2003 Vol. 18, No. 3

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Display Method:
Confidence Test Method for Normal Distribution
FU Hui-min, LIANG Zhao-hu
2003, 18(3): 305-312.
Abstract PDF(751KB) icon1688 icon389
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The normal population characteristics, such as the mean, standard deviation, percentile, percentage and coefficient of variation, are often tested in engineering. Based on the theory of confidence tests, the test methods for normal population characteristics are presented in this paper, which include the strong test, the weak test and the weak-strong test. Compared with the hypothesis tests and sampling inspections for normal distribution, the confidence tests can overcome the disadvantage that to accept a null hypothesis may simply mean that it is not rejected by significance hypothesis tests, and greatly improve the test precision. The confidence tests can also bring more convenience in engineering, as that the tests for the percentile and percentage of normal population that are difficult in hypothesis tests can be easily solved by the present method.
The Simulation of Coherent Structure in Turbulence Boundary Layer Using GAO-YONG Turbulence Equations
LIU Bo, GAO Ge
2003, 18(3): 313-321.
Abstract PDF(993KB) icon1791 icon389
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Unlike widely used turbulence models, the GAO-YONG model equations use no empirical coefficients or wall functions. And series form of energy equation corresponds to the scales of nonlinearity. In this paper, two-dimensional, incompressible turbulent boundary layer with zero pressure gradient is numerically simulated with GAO-YONG turbulence model. Employing staggered grid arrangement,an incompressible SIMPLE code is used. The calculation successfully simulates the coherent structures in the turbulent boundary layer and the effect of the order of the energy equation and grid scales on the coherent structures. All the results verify the adaptability of the equations to real intermittent turbulent flow.
Effect of Outer Flow on Internal Performance of Axisymmetric Vectoring Nozzle
ZHANG QUN-feng, LU Zhi-yong
2003, 18(3): 322-326.
Abstract PDF(625KB) icon1617 icon399
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The numerical simulation to study the internal flow characteristic of an axisym-metric vectoring nozzle under outer flow has been conducted with collocated finite volume scheme. The results of simulation have been compared with that of experiment. The effect of different NPR and outer flow on internal performance of axisymmetric vectoring nozzle with deflective angle of 20?has been analyzed. The investigation shows that the separation shock wave gives an important effect on internal performance of axisymmetric vectoring nozzle.
Study of Aeroengine Starting Tests at High/Low Temperatures and at Plateau
GUO Xin, YANG Zhi-jun
2003, 18(3): 327-330.
Abstract PDF(678KB) icon1814 icon522
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The paper analyzes the influences of the starting conditions on engine starting characteristics, and elucidates the advantages and disadvantages of several testing approaches under various testing conditions: natural ambient starting in a sea-level test cell, starting in a low temperature test cell,and in the mechanically simulated high altitude test cell meeting GJB241[1] requirements for high/low temperature starting test and plateau starting test.
Application of Microporous to Reducing Exhaust Noise of APU on MA60 Aircraft
WANG Zhan-xue, QIAO Wei-yang, LI Wen-Ian
2003, 18(3): 331-335.
Abstract PDF(599KB) icon1783 icon396
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The exhaust noise radiation of APU (Auxiliary Power Unit) on MA60 aircraft is serious. Effective sound treatment technology should be employed to control the exhaust noise. The measured spectrum of APU exhaust noise shows that typical exhaust noise spectrum is very broad. Two general regions can be distinguished. A broad hump of low frequency random noise centering in the 400-1000 Hz region normally is present, which often is substantially stronger when fully loaded. A second broad hump of high frequency random noise centers in speech interference region of 1000-5000 Hz,which is the frequency range of the ear's greatest acuity. Considering the measured spectrum and APU equipment,a microporous muffler is used for reducting of APU exhaust noise. The measured results show that the effect of microporous muffler for noise reduction of APU exhaust is very satisfactory.
Frequency Domain Analysis of Unsteady Separation Flow in Two Dimensional Subsonic Compressor Cascade
CHEN Shao-long, HOU An-ping, ZHOU Sheng
2003, 18(3): 336-342.
Abstract PDF(771KB) icon1694 icon391
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Numerical simulation was employed for the qualitative research on unsteady vortex shedding frequency in two-dimensional subsonic compressor cascade. Fast Fourier Transform Algorithm was adopted for the value of multi-dots' total pressure in nine different flow conditions. An acceptable criterion is advanced to distinguish the physical oscillation from the numerical oscillation; the vortex shedding frequency in numerical simulation is obtained under the nine different unsteady separated-flow conditions. In non-designed situation, large-dimensional unsteady open separated-flow emerges on the suction surface in two-dimensional subsonic compressor cascade and periodicity vortex shedding might be the primary movement fashion in separated-flow area and wake area dominated by separated-flow.
Mathematical Model for Twin Rotor Loads of a Coaxial Helicopter
ZHOU Guo-yi, HU Ji-zhong, CAO Yi-hua, WANG Jin-jun
2003, 18(3): 343-347.
Abstract PDF(469KB) icon2026 icon431
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The results of theoretical analysis and experiment have validated that the axially induced velocity distribution at the upper and lower discs of the coaxial twin rotor system is similar to that of the single rotor in hovering and forward flights. In this paper,by introducing an interaction factor and extending the first harmonic nonuniform inflow Pitt-Peters model for the single rotor helicopter to the coaxial helicopter, a simplified and practical mathematical model for coaxial twin rotor loads is formulated. This model avoids the complicated analysis and numerical calculations of the vortex models or CFD methods for obtaining the axially induced velocity at the upper and lower discs. Moreover, it can be employed for coaxial helicopter flight dynamics numeral simulation. The forces and moments on the sample coaxial twin rotor hub are calculated with the help of the math model. The computational results are in good coincidence with those from Russian model.
Gas Turbine Engine Emissions Measurement
LIU Gao-en, WANG Hua-fang, LU Pin, WANG Zhi-ping
2003, 18(3): 348-352.
Abstract PDF(506KB) icon1404 icon377
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With reference to " Aircraft Engine Emissions" promulgated by the convention on International Civil Aviation,we designed an emission measuring system. Emissions of two JT3D-7 gas turbine engines were measured by means of the system on the test rig of AMECO company. The measured Emissions Index EIco,EIHC,EINOx and SN of these two engines were compared with the JT3D-7 typical EI data. The accuracy of this system is about 3%, which was much better than the ICA's requirement (10%-15%). In the analytical formulations for the EI and AFR parameters of the convention, assumptions were made that all concentration measurements were of the " wet sample". In our practice, the CO2, CO and NOx concentration measurements were made on a "dry" basis. So we derived the corrected formulations for EI and AFR calculations of these engines. The data of experiments were varied in a quite wide range to prove that the sampling and measurement system is acceptable in engineering.
An Experimental Study of Efficient Pressure Distribution in a Turn-Over Channel with Ribs
LIU Lang, DING Shui-ting, TAO Zhi, XU Guo-qiang
2003, 18(3): 353-357.
Abstract PDF(481KB) icon1601 icon386
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The turn-over channel of turbine blade is an important part of the internal cooling structure of the turbine blade. Its flow performance is important for the design of cooling structure of the turbine blade. In this paper,a real turn-over channel of turbine blade is simplified and experimental study has been conducted. The paper demonstrates the investigation of the flow performance in a 180° turn-over channel with 90° parallel ribs and 60° parallel ribs respectively. The efficient pressure distribution was obtained along the channel in the inner part of these two turnover channels with 90° and 60° ribs is similar. Some efficient pressure increases along the channel due to irregular change of the channel shape. Correlation formulas of the coefficient of the efficient pressure are derived in the paper.
Level-Set Flamelet Modeling for Premixed Turbulent Combustion
YANG Cheng-ren, HOU Ling-yun, FU Wei-biao
2003, 18(3): 358-362.
Abstract PDF(532KB) icon1503 icon413
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Modeling for a lean premixed pre-evaporating combustor is presented. A detailed chemical reaction is considered. Mean location of lean premixed methane/air turbulent flame is modeled by Level-set approach and flamelet model. Comparison of calculations with experimental data indicates that the level-set flamelet approach is able to predict the major properties of the mean turbulent flame.
Simulation of the Performance of a Direct-Injection Stratified-Charge Rotary Combustion Engine
LI Li-jun, TANG Di-yi, FAN Jing, WANG Xiao-feng
2003, 18(3): 363-366.
Abstract PDF(452KB) icon1634 icon401
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A comprehensive computer simulation has been developed to predict the performance of a direct-injection stratified-charge rotary combustion engine by means of the zero-dimensional thermodynamic cycle model. With giving the model,the chamber pressure and temperature are available during a complete engine cycle. By the chamber pressure,the overall engine performance parameters can be calculated. The model can be used as an analytical tool for the preliminary design and development of the direct-injection stratified-charge rotary combustion engine.
Estimation of Critical Speed and Damping Ratio of a Rotor and Prediction of the Rotor Response at Critical Speed
LIAO Ming-fu, PU Qiu-hong, ZHONG Zhi-cai
2003, 18(3): 367-372.
Abstract PDF(626KB) icon1630 icon389
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This paper presents methods for estimating critical speed and damping ratio of a rotor and predicting the rotor response to imbalance at the critical speed. The estimation and prediction are carried out by means of the vibration values measured during the escalation stage of the rotor speed but below critical speed. In this way the critical speed and damping ratio can be obtained without running the rotor over its critical speeds, therefore a violent and dangerous vibration of the rotor at critical speed can be avoided. Additionally the prediction of the rotor response to imbalance at critical speed can give an assessment of condition of the rotor balance. Experimental results show that the critical speed and damping ratio can satisfactorily be estimated by these methods below 80 percent of the critical speed.
Sonic Fatigue Life Prediction of Aeroengine Structure
JIN Yi-shan, LI Lin
2003, 18(3): 373-377.
Abstract PDF(680KB) icon1776 icon496
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Sonic loading is a high frequency, broadband random process. Basic cycle counting methods,which are prevalently used in time domain,are difficult to be applied. According to present cumulative fatigue damage theories,the key to structure fatigue life analysis under sonic loading is to obtain the probability density function (pdf) of rainflow ranges directly form frequency domain. This paper analyzes some frequency domain approaches,which can obtain the pdf of rain-flow ranges from fatigue stress power spectral density (PSD) data. Some suggestions of promising method for aeroengine structural sonic fatigue analysis are given.
Life Prediction Considering Creep and Stress Relaxation for Gas Turbine Engine Hot Section
ZHOU Bai-zhuo, CONG Pei-hong, WANG Wei-yan, YANG Shi-jie
2003, 18(3): 378-382.
Abstract PDF(571KB) icon1901 icon414
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Accounting for creep and stress relaxations long-term life and low cycle fatigue life prediction method for gas turbine engine hot section is established. The long-term life and low cycle fatigue life of low pressure turbine blade for an aeroengine under real loading spectrum is analyzed by using this method. The results show that the established life prediction method is feasible.
The Effects of Phase Angle on Thermomechanical Fatigue Behavior and Life in DS Superalloy DZ125
ZHANG Guo-dong, LIU Shao-lun, HE Yu-huai, CHEN Rong-zhang, ZHOU Bai-zhuo
2003, 18(3): 383-387.
Abstract PDF(1068KB) icon1520 icon504
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Three types of test (in-phase,out-of-phase and-135 ° phase angle) were performed in directional solidification superalloy DZ125,with temperature cycling from 550'C to 1000 C. The results of experiment showed that DS superalloy DZ125 exhibited a crossover point of the in-phase and out-of-phase mechanical strain-life curves, - 135° phase angle lives were longer than that of in-phase and out-of-phase thermomechanical fatigue. Besides fatigue damage, creep damage and oxidation damage exist in thermal-mechanical fatigue. The effect of phase angle on TMF cyclic stress-strain response in DS superalloy DZ125 was investigated. Manson-Coffin e-quation, Ostergren method and microcrack propagation model were chosen to predict TMF life. The results of TMF life prediction showed that all of methods chosen were able to give a reasonable life prediction for DS superalloy DZ125.
A Method to Evaluate the Material Parameters of Viscoplastic Damage Uniform Constitutive Equations
LI Hai-yan, NIE Jing-xu
2003, 18(3): 388-393.
Abstract PDF(788KB) icon1781 icon440
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The viscoplastic damage uniform constitutive model and the constant evaluation method are reviewed, and a new simple method is presented to determine the material parameters of viscoplastic damage uniform constitutive equations. Then the genetic algorithm is used to optimize the parameters of the directionally solidified alloy DZ4. This method is proved to be reliable by the calculated saturation loops and creep curves.
The Vibration Performance of the Jeffcott Rotor System with SFD in Maneuver Flight
XU Min, LIAO Ming-fu
2003, 18(3): 394-401.
Abstract PDF(869KB) icon1932 icon417
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This paper sets up the differential equations of motion of a Jeffcott rotor system with squeeze film damper (SFD) and investigates its dynamic performance under maneuver flight. The result shows that the influence of maneuver flight on rotor vibration is evident, the additional centrifugal force and gyroscopic moment caused by maneuver flight will change the force acted on SFD. SFD can attenuate the transient vibration and stabilize the rotor system rapidly.
The Estimation of Random Vibration Response to Cylindrical Shell Excited Noise
CAO Mao-guo, LI Lin
2003, 18(3): 402-406.
Abstract PDF(393KB) icon1630 icon512
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This paper presents the estimated method for the power spectral density of vibration acceleration response of thin cylindrical shell excited by noise. The estimation is compared with the experience of a thin cylindrical shell excited by noise. They have a good agreement. Then a set of formula calculating the power spectral density of Von Mises stress response and its mean square value is given. The result can be applied to fatigue analysis.
Compressing for the Creep/Duration Load Spectrum with the Typical Condition Method
YANG Xing-yu, ZHAO Fu-xing
2003, 18(3): 407-410.
Abstract PDF(482KB) icon1528 icon415
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In this paper,a typical condition method is proposed for compressing the creep/ duration load spectrum of aeroengine. Using this method a lot of load conditions of a model of tur-boshaft aeroengine are compressed to four typical load conditions. The approach provides the technical basis for formulating the Simulation Mission Equivalent Test spectrum,and the Accelerated Mission Test spectrum,and assessing the strength and life of the turboshaft aeroengine components. The result of research shows that,in the existing conditions,the creep/duration load spectrum for the turbine blades,compressed by the typical condition method,can satisfy the application of engineering,and this method is reasonable and feasible.
Analysis of the Transient Ignition Proccess of Impulsive Microthruster
LI Shi-peng, ZHANG Ping
2003, 18(3): 411-414.
Abstract PDF(442KB) icon1667 icon429
Abstract:
Study of ignition transient characteristic of impulsive microthruster was conducted. The internal flow field of microthruster was simulated numerically by solving a 2-D symmetrical N-S equation with dp/dt transient combustion model and k-ε turbulent model. The pressure-time p-t curves and heat transfer status inside solid propellant were both obtained simultaneously. Compared with the test result,it is showed the transient model used in the numerical simu-lational is suitable for the phenomenon here.
Measurement and Analysis of Gaseous Parameters for Gas-Dynamic Resonance Tube Heating Process
AN Lian, LIANG Guo-zhu, TONG Xiao-yan
2003, 18(3): 415-419.
Abstract PDF(486KB) icon1628 icon400
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The experimental measurements of gaseous pressure and temperature histories at the end of the resonance cavities of three types of resonance tubes, i. e., cylindrical, cone and cone-cylinder shaped tubes were carried out by employing high frequency heat - resistant pressure transducers and thermocouples. The experimental results confirm that the intense oscillating shock wave accumulating dissipation is surely the major heating mechanism of the resonance tube. The gas in the tube is irreversibly compressed to a high time-averaged temperature over the stagnation temperature of the jet. The results also show that resonance tube heating effects are related to the pressure oscillations in the tubes,whereas the pressure oscillations are related to the pressure of the driving gas,and further,different types of resonance tubes have significantly different heating properties. The results are useful for actual designing of resonance tube igniters of liquid rocket engines and can be used as typical data for verifying correctness of numerical simulation.
Design for Adaptive Flight/Propulsion Control System Based on Wavelet Neural Networks
CHEN Mou, JIANG Chang-sheng, WU Qing-xian, CAO Bang-wu
2003, 18(3): 420-427.
Abstract PDF(702KB) icon1524 icon391
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In this paper, an adaptive H∞ control method based on wavelet neural network is proposed for the nonlinear uncertain systems. The controller is made up of equivalent controller and H∞ controller. The wavelet neural networks are used to approximate the nonlinear functions and the approximation errors of the neural networks are introduced to the adaptive law in order to improve the quality of the system. H∞ controller is designed for attenuating the external disturbance and approximation errors of the neural networks. The controller can not only guarantee the stability of the overall system,but also attenuate the effect of the external disturbance and approximation errors of the neural networks to a prescribed level. At last, based on forgoing designed control method a flight/propulsion control system has been designed and high angle attack flight simulation has been made. The simulation results suggest that the flight/propulsion control system is valid. They validate the availability of this control method for the uncertain nonlinear system too.
An Automatic Optimization Algorithm for the Linear Identification of System's Dynamic Model
WANG Wen-dong, ZHANG Sheng-liang, LI Jian, XIE Shou-sheng
2003, 18(3): 428-431.
Abstract PDF(365KB) icon1753 icon400
Abstract:
Aiming at linear time-varying, systems of which the static state characteristic is known, and through the analysis of the dynamic response data, a new linear model jumped by time is set up and an automatic optimization identification algorithm is programmed. And through this automatic optimization identification algorithm, jumping-times and parameters of the model are estimated. Through the analysis of a system identification example of X aero-engine EEC (engine electronic controller),the result shows this method is effective.
The Application of Engineering Database in Aeroengine Test
QIU Jun-fang, LEI Yong, LIU Gong-qing
2003, 18(3): 432-435.
Abstract PDF(548KB) icon1433 icon481
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On the basis of analyzing characteristic data of an aeroengine test, the data management using engineering database is studied. This paper also analyzes the E-R model for aeroengine test engineering database, the structure of aeroengine test engineering database, the interface of the data processing program with the aeroengine test engineering database,and the development of client module. The development of engineering database for aeroengine test has improved the efficiency of aeroengine test and ensured veracity and security of aeroengine test.
Flight Envelope Division Method in Aeroengine Control Study
WANG Jin, LI Jian, XIE Shou-sheng
2003, 18(3): 436-439.
Abstract PDF(384KB) icon1767 icon418
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According to the matrix perturbance analysis theory,this paper analyzes the effects of engine inlet parameter perturbance on coefficient matrix eigenvalues of engine model. And based on the analysis,the engine envelope is divided into several areas. In these areas,the structure parameter perturbations of engine model are varied within a designated range. The calculated results indicate that the division method of flight envelope is proper.
Robust Fault-Tolerant Control for Aeroengine Based on Solution of Riccati Equation
XU Qi-hua, LI Hua-cong
2003, 18(3): 440-443.
Abstract PDF(429KB) icon1600 icon380
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Using a feedback control law,a sufficient robust fault-tolerant condition is derived based on the solution of Riccati equation. The fault-tolerant condition can make an aeroengine possess integrity against both sensor failure and parameter perturbation of the engine model. According to the proposed robust fault-tolerant condition,a new design method and an iterative design procedure are presented through increasing gradually the state-weighted matrix in the Riccati equation. The design method was applied to a turbojet engine to demonstrate its effectiveness. It is proved to be very useful and effective with the satisfactory numerical simulation results of the robust fault-tolerant engine control system. The similar fault-tolerant condition and corresponding design method are also concluded in the case of actuator failure.
Single Gear Analysis Technique for the Detection of Gear Faults
MENG Tao, LIAO Ming-fu
2003, 18(3): 444-449.
Abstract PDF(1527KB) icon1920 icon440
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This paper presents a procedure of single gear tooth analysis for early detection and diagnosis of gear faults. The objective of this procedure is to develop a method for more sensitive detection of the incipient faults and locating the faults in the gear. The main idea of the single gear tooth analysis is that the vibration signals collected with high sampling rate are divided into a number of segments with the same time interval. The number of the signal segments is equal to that of gear teeth. The analysis of individual segment reveals more sensitively the changes of the vibration signals in both time and frequency domain caused by gear faults. In addition, the location of failed tooth can be indicated in terms of the position of the segment that deviates from normal segments. A numerical simulated signal and an experimental investigation verified the advantages of the single gear tooth analysis.
The Dynamic Characteristics Analysis of Planet Gear Train
WEI Da-sheng, WANG Yan-rong
2003, 18(3): 450-453.
Abstract PDF(346KB) icon1605 icon368
Abstract:
The multi-degree of freedom model has been established to describe the dynamic behavior of a planet gear train of the 2K-H type with five planet gears. The numerical integration of the equations of motion for the system has been done by the use of Gill's method. The dynamic response of the system under the stiffness excitation induced by the mesh between gears has been obtained,and the dynamic load of gears has been determined. The effects of the contact ratio of gears and the floating motion of the centroid of the sun gear on the dynamic characteristics have been discussed emphatically during the mathematical manipulation.
A Testing Instrument for the Box Against Pant of Some Turbojet Engine
LI Wen-feng, WANG Yong-sheng, WU Chang-ying
2003, 18(3): 454-457.
Abstract PDF(410KB) icon1570 icon368
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A testing instrument is described for the box against pant of some turbojet engine used for checking the breakdown within the electric circuit and for adjusting the whole machine functions,while the box against pant is being examined. Some stimulating signals, which are similar to that of the engines,are sent to the box against pant by the testing instrument,then some respondent signals are produced by the box. We receive, check and analyze these respondent signals in order to judge whether the box against pant runs in right order. This paper introduces the system function,the constitution,the working principle and its working process.
A Way for 3-Minitue Event Recording and Replaying in Aeroengine Test
YANG Xun
2003, 18(3): 458-461.
Abstract PDF(401KB) icon1538 icon354
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The function named 3-minitue events recording and replaying in computer-aided test system for aeroengine test is able to offer data for analysis afterwards. Firstly, the general method to create model for events is investigated in detail. Then the scheme for recording and replaying the data is discussed. At last the data structured is presented. On the basis of the method present,the function is achieved and has been used for aeroengine test.
2003, 18(3): 462-464.
Abstract PDF(268KB) icon1136 icon77
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