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Journal of Thermal Science 2022年第6期31卷 2411-2423页

作者： PENG Zhigang ouyang hua WU Yadong TIAN Jie School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Brose Electric Motors Company Limited Shanghai 201801China

To optimize the aerodynamic performance of the automobile cooling fan(ACF), the internal flow field of the original fan was numerically simulated. According to the theory of boundary vorticity dynamics(BVD), the distribution laws of the boundary vorticity flux(BVF) on the blade surface and the circumferential vorticity(CV) at the wake plane of the fan were analyzed, and the underlying various negative factors, such as vortex shedding, separated flow and complicated secondary flow, on the fan blade surface and its dynamic source were diagnosed. Combined with the velocity triangle theory, the mathematical relationship between the BVF diagnosis and the geometrical characteristics of the blade profile(hereinafter referred to as profile) is used to guide the design improvement of the blade. The analysis found that at the same speed, the extension and rotation of the profile could match a smaller input torque at the same flow rate and pressure rise, thereby improving the efficiency of the fan. The test results confirmed the above conclusion. The peak efficiency of the improved fan has been increased by 2.3%, and the aerodynamic performance in the low-flow-rate has been improved. The conclusion of the study shows the applicability of the BVD theory in the diagnosis and design improvement of ACF internal flow.

关键词： boundary vorticity flux automotive cooling fan design improvement blade profile

Modal Analysis of Axial Compressor Tip Rotating Instability under Varying Operating Conditions

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Journal of Thermal Science 2023年第4期32卷 1345-1356页

作者： LI Tao WU Yadong TIAN Jie ouyang hua School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China Engineering Research Centre of Gas Turbine and Civil Aero Engine Ministry of EducationShanghai Jiao Tong UniversityShanghai200240China

The full annulus numerical research was performed on a low-speed compressor rotor to investigate the rotating instability in the tip *** frequency spectra show the existence of rotating instability at narrow stable operating *** the decrease of flow rate,31 cells of flow disturbance can be found in the instantaneous flow *** distribution of vortex suggests that the circumferential propagation of the interaction between tip leakage vortex and adjacent blade brings about these *** dynamic mode decomposition(DMD)method and spatial discrete Fourier transform(SDFT)were applied to obtain the circumferential mode features,and the results indicate that the rotating instability is associated with the 31 cells of flow *** the DMD method was further applied on the pressure data from a circle and an annulus domain,so as to extract different mode components with the corresponding spatial structures,frequencies and *** results suggest that DMD modes can display the flow feature and explore the evolution of each instability source in the tip flow field.

关键词： axial compressor rotating instability flow structure circumferential mode dynamic mode decomposition

COMPUTATIONAL AND EXPERI-MENTAL STUDY ON TIP LEAKAGE VORTEX OF CIRCUMFERENTIAL SKEWED BLADES

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Chinese Journal of Mechanical Engineering 2007年第2期20卷 82-87页

作者： LI Yang ouyang hua DU Zhaohui School of Mechanical Engineering Shanghai Jiaotong University Shanghai 200030 China

In the steady operation condition, the experiments and the numerical simulations are used to investigate the tip leakage flow fields in three low pressure axial flow fans with three kinds of circumferential skewed rotors, including the radial rotor, the forward-skewed rotor and the back- ward-skewed rotor. The three-dimensional viscous flow fields of the fans are computed. In the experiments, the two-dimensional plane particle image velocimetry （PIV） system is used to measure the flow fields in the tip region of three different pitchwise positions of each fan. The results show that the computational results agree well with the experimental data in the flow field of the tip region of each fan. The tip leakage vortex core segments based on method of the eigenmode analysis can display clearly some characteristics of the tip leakage vortex, such as the origination position of tip leak- age vortex, the development of vortex strength, and so on. Compared with the radial rotor, the other two skewed rotors can increase the stability of the tip leakage vortex and the increment in the forward-skewed rotor is more than that in the backward-skewed one. Among the tip leakage vortices of the three rotors, the velocity of the vortex in the forward-skewed rotor is th6 highest in the circumferential direction and the lowest in the axial direction.

关键词： Low pressure axial flow fan Tip leakage vortex Particle image velocimetry (PIV) Eigenmode analysis

Numerical Investigation on Aeroelastic Behavior of Composite Material Plate Excited by Pulsed Air Jet

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Journal of Thermal Science 2018年第4期27卷 364-372页

作者： XIE Hairun WU Yadong WANG Anjenq ouyang hua School of Mechanical Engineering Shanghai Jiao Tong University

Nowadays, carbon fiber composite material is becoming more and more popular in aero engine industry due to its high specific strength and stiffness. Laminate carbon fiber composite material is widely used to manufacture the high load wide chord fan blade, containment casing, etc. The aeroelastic behavior of composite product is critical for the optimization of the product design and manufacturing. In order to explore its aeroelastic property, this paper discusses the coupled simulation of aerodynamic excitation applied on laminate composite material plate. Mechanical behavior of composite material plate is different from that of isotropic material plate such as metal plate, because it is anisotropy and has relative high mechanical damping due to resin between plies. These plates to be studied are designed using 4 different layup configurations which follow the design methods for composite fan blade. The numerical simulation of force response analysis mainly uses single frequency mechanical force input to simulate the electromagnetic shakers or other actuators, which could transmit mechanical force to the test parts. Meanwhile, pulsed air excitation is another way to "shake" the test parts. This excitation method induces aero damping into the test part and simulates the unsteady flow in aero engine, which could cause aeroelastic problems, such as flutter, forced response and non-synchronous vibration(NSV). In this study, numerical simulation using coupled method is conducted to explore the characteristics of laminate composite plates and the property of aerodynamic excitation force generated by pulsed air jet device. Modal analysis of composite plate shows that different ply stacking sequences have a significant impact on the plate vibration characteristics. Air pulse frequency and amplitude in flow field analysis are calibrated by hot wire anemometer results. As the air pulse frequency and amplitude are varied, incident angle of flow and layup configurations of plat

关键词： aeroelasticity pulsed air jet composite plate

TOPOLOGY OPTIMIZATION OF MULTIPLE INPUTS AND MULTIPLE OUTPUTS COMPLIANT MECHANISMS

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Chinese Journal of Mechanical Engineering 2007年第1期20卷 82-85页

作者： ZHANG xianmin ouyang Gaofei WANG hua School of Mechanical Engineenng. South China University of Technology Guangzhou 510640 China

An optimal topology design method for multiple inputs and multiple outputs compliant micro-manipulation system is presented. Firstly, the topology design problem is posed in terms of a multiple inputs load and several specified output deflections. The compliance and stiffness of the system are expressed by the mutual potential energy and strain energy, respectively, which can be controlled by a multi-critaria objective function. Secondly, based on the optimality criteria method, a model solution algorithm is presented. Finally, a numerical example is presented to show the validity oftbe presented technique. The optimal topology ofa 4 inputs and 4 outputs compliant mechanism is obtained by using the method, and the corresponding micro-positioning stage system is further designed.

关键词： Topology optimization Compliant mechanisms Micro-positioning

Numerical Simulation of Clocking Effect on Blade Unsteady Aerodynamic Force in Axial Turbine

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Journal of Thermal Science 2012年第5期21卷 474-482页

作者： LI Wei ZHU Xiao-cheng ouyang hua DU Zhao-hui Shanghai JiaoTong University Shanghai 200240 China

To give an insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically by using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has very small influence on the turbine efficiency in this investigation. The difference between the maximum and minimum efficiency is about 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passes through the mid-channel in the 2nd stator. The wake convective transportation and the blade circulation variation due to its impingement on the subsequent blade are the main mechanism affecting the pressure variation in blade surface.

关键词： Axial Turbine Clocking Effect Numerical Simulation

EXPERIMENTAL RESEARCH ON AERODYNAMIC PERFORMANCE AND EXIT FLOW FIELD OF LOW PRESSURE AXIAL FLOW FAN WITH CIRCUMFERENTIAL SKEWED BLADES

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Journal of Hydrodynamics 2007年第5期19卷 579-586页

作者： LI Yang ouyang hua DU Zhao-hui School of Mechanical Engineering Shanghai Jiaotong University Shanghai 200030 China

In this article, the low pressure axial flow fan with circumferential skewed rotor blade, including the radial blade, the forward-skewed blade and the backward-skewed blade, was studied with experimental methods. The aerodynamic performance of the rotors was measured. At the design condition at outlet of the rotors, detailed flow measurements were performed with a five-hole probe and a Hot-Wire Anemometer （HWA）. The results show that compared to the radial rotor, the forward-skewed rotor demonstrates a wider Stable Operating Range （SOR）, is able to reduce the total pressure loss in the hub region and make main loading of blade accumulating in the mid-span region. There is a wider wake in the upper mid-span region of the forward-skewed rotor. Compared to the radial rotor, in the backward-skewed rotor there is higher total pressure loss near the hub and shroud regions and lower loss in the mid-span region. In addition, the velocity deficit in the wake is lower at mid-span of the backward-skewed rotor than the forward-skewed rotor.

关键词： low pressure axial flow fan circumferential skewed blade aerodynamic performance exit flow field StableOperating Range (SOR)

Water Sources of Dominant Species in Three Alpine Ecosystems on the Tibetan Plateau,China

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Journal of Integrative Plant Biology 2008年第3期50卷 257-264页

作者： De-Yu Duan hua ouyang Ming-hua Song Qi-Wu Hu Institute of Geographical Sciences and Natural Resources Research the Chinese Academy of Sciences Beijing 100101 China Graduate University of the Chinese Academy of Sciences Beijing 100039 China

Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope （δD and δ^18O） values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species （Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum） in three typical ecosystems （forest, shrub and desert） were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ^18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.

关键词： δD δ^18O precipitation river water soil water Tibetan Plateau

The role of potential soil cavity on ground subsidence and collapse in coal mining area

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Journal of Coal Science & Engineering(China) 2010年第3期16卷 240-245页

作者： ouyang Zhen-hua Mine Safety Technology Research Branch State Key Laboratory of Coal Mining and Environment Protection China Coal Research Institute Beijing 100013 China

Based on five basic assumptions, of the ground subsidence and collapse was using theoretical analysis method, the nature revealed from the mechanics point. Divided into four phases as groundwater level descent, soil cavity formation, soil cavity expansion, and ground collapse emersion, the whole process of ground subsidence and collapse was analyzed in detail. The study shows that ground subsidence and collapse is the macro- scopic performance and inevitable result of the soil cavity expansion and development, and the dynamic mechanics is the spalling force induced by the groundwater falling. The activities of underground water play a very important role in the process from the formation of soil cavity to the production of ground subsidence.

关键词： potential soil cavity ground subsidence and collapse groundwater spalling force

Characterization of Hydraulic Fracture with Inflated Dislocation Moving Within a Semi-infinite Medium

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Journal of China University of Mining and Technology 2007年第2期17卷 220-225页

作者： ouyang Zhi-hua ELSWORTH Derek LI Qiang College of Natural Resources and Environmental Engineering Wuhan Univeristy of Science and Technology Wuhan Hubei 430081 China College of Energy and Geo-environmental Engineering Pennsylvania State University State College PA 16802 USA

Hydraulic fracturing is accompanied by a change in pore fluid pressure. As a result,this may be conveniently represented as inflated dislocation moving within a semi-infinite medium. Theory is developed to describe the pore pressures that build up around an inflated volumetric dislocation migrating within a saturated porous-elastic semi-infinite medium as analog to hydraulic fracturing emplacement. The solution is capable of evaluating the system behavior of both constant fluid pressure and zero flux surface conditions through application of a superposition. Characterization of horizontal moving dislocation processes is conducted as an application of these techniques. Where the mechanical and hydraulic parameters are defined,a priori,type curve matching of responses may be used to evaluate emplacement location uniquely. Pore pressure response elicited at a dilation,subject to pressure control is of interest in representing hydraulic fracturing where leak-off is an important component. The effect of hydraulic fracturing on fracture fluid pressure is evaluated in a poroelastic hydraulic fracture model utilizing dislocation theory. A minimum set of dimensionless parameters are defined that describe the system. Pore fluid pressures recorded during hydraulic fracturing of a well in the San Joaquin Valley of Central California is examined using the proposed model. The estimated geometry of the hydraulic fracture is matched with reasonable fidelity with the measured data.

关键词： volumetric dislocation: hydraulic fracturing dimensionless analysis pore pressure