2003 Vol. 18, No. 6

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Display Method:
Prediction Method for Correlation Coefficient AR(p) Series with Unequally Spaced Data
MA Xiao-bing, FU Hui-min
2003, 18(6): 713-716.
Abstract PDF(739KB) icon1436 icon469
Abstract:
A new prediction method for correlation coefficient stationary series with unequally spaced data is established. The prediction formulas and error estimations for the correlation coefficient AR(1) and AR(2) series are discussed in detail. The traditional interpolation method, which transfers the unequally spaced data to equally spaced data, may cause a great error in prediction. The results of calculations show that the precision of present method is higher than the traditional interpolation method.
Dynamic Characteristics Study of a Power Turbine Rotor of a Turbine Shaft Engine
DENG Wang-qun, GAO De-ping
2003, 18(6): 717-722.
Abstract PDF(809KB) icon1960 icon540
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This paper studies dynamic characteristics of a power turbine rotor of a new-type turbine shaft engine when finite element method is used.The dynamic characteristics of the rotor in different conditions,such as critical speeds,vibration shapes and unbalance responses,are respectively systematically calculated and analyzed.The first five-stage critical speeds,the curves of the first five-stage dominant vibration shapes and the first two-stage unbalance responses of the rotor are obtained.Furthermore,the influences of balance collars on dynamic characteristics of the rotor are also calculated.The experimental results show that the calculation model can factually express the dynamic characteristics of the rotor.This study provides references and bases for subsequent high speed dynamic balance of the rotor.
A Study of Vibration Fault of Combined Compressor
YANG Zhi-guo, MEI Qing, OU Yuan-xia, CHEN Yun-xi, XU Chang-gen
2003, 18(6): 723-726.
Abstract PDF(284KB) icon1556 icon459
Abstract:
The combined compressor rotor in not able to reach the maximum rating speed on test bench because its level of vibration is very high and exceeds vibration limits.This paper studies vibration of combined compressor by rotor dynamics analysis and experiments to discover the reason of fault.An advanced measure is taken and makes the combined compressor to operate normally.
Model and Simulation of Aeroengine Load Spectrum Related to Operation
SONG Ying-dong, SUN Zhi-gang
2003, 18(6): 727-731.
Abstract PDF(697KB) icon1995 icon466
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The paper presents a model of aero-engine load spectrum related to operation,and makes a statistic analysis for vertical overload factor spectrum of a fighter engine center of gravity.The model is proved reasonable.The results show that load spectrum related to operation can be described by Poisson stochastic processes,which are completely determined by four factors such as distribution of loading duration,distribution of loading arrival interval,frequency accumulation curve of loading duration and frequency accumulation curve of loading level crossing by Level Crossing Counting.The loading duration and the loading arrival interval yield exponent distribution.Based on the equivalent of the four factors,a simulation method for load spectrum related to operation is provided.As an example,the vertical overload factor spectrum of the engine is simulated.The results are satisfactory and show that this simulation method is correct.
Mechanisms of Low Cyclic Fatigue of DD6 Alloy at Elevated Temperature
LI Ying, SU Bin
2003, 18(6): 732-736.
Abstract PDF(865KB) icon2076 icon474
Abstract:
Low cycle fatigue mechanism of a single crystal nickel-base superalloy,DD6,has been investigated at 760℃ and 980℃.It was found that there were two kinds of sites where crack initiates,one being the surface of the specimens and the other being the sub-surface.Microcracks and oxide layer on the specimen surface are potential crack initiation sites in this superalloy.Secondary crack,reared ridge, and microcrack in the front of the main crack tip can all hinder crack propagation during low cycle fatigue.
Response of a Gear System with Time-Varying Mesh Stiffness to Torque Fluctuation
ZHANG Suo-huai, SHEN Yun-wen, DONG Hai-jun, LIU Meng-jun
2003, 18(6): 737-743.
Abstract PDF(377KB) icon1495 icon514
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The governing equation of a gear system is established.In the equation,the time-varying mesh stiffness,mesh damping,input and output torque fluctuations are considered.Due to the mesh stiffness of a gear pair,the governing equation represents a linear dynamic system with periodic time-varying coefficient.A-operator method (AOM) is used to obtain the approximate analytic solution.According to the results,A-operator method (AOM) overcomes the defaults of harmonic balance method and can keep all frequency components.In the response of the system,fundamental,double and composed frequency etc of time-varying mesh stiffness and torque fluctuation frequency coexist.A-operator method (AOM) takes less time than other numerical method.
Analysis of Meshing Behavior and Experiments of Spiral bevel Gears with High Contact Ratio
DENG Xiao-zhong, FANG Zong-de, WEI Bing-yang, YANG Hong-bin
2003, 18(6): 744-748.
Abstract PDF(371KB) icon1929 icon551
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Based on the simulation methods of TCA and LTCA,a new approach to the gear geometric surface design for increasing the contact ratio is proposed in the paper to supersede the traditional method which regards the contact path as being perpendicular to the root cone.We purpose to develop the design method for high contact ratio by means of sloping the contact path.The designed gear set has lower transmission error under load,reasonable load distribution and excellent meshing behavior.The experiments of the tooth root stress and noise testing have proved that the method is efficient for designing the high contact ratio gear set,and has some advantages of dynamic behavior and strength.
Study of the Statistical Rules for Flight Mission Profiles of Aero-Engine
CHENG Li, FENG Wei, CHEN Wei
2003, 18(6): 749-752.
Abstract PDF(655KB) icon1940 icon522
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Taking the equivalent fatigue damage of primary cycle as the character,the statistical rules for flight mission profiles of aero-engine are studied in this paper,mainly for different pilots'control actions.By using the actual flying data of a trainer engine,the low cycle fatigue damages of aero-engine made by different airplane pilots'control action in the same mission profile follow normal distribution,the values of normal distribution parameters in different mission profiles are different,but no salient change appears for different airplane pilots'control action.
State-of-the-Art and Prospect of Aircraft Engine Fault Diagnosis Using Gas Path Parameters
HAO Ying, SUN Jian-guo, BAI Jie
2003, 18(6): 753-760.
Abstract PDF(1276KB) icon2201 icon715
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Gas turbine engines are widely used in the fields of air,ground and ship,so it is much of importance to assess engine performance and diagnose its faults.This paper surveys the development of engine fault diagnosis and the main diagnosing methods including gas path analysis,non-linear mode methods and artificial intelligence methods.Finally,the prospect of studying engine fault diagnosis is presented.
Application of the Elliptic-Type Conditional Moment Closure Method to Turbulent Diffusion Bluff-Body Flames
LIU Tao, ZHANG Kan, MENG Kun, FANG Ren
2003, 18(6): 761-767.
Abstract PDF(1317KB) icon1535 icon552
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The elliptic-type conditional moment closure model is implemented to simulate nonpremixed turbulent bluff-body burner flames.The fuels are CH4/H2,CO/H2 and CH3OH.The k-ε turbulent model and SIMPLE method are employed in the computation.Results of average flow characteristics,conditional averaged temperature,OH,CO and NO concentrations are obtained.Reasonable agreement between experiments and predictions shows that the CMC model is capable of predicting the species concentration and temperature in turbulent nonpremixed combustion.Discrepancy on the rich side may partly be due to the singly conditional moment closure,or lack of adequate chemical kinetics on the rich side.
Numerical Solutions of 3D Unsteady Viscous Flow in a Two-Stage Fan
LIU Qian-zhi
2003, 18(6): 768-771.
Abstract PDF(326KB) icon1886 icon453
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The numerical simulations of the unsteady flow induced by rotor-stator interaction in a two-stage fan were carried out.A three-dimensional unsteady Navier-Stokes equations solver using a high-resolution finite difference has been developed.It can be used for the calculation of steady flow field with an implicit scheme.The solution of steady flow was firstly obtained by this code.The unsteady flow computations were started from this solution.The unsteady flow results show that the unsteady effects on inlet flow angles of blade rows are significant.The variations in inlet flow angles of stator blades are larger than that of rotor blades.In comparison with the steady flow solution,the increases in unsteady flow attack angle are larger than the decreases.The maximum increase is about 10 degrees.The variations in unsteady aerodynamic force on stator blades are also larger than that on rotor blades.The unsteady flow effects caused by several blade rows are different from that by single blade row.
Influences of the Downwash Flow from a Helicopter Rotor on the Performances of an Infrared Suppressor
WANG Xian-wei, HUANG Yong, LU Yu-xia
2003, 18(6): 772-776.
Abstract PDF(845KB) icon1836 icon546
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Experimental diagnostic study has been performed,and results show that the downwash flow had remark able impacts on the aerodynamic performances, characteristic temperatures,and infrared radiation.With the increase in the downwash flow velocity,the entrainment coefficient decreased,and the exhaust flow temperature increased,resulting in the rapid increases of the exhausting duct temperature and the suppressor surface temperature.And finally,the downwash flow at hovering condition caused an increase of total infrared radiation between 3～5 μm by about 35%.
An Analysis of the Starting Characteristics of Aeroengine
PIAO Ying
2003, 18(6): 777-782.
Abstract PDF(1055KB) icon2086 icon567
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Fast,reliable starting capability is one of the most important characteristics of aeroengine.The starting characteristics are affected by many factors,and the wide operating range makes it difficult to design starting control system.By numerical simulation and analysis of experimental data,a variety of influence factors of aeroengine starting were studied.
Stability Assessment Test Technology of a Turbofan Engine Inlet Temperature Distortion
ZHANG Tian-fei, YE Wei, LU De-yu, ZHAO Xiao-bin, WANG-Jin
2003, 18(6): 783-787.
Abstract PDF(362KB) icon2142 icon527
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This paper discusses the constitution and principle of temperature distortion generator.Based on the inlet temperature distortion experiments of a turbofan-engine,the critical thermal agitation values under each engine operating condition were ascertained,the distortion sensitivity coefficients of the engine were determined,and a practical technical aero-engine stability assessment method for inlet temperature distortion was presented.It is proved that the temperature distortion generator is a useful tool for aero-engine stability assessment.The successful development of a temperature distortion generator will have significant effects on the formulating of our country's assessment criterion of aero-engine inlet temperature distortion.
Effect on Stability of Compressor with Total Temperature and Pressure Distortions
DONG Jin-zhong, WANG Miao-miao
2003, 18(6): 788-793.
Abstract PDF(879KB) icon1870 icon490
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Response of compressor to the inlet combined distortions of pressure and temperature is emphasized in this paper.The mathematic model used in the paper is based on the one dimensional and time dependant Eulerian equations,taking into account of the work applied by compressor system,air bleeding and heating processes.The inlet-outlet assumptions of parallel compressor theory are modified, and the effect of three circumferential combined distortion modes of the compressor is calculated.The changes in compressor stability boundary under distortion conditions are given.According to the calculated results,it could be concluded that among the three combined distortion modes discussed in this paper,if total temperature and total pressure are in the same area,the compressor's stability margin descends to the utmost;if they are in separated areas,the stability boundary descends least;if the areas are partially overlapped, the boundary decreasing amplitudes lie between the former two cases,and this condition also exhibits some of their characteristics.
On the Spatial Instability of a Conical Sheet
YUE Ming, YANG Mao-lin
2003, 18(6): 794-798.
Abstract PDF(286KB) icon1895 icon484
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A temporal instability analysis of a conical sheet is carried out.A dispersion relation of a conical sheet for both axisymmetrical and antisymmetrical disturbances is presented.The dispersion relation has been solved numerically and typical results are given.For both axisymmetrical and antisymmetrical disturbances,the increase in sheet cone half-angle reduces the wave growth rate and the range of instability,and shifts the dominant wave of the disturbances to a longer wavelength.For antisymmetrical disturbances,the sheet cone half-angle inhibits the reduction of the growth rate, and two local maxima of the growth rate exist in this case.The two maximum growth rates correspond to waves with different wavelengths,and the growth rate and the range of instability of the short wavelength wave are much less than that of the long one.It is shown that both long and short wavelength waves affect the breakup of the conical sheet,and sheet is easy to breakup under the effect of short wavelength wave.
A Calculation of Spray Parameters of Pressure-Swirl Atomizer
YANG Jian-hiu, FAN Wei-jun, YANG Mao-lin
2003, 18(6): 799-802.
Abstract PDF(356KB) icon1880 icon470
Abstract:
Based on the results of the linear stability analysis and the experimental correlation of conical liquid sheet break-up length of pressure-swirl atomizer,combined with the structure parameters of pressure-swirl atomizer and simplified flow model,the depth h_b of the conical liquid sheet at the point of break-up can be obtained through calculation,then Sauter mean diameter SMD can be determined from h_b.The results by this method agree well with experiments and Jasuja's relative experimental correlation.The calculating method in this paper can be used to pre-estimate spray parameters of pressure-swirl atomizer.
A Preliminary Investigation of Low-Frequency Combustion Instability in a Model Combustor
ZHAO Zhen, GUO Zhi-hui, HUANG Yong, LIU Gang
2003, 18(6): 803-807.
Abstract PDF(645KB) icon1932 icon437
Abstract:
A preliminary investigation of low frequency combustion instability has been conducted in an atmospheric combustion facility.The result indicates that at higher equivalence ratios,typically above 06,the combustion process becomes highly unstable,exhibiting large-amplitude pressure oscillations at some frequencies between 200 Hz and 235 Hz.The frequency and amplitude of instability grow with increasing premixed gas injection velocity.The result also shows that the instability mode changes when the exit area of the combustor decreases to some critical value.
Experimental Investigation of Combustion Performance of U-Type Flame Holder
ZHENG Dian-feng, ZHANG Hui-qiang, LIN Wen-yi, WANG Jia-hua
2003, 18(6): 808-812.
Abstract PDF(667KB) icon1839 icon422
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The combustion performance of a U-type flame holder has been experimentally investigated and compared with that of V-type and double V-type flame holders.The combustion-experimental results show that the ignition performance of V-type and U-type flame holders is better than that of the double V-type flame holder under ad hoc case of fuel supplying,and the combustion efficiency of the U-type flame holder is the highest among these flame holders.Furthermore,it is shown that the proposed flame holder of U-type has successfully improved the disadvantage of double V-type flame holder under the circumstance of fuel supplied in the upstream of flame holder,and has the advantages of both other flame holders.The cold-state test results show that the flows in the flame stability tube of U-type are typical three-dimensional and have stronger recirculating zone and low velocity zone in downstream of flame holder than that of double V-type flame holder.It is the reason why the combustion performances of double V-type flame holder are ameliorated by the U-type.
Investigation of Performance of an Engine Oil Cooling System
YANG Chun-xin, ZHANG Li-na, GUO Hui
2003, 18(6): 813-818.
Abstract PDF(351KB) icon2000 icon502
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This paper establishes a new method of obtaining the performance of an engine oil cooling system.The method involves the equation of heat gain of the oil passing through an engine and performance calculations of oil heat exchangers.When the heat exchange between oil and ambient in the oil heat exchanger cannot be ignored,the complex heat transfer processes could be treated as two independent approaches,heat transfer from oil to cooling fluid as well as from coolant,to ambient.Each separate approach is a simple heat transfer problem for which an analytic solution can be acquired easily,and then the real outlet temperature value of oil is obtained by a linear combination correlation of these two solutions.Based on the theoretical analysis,a more effective NTU correlation of the heat exchanger is deduced under the operating condition.This method has been well verified by the experimental data of an engine and can be used to calculate the performance and estimate the heat-sinking capability of the oil cooling system of engine in severe condition.
Parametric study of Heat Receiver Mass in Space Solar Dynamic System
CUI Hai-ting, YUAN Xiu-gan, XING Yu-ming
2003, 18(6): 819-823.
Abstract PDF(301KB) icon1555 icon524
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To reduce the heat receiver mass,a mathematical and physical model of heat receiver for NASA 2 kW in space solar dynamic power system is formulated.The numerical simulations are performed and the effects of the structural and operational parameters on the heat receiver mass are analyzed.The results of the study indicate that structural parameters such as diameter,and number of the working fluid tube and,operational parameters such as compressor gas inlet temperature,rotating speed of the turbine and the recuperator effectiveness affect the heat receiver mass.Appropriate selection of these variables can distinctly reduce the weight of heat receiver.The calculated results can be used for the mass optimization of heat receiver.
Numerical Computation of Low Leakage and High Endurance Brush Seal
XIE Xiao-jun, KANG Ning
2003, 18(6): 824-826.
Abstract PDF(271KB) icon2056 icon489
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A new style of brush seal with low leakage and high endurance was studied in this paper by the method of the aerodynamic computation.The steady compressible N-S equations were solved numerically to simulate the three dimensional flow in the brush seal structure with the aid of the commerical software STAR-CD.The leakages of the brush seal were calculated for serveral pressure differences.The brush seal structure was evaluated according to the computed leakages.The above results showed that:the leakages become larger with the increase of the pressure difference;the leakages of the new brush seal were smaller than that of the old brush seal;the leakages of the seventy-model were slightly smaller than that of the seventy-five-model.This study indicates that the increase of the angle between the brush seal layers can reduce the leakeges.
Numerical Analysis and Comparison of the Tip-Clearance Flow of a High-Loading Transonic Compressor
JING Rong-qiang, LI Min-jiang, GUI Xing-min
2003, 18(6): 827-831.
Abstract PDF(892KB) icon1973 icon529
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A 3D numerical simulation software was developed to calculate the tip-clearance flow of ATS-2,a high-loading transonic compressor,and the results were compared with the experiments.The results of numerical simulation are in accordance with that of experiments.The comparison between the viscous and non-viscous simulations shows that the intensive blockage area is caused by shock-leakage flow interaction.The viscosity weakens the blockage area,both in size and intensity.With the increase of the tip-clearance,the blockage area grows in the radial and axial directions with the total pressure ratio,efficiency and mass flow decreasing.
Top Level Design of Micro Turbine Jet Engine
HUANG Guo-ping, LI Bo, WEN Quan, LIANG De-wang
2003, 18(6): 832-838.
Abstract PDF(1098KB) icon2934 icon621
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The top-level design of micro turbine jet-engine is presented in the paper.Firstly,the relationship between dimensions and performance of micro turbine engine is analysed.Results show that micro turbine engines have potential larger ratio of thrust to weight than conventional engines.A preliminary design of a micro turbine engine is illustrated on the basis of the related technologies that can be achieved recently.Parametric analysis of performance,such as:thrust,specific fuel consumption,energy efficiency,exhaust gas temperature,was performed by changing one or two of 7 variables.In order to assess if the design of the micro turbine engine is capable of generating the reguired thrust when put into practice,a convenient criterion is formulated,and three designs of micro turbine engine are obtained for high,moderate and low performance.
Additional Drag Correction of Aircraft Engine on Test Facility
GUO Xin, LIU Tao, WEN Gang
2003, 18(6): 839-844.
Abstract PDF(528KB) icon1576 icon503
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Additional drag (inlet/outflow momentum drag) is an important part of the engine thrust on the test bench.It is very significant for improving the precision of the engine test thrust so that the additional drag is accurately measured.This paper introduces the gross thrust and contrast calibration of test facility.At the same time,this paper studies the method of correction of additional drag which takes place during engine tsting on outdoor test stand,ground test bed and altitude test facility.Lastly,this paper gives the results of comparison testing between two altitude test facilities (Muscovite and Chinese),also gives the results of comparison testing between that of altitude test facility and ground test bed.
Application of Neural Networks to Areoengine Adaptive Modeling
WANG Xin-de, SUN Jian-guo, LI Song-lin
2003, 18(6): 845-849.
Abstract PDF(357KB) icon1655 icon438
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In this paper a new method based on neural networks is proposed for aeroengine adaptive real time modeling.It is thought that output data of aeroengine will bias their nominal values in any cases of non-nominal work.So the biases of output data can be used to represent the non-nominal work conditions of the aeroengine and to constitute the augment state variables.Kalman filter is designed to estimate these biases.Then the unmeasured outputs of the onboard model of the areoengine can be modified by the estimation of the unmeasured biases which are obtained through the mapping relation constructed between the measured output biases and unmeasured ones and trained by the BP neural networks offline.After modification,outputs of onboard model are the same as those of the real aeroengine,and real time onboard model has the abilities of adaptation.

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