2008 Vol. 23, No. 11

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Optimization method by combination of wavelet neural networks and genetic algorithm
WANG Bao-guo, LIU Shu-yan, QIAN Geng, NAN Xi, GUO Yu-hang
2008, 23(11): 1953-1960.
Abstract PDF(580KB) icon1624 icon434
Abstract:
An optimization method based on the combination of wavelet neural networks(WNN)and Pareto genetic algorithm was proposed,and was applied to the numerical optimization in internal flows.WNN is composed of input layer,hidden layer and output layer.It replaces the commonly used Sigmoid activation function in back propagation(BP) neural networks by Morlet wavelet generating functions in hidden layer.Pareto genetic algorithm has great global optimum ability and optimization efficiency.Generally,it can always gain uniformly-distributed Pareto optimal solution set.Typical algorithm examples indicate that this algorithm can complete approaching and mapping of non-linear function quickly,efficiently and accurately,with great generalization ability.
Design and analysis of thermal structure of inlet of scramjet
WEI Xin, SUN Bing, ZHENG Li-ming, ZHANG Jie
2008, 23(11): 1961-1965.
Abstract PDF(908KB) icon2154 icon488
Abstract:
Based on the thermal environment of the inlet surface of the scramjet,the structure thermal protection was proposed to provide efficient protection for the inlet surface.Two thermal structure schemes for the inlet surface were designed,including net structure and corrugated sheet structure.And the thermal protection effect of two schemes was simulated.The results indicate that,two thermal structures could achieve efficient thermal protection within the permissible temperature range.Based on comparative analysis,it shows that the corrugated sheet structure has better thermal protection effect.
Configuration design study for 2-D hypersonic airbreathing vehicle
JIN Liang, LIU Jun, LUO Shi-bin, WANG Zhen-guo
2008, 23(11): 1971-1975.
Abstract PDF(457KB) icon1695 icon499
Abstract:
A numerical study of different 2-D hypersonic airbreathing vehicle configurations under Mach 6 has been performed to analyze the aerodynamic characteristics,the airframe upper surface geometries considered in the present work include the Von Karman curve and straight line,the combustor configurations included the tandem backward facing step and tandem expansion straight line,the nozzle shapes included the power law curve and straight line.A second-order Roe scheme with a minmod limiter was used for space descretization,and Menter's k-ω SST(Shear stress transport) turbulence model was used for predicting the turbulence flows,the CFD-derived pressure and friction distributions were numerically integrated to compute the lift,drag and pitch moment,and the influence of each configuration design on the global aerodynamic characteristics have been analyzed,which provided assistance for the design of the hypersonic airbreathing vehicle.
Effects of jet blowing on the side force of forebodies with different cross section
ZENG You-bing, Lv Zhi-yong
2008, 23(11): 1976-1981.
Abstract PDF(924KB) icon1273 icon477
Abstract:
The aim of this paper is to study the effects of normal and tangential blowing on the side force of forebodies with different cross section.Based on the measurement test of forces in a wind tunnel,the test results were presented.Furthermore,the influence of angle of attack,the blowing means,the pointing angle of tangential blowing and the cross section of the forebodies on the side force were discussed.The results show that,both normal and tangential blowing are effective means of flow control,the influence of blowing on the cone-cylinder is strongest,followed by the influence of blowing on the elliptic forebody and on chine forebody.
Multidisciplinary design optimization of a cooling vane
SONG Ying-dong, ZHANG Fu-jun, YUE Zhu-feng, CAI Xian-xin
2008, 23(11): 1982-1987.
Abstract PDF(1847KB) icon1682 icon477
Abstract:
A multidisciplinary design optimization(MDO) procedure for a vane with jet impinging cooling,film cooling of slots and holes,pin-fin array cooling was proposed in this paper.The structure of the vane and the prediction method of heat transfer were discussed and some of the formulas are presented.A mathematic model is established for multidisciplinary design optimization of a vane.A vane of a gas turbine is taken as an example to be optimized by using the procedure presented in this report.The obtained results show that the presented procedure is efficient.
Test analysis of blades vibration load and viration characteristics on the condition of rotor and stator rubbing
LI Yong, JIANG Guang-yi, WANG De-you, LI Qi-han
2008, 23(11): 1988-1992.
Abstract PDF(5792KB) icon1771 icon453
Abstract:
The blade load test method on the condition of rotor and stator rubbing was studied,the vibration characteristics of blade under rub-impact forces and friction forces were tested,and the time load and frequency spectrum of blade and casing under wallop were presented.This proves that,under different rub-impact forces,the blade doesn't generate sympathetic vibration,and is only subject to bending moment.All these provide a basis for intensity analysis of rotating machine on the condition of rotor and stator rubbing.
Geometry number of rolling element bearings and estimation of characteristic octave frequencies of bearing defects
LIAO Ming-fu, MA Zhen-guo, LEI Jian-yu
2008, 23(11): 1993-2000.
Abstract PDF(2576KB) icon1594 icon463
Abstract:
Geometry number was introduced in this paper.According to the geometry relationship of rolling element bearing and the statistics of 1274 bearing models,it was found that bearing geometry number of bearings of the same series of is relatively constant,but it is quite different for different series of bearing.Geometry numbers of 45 series can be classified to 7 basic types.A method to estimate characteristic octave frequencies of defect in inner race and outer race was introduced.The method is based on number of balls,the geometry number and series of bearing.Since geometry numbers are provided and the number of balls and the series of bearing can easily be obtained in practice,the method is helpful for detecting defects in bearings.
Three dimensional numerical simulation of enhancing jet mixing with microjet
LI Ting, Eriqitai, LI Jia-jun
2008, 23(11): 1996-1970.
Abstract PDF(1250KB) icon1583 icon400
Abstract:
Computational fluid dynamics is employed to numerically simulate the flow of round jet with microjet.With microjet technology,it's possible to control efficiently IR of jet flow.And,vortexes in flow direction are generated to enhance the mixing between jet flow and ambient air.Therefore the high temperature area of jet is decreased.The penetration and outlet width of microjet is the decisive factor to suppress the high temperature area and affect the mixing.
Post-impact compressive strength experiment of T300/BMP316 composite laminates
CUI Hai-po, WEN Wei-dong
2008, 23(11): 2001-2006.
Abstract PDF(683KB) icon1668 icon448
Abstract:
Experiment study on impact damage and residual compressive strength had been done on T300/BMP316 composite laminates with different layer parameters.The results show that although the residual compressive strength gradually decreased with the increasing impact energy,there is no linear relationship between of them.The layer parameters has effect on the long-axis direction of impact damage figure,but hasn't influence on the impact damage area.The residual compressive strength has no direct relationship with the impact damage area.
Comparative study of multiaxial high-cycle fatigue-prediction criteria
SHI Xin-hong, BAO Rui, ZHANG Jian-yu, FEI Bin-jun
2008, 23(11): 2007-2015.
Abstract PDF(764KB) icon1664 icon445
Abstract:
Six common fatigue-prediction criteria for multiaxial high-cycle fatigue analysis were analyzed with several materials and loading data.The selected criteria cover: equivalent stress criteria,stress invariant criteria and critical-plane stress criteria in current investigations.The experimental data covered 10 kinds of metal materials,including alloy steel,low-carbon steel and aluminum alloy and cast iron,under proportional and non-proportional loading conditions respectively.The analytical results show that,the predicted results for low-carbon steel and alloy steel are better than that for other materials,and the predicted result for proportional loading is better than that for non-proportional loading.Papadopoulos criterion,Susmel criterion and Liu criterion show better prediction capability than the other three criteria.However,the prediction results of all six criteria for cast-iron materials are dissatisfactory.
Analysis method for the strain fatigue life reliability of a disk concerning failure correlation of multi critical sites in the same stress level
MA Shuang-yuan, LU Shan
2008, 23(11): 2016-2020.
Abstract PDF(413KB) icon1779 icon465
Abstract:
In order to calculate strain-fatigue life reliability of a disk more accurately,considering the failure correlation of the disc with multi-critical sites in the same stress level,a method for analysis of strain-fatigue life reliability was proposed.A strain-fatigue life reliability interfere model based on generalized strength and generalized stress was set up,and H-L method was used to evaluate the fatigue life reliability at a failure site.As a fan disk usually contains multi critical sites in the same stress level,the strain-fatigue life reliability of the disk concerning multi failure sites correlation was acquired through the Hohenbichler's integral method.Finally,an example of strain-fatigue life analysis of the disk was given to demonstrate the efficiency of the method.The relationship of the correlation coefficient between the failure functions and the correlation coefficient between random variables in the stain-life model is discussed.Also the relationship of the correlation coefficient between the failure functions and the probabilistic fatigue life of the fan disk concerning multi failure sites correlation is illustrated.
Application of stochastic response surface method in the structural stochastic response
GUO Zhi-wei, BAI Guang-chen
2008, 23(11): 2021-2025.
Abstract PDF(3881KB) icon1874 icon497
Abstract:
Classical response surface method approaches the structural stochastic response using a group of general polynomials,but this method can not guarantee convergence.Stochastic response surface method can compensate the drawback of the classical response surface.Two numerical examples and a practical example of an aero engine disk were presented herein to validate stochastic response surface method.The results show that,with the increasing order of polynomial chaos,the probability density curve of a response approaches the results from Monte Carlo simulations.
Protection of a rotor against violent vibrations caused by a crack in elastic supports by using active elastic support/dry friction dampers
WANG Si-ji, LIAO Ming-fu
2008, 23(11): 2026-2030.
Abstract PDF(833KB) icon2002 icon450
Abstract:
The dynamic behavior of rotor systems with a cracked elastic support was analyzed.Experimental investigations of rotor vibration characteristics,in particular,caused by a crack in elastic supports by using the control of an active elastic support/dry friction damper,was carried out,It is proven that the damper is effective to reduce rotor vibration caused by cracked elastic supports.Experimental results show that the damper with the P control method,can be achieved with the emergency shutdown,and plays a key role of protecting rotor systems.
Elastic property prediction of 2.5 dimensional woven structures
ZHENG Jun, WEN Wei-dong, CUI Hai-tao, GAO Jian-hui
2008, 23(11): 2031-2035.
Abstract PDF(430KB) icon1689 icon433
Abstract:
Based on the hypothesis of rectangle and biconvex section shape of the yarn,and different collocation between the inner warp and outer warp,thickness,section shape of the same structure being considered especially,a model for predicting the elastic property of 2.5-D woven composites was developed.To verify the elastic model,62 samples of 2.5-D woven composites with 6 various structures were selected and the elastic properties were measured.Experiment results are in good agreement with the outcomes of the model.Further,it is shown that the difference between the inner warp and outer warp can't be ignored in predicting the elastic property of 2.5-D woven composites.
Investigation on the mechanism of wave and flame in the deflagration to detonation transition process
HE Xiao-min, ZHANG Peng-gang
2008, 23(11): 2036-2042.
Abstract PDF(1046KB) icon2008 icon451
Abstract:
A series of single-shot detonation experiments was performed to characterize the deflagration to detonation transition(DDT) process for H2/Air mixtures in a 60 mm square tube that was 2 m in length.High-speed digital imaging was used to track flame propagation beginning from the ignition,and simultaneous seven high-speed pressure transducers,mounted along the tube wall between 850～1200 mm,were used to record progress of the compression and shock wave.According to high-speed images,it is found that DDT process has five phase:① Normal combustion is initiated by an electric spark and its velocity is only 0～15 m/s;② Flame acceleration and deflagration formation which propagates with 500～1000 m/s;③Hot spots appear along the tube wall;④ formation of explosion center which creates blast wave;⑤ formation of strong detonation wave which propagates with 1800～2000 m/s.In the zone from 850 to 1 200 mm,which pressure transducers were mounted,the maximum pressure value firstly rises from 1.5 MPa to 7 MPa,then down to 2～3 MPa,and the detonation wave velocity is about 2000～2100 m/s,which is suit with the result achieved from the high-speed digital imaging.
Evaporation characteristics of a single dodecane droplet heated by coupled thermal radiation and convection
SUN Feng-xian, WANG Yin-yan
2008, 23(11): 2043-2048.
Abstract PDF(2333KB) icon2171 icon474
Abstract:
For a single dodecane droplet in the thermal environment of combined convection and radiation,the evaporation characteristics were investigated numerically.The internal absorption model of thermal radiation and the surface absorption one was separately combined with the limited conductivity model of droplet.The transient dependence of thermal properties on temperature and components was taken into account along with the transient relative velocity of gas flow to the droplet.The evolvements of droplet radius,temperature and evaporating rate under various convective conditions and various temperatures of thermal radiation were presented.The differences between the predicted results by the two thermal radiation models were compared,and the effect of thermal radiation on droplet evaporation was analyzed.The results show that,the predicted values of droplet lifetime by the two thermal radiation models are relatively less different.But the internal absorption model can reveal the characteristics of energy supply to droplet surface.The effect of thermal radiation on the droplet evaporation is small when the temperature of thermal radiation equals to that of the gas flow,but it becomes very significant at a temperature higher than that of gas flow.
Experimental study on DDT using soot records
ZHANG Peng-gang, HE Xiao-min, ZHANG Jing-zhou
2008, 23(11): 2049-2054.
Abstract PDF(1381KB) icon1725 icon459
Abstract:
In order to understand the process of shock movement,soot records were obtained by arranging a window of 60 mm×1 380 mm laterally onto a square donation tube.A series of single detonation experiments were conducted to study the performance of C2H2/air and H2/air mixtures in square detonation tube.The pressure transducers and ion-probes were utilized to measure the pressure and velocity in the tube,respectively.The results indicate that : ① Soot records is one of direct and effective means;② Overdriven detonation appears only once and several blasts appear in DDT(Deflagration to detonation transition);③ The dimension of acetylene is less than that of hydrogen under the same initial condition.
Validation of an uncoupled solver of non-equilibrium flow for shock-induced combustion
SUN Ming-bo, LIANG Jian-han, WANG Zhen-guo
2008, 23(11): 2055-2061.
Abstract PDF(757KB) icon1663 icon506
Abstract:
An improved uncoupled solver of non-equilibrium flow was introduced and developed in this study.The splitting of convective species flux was uncoupled from the N-S equations and based on the splitting result of the convective density flux.Inviscid flux was calculated with fifth-order weighted essentially non-oscillatory scheme.Simplified implicit formulation was adopted to deal with the stiffness generated by the chemical reacting source term of every separate species equation.Shock-induced combustion phenomena of a blunt body in stoichiometric H2/O2 and H2/Air mixture were calculated to validate the solver.The steady and unsteady shock-induced combustion flowfields agree favorably well with the experimental observation.Oscillating frequencies of unsteady case agree well with the experimental data.The results indicate that the method is sufficiently efficient in the application to multi-species and multi-reaction flow.
Effect of structure of gas generator on combustion performance
LI Qing, LI Qing-lian, WANG Zhen-guo
2008, 23(11): 2062-2067.
Abstract PDF(819KB) icon1599 icon544
Abstract:
Hot tests were conducted and experimental data was analyzed in order to select an optimal structure for gas generator.The combustion performance was analyzed and the size of injectors,the characteristic chamber length and the geometric characteristic of combustor was examined.The results suggest that:In a certain extant enlarging the size of injectors does not affect the combustion efficiency,at the same time the ignition delay is shorten and the boundary of adjustment of mass flow rate is expanded;Increase of characteristic chamber length benefits combustion efficiency;Geometric characteristic of combustor also has a great impact on combustion efficiency.The flame segment of converge-diverge shape influences the combustion process,and then decreases the combustion efficiency.The combustor with converge-diverge shape is not recommended during the design of gas generator.
Experimental investigation on two-phase and multi-cycle sector-PDE
GONG Ji-shuang, FAN Yu-xin, WANG Jia-hua
2008, 23(11): 2068-2074.
Abstract PDF(1223KB) icon1654 icon471
Abstract:
A sector-PDE(pulse detonation engine) with an internal diameter of 90 mm and an external diameter of 200 mm was designed.Its length is 1 500 mm and its sector angle is 60°.Two types of air-valves(orifice type and vortices type,respectively) were used to get appropriate mixture of air and oil,and their performances on detonation were compared.The results indicated that the designed PDE could operate at a frequency up to 40 Hz.In addition,the text gives the results of different shock-wave reflectors' comparison: the inverted reflector has high performance on initiating detonation.
Numerical simulation of flow and heat transfer in turbine cooling system of a turbofan engine
LI Na, JI Hong-hu
2008, 23(11): 2075-2081.
Abstract PDF(2314KB) icon1752 icon495
Abstract:
The flow and heat transfer characteristics of a complex turbine cooling system were numerically simulated,which was a multi-cavity,multi-inlet and multi-outlet system installed in a typical small turbofan engine.The cooling system includes the cavity behind the high pressure turbine disc,the cavity in front of the low pressure turbine disc,supporting guide vane cavity,bearing cavity,and some connecting cooling air passages.In this study,the computational grids in both fluid domain and solid domain were established together,the heat transfer between the two domains was calculated conjointly.Based on the results,the influence of structural parameters and pneumatic parameters on the temperature distribution of the system,especially for the bearing cavity,was analysed,and then some measures were taken to lower down the temperature of beating cavity.This study shows the potential power of numerical simulation of fluid flow and heat transfer in complex flow system,helping to improve system design.
Investigation of film cooling effectiveness for double fan-shaped holes
LIAO Nai-bing, ZHU Hui-ren, LI Guang-chao, XU Du-chun
2008, 23(11): 2082-2087.
Abstract PDF(1018KB) icon1609 icon461
Abstract:
This paper presents detail measurements of film cooling effectiveness in a flat plan for a row double fan-shaped holes.The streamwise angle of hole was 45°and the diameter of hole was d.The pitch-to-diameter ratio(p/d) contained 2,3 and 4.The momentum flux ratios varied from 1 to 4 and the turbulence level contained 0.4% and 8%.The result indicated that the double fan-shaped holes made significant improvement of film cooling effectiveness compared with the round holes.The variety of the p/d had great effects on film cooling effectiveness.Increasing the momentum flux ratio lead to large improvement of film cooling effectiveness at the p/d=2,while the momentum flux ratio had small effects on it at the p/d=4.The enhancement of turbulence level lead to obvious decrease in film cooling effectiveness when p/d is large and the momentum ratio is high.
Versatile core engine technology for turboshaft(turboprop)/turbofan(turbojet) engines
YIN Ze-yong, ZENG Yuan-jiang, SHI Jian-cheng, LUO An-yang
2008, 23(11): 2088-2094.
Abstract PDF(771KB) icon1813 icon610
Abstract:
The development of aero-engine technology makes it necessary to study the versatile core engine technology.Versatile core engine technology not only increases the number of the common parts of the developed engines,reduces its research and development periods,but also improves the performances of all the types of the developed engines.Aero-engines of different kinds with a certain power/thrust class could be derived from the corresponding versatile core engine with a certain mass flow amount.The design of versatile core engine must make a compromise between strength and aero-dynamic performance,and its components must be able to work effectively and stably within a wide range of operation;moreover,the versatile core engine should allow some small changes in the follow-up development.This paper discusses the issues for the turbine stage numbers and the compressor form in the conceptual design of a medium-small scale versatile core engine.
Effects of rotating inlet distortion on aerodynamic stability and stall inception of axial-flow compressor
ZHANG Huan, HU Jun, TU Bao-feng, WANG Zhi-qiang, ZHAO Yong
2008, 23(11): 2095-2100.
Abstract PDF(906KB) icon2259 icon434
Abstract:
Effects of rotating inlet distortion on the aerodynamic stability of compressor were carried out in a 2-stage low speed compressor.The results show that the rotating screen in the upstream has great impact on the aerodynamic stability and total static pressure rise ratio of the compressor.When the rotating screen rotates at a different direction with the compressor,the pressure rise ratio and flow coefficient of stable boundary point vary little.If both have the same rotation direction,the speed of the rotating screen has big effect on both of the stability and the pressure rise ratio,especially between 40～60 percent of rotor speed.Through analysis of the variation of amplitude of characteristic frequency,it's concluded that the rotating stall induced by the low-total-pressure area produced by rotating screen will appear in the compressor.If the mass flow continues to decrease,the compressor will enter into natural rotating stall state.The experimental results of stall inception process reveal that the rotating inlet distortion can't affect the stall inception of the compressor.
Investigation of the role of aziridine bonding agents on the aging of the composite solid rocket propellant(CSRP)
Amged A Ali, ZHANG Jian-wei, CAI Guo-biao
2008, 23(11): 2101-2106.
Abstract PDF(536KB) icon1901 icon691
Abstract:
The role of bonding agents on the aging characteristics is one of the important research topics.Aging program of the prepared propellant samples was conducting as follows:Five samples,two free of bonding agents,and three containing an aziridine based bonding agents(MAPO,HX-752,MAT4),four samples based on different bonding and curing agents all were aged at 70 ℃.The prepared bonding agent "MAT4" gave remarkable improvements and resulted in highly stable mechanical properties comparing with HX-752 or MAPO.The selected bonding agents family inhibited the rate of decomposition of the propellants during the aging periods and supported the propellant matrix against decomposition at the elevated temperatures.
Three dimension numerical simulation on air inlet of solid ducted rocket
ZHANG Yong-zhi, LI Zhuo, LI Hai-long
2008, 23(11): 2107-2113.
Abstract PDF(1848KB) icon2045 icon454
Abstract:
Based on the N-S equation,standard k-ε turbulence model,the FLUENT was used to simulate the kind of air inlet of solid ducted rocket.The paper researched the front,the lip,the interior and the back of the air inlet at vary Mach number.The simulation of results indicated that with Mach number increased and the total pressure recovery coefficient decreased.The flow is complex in the interior of air inlet,pressure is relatively high at exit of air inlet but the outflow is basically fluent and uniformity.
Stationary numerical simulation of flow separation and side load in nozzle
LIU Ya-bing, WANG Chang-hui, XU Xiao-yong
2008, 23(11): 2114-2118.
Abstract PDF(1813KB) icon1865 icon469
Abstract:
A three-dimensional,viscous and steady numerical simulation about serpentine flow was conducted for a high-altitude nozzle of a liquid rocket engine on the ground.The results with different inlet pressure were obtained by utilizing FLUENT software.The transformation of shock pattern and the distribution of unsymmetrical separation and side load in the nozzle were primarily predicted by those results.The simulation provides a key basis for further study.
Investigation on two-phase pulse detonation rocket engine with solenoid valve
WANG Yu-qian, FAN Wei, YAN Chuan-jun, LI Qiang, LI Jian-ling
2008, 23(11): 2119-2123.
Abstract PDF(994KB) icon1680 icon455
Abstract:
In order to increase the operation frequency of a pulse detonation rocket engine(PDRE),a PDRE model with solenoid valve was designed whose diameter and length was 30 mm and 1 000 mm respectively.The model was operated with kerosene as fuel,compressed oxygen as oxidizer and nitrogen as purge gas.The PDRE model could steadily operate at the frequency of 20～30 Hz after taking such measures as selecting high-speed large flow solenoids,heating the fuel and assembling Shchelkin spiral.While the operation frequency is 30 Hz,the peak valuable of detonation wave pressure is 2.2 MPa.The time-averaged thrust of PDRE increases almost linearly with the operation frequency.
Integrated diagnosis of aeroengines' gas path faults using artificial neural network
QU Jian-ling, TANG Chang-sheng, XIAO Hui-xiong, LI Wan-quan
2008, 23(11): 2124-2127.
Abstract PDF(617KB) icon1997 icon450
Abstract:
In order to improve diagnosis accuracy,a new algorithm of integrated diagnosis of aeroengines' gas-path faults using artificial neural network was proposed.The integrated diagnosis system of neural network was established by integration of four subsystems.Pretreated fault data obtained from flight data was put respectively into the generalized regression neural network subsystem and the back-propagation neural network subsystem for fault diagnosis.Then,a new information fusion algorithm was studied to integrate the two outputs.Fault characteristic in the final output was more obvious so that diagnosis accuracy was improved.The test shows that,the new information fusion algorithm is well-effective and of a high practical value.
Robust PI speed control of two-stroke engine via LMI approach
PAN Song, WEI Min-xiang
2008, 23(11): 2128-2132.
Abstract PDF(1719KB) icon1583 icon397
Abstract:
A nonlinear two-stroke engine model was constructed using a mathematical tool of stepwise regression.Taylor expansion method was used around an equilibrium point during the linearizing process,and the linearized model was reached.A method for designing robust proportional-integral(PI) controller was presented.The problem of parameter designing of the robust PI controller was solved with linear matrix inequalities(LMIs) approach.The controller switching was designed based on the idea of parallel distributed compensation(PDC) to Takagi-Sugeno fuzzy model.Simulation and experiments on the engine-dynamometer show that the proposed controller can keep the engine speed in 2.3% under 11% disturbance and can achieve the anticipated robust performance.
Condition monitoring for aero-engine based on chaos exponents of dynamic system
LI Tian-liang, HE Li-ming, CHENG Bang-qin, ZOU Shi-jun
2008, 23(11): 2133-2136.
Abstract PDF(431KB) icon1551 icon456
Abstract:
The instability condition of aeroengine was studied in light of chaos and fractal theories,the chaotic character exponents of aeroengine in the process of entering instability condition were calculated.First,the pressure signal was denoised with wavelet method,and then the phase space of the engine was reconstructed.The method to calculate correlation integral was improved,then,the Lyapunov exponents and correlation dimension were calculated with the method of sliding window.The results show that the chaos exponents changed markedly as the condition of aero-engine varies,as a consequence,the chaos exponents can be used to identify the aero-engine condition and as a new method to study the dynamic characteristics.
Study on fuel metering for the micro turbine engine
MEI Kun-nian, ZHANG Tian-hong
2008, 23(11): 2137-2141.
Abstract PDF(638KB) icon1673 icon440
Abstract:
This paper analyzed how to improve the fuel metering accuracy for the micro turbine engine(MTE).According to the working mechanism of the dynamoelectric gear pump,the fuel flow delivered by the pump is dependent on the amplitude of the supply voltage,the duty cycle of the supply voltage and the output pressure of the pump.When the demanded quantity of the fuel flow is given,the duty cycle of the supply voltage can be calculated from the amplitude of the supply voltage and the output pressure,which is validated by a series of calibration experiments.Comparing with the formal metering method,without consideration of the output pressure,this novel method can improve the metering accuracy distinctly,and will be helpful for the MTE starting process controlling.
Modification and loaded contact analysis of spur face gears
ZHAO Ning, GUO Hui, FANG Zong-de, WEI Bing-yang
2008, 23(11): 2142-2146.
Abstract PDF(1812KB) icon1810 icon555
Abstract:
A profile modification method for the spur face gears was proposed.The parabolic transmission error was obtained by profile modification for the rack cutters of the pinion and the shaper.The computational models for tooth contact analysis(TCA) and loaded tooth contact analysis(LTCA) of the face gears were established.The research results indicate that the new design can effectively avoid the edge contact,increase effective contact ratio and reduce the loaded transmission error with more uniform load distribution,thereby improving the transmission's stability.
Design of geometry transmission errors of helical face-gear drive
SHEN Yun-bo, FANG Zong-de, ZHAO Ning, GUO Hui
2008, 23(11): 2147-2152.
Abstract PDF(1143KB) icon1761 icon475
Abstract:
The geometry transmission errors of modified helical face-gear drive was investigated in the paper.A new version of face-gear drive geometry was proposed as envelopes of two parabolic racks of the pinion and shaper in the profile to improve the continuity and stability.The results show the transmission errors of helical face-gear drive with only modified helical pinion is an asymmetric one,and symmetric function parabolic transmission errors,no matter alignment or misalignment,were caused by the new geometry with tooth surfaces modified,while the factors of parabolic a1,as and parameter u0 of parabola apex were designed.

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