viscosity,so that the solution could not be polluted.Baldwin-Lomax Turbulence model is applied to programming.The programm has been verified by plate laminar flow,plate turbulent flow and Goldman Turbine vane flow.Firstly,the calculation of the plate laminar flow coincided with Blasius similarity solution;Secondly,the result of the plate turbulent flow was confirmed well with empirical formula and the calculation of Wilcox;Finally, with respect to the Goldman turbine vane flow field,the comparision was made between calculated results and experimental data of pressure distribution over blade profile.It indicated their consistency except fluctuations of the calculated results at leading and trail edge of vane blade.The source of the fluctuations lied in simple H type grid which could not describe the true blade profile and caused so big shear that the calculation scheme was deteriorated.The calculated Mach contour lines agreed to the simulation results of China.All of those indicated that the programm suits to designing system of turbomachinery.
FRACTURE MECHANICS ANALYSIS OF FATIGUE STRENGTH OF LAP-WELDED JOINTS
Ding LeiFan, Yinhe
1997, 12(3): 309-312,335.
Abstract PDF(287KB) icon1666 icon444
Abstract:
According to the elastic fracture mechanics,a parameter of lap stress intensity Kθ was used to describe the fatigue strength of lap-welded joints.Various influential factors of the Kθ have been analysed by finite element method.Therefore an empi rical formula for Kθ was deduced.From fatigue experiments of the lap-welded joints specimens made by two kinds of material(GH150 and 1Cr18Ni9Ti),two △K-N curves were obtained.The fatigue life of various complicated lap-welded joints can be estimated more accurately with the △K-N curves presented in this paper.
FAULT DIAGNOSIS OF ROTATING MACHINERY USING BACK PROPAGATION NEURAL NETWORK
Liu Zhansheng, Wu Xinhua, Xia Songbo
1997, 12(3): 313-316,335.
Abstract PDF(718KB) icon1911 icon436
Abstract:
The faults of rub between rotor and stator,misalignment test rig of the shafting,and unbalance of the rotor are simulated at a compressor test rig.The normal vibration signals of the rotor and the signals of the various emerging faults are registered and sampled by an automatic signal proceessor.Then a new-developed back propagation neural network is employed to learn the fault diagnosis from the sampled faults and a new method for accelerating the learning speed has been proposed in this paper.
PREDICTION OF TURBULENT SEPARATED FLOWS WITH A LOW REYNOLDS NUMBER NONLINEAR K-ε MODEL
Zhu Guangsheng, Zhang Yuelin, Sun Rong, Zhao Guang
1997, 12(3): 317-320,336.
Abstract PDF(302KB) icon2129 icon456
Abstract:
A new low Reynolds number nonlinear K-ε model is presented,in which two correction functions for the near-wall flow and a nonlinear expression for the Reynolds stress are incorporated.Several backstep separated flows with two different expansion ratios are numerically studied by using the above model and a standard K-ε model.In comparision with experimental data,the results obatined show that the predictions of the presented nonlinear model are obviously improved over these of the standard K-ε model in respect of various flow parameters,such as reattachment length,time mean velocities and Reynolds stress components.Also,the presented model is the partial differential Reynolds stress model in prediction of the Reynolds stress components.
AN EXPERIMENTAL ANECHOIC RESEARCH OF PERFORATED PLATES FOR NACELLE LINER
Zeng Wu, Li Yunmin
1997, 12(3): 321-323,336.
Abstract PDF(603KB) icon1958 icon375
Abstract:
An experimental anechoic research of perforated plates for nacelle liner has been completed under conditions of different rotor speeds and inlet Mach numbers.The duct,which was lined with single segment or three segments made of the perforate honeycomb plates or had a hard wall,was installated on a transonic axial compressor facility at BUAA.The experimental results discovered some anechoic features of the perforated plate honeycomb structure and enriched data base for designing the engine nacelles.A new nacelle liner,which has larger cavity-depth and open area ratio,has been designed. The largest noise reduction can reach to 10,5 dB under the condition that the acoustic treatment length is only 30 cm.
A SYSTEM FOR MEASURING IGNITION DELAY TIME
Bi Qun, Tan Haoyuan
1997, 12(3): 324-326,336.
Abstract PDF(547KB) icon1622 icon379
Abstract:
A measuring system for ignition delay time,which consists of an Intel 8253 chip,a microcomputer,an electric magnetic valve and an ultraviolet photodiode was developed.It can realize the real-time and on-line measurement with precision of 0.001 second.The system has been used successfully in measuring of ignition delay time to appraise the performance of a catalytic igniter.

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