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Experimental Study of Effects of Tip Geometry on the Flow Field in a Turbine Cascade Passage

Journal of Thermal Science 2015年第1期24卷 1-9页

作者： MA Hongwei WANG Lixiang National Key Laboratory of Science and Technology on Aero-Engines Collaborative Innovation Center of Advanced Aero-Engine School of Energy & Power Engineering Beihang University

This study investigates the effects of blade tip geometry on the flow field of a turbine cascade at the incidence angle of 0 degree experimentally. The tests were performed in a low-speed turbine cascade wind tunnel. The Reynolds number based on the blade chord was about 172300 at the exit. Traverses of the exit flow field were made in order to measure the overall performance. The effects of using fiat tip and grooved tip with a chord-wise channel were studied. The case with the flat tip is referenced as the baseline. The tip clearances are all 1 mm measuring 0.84 percent of the blade span. The depth of channel is *** flow field at 10% chord downstream from the cascade trailing edge was measured at 38 span-wise positions and 26 pitch-wise positions using a mini five-hole pressure probe. The static pressure distribution on the tip end wall is measured at 16 pitch-wise stations and 17 chord-wise stations. Results show that there exists great pressure gradient in the pressure side for the fiat tip and the pressure side squealer tip, which means strong leakage flow. The pressure gradient from the pressure side to the suction side is greatly decreased for the grooved tip, and the resulting leakage flow is weaker. The core of the leakage vortex moves closer to the suction side for the pressure side squealer tip and farther away from the suction side for the suction side squealer tip. The pressure side squealer has little advantages over the fiat tip in improving the flow capacity and reducing the overall losses. The suction side squealer tip and grooved tip can effectively decrease the intensity of the tip leakage vortex, improve the flow capacity and reduce loss of the turbine cascade passage and the grooved tip performs the best.

关键词： blade tip geometry turbine cascade flow field effect

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A direct-variance-analysis method for generalized stochastic eigenvalue problem based on matrix perturbation theory

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Science China(Technological Sciences) 2014年第6期57卷 1238-1248页

作者： QIU ZhiPing QIU HeChen Institute of Solid Mechanics Beihang University

It has been extensively recognized that the engineering structures are becoming increasingly precise and complex,which makes the requirements of design and analysis more and more *** the uncertainty effects are indispensable during the process of product ***,iterative calculations,which are usually unaffordable in calculative efforts,are unavoidable if we want to achieve the best *** uncertainty effects into consideration,matrix perturbation methodpermits quick sensitivity analysis and structural dynamic re-analysis,it can also overcome the difficulties in computational *** to the situations above,matrix perturbation method has been investigated by researchers worldwide ***,in the existing matrix perturbation methods,correlation coefficient matrix of random structural parameters,which is barely achievable in engineering practice,has to be given or to be assumed during the computational *** has become the bottleneck of application for matrix perturbation *** this paper,we aim to develop an executable approach,which contributes to the application of matrix perturbation *** the present research,the first-order perturbation of structural vibration eigenvalues and eigenvectors is derived on the basis of the matrix perturbation theory when structural parameters such as stiffness and mass have *** the first-order perturbation of structural vibration eigenvalues and eigenvectors with the probability theory,the variance of structural random eigenvalue is derived from the perturbation of stiffness matrix,the perturbation of mass matrix and the eigenvector of baseline-structure *** the Direct-VarianceAnalysis(DVA)method is developed to assess the variation range of the structural random eigenvalues without correlation coefficient matrix being *** feasibility of the DVA method is verified with two numerical examples(one is trusssystem and the other is wing struct

关键词： matrix perturbation theory generalized stochastic eigenvalue problem structure with random parameter direct variance analysis

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Response analysis based on smallest interval-set of parameters for structures with uncertainty

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Applied Mathematics and Mechanics(English Edition) 2012年第9期33卷 1153-1166页

作者：王晓军王磊邱志平 Institute of Solid Mechanics Beihang University

An integral analytic process from quantification to propagation based on limited uncertain parameters is investigated to deal with practical engineering problems. A new method by use of the smallest interval-set/hyper-rectangle containing all exper- imental data is proposed to quantify the parameter uncertainties. With the smallest parameter interval-set, the uncertainty sponse and the least favorable response propagation evaluation of the most favorable re- of the structures is studied based on the interval analysis. The relationship between the proposed interval analysis method （IAM） and the classical IAM is discussed. Two numerical examples are presented to demonstrate the feasibility and validity of the proposed method.

关键词： quantification analysis smallest interval-set/hyper-rectangle uncertain structural response most favorable response least favorable response

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Fatigue reliability based on residual strength model with hybrid uncertain parameters

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Acta Mechanica Sinica 2012年第1期28卷 112-117页

作者： Jun Wang Zhi-Ping Qiu Institute of Solid Mechanics Beihang University100191 BeijingChina

The aim of this paper is to evaluate the fatigue reliability with hybrid uncertain parameters based on a residual strength model. by solving the non-probabilistic setbased reliability problem and analyzing the reliability with randomness, the fatigue reliability with hybrid parameters can be obtained. The presented hybrid model can adequately consider all uncertainties affecting the fatigue reliability with hybrid uncertain parameters. A comparison among the presented hybrid model, non-probabilistic set-theoretic model and the conventional random model is made through two typical numerical examples. The results show that the presented hybrid model, which can ensure structural security, is effective and practical.

关键词： Fatigue reliability Residual strength Ran- dom model Non-probabilistic set-theoretic model Hybrid model

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Experimental Study of Effects of One Kind of Tangentially Non-uniform Tip Clearance on the Flow Field at an Exit of a Compressor Cascade Passage

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Journal of Thermal Science 2010年第1期19卷 7-13页

作者： Hongwei MA Jinghui ZHANG Jun ZHANG School of Jet Propulsion Beihang University Beijing 100191 China National Key Laboratory of Science and Technology on Aero-Engines Beijing 100191 China

This paper presents an experimental investigation of effects of one kind of tangentially non-uniform tip clearance on the flow field at an exit of a compressor cascade *** tests were performed in a low-speed large-scale cascade with the uniform tip clearance and the non-uniform *** three-dimensional flow field was measured at the exit at three incidence angles of 0°,5°,and 8° using a mini five-hole pressure *** measurement results show that the non-uniform tip clearance can moderate the leakage flow and blow down more low-energy fluids at the tip corner and decrease the accumulation of low-energy fluids which cause the flow blockage in the blade *** the meantime,the non-uniform clearance can weaken the tangential migration of the low-energy fluids in the endwall boundary layer and reduce the secondary loss and the flow blockage in the tip region.

关键词： compressor cascade clearance leakage flow secondary flow vortex

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A direct probabilistic approach to solve state equations for nonlinear systems under random excitation

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Acta Mechanica Sinica 2016年第5期32卷 941-958页

作者： Zheng Lv Zhiping Qiu Institute of Solid Mechanics Beihang University

In this paper, a direct probabilistic approach（DPA） is presented to formulate and solve moment equations for nonlinear systems excited by environmental loads that can be either a stationary or nonstationary random *** proposed method has the advantage of obtaining the response＇s moments directly from the initial conditions and statistical characteristics of the corresponding external excitations. First, the response＇s moment equations are directly derived based on a DPA, which is completely independent of the It？/filtering approach since no specific assumptions regarding the correlation structure of excitation are *** solving them under Gaussian closure, the response＇s moments can be obtained. Subsequently, a multiscale algorithm for the numerical solution of moment equations is exploited to improve computational efficiency and avoid much wall-clock time. Finally, a comparison of the results with Monte Carlo（MC） simulation gives good ***, the advantage of the multiscale algorithm in terms of efficiency is also demonstrated by an engineering example.

关键词： Direct probabilistic approach Nonlinear dynamic system Nonstationary random process Response’s moments Multiscale algorithm

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Effects of Probe Support on the Stall Characteristics of a Low-Speed Axial Compressor

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Journal of Thermal Science 2016年第1期25卷 43-49页

作者： Hongwei Ma Shaohui Li Wei Wei National Key Laboratory of Science and Technology on aero-Engines Collaborative Innovation Center of Advanced Aero-EngineSchool of Energy&Power EngineeringBeihang UniversityBeijing100191 China beijing Institute of Space Launch Technology Nanyuan Rd.Fengtai Dist.Beijing100076China China Academy of Aerospace Aerodynamics(CAAA) Yungangxi Rd.Fengtai Dist.Beijing100074China

In order to investigate the effects of probe support on the stall characteristics of micro compressors, an experiment was carried out on a large-scale low-speed research compressor according to the principle of geometric similarity. A cylindrical probe support intruding to 50% blade span was mounted at 50% chord upstream from the rotor blade leading edge. The static pressure rise characteristic of the compressor is measured, with and without the probe support respectively. The dynamic compressor behavior from pre-stall to full stall was also measured. The results indicate that the stability margin of the compressor is lowered after installing the probe support. The stall inception is aroused by modal wave disturbances. The disturbances developed into two stall cells smoothly before installing the probe support, while the disturbances first developed into a single stall cell then splitting into two stall cells after installing the probe support. The presence of probe support lowers the initial intensity of the rotating stall of the compressor, while it doesn't alter the intensity of the rotation stall after the compressor enters into full stall.

关键词： Probe support Compressor Stability Margin Stall inception Intensity/frequency of rotating stall

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A collocation interval analysis method for interval structural parameters and stochastic excitation

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Science China(Physics,Mechanics & Astronomy) 2012年第1期55卷 66-77页

作者： QI WuChao QIU ZhiPing Institute of Solid Mechanics Beijing University of Aeronautics and Astronautics Beijing 100191 China

Uncertainty propagation, one of the structural engineering problems, is receiving increasing attention owing to the fact that most significant loads are random in nature and structural parameters are typically subject to variation. In the study, the collocation interval analysis method based on the first class Chebyshev polynomial approximation is presented to investigate the least favorable responses and the most favorable responses of interval-parameter structures under random excitations. Compared with the interval analysis method based on the first order Taylor expansion, in which only information including the function value and derivative at midpoint is used, the collocation interval analysis method is a non-gradient algorithm using several collocation points which improve the precision of results owing to better approximation of a response function. The pseudo excitation method is introduced to the solving procedure to transform the random problem into a deterministic problem. To validate the procedure, we present numerical results concerning a building under seismic ground motion and aerofoil under continuous atmosphere turbulence to show the effectiveness of the collocation interval analysis method.

关键词： uncertainty propagation interval analysis Taylor series expansion Chebyshev polynomial Pseudo excitation method

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Lateral Flight Stability of Two Hovering Model Insects

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Journal of bionic Engineering 2014年第3期11卷 439-448页

作者： Na Xu Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Beihang University Beijing 100191 P. R. China

The longitudinal disturbance motion of different insects at hovering flight has the same modal structure. Here, we consider the case of lateral motion. The lateral dynamic flight stability of two model insects, hoverfly and honeybee, at hovering flight is studied. The method of computational fluid dynamics is applied to compute the stability derivatives. The techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. Results show that the lateral disturbance motion of the hoverfly has three natural modes of motion： an unstable divergence mode, a stable oscillatory mode and a stable subsidence mode, and the flight is unstable; while the honeybee has a different modal structure （a stable slow subsidence mode, a stable fast subsidence mode, and a nearly neutrally stable oscillatory mode） and the flight is nearly neutrally stable. The change in modal structure between the two insects is due to their roll-moment/side-velocity derivative having different sign, and the sign difference is because that the hoverfly has a relatively small, but the honeybee has a relatively large, distance between the wing roots and the center of mass. Thus, unlike the case of longitudinal motion, for lateral motion, some insects have different modal structures and stability properties from others.

关键词： insect hovering flight dynamic flight stability modal structure

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Fuzzy finite difference method for heat conduction analysis with uncertain parameters

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Acta Mechanica Sinica 2014年第3期30卷 383-390页

作者： Chong Wang Zhi-Ping Qiu Institute of Solid Mechanics Beihang University

A new numerical technique named as fuzzy finite difference method is proposed to solve the heat conduction problems with fuzzy uncertainties in both the phys- ical parameters and initial/boundary conditions. In virtue of the level-cut method, the difference discrete equations with fuzzy parameters are equivalently transformed into groups of interval equations. New stability analysis theory suited to fuzzy difference schemes is developed. based on the parameter perturbation method, the interval ranges of the uncertain temperature field can be approximately predicted. Subsequently, fuzzy solutions to the original difference equations are obtained by the fuzzy resolution theorem. Two numerical examples are given to demonstrate the feasibility and efficiency of the presented method for solving both steady-state and transient heat conduction problems.

关键词： Heat conduction Fuzzy uncertainties Finitedifference method Parameter perturbation Stability analysis

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