2004 Vol. 19, No. 6

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Integral Estimate Method for Incomplete Data
FU Hui-min, WANG Hua-sheng
2004, 19(6): 741-744.
Abstract PDF(687KB) icon1463 icon443
Abstract:
A new method of integral estimate for incomplete data is presented in this paper.The integral parameter estimators and their covariance are derived.The integral estimate method for the location-scale distributions are discussed at some length.The method extends traditional regression analysis that is only suitable for complete data to incomplete data.Thus it is applicable even when there is only one failure data while the traditional method requires more failure data in a state.As the crosswise information among the incomplete data in different states is exploited and applied,the number of specimens for determining the distribution parameters in all states by the method is about the same as that of the specimens in one state by the traditional method when the precision is equal,which shows the method has the advantage of small sample.
Reliability Assessment and Life Prediction for Satellite Engine
WANG Ping-hui, FAN Ben-yao, FU Hui-min
2004, 19(6): 745-748.
Abstract PDF(658KB) icon1845 icon517
Abstract:
The method of reliability assessment and life prediction for zero-failure data of satellite engines is presented in the paper.Thus the one-sided lower confidence limits of reliability and life for zero-failure data can be calculated by the method.The reliability assessment and life prediction of the two-parameter Weibull and log-normal distributions are discussed at some length.The method for strong test and weak test of satellite engines are established,which can inspect and control the quality of satellite engines with a high precision.The method has been used in the reliability assessment and life prediction of some satellite engines successfully.
Influence of Micro-Structural Geometry on Composite Initial Yielding Surfaces
SONG Ying-dong, SUN Zhi-gang, LEI You-feng, GAO De-ping
2004, 19(6): 749-754.
Abstract PDF(334KB) icon1814 icon574
Abstract:
The unified macro and micro mechanics constitutive model was used to investigate the influence of micro-structural geometry,such as fiber shape and fiber packing array,on the composite initial yielding surfaces under multi-axial loading.Under longitudinal stress,composites reinforced by fibers with square cross section have the same yielding stress as the ones reinforced by fibers with cyclic cross section.Fiber packing array has no effect on the yielding stress.In the presence of transverse or shear stresses, the composite initial yielding surface with square cross section fibers is inside of the one of composite with square cross section fibers.Composite with hexagon fiber array has the lowest yielding stress;however,composite with square-diagonal fiber array has the highest.
Study of Elastic-Plastic Constitutive Model for Single Crystal Nickel-Based Superalloy
DING Zhi-ping, LIU Yi-lun, YIN Ze-yong, YAN Zhi-guo, CHENG Xiao-ming
2004, 19(6): 755-761.
Abstract PDF(489KB) icon2052 icon463
Abstract:
The correlation of crystal orientation to yield characteristic of FCC single crystal is not good when Hill's (1948) yield criterion is used to describe the elastic-plastic deformation of FCC single crystal.Taking into account the effects that the components of tension stress are coupled with components of torsion stress when off-axis loads are applied to orthotropic material,Hill's yield criterion for plastically orthotropic solids is modified by adding an invariant which is composed of quadratic product item of components of deviatoric stress tensor,as a results,a new yield criterion for single crystal Nickel-based superalloy is put forward in the present paper in terms of the characteristics of single crystal Nickel-based superalloy.Using the new criterion to predict the yield stresses of single crystal Nickel-based superalloy DD3,the correlation to experiments is very good and more accurate than that of Hill's at 760℃.Equivalent stress adapted to the new criterion is defined.Thinking of the yield function as a plastic potential function from the associated flow rule and with reference to the isotropic hardening model,the elastic-plastic constitutive model for single crystal Nickel-based superalloy is constructed and the corresponding elastic-plastic matrix is educed.New yield criterion and its equivalent stress will be reduced to Von Mises yield criterion and corresponding equivalent stress for isotropic material.
Crystalline Thermo Visco-Plastic Deformation and Damage of Directionally Solidified Turbine Blade
ZHANG Ke-shi, YANG Shi-jie, ZHOU Bai-zhuo
2004, 19(6): 762-770.
Abstract PDF(1120KB) icon1948 icon418
Abstract:
A single crystalline thermo visco-plastic constitutive model associated with an iterative algorithm was introduced.They can be used to describe the stress-strain relationship of a single crystal in an anisothermal process,and also to describe the crystalline creep and damage of a single crystal under slipping mechanism.This model and algorithm were applied to the analyses of anisothermal visco-plastic creep and damage of an air-cooled directional solidification turbine blade taking into consideration of the column crystalline grain structure.The analysis show that under the condition considered in the present paper,the air cooled directional solidification turbine blade is under going a relatively low stress,and the induced blade tip creep elongation is not more than 0.06 mm in 500 working hours.
An Investigation of J Integral Evaluation Method for Cylindrical Bars with Circumferential Crack
YU Hui-chen, XIE Shi-shu, HE Feng-wei, ZHANG Yan-ji
2004, 19(6): 771-775.
Abstract PDF(378KB) icon1349 icon518
Abstract:
Finite element method was used to analyze the J integral evaluation method for a cylindrical specimen with deep circumferential crack under axial or torsional load.First,the relationship between axial or torsional load and axial or angular displacement of cylindrical specimens with different circumferential crack depth was determined.Then,two methods were used to calculate the J integral.One is the simple method that calculates the J integral by a single specimen's load-displacement relationship;the other is the energy method.The J integral obtained by the simple method agrees well with that determined by the energy method using multiple medium carbon steel specimens with a circumferential crack,as far as the crack depth is deep enough or the axial or angular displacement is small.
Structure Optimization Based on Global Control Fuzzy Genetic Algorithms
GUO Hai-ding, LI Xiang-ping
2004, 19(6): 776-781.
Abstract PDF(892KB) icon1929 icon630
Abstract:
A global control Fuzzy Genetic Algorithm (FGA)was applied to the structure optimization.The method given here differs from the standard GA methods (SGA) in taking the whole process of Genetic Algorithm selection,crossover,mutation and the change of searching space into global fuzzy control.The quality of FGA method is verified using two typical mathematical multi-peak functions.The results of simulation show that this kind of fuzzy genetic algorithms can efficiently avoid being entrapped into local optimum and obtain a higher efficiency of optimizing process.A rivet structure,which contains integer and discrete variables,was optimized with FGA method.It shows that a better connecting efficiency with less converging steps can be obtained.
Analysis of Active Vibration Isolation System Based on Magnetostrictive Actuator
ZHANG Lei, LIU Yong-guang, FU Yong-ling, HE Lin
2004, 19(6): 782-785.
Abstract PDF(685KB) icon1878 icon515
Abstract:
Based on the constitutive equation of magnetictive material,the model of the whole Active Vibration Isolation System (AVIS) was put forward and its dynamics and stability of the control system was analyzed.Simulation results show that the parameters of the upper mass have much more influence on the active force of the actuator,and stiffness of the lower mass effects isolation performance while the absolute acceleration of the middle mass is adopted as feedback.For the feedforward control scheme,system stability would not be influenced by the frequency variation,though the feedback link can reduce its stability margin.In the feedback control scheme,the time delay effect of the secondary path may cause the system unstable when the vibration frequency increases.
An Aerodynamic Performance Study of Different Swept-Curved Compressor Cascades under Different Operating Conditions
ZHAO Gui-jie, CHEN Fu, SONG Yan-ping, BIAN Zhao-xi, WANG Zhong-qi
2004, 19(6): 786-791.
Abstract PDF(891KB) icon1659 icon453
Abstract:
Investigations in recent years showed that three-dimensional blade design using end bend,sweep and dihedral could reduce endwall loss,improve efficiency and stable operating range.STR (straight),SWF (forward swept),SCB (incorporating forward swept and positive curved) and SWB (backward swept) rectangular compressor cascades have been studied at design and off-design incidences to verify if SCB can achieve better aerodynamic performance.All types of swept or curved blades considered are symmetric to midspan,consisting of an circular arc section in the central part and swept or curved sections toward the endwalls.The effect of incidence change on the distribution of exit total pressure loss and secondary flow vectors of the compressor cascades has been experimentally investigated.Ink-trace flow visualization on blade surfaces was also conducted in a part of incidences.Compared with straight cascade,mechanisms of the total pressure loss increase and decrease with the change of incidence of various swept cascades at different spanwise positions were analyzed.The results show that compared to swept-forward cascades, the swept-curved cascade further prevents the low energy fluid accumulation, which may induce separation in the endwall/suction surface corner region;therefore,remarkably reduce total pressure loss in that region.Even at larger positive incidence the total loss of the swept-curved cascade increases smoothly and no flow separation was observed in the corner.In general,the total pressure loss of swept-curved cascade is not sensitive to incidence change.The study supports the conclusion that SWF and SCB conduce to the improvement of stall margin near the endwall even at higher incidence.Moreover,it is supposed that better aerodynamic performance of SCB can be achieved by increasing design incidence at midspan and by optimizing the matching of swept blade angle and height,and curved blade angle and height.
CFD Analysis of Aerodynamic Characteristics for the Ducted Tail Rotor and Its Aerofoil
CAO Yi-hua, CHEN Ke, WANG Jian, YIN Wan-li
2004, 19(6): 792-797.
Abstract PDF(754KB) icon1756 icon465
Abstract:
Calculation of lift-drag characteristics of OAF and NACA63a312 airfoil at low speed using Jameson/TVD mixed scheme was carried out.The feature of the method is that finite volume approach was used for numerical approximation and Runge-Kutta time-stepping advance was used to solve the Euler/Navier-Stokes equations.Comparing the numerical results with the published NASA's experimental results, it proves that the method developed here is suitable for the calculation of the rotor aerodynamics.Furthermore,a model based on circular tiny momentum theory and blade element theory is established for the study of thrust and power of the rotor under different conditions.The results of computation validate the feasibility of this model.
The Duct Fan Design and Test for WIG Craft
TU Qiu-ye, WANG Xiao-feng, SHEN Hong-cui, YUAN Chang-hua, YE Xiu-nai
2004, 19(6): 798-801.
Abstract PDF(651KB) icon2328 icon495
Abstract:
Ducted fan is recommended as a small WIG (wing in ground-effect) craft propulsion system instead of a propeller,because it not only provides enough startup thrust but also keeps the water from disturbing the propeller tips.The vortex distribution model of the ducted fan was established,and the numerical results were used to substitute the Prandtl Loss.Through the extension of Betz conditions to the ducted fan, a complete method of ducted fan design was established.The performance of a ducted fan model tested in the wind tunnel shows a satisfactory result.
Simulation and Experiment Validation of a Two Dimensional Asymmetric Ramp Nozzle
LI Nian, ZHANG Kun-yuan, XU Jing-lei
2004, 19(6): 802-805.
Abstract PDF(542KB) icon2072 icon593
Abstract:
The CFD software FLUENT was used to simulate the flow in the 2D asymmetric ramp-nozzle.The effect of four widely used turbulent models and three kinds of grid density on the numerical results were discussed.All the numerical results are compared with the experimental data published by NASA and agree with each other very well.It shows that FLUENT software with medium grid density and RNG k-ε model can quickly yield accurate result,so it is very suitable for the internal and external flow simulation of a 2D asymmetric ramp nozzle with hypersonic free stream.
The Numerical Study of the Cowl Effect on the Sidewall Compression Hypersonic Inlet and Isolator
XU Jing-lei, ZHANG Kun-yuan
2004, 19(6): 806-810.
Abstract PDF(746KB) icon1695 icon527
Abstract:
The N-S equation and RNG k-ε turbulence model are adopted to analyze the internal flow field of the side wall compression hypersonic inlet and its isolator for RBCC engine.The main point is focused on the effect of cowl position on the flow field and the related phenomena with a free stream Ma=6.The results show that if the cowl position relative to the throat section is moved forward,it has greater effect on the degrees of flow homogeneity at the outlet section than the cowl aft-positioned case.The effects on the total compression ratio,the intense of the cowl shock, the captured mass flow rate and the total pressure recovery are also greater.
Numerical Investigation of the Optimal Endwall Fence Location with the Variation of Incidences
LIU Yan-ming, ZHONG Jing-jun, WANG Song-tao, FENG Guo-tai
2004, 19(6): 811-815.
Abstract PDF(406KB) icon1701 icon448
Abstract:
Numerical simulation has been carried out to investigate the variation of the optimal end-wall fence location with different incidences of compressor cascade.The results show that the optimal location is at 40% pitch away from the pressure side of the blade at positive incidences.At negative incidences, it has the trend to move near to the pressure side.
Numerical Investigation of the Secondary Flow Control in a Compressor Cascade Using Endwall Fences
ZHONG Jing-jun, LIU Yan-ming, FENG Guo-tai
2004, 19(6): 816-821.
Abstract PDF(1031KB) icon1909 icon569
Abstract:
The numerical simulation has been carried out to investigate the effect of endwall fence on the secondary flow in a compressor cascade.The results show that the boundary layer fences can reduce the strong cross-flow from the pressure surface to the suction surface near the cascade endwall.A counter-rotating streamwise vortex is formed over the fence and the strength of the passage vortex is diminished.It is found that the fences are most effective when they are located 30 percent pitchwise from the pressure surface of the blade.For the optimum endwall fence location,the cascade loss can be reduced 7～9 percent compared with the conventional cascade.
The Effects of Reynolds Number on the Characteristics of the Low Pressure Turbine
LI Wei, ZHOU Zheng-ping, ZHAO Xiao-lu
2004, 19(6): 822-827.
Abstract PDF(724KB) icon1912 icon621
Abstract:
The effect of Reynolds number on the characteristics of the Low Pressure Turbine (LPT) was investigated and the variations of flow structures with Reynolds number were analyzed by numerical simulation.The results show that the efficiency of LPT is decreased with the reduction of Reynolds number,and the relationship between the efficiency and Reynolds number change is non-linear.Obvious changes of blade surface velocity distribution at different Reynolds number can be found,which induce the increases of profile loss and secondary flow loss.The results also show that the design of blade surface velocity distribution has significant influence on turbine characteristics change with Reynolds number.It is very important to the aerodynamic design of LPT which is intended to operate at low Reynolds number conditions.
Numerical Simulation of the Influence of Endwall Fence Height on the Secondary Flow in Compressor Cascade
LIU Yan-ming, ZHONG Jing-jun, HUANG Hong-yan, WANG Song-tao
2004, 19(6): 828-833.
Abstract PDF(723KB) icon1779 icon506
Abstract:
The numerical simulation has been carried out to investigate the effect of the endwall fence height on the secondary flow in compressor cascade.The results show that there is a counter-rotating streamwise vortex formed over the fence.With the increase of fence height,losses around the fence increase and the strength of crossflow decreases.The optimal fence height is 1/3 of the inlet boundary layer thickness, which can reduce the total energy loss by 9%.The computation and test results agree well.
Development of a Surge Preventive Control System Applied to the Kunlun Aeroengine
XING Jia-rui, ZHANG Shao-ji, JIANG Cai-hong, MA Ya-quan
2004, 19(6): 834-837.
Abstract PDF(330KB) icon1799 icon464
Abstract:
This paper presents the development of KUNLUN engine surge preventive control system.It describes the design method and the validity check criteria,which is used to evaluate the effectiveness of this system.The digital dual-redundancy controller satisfies the weapon launching requirement of a fighter with multi-kind missiles and cannon.Its anti-surge performance has been demonstrated successfully in the evaluation flight test throughout its flight envelope.
Aeroengine LQR Control Based on Fuzzy-Neural Networks
LIU Jian-xun, LI Ying-hong, CHEN Yong-gang, WANG Cheng
2004, 19(6): 838-843.
Abstract PDF(985KB) icon2053 icon459
Abstract:
To solve the problem of Linear Quadratic Regulator (LQR) in aeroengine multivariable control,a modified LQR method based on a kind of fuzzy-neural networks was presented.First,we chose some representative operation points in the engine flight envelope,and designed the LQR controller for each operating point separately.Then,Adaptive-Network-based Fuzzy Inference System (ANFIS) was utilized to synthesize each linear controller to make a nonlinear controller.The inputs of ANFIS are flight altitude and Mach number,and the output is a feedback matrix,which represents the design results.The design of other operation points in the engine flight envelope can be conveniently deduced by the inference system.The ANFIS was trained offline,so we concluded that the method could compensate the short comings of the LQR control.Simulation results were given for a specific turbofan.The design process was analyzed,and the results prove the validity of the method.
Applications of Support Vector Machines to Aeroengine Fault Diagnosis
WEI Xun-kai, LU Cheng, WANG Cheng, LU Jian-ming, LI Ying-hong
2004, 19(6): 844-848.
Abstract PDF(833KB) icon2570 icon549
Abstract:
An aeroengine fault diagnosis method based on support vector machines is presented.After extracting fault symptoms via proper equipments or methods,support vector machines were adopted to set up correlation between fault symptoms and fault patterns and to realize the classification of faults. Support vector machines are specially designed for good generalization ability under the condition that only small samples set is available.Applying this method to a certain engine,the diagnostic results are satisfactory,and it is referable to develop diagnostic system for newly-developed engines.
Experimental Study of Reverse Flow Combustion in A Turbulent Flow Field Using PIV
GE Bing, ZANG Shu-sheng, ZHOU Jian-guang, WENG Shi-lie
2004, 19(6): 849-854.
Abstract PDF(420KB) icon1531 icon452
Abstract:
Experiments have been performed to investigate the differences between the propane/air turbulent diffusion reactive flow past blunt-body and the cold airflow under the same condition.By (Particle Image Velocimetry) PIV technique,the reactive flow fields and the cold flow fields were measured for 4 different operating modes.The velocity fields have been acquired successfully.The results show that although in general the velocity distributions of reactive flow are similar to that of cold flow,compared to the cold flow,it was found that the center of the reverse-flow zone is higher;the dimension of the reverse-flow zone is bigger;the maximum reverse flow velocity decreases and the flow fields become more turbulent.It is suggested that it is unacceptable to use cold flow experiment to simulate the reactive flow field when turbulent diffusion flame is researched in-depth.
Numerical Simulation of Unsteady Hot Streak Migration in a 1-1/2 Stage Turbine
LIU Gao-wen, LIU Song-ling
2004, 19(6): 855-859.
Abstract PDF(795KB) icon2050 icon551
Abstract:
Two-dimensional unsteady Navier-Stokes simulations were applied to the cascades of the typical first-stage turbine blade and second-stage guide vane to study the effects of combustor hot streaks on the flow and temperature fields.The predicted results show that the existence of hot streak has small impacts on the time-averaged static pressure around the turbine blade airfoils,but will increase the unsteadiness of static pressure around the first-stage rotor blades and second-stage guide vanes.The simulations verify the facts of the blade pressure surface overheating induced by the hot streaks, and there is similarly effect on the increase of the guide vane pressure surface temperature.
Numerical Investigation on Mechanism of Heat Transfer Augmentation in Lamilloy
QUAN Dong-liang, LIU Song-ling, LI Jiang-hai
2004, 19(6): 860-865.
Abstract PDF(897KB) icon1845 icon461
Abstract:
A simplified heat transfer model was used to analyze Lamilloy cooling characteristics.The results show that the parameter f,adiabatic effectiveness of film cooling at gas side and the internal heat transfer efficiency are important parameters in the design optimization.In order to learn how the internal flow patterns affect the overall cooling effectiveness of Lamilloy,conjugate numerical simulation were carried out for a double wall without pin fin and five Lamilloy cooling configurations with the same hole diameter,spacing and pin fin height.The numerical results show that Lamilloy have higher cooling effectiveness than the double wall.The coolant through the walls took off most of the heat, transferred from hot gas to the Lamilloy,and the heat transfer on internal surface of outlet plate was the major mechanism to remove the heat.The existence of pin fin increases heat transfer area and the amount of heat transfer in Lamilloy, and the uniformity of temperature in Lamilloy can be improved by proper design of pin fin.
Numerical Simulation of Liquid Injector Dynamics
YANG Li-jun, ZHANG Xiang-yang, GAO Fang, ZHANG Zhen-peng
2004, 19(6): 866-872.
Abstract PDF(916KB) icon1777 icon449
Abstract:
In order to study the dynamic characteristics of liquid rocket engine injectors,theoretical analysis has been carried out for the plane orifice and centrifugal injectors."Frequency Method" was used for the numerical simulation of the injector dynamics.The results show that with the increase of pulse frequency,the flux swing of the plane orifice and centrifugal injectors decreases and the phase shift increases.With the increase of pressure,the flux swing increases and the phase shift decreases.Under the same condition,with the increase of the plane orifice injector's length or the geometric characteristics of centrifugal injectors,the swing decreases and the phase shift increases.With the increase of the spout length of centrifugal injectors,the phase shift increases while the swing is not affected remarkably.These results agree well with foreign investigations and establish the basis for further study.
Radiation inside a Low Power Argon Arcjet Thruster
XIAO Ying-chao, LIU Yu, ZHANG Guo-zhou
2004, 19(6): 873-878.
Abstract PDF(417KB) icon2080 icon482
Abstract:
To investigate radiation loss inside the low power argon Arcjet Thruster,numerical simulations and analyses were carried out by using radiation and no radiation models contrastively.Non-oscillatory and Non-free-parameters Dissipative finite difference scheme with second order accuracy was employed to solve Navier-Stokes equations coupled with electromagnetic and radiant source terms,and implicit residual-smoothing technique was adopted to accelerate numerical converging.Finite control volume integral approach was developed to discrete elliptic partial differential equation of electromagnetic field,and successive over relaxation method was introduced to expedite numerical converging.By virtue of numerical simulations,flow distributions within the thruster, thrust, specific impulse and thrust efficiency of the thruster in radiation and no radiation models are presented.Results of the study show that 0.137% lower specific impulse and 1.03% lower thrust efficiency are obtained in radiation model,compared with no radiation model,and radiation loss has little effect on performance of low power Arcjet Thrusters.

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