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Experimental Study on Geometry Characteristics of Turbulent Premixed Flames for Natural Gas/Air Mixtures

Journal of Thermal Science 2025年第1期34卷 268-282页

作者： ZHENG Weilin WANG Qijiao XIAO Huahua CHEN Xiaoxiao XIE Fan ZENG Wen Liaoning Key Lab of Advanced Test Technology for Aerospace Propulsion System Shenyang Aerospace UniversityShenyang 110136China State Key Laboratory of Fire Science University of science and Technology of ChinaHefei 230027China AVIC Shenyang Aircraft Design and Research Institute Shenyang 110035China

In this study,focusing on the geometry characteristics of spherical expanding flame,the turbulent premixed flames of natural gas/air mixtures were investigated in a fan-stirred turbulent *** effects of initial temperature(T=300-400 K),initial pressure(P=0.1-0.3 MPa),turbulence intensity(u'=1.0-2.7 m/s),oxygen volumetric percentage(φ(O_(2))=15%-21%)and carbon dioxide volumetric percentage(φ(CO_(2))=0-20%)were delved *** flame profile under the Cartesian coordinate system was derived from the schlieren images taken by the high-speed ***,from both macroscopic and microscopic perspectives,the influence of experimental conditions on the flame geometry characteristics was explored through flame front extraction,wavelet decomposition and network *** results demonstrate that for significant flame wrinkling,changes in species concentrations and turbulence intensity have more pronounced effects on the flame wrinkling *** wrinkling of the flame front maintains a certain degree of similarity,as evidenced by the locally concentrated distribution of the angles of the maximum fluctuation *** disturbance energy under large-scale(D6-D8)disturbances exhibits relatively high values with a similar trend,exerting a significant impact on the geometry characteristics of the flame *** peaks of correlation degree are scattered either with the decomposition scale or the development of flame radius,indicating no linear correlation between different detail ***,the probability distribution of node degrees in key wrinkled regions exhibits different trends with that of large-scale wrinkling and disturbance energy,especially with changes in initial *** occurs because the number of key wrinkles varies based on the perturbation's strength or the region's ***,an increase in the fluctuation frequency of the flame's local radius may not necessarily lead to an increase in the number of key folded regions.

关键词： geometry characteristics large-scale wrinkling wavelet decomposition network topology fan-stirred turbulent combustor

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Hybrid ROCOV/Waveform Similarity Coefficient Based Protection for DC Lines in HVDC Grids

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CSEE Journal of Power and Energy systems 2024年第6期10卷 2423-2433页

作者： Wenxia Sima Zhengzheng Fu Ming Yang Tao Yuan Pan Duan Potao Sun State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqing 400044China School of Automation Chongqing University of Posts and TelecommunicationsChongqing 400065China

DC line protection with high speed and strong robustness against high fault resistance is essential in highvoltage direct current(HVDC)*** conventional voltagederivative-based protections for DC lines exhibit the problem of low reliability on the occurrence of high-impedance *** this paper,fault traveling waves at the fault point and at the line side of the DC reactor are first analyzed using phasemodal *** on the theoretical analysis of the modal fault-component voltages at the line side of the DC reactor,a novel hybrid protection scheme utilizing the single-ended rate of change of voltage(ROCOV)and waveform similarity coefficient is *** utilizes the hybrid ROCOV criterion and waveform similarity coefficient to identify the faulted line and the amplitudes of the 0-and 1-mode fault-component voltages to identify fault type,and the polarities of the 0-and 1-mode fault-component voltages to identify faulted *** under various fault conditions verify that the proposed protection scheme can achieve fast and reliable identification of faulted line,fault type,and faulted pole in 1 ms,and effectively improve the reliability against high-impedance faults up to 1200.

关键词： DC line protection MMC-HVDC grid phasemodal transformation ROCOV waveform similarity coefficient

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Design memristor-based computing-in-memory for AI accelerators considering the interplay between devices, circuits, and system

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Science China(Information Sciences) 2023年第8期66卷 243-253页

作者： Junjie AN Linfang WANG Wang YE Weizeng LI Hanghang GAO Zhi LI Zhidao ZHOU Jinghui TIAN Jianfeng GAO Chunmeng DOU Qi LIU School of Microelectronics University of Science and Technology of China State key Lab of Fabrication Technologies for Integrated Circuits Institute of MicroelectronicsChinese Academy of Sciences School of Microelectronics University of Chinese Academy of Sciences Frontier Institute of Chip and System State Key Laboratory of ASIC and System Fudan University

Recent advances in developing beyond von Neumann architectures have moved the memristive devices to the forefront as one of the key enablers to realizing memristive computing-in-memory(m CIM)structures, which shows a great promise to boost the energy-efficiency and the performance of artificial intelligence(AI) chips. In this study, by considering the interactions between devices, circuits, and systems in the m CIM design, we propose several cross-layer design techniques, including(1) the BL-SL interactive forming protection(BSIFP) circuit that can reduce the voltage drop on the selected transistor, suppress the current overshoot by 65.96%, and improve the bit-cell density by more than 10.19%,(2) the clamping transistor trimming scheme(CTTS) to prevent the multiply-and-accumulate(MAC) signal margin degradation from chip-to-chip resistance variations, and(3) dynamic input-parallelism and output-precision(DIPOP) that can reduce the energy cost by 22.92% in a typical inference task with negligible accuracy loss. The results demonstrate the significant role of the cross-layer-interactive approach and provide a preliminary guideline for highly-efficient m CIM design.

关键词： memristor resistive memory computing-in-memory artificial intelligence cross-layer co-design

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Analysis of SF6 decomposed products by fibre-enhanced Raman spectroscopy for gas-insulated switchgear diagnosis

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High Voltage 2024年第1期9卷 206-216页

作者： Jianxin Wang Weigen Chen Pinyi Wang Fu Wan Zhixian Zhang Shoufei Gao Yingying Wang School of Electrical Engineering Chongqing UniversityChongqingChina State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina Institute of Photonics Technology Jinan UniversityGuangzhouChina

Sulphur hexafluoride(SF6)decomposed products analysis is highly critical in the earlystage fault diagnosis of gas-insulated switchgear(GIS).Spectrum technology outperforms traditional methods on non-invasiveness,no sample preparation,and no ***,the authors present an improved fibre-enhanced Raman spectroscopy(FERS)as a comprehensive analytical tool to detect a suite of SF_(6)decomposed products(SO_(2)F_(2),SOF_(2),SO_(2),H_(2)S,CF_(4),OCS,CO_(2),and CO).The FERS approach is combined with two iris diaphragms for spatial filtering and a rear-end reflector for additional Raman signal *** of detection down to 1×10^(−6)–8×10^(−6)are achieved for different SF6 decompositions,and quantification of an undefined multigas,sampled from an 800 kV GIS in service,is realised utilising SF6 as the internal standard gas and with a maximum error of 5.5%.The GIS is diagnosed according to the results and confirmed by an on-site *** authors foresee that this technique will provide a route for trace gas analysis in the power industry.

关键词： SF6 diagnosis fibre

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Theoretical and experimental research on static stiffness,performance,and lift-off characteristics of multi-layer gas foil thrust bearings

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Friction 2024年第11期12卷 2458-2479页

作者： Yang HU Pengjing DING Fangling WU Xiaojing WANG Bo LIANG Yonggang MENG School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200072China Aviation Key Laboratory of Science and Technology on Aero Electromechanical System Integration Nanjing Engineering Institute of Aircraft SystemsNanjing 211106China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

In this study,a new comprehensive fully coupled elastic–hydrodynamic model is developed for a multi-layer gas foil thrust bearing(GFTB).The interaction effects among the top foil,back board,middle foil,and bottom foil,as well as the Coulomb friction effect,are *** stiffness and static characteristics obtained by the experimental and theoretical approaches are in good agreement,which verifies the accuracy of the *** contribution of each foil layer to the overall stiffness and the load-carrying mechanism are *** effects of the load,preload,and rotational speed on the static performance are investigated ***,start–stop tests are performed to achieve the lift-off speed,start-up torque,and shut-down torque under various operating conditions.

关键词： multi-layer gas foil thrust bearing(GFTB) load carrying mechanism static performance

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Unveiling first self-healing in metallised film capacitor:A macro-micro analysis

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High Voltage 2025年第2期10卷 362-373页

作者： Yushuang He Feipeng Wang Guoqiang Du Lei Pan Jian Li Hongming Yang Xiao Zhang Zhicheng Zhang Kaizheng Wang State Key Laboratory of Power Transmission Equipment Technology School of Electrical EngineeringChongqing UniversityChongqingChina School of Electrical&Information Engineering Changsha University of Science and TechnologyChangshaChina National Key Laboratory of Science and Technology on Vessel Integrated Power System Naval University of EngineeringWuhanChina Xi'an Key Laboratory of Sustainable Energy Material Chemistry School of ChemistryXi'an Jiaotong UniversityXi'anChina Faculty of Electrical Engineering Kunming University of Science and TechnologyKunmingChina

Metallised film capacitors(MFCs)are renowned for their unique self-healing(SH)properties,which bestow them with exceptional reliability and stability in the face of intense electric fields,high voltages,and pulse power ***,the exploration of SH characteristics concerning single-layer dielectric film remains insufficient for advancing MFC reliability *** establish the theoretical correlation of SH characteristics from the device to the film in the MFCs,this work developed a simulation model to analyse the SH dynamic behaviour in the *** effects of coupling capacitors,arc resistance and insulation resistance on the macroscopic characteristics(voltage drop and pulse current)are focused during the SH process in *** results indicate that SH is primarily associated with the voltage drop duration rather than the sampling ***,the SH process in MFC is characterised as an abrupt decrease in voltage to its minimum *** refinement enhances the SH energy dissipation model of *** quantified relationship between the macroscopic characteristics and microstructure evolution(polypropylene decomposition and aluminium electrode vaporisation)is established in MFCs under diverse SH energy *** SH energy and duration increase,the proportion of energy attributed to polypropylene decomposition increases,resulting in multi-layer ablation and adhesion within the metallised film and a pronounced deterioration in MFC electrical *** examination of macro-micro perspectives sheds new light on the intricate mechanisms governing the SH behaviour in MFCs,offering valuable insights for the advancement of their design,reliability evaluation,and performance optimisation in diverse electrical applications.

关键词： pulse current reliability evaluation polypropylene decomposition aluminium electrode vaporisation voltage drop metallised film capacitors macro micro analysis metallised film capacitors mfcs

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Influence of positive DC electric field on rime icing on the insulator and its experimental verification in the natural environment

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High Voltage 2023年第5期8卷 954-966页

作者： Zongyuan Liu Yuyao Hu Xingliang Jiang Lei Chen Mingchen Chi Feiyan Han Chong Zhao College of Electrical and Electronic Engineering Shandong University of TechnologyZiboChina State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina

The electric field imposes a significant effect on ice accretion on the *** impact of an AC electric field on insulator icing in an artificial climate chamber has been *** with AC,DC electric field exerts an attraction on supercooled water droplets,which is more detrimental to the power ***,the icing on energised insulators is rarely studied in the natural *** the present research,an electrical,fluid coupled‐field simulation was carried out on the *** force characteristics and motion deviation features of water droplets at different positive DC electric field strengths were *** this basis,rime icing on the insulator energised with different positive DC voltages was investigated in the *** show that the charged droplet shifts along the electric field line under a positive DC *** deviation degree of the droplet increases with the increment of the voltage and droplet size and decreases with an increase in wind *** the voltage rises,the surface roughness,icing amount and icing length of rime ice‐covered insulator ***,compared with that without energisation,the local collision coefficient,icing amount and icing length increase by 17.6%,46.4%and 63.9%,respectively,under a 40 kV DC voltage.

关键词： insulator field positive

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Differential Protection Method of Stator and Rotor Current With Different Frequencies for Variable Speed Pumped Storage Units

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IEEE Transactions on Power Delivery 2025年第3期40卷 1531-1539页

作者： Qiao, Jian Yu, Haoyuan Wang, Yikai Wang, Kai Yin, Xin Chen, Linxu State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources Baoding071003 China Wuhan University of Technology School of Automation Wuhan430070 China

Rotor winding short-circuit fault (RWSF) is a common fault type of variable speed pumped storage unit (VSPSU). However, the RWSF protection in engineering typically depends on the integrated over-current protection of the AC excitation system, which has poor sensitivity to reflect the RWSF and makes it difficult to fulfill the requirements of safe operation of VSPSU. Inspired by transformer differential protection, a different frequency differential protection method using both stator and rotor phase currents is proposed. In terms of working principle and structure, the stator and rotor windings of the VSPSU are similar to the primary and secondary windings of the transformer, and there are conditions for differential protection. Furthermore, the Clark transformation is used to analyze the characteristic changes of stator and rotor currents after the RWSF. On this basis, the criterion form of different frequency differential protection is constructed based on the trapezoidal area method. Finally, the effectiveness of the proposed method is verified by dynamic simulation experiments. © 1986-2012 IEEE.

关键词： Stators

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3D reconstruction and defect pattern recognition of bonding wire based on stereo vision

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CAAI Transactions on Intelligence technology 2024年第2期9卷 348-364页

作者： Naigong Yu Hongzheng Li Qiao Xu Ouattara Sie Essaf Firdaous Faculty of Information Technology Beijing University of TechnologyBeijingChina Beijing Key Laboratory of Computing Intelligence and Intelligent System Beijing University of TechnologyBeijingChina Engineering Research Center of Digital Community Ministry of EducationBeijingChina College of Robotic UniversitéFélix Houphouët‐BoignyAbidjanCôte d’Ivoire

Non-destructive detection of wire bonding defects in integrated circuits(IC)is critical for ensuring product quality after ***-processing-based methods do not provide a detailed evaluation of the three-dimensional defects of the bonding ***,a method of 3D reconstruction and pattern recognition of wire defects based on stereo vision,which can achieve non-destructive detection of bonding wire defects is *** contour features of bonding wires and other electronic components in the depth image is analysed to complete the 3D reconstruction of the bonding *** to filter the noisy point cloud and obtain an accurate point cloud of the bonding wire surface,a point cloud segmentation method based on spatial surface feature detection(SFD)was *** can extract more distinct features from the bonding wire surface during the point cloud segmentation ***,in the defect detection process,a directional discretisation descriptor with multiple local normal vectors is designed for defect pattern recognition of bonding *** descriptor combines local and global features of wire and can describe the spatial variation trends and structural features of *** experimental results show that the method can complete the 3D reconstruction and defect pattern recognition of bonding wires,and the average accuracy of defect recognition is 96.47%,which meets the production requirements of bonding wire defect detection.

关键词： bonding wire defect detection point cloud point cloud segmentation

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Design of a linear-rotary ultrasonic motor for optical focusing inspired by the bionic motion principles of the earthworms

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International Journal of Smart and Nano Materials 2022年第2期13卷 346-365页

作者： Yingzhi Wang Jie Deng Shijing Zhang He Li Weishan Chen Yingxiang Liu State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbinHeilongjiang ProvinceChina

Multi-motor configuration of multi-DOF(degree of freedom)optical system is a major source of redundant structure,putting a limitation on the simple and miniaturized ***,a novel two-DOF ultrasonic motor(USM)is proposed to provide a feasible method of application in the lens autofocus of the optical *** proposed USM operates by one longitudinal mode and two orthogonal bending modes,which is inspired by the bionic motion principle of the *** frequency degeneration among the three working modes is per-formed,and the working principle of the USM is verified via the FEM simulation.A prototype of the two-DOF USM is fabricated,and its mechanical output characteristics are *** experimental results indicate that the prototype achieves the maximum rotary and linear speeds of 3319.6 rpm and 57.6 mm/s,***,we demonstrate the result of a simple focusing experiment using the prototype and obtain a series of clear pictures,which verifies the feasibility of application in the optical focusing system.

关键词： Ultrasonic motor bondedtype two-DOF motions optical focusing bionic motion

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