Lei Zhang

North China Electric Power University

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Qian Zhang

North China Electric Power University

Songling Wang

China Tobacco

Mingzhi Yang

Central South University

Song Ling Wang

North China Electric Power University

Chenxing Hu

Beijing Institute of Technology

Ziwen Zhang

Anhui University

Xi Tian

North China Electric Power University

Ruiyang He

Dana-Farber Cancer Institute

Jinhua Lang

North China Electric Power University

Liang Zhang

Tarim University

Cooperative Institutions

North China Electric Power University

Central South University

Chinese Academy of Sciences

China Electric Power Research Institute

China Academy of Space Technology

University of Chinese Academy of Sciences

Tsinghua University

Zhejiang University

Ministry of Transport

Northwestern Polytechnical University

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Numerical study of the influence of hydrofoil hydrodynamic performance considering near-free surface

Brodogradnja (2025)

Yuanhui Wei Jianing Zhang Kaihao Liu Jiazhen Pan Lei Zhang

Bionic flapping hydrofoil motion is increasingly used in bionic underwater robots. However, many scholars have focused their attention on the navigation problem in deep-water environments, thus ignoring changes in the hydrodynamics of hydrofoils under the action of the near-free-surface effect. This paper studies and explores the hydrofoil motion in near-free surfaces through the RANS viscous flow numerical simulation method, combined with overset mesh and adaptive mesh technology. Three different forms of motion are studied respectively, including a stationary fixed, a single-degree-of-freedom pitch and a two-degree-of-freedom heaving-pitching coupled hydrofoil. The effects of varying the immersion depth d on the lift and thrust generated were analyzed. Results indicate noticeable differences in the free surface action among different motion forms. When the water depth is less than one chord length C, the lift and thrust of the three motion forms decreased rapidly decrease. When d/C=1~1.5, the static fixed hydrofoil lift and thrust gradually approach the deep-water state. When d/C>2, the pitching motion of a single degree of freedom also tends to be stable. The two-degree-of-freedom motion is d/C>3. This finding shows that the effect of the near-free surface is closely related to the vertical motion. The greater the vertical motion is, the more severe the effect.

Free surface

10.21278/brod76108

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Study on Automobile Fault Diagnosis Based on Fuzzy and Logical Reasoning

Mechanical & Electrical Engineering Magazine (2005)

Lei Zhang

Considerating the complexity and fuzzy of the relations between the fault-appearance and the fault-cause,a method based on fuzzy and logic is proposed.In this paper,the model of the fault diagnosis of fuzzy logic diagnosis is set up;according to the defects of the conventional method of setting up the fuzzy diagnosis matrix,a process that adopts artificial intelligence and expert knowledge to set up the matrix is proposed.Finally,we made a diagnosis for the automobile as example,which validated that the method has high correctness.

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Retraction Notice: Design of Wind Turbine Blade with Thick Airfoils and Flatback and its Aerodynamic Characteristic

The Open Mechanical Engineering Journal (2016)

Lijun Xu Lei Xu Lei Zhang Ke Yang

large-scaled blade has posed many problems related to design and production. After introducing the features of blade with thick airfoils and flatback, based on relevant parameters of Huaren 100 kW wind turbine, the paper designed blade with thick airfoils and flatback, introduced blade parameter design, and analyzed the aerodynamic performance of blades using GH bladed software, obtaining the relationship between power output of wind turbine with blade tip speed ratio Cp. Furthermore, it analyzed the aerodynamic performance of original design blades, modified blades and Huaren 100 kW blades, and assessed the aerodynamic performance of modified blade.

10.2174/1874155x01610010202

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Structural optimization of the low-pressure Venturi injector with double suction ports based on computational fluid dynamics and orthogonal test

Desalination and Water Treatment (2021)

Lei Zhang Zhengying Wei Qian Zhang

In the low-pressure irrigation system, a Venturi injector of low working pressure and energy consumption with a double-suction port was designed.The computational fluid dynamics method was used to simulate the inner flow field of Venturi injectors to obtain hydraulic performances.Taking the fertilizer mixing concentration as the evaluation index, an orthogonal test of six factors and five levels was designed to acquire the optimal structure with numerical calculation.The parameters in the optimal structure were as follows: the convergence angle 24°, the throat contraction ratio 0.2, the throat length-diameter ratio 2.0, the expanding angle 6°, the inclination angle 50°, and the number of suction port 2. Compared with the Venturi injector with a single suction port of inclination angle 90°, fertilizer suction discharge and mixing concentration of the double-suction port structure were increased by 236% and 198.8%, respectively.The double-suction port structure with an inclination angle 50° has better performances, including lower starting working pressure, more fertilizer suction discharge and mixing concentration, and is suitable for the low-pressure irrigation system.

Venturi effect

10.5004/dwt.2021.26739

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Dynamic Performance Evaluation of Variable Speed Pumped Storage Units based on Multiple Physical Fields of Hydraulic, Machinery, and Electricity

2022 4th Asia Energy and Electrical Engineering Symposium (AEEES) (2024)

Lei Zhang Gui Zhong-hua Li Shan-ying Yan Yi-an Liantao Ji

China's pumped storage power stations have entered a peak period of construction, and variable speed pumped storage units such as Feng-ning have gradually started debugging and operation. Scientific and comprehensive assessment of the dynamic performance of variable speed pumped storage units is of great significance for improving the operating characteristics of units and promoting the healthy development of variable speed pumped storage technology. This article analyzes the dynamic performance indicators of variable speed pumped storage units, and subdivides the performance indicators of variable speed pumped storage units from three aspects: hydraulic, mechanical and electric. A comprehensive evaluation index system for the dynamic performance of variable speed pumped storage units is constructed, and the plan is to use this evaluation system for the performance evaluation of Feng-ning pumped storage units.

10.1109/aeees61147.2024.10544492

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Simulation of Broadband Noise Sources of an Axial Fan under Rotating Stall Conditions

Advances in Mechanical Engineering (2014)

Lei Zhang Rui Wang Songling Wang

Study on the influence of rotating stall on the aerodynamic noise of axial fan has important value to warn of the occurrence of stall through monitoring the noise variations. The present work is to analyze the aerodynamic noise before and after the phenomenon of rotating stall by solving Navier-Stokes equations, coupled with the throttle condition and the broadband noise sources model. The impeller exit rotational Mach number and rotational Reynolds number are separately 0.407 and 8.332 × 10 6 . The results show that the aerodynamic noise source of the fan is mainly the rotation noise under the design condition. The vortex noise accounts for the major part of fan noise after the occurrence of stall, and the maximum acoustic power level of the fan appears in the rotor domains. In the evolution process from the stall inception to the stall cell, the high noise regions of the rotor develop along the radial, circumferential, and axial directions, and the area occupied by high noise regions increases from 33% to 46% impeller channels area. On rotating stall condition, the high noise regions occupying about 46% impeller channels area propagate with the stall cell along the circumferential direction at a half of rotor speed.

Stall (fluid mechanics)

Mechanical fan

Axial Compressor

10.1155/2014/507079

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Citations (22)

Aggregating Deep Convolutional Feature Maps for Insulator Detection in Infrared Images

IEEE Access (2017)

Zhenbing Zhao Xiaoqing Fan Guozhi Xu Lei Zhang Yincheng Qi

Insulator detection using an infrared image is challenged by variance of temperature, orientations, and a cluttered background. A robust and discriminative representation of insulators in electric power systems is needed. This paper proposes a novel method for generating this type of representation in infrared images by taking advantage of high-level discriminative Convolutional Neural Networks (CNNs) to feature the extraction framework and the deformation invariant nature of the Vector of Locally Aggregated Descriptors (VLAD) aggregator. Different from existing methods, we delve deep into the convolutional feature maps. We first extract deep activation maps from convolutional layers of a pretrained deep model and replace the last three fully-connected layers with a VLAD pooling layer to generate the representation of an insulator. Then, we train a Support Vector Machine (SVM) for binary classification. To further verify the effectiveness and robustness of our proposed feature, an insulator detection pipeline based on an object proposal is introduced. The experimental results show that our proposed method can achieve an accuracy of 93%. Meanwhile, the detection results demonstrate that our insulator detection pipeline has satisfied performance goals.

Discriminative model

Robustness

Local Binary Patterns

10.1109/access.2017.2757030

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Citations (65)

Flow and Noise Characteristics of Centrifugal Fan under Different Stall Conditions

Mathematical Problems in Engineering (2014)

Lei Zhang Shoufang Liang Chenxing Hu

An implicit, time-accurate 3D Reynolds-averaged Navier-Stokes (RANS) solver is used to simulate the rotating stall phenomenon in a centrifugal fan. The goal of the present work is to shed light on the flow field and particularly the aerodynamic noise at different stall conditions. Aerodynamic characteristics, frequency domain characteristics, and the contours of sound power level under two different stall conditions are discussed in this paper. The results show that, with the decrease of valve opening, the amplitude of full pressure and flow fluctuations tends to be larger and the stall frequency remains the same. The flow field analysis indicates that the area occupied by stall cells expands with the decrease of flow rate. The noise calculation based on the simulation underlines the role of vortex noise after the occurrence of rotating stall, showing that the high noise area rotates along with the stall cell in the circumferential direction.

Stall (fluid mechanics)

Centrifugal fan

Mechanical fan

10.1155/2014/403541

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Citations (7)

A New Active Vibration Isolation Control Method Based on CMAC Neural Network

Lei Zhang Fu Yong Ling Lin He

In terms of the nonlinearity in active vibration isolation system and the deficiencies of the generally used control methods, a new adaptive neuro-control method was proposed. In the new control structure, a CMAC (cerebellar model articulation controller) network was adopted as controller, and an improved simultaneous perturbation algorithm, which was proven a stochastic gradient approximation method, was proposed to update controller weights without modeling the secondary path. The performance of the control method was verified by numerical simulation, and simulation results showed that the proposed method has preferable isolation performance for system with nonlinearity when compared with filtered LMS method

Isolation

10.1109/icit.2005.1600832

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Citations (2)

Research on Drag-reduction Characteristic of Non-smooth Surface Riblet Structure on Aerofoil Blade of Centrifugal Fan

Proceedings of the CSEE (2013)

Lei Zhang

The drag reduction characteristics of riblet structure on aerofoil blade of the G4-73 centrifugal fan were numerically simulated based on RNG k-e turbulence model with Fluent.The relative position's influence law to riblet structure's drag reduction effect was investigated ulteriorly.Results are show:Riblet structure still has good drag reduction effect on blade.The best drag reduction effect has been gotten with riblet width s=0.1mm,with the greatest drag reduction efficiency of 9.65%.And under the design flow of fan,the drag can be reduced by 2.96%.The mean velocity of near-wall region on riblet surface has a significant increase than smooth surface,boundary normal velocity gradient decreases.Turbulent kinetic energy and turbulent intensity is lower than smooth surface obviously,the drag reduction effect of riblet structure on aerofoil blade is verified.When riblet structure relative position is at the tail of aerofoil,riblet surface causes large increases in the viscous drag with increasing velocity,lead to total drag increases and drag reducing efficiency reduces,even creates the drag increasing phenomenon.The present results can be used to provide a valuable reference for optimization of centrifugal fan blade modification and performance improvement.

Centrifugal fan

Position (finance)

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