检索结果-南通市图书馆

Journal of Thermal Science 2013年第5期22卷 439-446页

作者： wei jia Huoxing Liu National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power Engineering Beihang University

Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall. Besides, shroud leakage flow is one of the dominant sources of secondary flow in tur- bomachinery, which not only causes a deterioration of useful work but also a penalty on turbine efficiency. It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution signifi- cantly different to those measured. Even so, the influence of shroud leakage flow is seldom taken into considera- tion during the routine of turbine design due to insufficient understanding of its impact on end wall flows and tur- bine performance. In order to evaluate the impact of tip shroud geometry on turbine performance, a 3D computa- tional investigation for 1.5-stage turbine with shrouded blades was performed in this paper. The following ge- ometry parameters were varied respectively：

关键词： labyrinth seal tip shroud geometry shroud leakage flow turbine performance high-loaded turbine

Numerical Investigation of the Interaction between Mainstream and Tip Shroud Leakage Flow in a 2-Stage Low Pressure Turbine

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2014年第3期23卷 215-222页

作者： jia wei LIU Huoxing National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics School of Energy and Power Engineering Beihang University

The pressing demand for future advanced gas turbine requires to identify the losses in a turbine and to understand the physical mechanisms producing them. In low pressure turbines with shrouded blades, a large portion of these losses is generated by tip shroud leakage flow and associated interaction. For this reason, shroud leakage losses are generally grouped into the losses of leakage flow itself and the losses caused by the interaction between leakage flow and mainstream. In order to evaluate the influence of shroud leakage flow and related losses on turbine performance, computational investigations for a 2-stage low pressure turbine is presented and discussed in this paper. Three dimensional steady multistage calculations using mixing plane approach were performed including detailed tip shroud geometry. Results showed that turbines with shrouded blades have an obvious advantage over unshrouded ones in terms of aerodynamic performance. A loss mechanism breakdown analysis demonstrated that the leakage loss is the main contributor in the first stage while mixing loss dominates in the second stage. Due to the blade-to-blade pressure gradient, both inlet and exit cavity present non-uniform leakage injection and extraction. The flow in the exit cavity is filled with cavity vortex, leakage jet attached to the cavity wall and recirculation zone induced by main flow ingestion. Furthermore, radial gap and exit cavity size of tip shroud have a major effect on the yaw angle near the tip region in the main flow. Therefore, a full calculation of shroud leakage flow is necessary in turbine performance analysis and the shroud geometric features need to be considered during turbine design process.

关键词： tip shroud leakage flow entropy rise low pressure turbine aerodynamic loss

Numerical investigation of the interaction between upstream cavity purge flow and main flow in low aspect ratio turbine cascade

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2013年第1期26卷 85-93页

作者： jia wei Liu Huoxing National Key Laboratory of Science and Technology on Aero-Engines Aero-Thermodynamics School of Energy and Power Engineering Beihang University

In modern gas turbines, rim seal located between the stator-disc and rotor-disc is used to prevent hot-gas ingestion into the inner stage-gap of high pressure turbine. However, the purge flow supplied to the cavity through the rim seal interacts with the main flow, producing additional aerodynamic loss due to the mixing process which plays a significant role in the formation, development and evolution of downstream secondary flow. In this paper, a set of cascade representative of low aspect ratio turbine is selected to numerically investigate the influence of upstream cavity purge flow on the hub secondary flow structure and aerodynamic loss. Cascade with/without upstream cavity and four different purge mass flow rates are all taken into account in this simulation. Then, a deep insight into the loss mechanism of interaction between purge flow and main flow is gained. The results show that the presence of cavity and purge flow has a significant impact on the main flow which not only changes the vortex structure in both the passage and upstream cavity, but also alters the cascade exit flow angle distribution along the spanwise. Moreover, aerodynamic loss in the cascade rises with the increase of purge flow rate while the sealing effect is also enhanced. Therefore, the effect of upstream cavity purge flow must be considered in the process of turbine aerodynamic design. What is more, it is necessary to minimize the purge flow rate in order to reduce aerodynamic loss on the premise of satisfying cooling requirements.

关键词： Aerodynamic loss Low aspect ratio Purge flow Turbine Upstream cavity

Multi-agent consensus with time-varying delays and switching topologies

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2014年第3期25卷 489-495页

作者： jia wei Huajing Fang School of Automation Huazhong University of Science and Technology College of Engineering Huazhong Agricultural University

The consensus problems of multi-agents with time-varying delays and switching topologies are studied. First, assume that an agent receives state information from its neighbors with fixed communication delays and processes its own state information with time-varying self-delay respectively. The state time-delay feedback is introduced into the existing consensus protocol to begenerate an improved protocol. Then a sufficient condition is derived which can make the system with time-varying self-delays achieve the consensus. On this basis, a specific form of consensus equilibrium influenced by the initial states of agents, time-delays and state feedback intensity is figured out. In addition, the multi-agent consensus is considered with time-varying topologies. Finally, simulations are presented to il ustrate the validity of theoretical results.

关键词： consensus multi-agent system time-varying delay switching topology convergence analysis.

The Impact of Cigarette Smoking on Metabolic Syndrome

在线全文

学校读者我要写书评

暂无评论

Biomedical and Environmental Sciences 2013年第12期26卷 947-952页

作者： jia wei Ping Department of Endocrinology and Metabolism Shanghai Jiao Tong University Affiliated Sixth People’s Hospital Shanghai Clinical Center for Diabetes Shanghai Diabetes Institute Shanghai Key Laboratory of Diabetes Mellitus Shanghai Key Clinical Center for Metabolic Disease

Metabolic syndrome （MetS） is a constellation of interconnected cardiometabolic disorders, including obesity, hyperglycemia, dyslipidemia, and elevated blood pressure. MetS is a precursor to type 2 diabetes mellitus （T2DM） and cardiovascular disease （CVD）; it increases the risk of T2DM by 3-4 times[11 and the risk of CVD by 1.4-fold[21, and is more prevalent in obese individuals. As the obesity rates increase, the prevalence of MetS in the population is increased. In 2006, the global prevalence of MetS in adults was estimated to be 20%-25%TM, and in China, in 2007-2008, using the criteria of the Chinese Joint Committee for Developing Chinese Guidelines on Prevention and Treatment of Dyslipidemia in Adults （JCDCG）, it reached 21.9% among the adult population aged 〉20 vears old[4].

关键词： The Impact of Cigarette Smoking on Metabolic Syndrome

Precise and efficient Chinese license plate recognition in the real monitoring scene of intelligent transportation system

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2022年第3期29卷 1-14页

作者： jia wei Gong Chao School of Computer Science and Information Engineering Hefei University of TechnologyHefei 230009China

In this paper, the performance of you only look once(YOLO) series detectors on Chinese license plate recognition(LPR) in the real intelligent transportation system(ITS) monitoring scene is investigated. Specially, a precise and efficient automatic license plate recognition(ALPR) system based on the YOLOv4 detector is proposed. The proposed ALPR system contains three stages including vehicle detection, license plate detection(LPD) and LPR. In vehicle detection stage, YOLOv4 detector is directly applied. In LPD stage, YOLOv4-tiny detector is exploited. In the last stage, the YOLOv4-tiny detector with attention mechanism for LPR is proposed to use. In addition, a large Chinese license plate dataset containing 10 500 images collected from all 31 provinces in the Chinese mainland is created. This Chinese license plate dataset is named Hefei University of Technology license plate version 1(HFUT-LP v1). Particularly, HFUT-LP v1 dataset is collected in the real ITS monitoring scene. In order to compare the performance of different object detection algorithms for ALPR, a variety of object detection algorithms are used to make a comprehensive performance evaluation. Experimental results show that the proposed ALPR system achieves very high accuracy and has very fast processing speed, which is suitable for real-time LPR.

关键词： license plate detection(LPD) license plate recognition(LPR) YOLOv4-tiny detector attention mechanism intelligent transportation

Enhance the Performance of Directional Feature-based Palmprint Recognition by Directional Response Stability Measurement

在线全文

学校读者我要写书评

暂无评论

Machine Intelligence Research 2024年第3期21卷 597-614页

作者： Haitao Wang wei jia School of Computer Science and Information Engineering Hefei University of TechnologyHefei230009China

Palmprint recognition is an emerging biometrics technology that has attracted increasing attention in recent years. Many palmprint recognition methods have been proposed, including traditional methods and deep learning-based methods. Among the traditional methods, the methods based on directional features are mainstream because they have high recognition rates and are robust to illumination changes and small noises. However, to date, in these methods, the stability of the palmprint directional response has not been deeply studied. In this paper, we analyse the problem of directional response instability in palmprint recognition methods based on directional feature. We then propose a novel palmprint directional response stability measurement (DRSM) to judge the stability of the directional feature of each pixel. After filtering the palmprint image with the filter bank, we design DRSM according to the relationship between the maximum response value and other response values for each pixel. Using DRSM, we can judge those pixels with unstable directional response and use a specially designed encoding mode related to a specific method. We insert the DRSM mechanism into seven classical methods based on directional feature, and conduct many experiments on six public palmprint databases. The experimental results show that the DRSM mechanism can effectively improve the performance of these methods. In the field of palmprint recognition, this work is the first in-depth study on the stability of the palmprint directional response, so this paper has strong reference value for research on palmprint recognition methods based on directional features.

关键词： Biometrics palmprint recognition directional response stability directional coding-based methods directional feature

Heuristic algorithm based on the principle of minimum total potential energy(HAPE):a new algorithm for nesting problems

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第11期12卷 860-872页

作者： Xiao LIU jia-wei YE School of Civil and Transportation Engineering South China University of Technology Guangzhou 510640 China

We present a new algorithm for nesting *** equally spaced points are set on a sheet,and a piece is moved to one of the points and rotated by an *** the point and the rotation angle constitute the packing attitude of the *** propose a new algorithm named HAPE(Heuristic Algorithm based on the principle of minimum total Potential Energy) to find the optimal packing attitude at which the piece has the lowest center of *** addition,a new technique for polygon overlap testing is proposed which avoids the time-consuming calculation of no-fit-polygon(NFP).The detailed implementation of HAPE is presented and two computational experiments are *** first experiment is based on a real industrial problem and the second on 11 published benchmark *** a hill-climbing(HC) search method,the proposed algorithm performs well in comparison with other published solutions.

关键词： Packing Cutting Nesting Irregular Heuristic algorithm Minimum total potential energy

Modeling fluid–particle interaction in dilute-phase turbulentliquid–particle flow simulation

在线全文

学校读者我要写书评

暂无评论

Particuology 2010年第2期8卷 150-160页

作者： Kunn Hadinoto jia wei Chew School of Chemical and Biomedical Engineering Nanyang Technological University Singapore 637459 Singapore Department of Chemical and Biological Engineering University of Colorado Boulder CO 80309 USA

The present work examines the predictive capability of a two-fluid CFD model that is based on the kinetic theory of granular flow in simulating dilute-phase turbulent liquid-particle pipe flows in which the inter- stitial fluid effect on the particle fluctuating motion is significant. The impacts of employing different drag correlations and turbulence closure models to describe the fluid-particle interactions （i.e. drag force and long-range interaction） are examined at both the mean and fluctuating velocity levels. The model pre- dictions are validated using experimental data of turbulent liquid-particle flows in a vertical pipe at different particle Reynolds numbers （Rep 〉 400 and Rep 〈 400）, which characterize the importance of the vortex shedding phenomenon in the fluid-phase turbulence modulation. The results indicate that （1） the fluctuating velocity level predictions at different Rep are highly sensitive to the drag correlation selec- tion and （2） different turbulence closure models must be employed to accurately describe the long-range fluid-particle interaction in each phase. In general, good agreement is found between the model predic- tions and the experimental data at both the mean and fluctuating velocity levels provided that appropriate combinations of the drag correlation and the turbulence closure model are selected depending on Rep. 2009 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

关键词： Slurry flowLiquid-particle flowKinetic theory of granular flowDrag correlationTurbulence

A fluidized-bed model for NiMgW-catalyzed CO2 methanation

在线全文

学校读者我要写书评

暂无评论

Particuology 2020年第2期18卷 55-64页

作者： Chunmiao jia Yihu Dai Yanhui Yang jia wei Chew School of Chemical and Biomedical Engineering Nanyang Technological UniversitySingapore 637459Singapore Institute of Advanced Synthesis Nanjing Tech UniversityNanjing 211800Jiangsu ProvinceChina Singapore Membrane Technology Center Nanyang Technological UniversitySingapore 637141Singapore

The reduction of carbon dioxide to methane by hydrogen("CO2 methanation")using renewable energy is a promising process for recycling *** catalysts and better reactors are both required for the practical application of CO2 *** study examines how the operating parameters affect CO2 methanation in a highly efficient fluidized-bed *** first measured the kinetics of the CO2 methanation reaction using an NiMgW catalyst,which has been reported to exhibit superior catalytic *** then developed a fluidized-bed reactor model based on an earlier model for CO2 *** fluidized bed model indicated that the NiMgW was indeed superior to two other previously studied catalysts in terms of faster conversion of reactants and higher concentrations of product CH4 throughout the *** overall rate of production of CH4 increased with temperature and H2/CO2 ratio and decreased as the inlet reactant flow rate,catalyst particle diameter,and catalyst particle sphericity increased.

关键词： Fluidized-bed reactor model CO2 methanation NiMgW catalyst Reaction kinetics Sensitivity analysis