1999 Vol. 14, No. 3

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FUZZY THEORY OF NONDESTRUCTIVE TESTING AND ITS APPLICATION
Fu Huimin, Liu Dengdi
1999, 14(3): 225-230.
Abstract PDF(2214KB) icon1346 icon427
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The uncertainty in the flaw size determination and the flaw detection has been studied,and a fuzzy theory of nondestructive testing (NDT) is established.The mathematical relations between the measured flaw sizes by NDT and the actual flaw sizes is presented.The distribution of true flaw sizes is obtained at a given measured flaw size.Fuzzy interval evaluation and membership degree of the flaws exceeding the specified size are given.Thus a quantitative method for determining the actual flaw size is successfully developed to make full use of the measured flaw sizes from different NDT sources.The new concepts of fuzzy life estimation,fuzzy fracture criterions,fuzzy damage tolerance design,fuzzy assessment of the pressure vessel integrity should be put forward on the basis of the fuzzy theory of NDT.
EFFECT OF ARRANGEMENT OF STAGGERED PIN FINS ON HEAT TRANSFER OF ROTATING RECTANGULAR DUCTS
Ji Honghu, Wang Baoguan, Wang Daijun, Deng Huayu
1999, 14(3): 231-236.
Abstract PDF(359KB) icon1808 icon406
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An experimental research was conducted to investigate the effect of the arrangement of staggered pin fins on convective heat transfer of rotating rectangular ducts.Six test models were used in this experiment, which cover a parameter range of Sn/d =5.0,6.5 and 8.0, Sp/Sn =1.2,1.6 and 2.0,where d is the diameter of the pin fin, Sn and Sp ,are the transverse space and twice the axial space between pin fins respectively.The results in the experimental range show that,the axial parameter, Sp/Sn between 1.2 and 1.6 will give the best result;in the transverse direction Sn/d=5.0 gives the highest heat transfer coefficient,but the pressure drop caused by this arrangment should be considered.
EFFECT OF TRAILING EDGE EJECTION OF TURBINE BLADES ON HEAT TRANSFER OF COOLING PASSAGE WITH STAGGERED PIN FINS
Ji Honghu, Wang Baoguan, Wang Daijun, Deng Huayu
1999, 14(3): 237-241.
Abstract PDF(365KB) icon2035 icon414
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An experimental research was conducted to simulate the effect of trailing edge ejection of turbine blades on heat transfer of the inner cooling passage with staggered pin fin array.The test model was a rotating rectangular duct with staggered pin fin array.The parameter of Sn/d equals 6.5 and Sp/Sn takes a value of 1.2,where d is the diameter of the pin fin, Sn and Spare the transverse space and twice the axial space between pin fins respectively.The angle between the long side of the rectangular duct and the rotation axis is 20 degree.The effects of the ratio between the total area of the trailing edge ejection holes A0 and the maximum cross section area of the duct A ,Reynolds number Re ,rotation number R0 and other relevant parameters on heat transfer were investigated.The heat transfer characteristics of the rotation rectangular duct with trailing edge ejection were compared to those with top end ejection.
THERMAL ANALYSIS MODELS AND TEMPERATURE FIELD CALCULATION OF BEARING OIL CAVITY IN AN AEROENGINE
Li Jian, Liu Zhiquan, Yuan Peiyi
1999, 14(3): 242-246.
Abstract PDF(1633KB) icon2401 icon416
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Endurance and reliability of an aeroengine and its bearings are closely related to the thermal state of thebearing oil cavity.The major heat sources which affect the thermal behavior of the bearing oil cavity in an aeroengine are analysed.The models for calculating bearing heat generation,graphite seal heat generation,heat leaking from the graphite seal,convection coefficients and temperature fields of the bearing oil cavity are established.The thermal balance coupled equations of the bearing oil cavity are derived from these models by thermal net method and are solved by quasi-Newtonian method.The steady state temperature fields of the bearing oil cavity are obtained from the solutions of 10 different operation conditions and are consistent with the experimental results in general.
EFFECTS OF FILM COOLING ON INTERNAL HEAT TRANSFER COEFFICIENTS OF A SQUARE CHANNEL
Wu Hong, Deng Hongwu, Tao Zhi
1999, 14(3): 247-250.
Abstract PDF(285KB) icon1621 icon392
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Effects of film cooling on the distribution of internal heat transfer coefficients of turbulent flow through a square channel were investigated experimentally and numerically.The main factors were the inlet Reynolds number and the hole distance ratio under turbulent condition.The investigation showed that the internal heat transfer coefficient was increased greatly with the increase of the inlet Reynolds number whereas its variation was not monotonous with the change of the hole distance ratio.The change of internal heat transfer characteristics was not obvious with hole distance variation.
RADIATION HEAT-FLUX DISTRIBUTION CALCULATION ON COMBUSTOR WALL BY MONTE-CARLO METHOD
Zhang Jianqiang, Zhu Gujun
1999, 14(3): 251-254.
Abstract PDF(1448KB) icon1607 icon450
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The calculation of the radiation heat-flux on combustor wall and in outlet by Monte-Carlo method takes into account the effects of radiation energy emitted from any single element on all other elements.The calculation gives better prediction of the radiation process in a gas turbine combustor.The radiation heat-flux densities of combustor wall and outlet can be calculated by Monte-Carlo method,provided the temperature,dioxide-carbon partial pressure and water vapor partial pressure distribution in a combustor are known.The changes of gas absorptivity and emissivity in the combustor have been taken into account.A complete computation procedure and related error analysis have been described in detail.A numerical example is given and the calculated results are reasonable.
INFLUENCES OF MAINSTREAM TURBULENCE AND END-WALL EFFECT ON CONVECTIVE HEAT TRANSFER OF TURBINE BLADE
Zhu Huiren, Xu Duchun, Guo Tao, Liu Songlin
1999, 14(3): 255-259.
Abstract PDF(946KB) icon1971 icon438
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The influences of mainstream turbulence,end-wall effect and mainstream Reynolds number on the beginning location of transition,transition length and heat transfer both in the middle region and root region of a turbine blade were comparatively studied.A five-blade linear cascade in a large-scale low-speed opening wind tunnel was used in the experiment.A thin-foil thermocouple technique was applied to determining the heat transfer coefficients on the blade surface.Three row of thermocouple located 5 mm,30 mm and 150 mm in the span-wise direction of blade from end-wall.The mainstream Reynolds number changed from 60000 to 240000.The mainstream turbulence varied from 0 75% to 13 5%.The results showed that the mainstream turbulence enhanced heat transfer coefficients on the suction surface to a great extent,and also increased the heat transfer coefficients on the pressure surface.Both onset and end of transition on the suction surface boundary layer move forward with increase of mainstream turbulence intensity.The end-wall effect region emerged at the root region of x/C >0 24 of suction surface for the present turbine blade.The end-wall effect raised on the heat transfer coefficients for a low mainstream turbulence,but diminished for a high mainstream turbulence at the end-wall effect region.The influence of mainstream turbulence on the heat transfer coefficients vanished at the end-wall effect region.
PERFORMANCE OPTIMIZATION OF HIGH THRUST-WEIGHT RATIO TURBOFAN ENGINE
Zhu Zhili, Wang Xiaobo
1999, 14(3): 260-264.
Abstract PDF(1792KB) icon1970 icon468
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The optimization of installation performance was completed by the comprehensive optimal method for the high thrust-weight ratio turbofan engine.The propulsion system performance model of the variable geometry turbofan engine served as the base,and the maximum of install thrust,minimum of install SFC and minimum of the inlet temperature of turbine were taken as the optimization modules respectively.The calculation and the following analysis showed that the propulsion system performance can be improved significantly by multiple parameter performance seeking control for the turbofan engine with afterburner.The improvements are as follows:(1)the supersonic cruise install thrust can be increased by about 8% on the module of maximum thrust;(2)the subsonic cruise install SFC can be decreased by 2% on the module of minimum SFC;and (3) the turbine inlet temperature can be lowered by about 25 K at the constant install thrust on the module of minimum temperature.
NUMERICAL SIMULATION OF ROTOR-STATOR INTERACTION IN A TRANSONIC COMPRESSOR STAGE AT OFF-DESIGN CONDITIONS
Ren Yuxin, Shen Mengyu, Liu Qiusheng
1999, 14(3): 265-269.
Abstract PDF(409KB) icon1964 icon472
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A numerical method is developed for simulation of rotor-stator interactions in a compressor or turbine stage.This method solves quasi-three-dimensional Navier-Stokes equations by an implicit high resolution finite volume method.A fully conservative method is designed to compute the inviscid and viscous flux at the interface of rotor and stator grids.Numerical results of rotor-stator interactions in a transonic compressor stage at off-design conditions are presented.The mechanism of rotor-stator interactions in this compressor stage is discussed in terms of the computational results.
EXPERIMENTAL RESEARCH AND ANALYSIS OF SLOPED SLOTTED CASING TREATMENT
Chu Wuli, Zhu Junqiang, Liu Zhiwei
1999, 14(3): 270-274.
Abstract PDF(673KB) icon1679 icon463
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Compressor endwall treatments,such as grooves and slots can effectively delay stall and increase the weight flow range of a compressor,but the efficiency decreases.A new kind of casing treatment,called as sloped slotted casing treatment,has been designed,which absorbs the advantages of traditional casing treatments.The overall performance of compressor rotor with sloped slotted casing treatment is measured at a single axial flow compressor.The effects of the axial overlapping amount and back cavity volume on stall margin and efficiency have been found.In each case,its characteristics with the casing treatment are compared to those without it.The results show that the new kind of casing treatment can effectively increase the stall margin and efficiency.Both flow suction and injection from the treatment region makes a stall margin improvement.
EXPERIMENTAL INVESTIGATION OF ENDWALL FLOW IN A TURBINE CASCADE
Dong Zhirui, Liu Songling, Zhang Yujin, Xu Duchun
1999, 14(3): 275-280.
Abstract PDF(931KB) icon2036 icon545
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The flow field of straight HP turbine cascade was investigated experimentally in a large-scale low-speed open-loop cascade heat transfer wind tunnel.Three-dimensional flow fields near the endwall of the cascade were measured by using five-hole probe at five different Re .Cotton thread and floating small ball are applied to visualization of the flow fields.The experimental results show that the pressure side leg of the horseshoe vortex destroys the structure of the incoming flow boundary layer,when it moves from Pressure Side (PS) to Suction Side (SS).Behind the pressure side leg,a new boundary layer is generated near the endwall in the cascade.The new boundary layer goes from PS to SS.However,its thickness is thinner than that in the incoming flow.The 3D-flow region occupies 40% flow passage of turbine cascade.The increase of Re intensifies 3D-flow near endwall.From the photos of flow visualization it can be seen that corner vortex is generated and developed near the suction surface of blade/endwall junction,and forms a triangle region on the suction surface.The size of visualized passage vortex is consistent with measurement result.
NUMERICAL SIMULATION OF PLUG NOZZLE FLOWFIELDS AT DIFFERENT AMBIENT PRESSURES
Zhuge Weilin, Zhang Yangjun, Zhang Baoning, Chen Ronghui
1999, 14(3): 281-284.
Abstract PDF(374KB) icon2069 icon447
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A type of circular multi-thruster plug nozzle has been designed,and its flow fields at different ambient pressures were simulated numerically by solving axisymmetric Reynolds-averaged Navier-Stokes equations with a finite-volume formulation.The simulations based on single equation and two equations turbulent models were compared.The results of the both models at proper mixing length were consistent in general.This type of plug nozzle embodies the main advantages of plug nozzles.
AEROACOUSTIC CALCULATION OF A TRANSONIC PROPELLER BY USING KIRCHHOFF METHOD
Ma Liang, D. Lohmann, M. Kuntz
1999, 14(3): 285-288.
Abstract PDF(588KB) icon1583 icon447
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The aeroacoustic field generated by a transonic two-blade Hartzell propeller was calculated by using Kirchhoff method.The Kirchhoff surface was defined as a nonrotating cylinder surrounding the whole propeller blade.The aerodynamic flowfield was firstly computed by using the Flower code running in the Euler mode,then the farfield acoustic pressure was calculated with the Kirchhoff method.A detailed numerical study revealed the influence of the radius and height of the cylinder on the acoustic pressure in the farfield.The results obtained by the Farassat's linear method were also presented and compared with the presented results.The comparison of the results obtained by both the methods with experimental data demonstrated that the Kirchhoff method considering most of the nonlinear effects gave a better results than the linear method.
A CONSIDERATION OF TWO EQUATION TURBULENCE MODEL
Liang Dewang, Lu Bing
1999, 14(3): 289-292.
Abstract PDF(734KB) icon2083 icon408
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A concept of "two-layer" turbulence model is proposed which employs an algebraic turbulence model in near wall area and a two-equation turbulence model in outer area or far wall area.The flows over a flat plate with M =0 3 uniform inflow and in a 90°rectangular bent duct with non-uniform velocity and high turbulence inflow are calculated respectively by use of the "two layer" turbulence model and two equation turbulence model with low Reynolds number modification.The obtained results show that the "two layer" turbulence model can predict the distribution of velocity and wall stress for external flow and the boundary layer thickness and main velocity for internal flow more accurately than the two equation turbulence model.Therefore the "two layer" model is a powerful tool in engineering.
NUMERICAL SIMULATION OF ANTI-SWIRL ARRANGEMENTS FOR SUPPRESSING ROTOR/SEAL INSTABILITY
He Lidong
1999, 14(3): 293-296.
Abstract PDF(292KB) icon1578 icon398
Abstract:
A nonlinear oscillator model,which is usually used to study the dynamic characteristics of structures in flow,has been applied to the nonlinear dynamic characteristics of rotor/seal system.Emphasis is put on the effects of the nonlinear unsteady flow in the small clearance on the rotor dynamic characteristics.The mechanism of anti-swirl arrangements for suppressing rotor/seal instability is considered.The comparison between the theoretical and experimental results of a rotor/seal system is in a reasonable agreement and shows that this method provides a theoretical basis for application of anti-swirl technique to engineering practices.
INVESTIGATION ON LOAD DISTRIBUTIONS AMONG CONTACT BEARINGS OF DOUBLE CIRCULAR ARC HELICAL GEARS
Wu Baolin, Shao Jiahui, Meng Huirong
1999, 14(3): 297-300.
Abstract PDF(281KB) icon1401 icon459
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A dynamic analysis approach is provided to investigate the load distributions among contact bearings of double circular arc helical gears and a computer program is worked out for calculating the load distributions.The dependences of load distribution variation on the main factors are analyzed through a series of parametric studies.It can be concluded that the variation of the rotational speed of the gears has no effect on the load distribution factor in conventional range of rotational speed;However,the load distribution factor can be reduced by decreasing the contact ratio,increasing the transmitted torque as well as improving the gear accuracy;the load distribution factor has a peak which changes with the increase in the helix angle at the same transmitted torque and contact ratio.
RELIABILITY OF ENGINE BLADE NONDESTRUCTIVE TESTING
Liu Dengdi, Fu Huimin
1999, 14(3): 301-304.
Abstract PDF(1422KB) icon1707 icon532
Abstract:
The attention has focused on quantifying the capability of nondestructive testing (NDT) system for guaranteeing structural safety through damage tolerance analysis.A method of reliability assessment for engine blades NDT is presented,which can determine exactly the probability of flaw detection(POD)and assess the probability of flaws missed(POM)in the engine blades,as well as control the largest size of the flaws missed at inspections with high probability of flaw detection and confidence level.This method also raises the flaw detection probability and prevents the flight accidents caused by the missed flaws in engine blades.
ROBUST H∞ OUTPUT FEEDBACK CONTROL OF STRUCTURED AND UNSTRUCTURED PARAMETER UNCERTAIN SYSTEM FOR AEROENGINE
Wang Xi, Zeng Qingfu
1999, 14(3): 305-308.
Abstract PDF(272KB) icon1715 icon410
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The robust stability and robust performance of aeroengine mixed uncertain system are analyzed.By introducing structured singular value μ synthesis method,the robust H∞ output feedback control is investigated under mixed structured and unstructured parameter perturbations.Disturbance rejection and servo tracking performance with the designed controllers for aeroengine uncertainty systems are simulated on a nonlinear model of twin-spool turbojet engine.
TRANSIENT THERMAL ANALYSIS OF A HELICOPTER GEAR TRANSMISSION SYSTEM
Liu Zhiquan, Shen Yunwen, Chen Guoding, Su Hua
1999, 14(3): 309-312.
Abstract PDF(899KB) icon1800 icon422
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Survivability of a gear transmission system in attack helicopter after Loss-Of-Lubrication (LOL) is greatly dependent on the transient temperature fields of the systems.A helicopter gear transmission system was researched.A method is put forward to calculate the transient temperature fields of this system after LOL and the models for power losses and heat transfer (convection) coefficients are established.In these models,the time-variance characteristics of thermal physical parameters,such as viscosity,thermal conductivity are considered.A computer program is worked out for calculating the transient temperature fields of the system on the basis of these models.In the computation,the calculational results of the steady state temperature field in the transmission system are used as initial values of the transient temperature fields and the time steps are properly controlled so as to prevent "data oscillation".The transient temperature fields of the gear transmission system are obtained from the computation and can serve for predicting the survivability of the gear transmission system.
APPLICATION OF SQP TO ACCELERATION CONTROL OF TURBOFAN ENGINE
Chen Guangming, Fan Ding
1999, 14(3): 313-316.
Abstract PDF(338KB) icon1882 icon507
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The optimal control for turbofan engine acceleration control has been investigated.The optimal method used in this paper is Sequential Quadratic Programming(SQP),one of the most successful methods for solving nonlinear constrained problem.Many limits in the process of engine acceleration have been studied such as compressor surge margin,overtemperature limit,overspeed limit,rich extinction in combustor,the maximum fuel flow and limit of the actuator property.The results of simulation show that SQP method is suitable and feasible in solving the problem of aero-engine acceleration control;the engine potentialities are brought into full play and the engine acceleration performance is improved greatly.
MODELLING AND SIMULATION OF MAIN FUEL CONTROL SYSTEM FOR A TURBOFAN ENGINE
Cheng Tao, Qi Ying, Meng Qingming
1999, 14(3): 317-319.
Abstract PDF(428KB) icon2138 icon410
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A turbofan engine and its main fuel control system with hydromechanical regulator are studied.The rotational speed control system and the acceleration control system are modelled according to the analysis of the engine control program.The temperature sensor,temperature amplifier and blade control system are also modeled.According to thse mathematical models,all systems are simulated with the SIMULINK in toolbox of MATLAB.This work has important value for further research and improvement in the engine main fuel control system.
PRELIMINARY RESEARCH ON RELIABILITY DESIGN METHOD OF MECHANICAL COMPONENT VIBRATION
Tian Aimei, Wang Yanrong
1999, 14(3): 320-322.
Abstract PDF(217KB) icon1689 icon505
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A method is presented to evaluate the reliability of a mechanical component vibration.An interference reliability model for the exciting frequency and the natural frequency of the component has been established.The reliability computation formula has been deduced by use of Goodman curve and its application conditions for the forced resonant response that can damage the component.In general,this method can be applied to the components,for which the modal frequencies can be separated,such as the turbine blades.
A SFEM FOR ANALYZING RELIABILITY OF VIBRATING STRUCTURAL COMPONENTS
Cui Haitao, Wen Weidong
1999, 14(3): 323-325.
Abstract PDF(287KB) icon2029 icon447
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Material characteristics,geometrical properties of structural components and loads are variables.As a result,the fatigue strength is analyzed by means of random variables.A stochastic FEM for analyzing the reliability of vibrating structural components is proposed.The theoretical basis for increasing the fatigue strength is provided.A cantilever beam has been taken as a numerical example.The correctness of this method is verified by an experiment.

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