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electric characteristic and cavitation bubble dynamics using underwater pulsed discharge

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Plasma Science and Technology 2019年第7期21卷 16-22页

作者： Minglei SHAN Bingyan CHEN Cheng YAO Qingbang HAN Changping ZHU Yu YANG Jiangsu Key Laboratory of Power Transmission and Distribution Equipment Technology Changzhou 213022People’s Republic of China College of Internet of Things Engineering Hohai UniversityChangzhou 213022People’s Republic of China Key Laboratory of Unmanned Aerial Vehicle Development&Data Application of Anhui Higher Education Institutes Wanjiang University of TechnologyMa’anshan 243031People’s Republic of China

Underwater pulsed discharge is widely applied in medicine, machining, and material *** induced cavitation bubble and subsequent cavitation collapse are considered the major motivations behind these applications. This paper presents an underwater pulsed discharge *** experimental setup is established to induce and investigate the cavitation bubble assisted with a high-speed camera. Three aspects, including the characteristic of the discharge with different applied voltages and conductivities, the evolution of the cavitation bubble profile, and the energy efficiency of cavitation bubble inducing, are investigated, respectively. Especially, the mechanism of pre-discharge time delay in the low field intensity case is explained using the Joule heat *** results show the validity of the underwater pulsed discharger and experimental setup. The present underwater pulsed discharger is proved to be a simple, portable, and easy-to-implement device for the investigation of cavitation bubble dynamics.

关键词： underwater pulsed discharge cavitation bubble electric discharge characteristic high-speed camera

electric-field-induced microstructure modulation of carbon nanotubes for high-performance supercapacitors

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Frontiers of Materials Science 2019年第3期13卷 270-276页

作者： Chengzhi LUO Guanghui LIU Min ZHANG School of Electronic and Computer Engineering Peking UniversityShenzhen 518055China Shenzhen China Star Optoelectronics Technology Co. Ltd.Shenzhen 518132China

The growth direction,morphology and microstructure of carbon nano-tubes(CNTs)play key roles for their potential applications in electronic and energy storage ***,effective synthesis of CNTs in high crystallinity and desired microstructure still remains a tremendous *** we introduce an electric field for controlling the microstructure formation of *** reveals that the electric field not only make CNTs aligned parallel but also improve the density of ***,the microstructures of CNTs gradually change under electrical *** is,graphite sheets are transformed from the"herringbone"structure to a highly crystalline structure,facilitating the transportation of *** to the improved aligned growth direction,high density and highly crystalline microstructure,the electrochemical performance of CNTs is greatly *** the CNTs are applied in supercapacitors,they present a high specific capacitance of 237 F/g,three times higher than that of the CNTs prepared without electrical *** microstructure modulation of CNTs by electric field would help to construct high performance electronic and energy storage devices.

关键词： carbon nanotube electric field microstructure control supercapacitor electrochemical performance

electric discharge phenomenon in dielectric and electrolyte medium

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Advances in Manufacturing 2018年第4期6卷 457-464页

作者： Mukesh Kumar Sindhu Debasish Nandi Indrajit Basak Department of Mechanical Engineering. NIT Durgapur. Durgapur 713209. India Department of Mechanical Engineering JIS College of Engineering Kalyani 741235 India

electric discharge is a common tool nowadays for machining of materials. It may be through a liquid medium or through air. Any metals, hard alloys, and nonmetals can be machined using the energy of electric discharge. In electric discharge machining (EDM), the discharge occurs between two electrodes through a liquid medium and it is applicable only for electrically con ducting materials and alloys. In electrochemical discharge machining (ECDM), the medium is an aqueous electrolyte and it is of two types. In the first type, the discharge occurs between two electrodes. One of the electrodes is the workpiece, and the other is the tool. In the second type, the discharge occurs between one electrode and an electrolyte. It is used for electrically nonconducting materials and the discharge energy is utilized maintaining the nonconducting workpiece in proximity of the discharge. All these electrical discharges are transient phenomena and do not result in a stable discharge in the form of arc. The output parameters depend on the discharge energy that requires precise control to maintain the accuracy of the machining. For micromachining, the control of the discharge is paramount both in terms of energy and pattern. Using various shaped tools, machining media with additives, different types of applied potentials, and supporting mechanical motions are some of the attempts made to improve the machining output. Optimization of these parameters for machining particular materials (or alloys) is a popular field of research. The present work is directed toward the investigation of discharge initiation and development by analyzing the cell current and discharge voltage relationship for both EDM and ECDM. The rectangular direct current (DC) pulse with different frequencies and the duty factor (on-off time ratio) are used for investigation. Observations on the voltage-current relationship are made for the external potential prior to discharge at discharge and above the discharge potenti

关键词： electric discharge electric discharge machining (EDM) Electrochemical discharge machining (ECDM) Pulsed direct current (DC) Duty factor

Multi-objective optimization for electric water heater using mixed integer linear programming

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Journal of Modern Power Systems and Clean Energy 2019年第5期7卷 1256-1266页

作者： Mei WU Yu-Qing BAO Jinlong ZHANG Tongzhou JI NARI School of electrical and Automation Engineering Nanjing Normal UniversityNanjingChina Engineering Laboratory of Gas-electricity Integrated Energy of Jiangsu Province Nanjing Normal UniversityNanjingChina

Due to the capacity of thermal storage,electric water heater(EWH)is one of the best candidates for demand response ***,few attentions are given to the modeling and optimization of EWHs with thermostatically-controlled automatic water mixer(TCAWM).In this paper,differential thermodynamic model is established for EWHs with TCAWM and a piecewise linear approximation method is performed for the nonlinear thermodynamic *** multi-objective optimization model is established by introducing an index reflecting the comfort degree of users,so that the optimal energy usage of the EWH can be obtained by mixed integer linear *** examples verify the effectiveness of the proposed method.

关键词： Demand response electric water heater Thermostatically-controlled automatic water mixer Mixed integer linear programming

Improving reliability of distribution networks using plug-in electric vehicles and demand response

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Journal of Modern Power Systems and Clean Energy 2019年第5期7卷 1189-1199页

作者： Omid SADEGHIAN Morteza NAZARI-HERIS Mehdi ABAPOUR S.Saeid TAHERI Kazem ZARE Faculty of electrical and Computer Engineering University of TabrizTabrizIran Department of electrical Engineering Faculty of EngineeringSarab BranchIslamic Azad UniversitySarabIran

Nowadays,utilities aim to find methods for improving the reliability of distribution systems and satisfying the customers by providing the continuity of power *** methodologies exist for utilities to improve the reliability of *** this paper,demand response(DR)programs and smart charging/discharging of plug-in electric vehicles(PEVs)are investigated for improving the reliability of radial distribution systems adopting particle swarm optimization(PSO)*** analysis is accomplished due to the positive effects of both DR and PEVs for dealing with emerging challenges of the world such as fossil fuel reserves reduction,urban air pollution and greenhouse gas ***,the prioritization of DR and PEVs is presented for improving the reliability and analyzing the characteristics of distribution *** reliability analysis is performed in terms of loss of load expectation(LOLE)and expected energy not served(EENS)indexes,where the characteristics contain load profile,load peak,voltage profile and energy *** simulations are accomplished to assess the effectiveness and practicality of the proposed scheme.

关键词： Plug-in electric vehicles(PEVs) Demand response(DR) Reliability improvement electric distribution system Expected energy not served(EENS)

Three-dimensional electric potential induced by a point singularity in a multilayered dielectric medium

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Applied Mathematics and Mechanics(English Edition) 2019年第9期40卷 1327-1334页

作者： Xu WANG P. SCHIAVONE School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 China Department of Mechanical Engineering University of Alberta 10-203 Donadeo Innovation Centre for Engineering Edmonton Alberta T6G 1H9 Canada

A simple and effective method is proposed to derive the three-dimensional electric potential induced by a point singularity of any type in an N-phase dielectric medium composed of N-2 intermediate dielectric layers of equal thickness encased in two semi-infinite dielectric media. The point singularity can include a point charge or a point electric dipole. The original boundary value problem for the N-phase medium is reduced to the determination of a single unknown three-dimensional harmonic function through satisfaction of the continuity conditions across all of the N-1 perfect planar interfaces. The single harmonic function can be completely determined after analytically solving the resulting linear recurrence relations, which are independent of the type and the specific location of the singularity. When the singularity is a point charge, we obtain the self-energy of the point charge expressed in terms of a single function and the Coulomb force on the point charge expressed in terms of the negative derivative of this function.

关键词： multilayered dielectric medium point charge point electric dipole linear recurrence relation analytical solution

Accommodation of curtailed wind power by electric water heaters based on a new hybrid prediction approach

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Journal of Modern Power Systems and Clean Energy 2019年第3期7卷 525-537页

作者： Yang YU Zengqiang MI Xiaoming ZHENG Da CHANG State Key Laboratory of Alternate electrical Power System with Renewable Energy Sources North China Electric Power UniversityBaoding071003China Hebei Key Laboratory of Distributed Energy Storage and Micro-grid North China Electric Power UniversityBaoding071003China

Wind power curtailment is of great importance with the increase of large-scale wind power connected to the grid. A new concept of redundant wind power accommodated by dispatching electric water heaters(EWHs) is developed in the paper. Precise predictions of wind power and EWHs load power are the basis for this work. A hybrid multi-kernel prediction approach integrating an adaptive fruit fly optimization algorithm(AFOA)and multi-kernel relevance vector machine(MKRVM) is proposed to deal with the sample distribution of multisource heterogeneous features uncovered by an energy entropy method, where AFOA is used to determine the kernel parameters in MKRVM adaptively and avoid the arbitrariness. For the large computation of the prediction approach, parallel computation based on the Hadoop cluster is used to accelerate the calculation. Then, an economic dispatching model for accommodating wind power is built taking into account the penalty of curtailed wind power and the operation cost of EWHs. The proposedscheme is implemented in an intelligent residential *** results show that the optimization performance of the hybrid prediction approach is superior to those of four usual optimization algorithms in this case. Regular or orderly scheduling of EWHs enables accommodation of superfluous wind power and reduces dispatch cost.

关键词： Wind power curtailment electric water heaters(EWH) Dispatching model Relevance vector machine Prediction model

Investigation on the Influence of Refrigerant Charge Amount on the Cooling Performance of Air Conditioning Heat Pump System for electric Vehicles

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Journal of Thermal Science 2019年第2期28卷 294-305页

作者： LI Kang LAN Jiao ZHOU Guoliang TANG Qitian CHENG Qia FANG Yidong SU Lin School of Energy and Power Engineering University of Shanghai for Science and Technology

The application of air conditioning heat pump(ACHP) in electric vehicles could lead to significant electrical power saving effect. As for an air conditioning heat pump system for electric vehicles, the influence of refrigerant charge amount should be investigated during the design phase. In this study, experimental method was employed to investigate the influence of the refrigerant charge amount on the performance of the ACHP system. The results showed that the refrigerant charge amount had different influence on the refrigerant properties at various locations within the system. The coefficient of performance and pressure-enthalpy diagram were calculated, and showed a close relationship with refrigerant charge amount under different compressor speeds. The degree of subcooling and the degree of superheating were recorded and the critical charge amount was determined by a typical practical test method. In addition, the critical refrigerant charge amount determined by the experimental method was also compared with two typical void fraction correlation models, and the model with consideration of two phase stream reaction of the refrigerant showed a good estimation accuracy on the critical charge amount.

关键词： air conditioning heat pump electric vehicle critical refrigerant charge cooling performance

Humidity effects on the ground-level resultant electric field of positive DC conductors

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Plasma Science and Technology 2019年第7期21卷 6-15页

作者： Haibing LI Jie ZHU Wei YANG Xu ZHANG Donglai WANG Junyu ZHU Xingming BIAN State Key Laboratory of Alternate electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206People’s Republic of China State Key Laboratory of Advanced Transmission Technology Global Energy Interconnection Research InstituteBeijing 102211People’s Republic of China State Grid Suzhou electric Power Supply Company Suzhou 215008People’s Republic of China

The effects of humidity on the ground-level resultant electric field around positive DC conductors were studied both experimentally and numerically. Experiments were carried out in an artificial climate chamber, the results of which showed that the photon count and the groundlevel resultant electric field strength both increased with increasing relative humidity. Numerical calculations for different values of relative humidity were carried out, including solutions of the positive corona inception voltage and the ion-flow field, for which a photoionization model and the upstream finite element method were employed, respectively. In order to analyze the effects of humidity, three main factors were considered: the ionization coefficient, the attachment coefficient in the photoionization model and the modified ion mobility of the charged water particles. The results indicated that, with increasing relative humidity, increasing values of the effective ionization coefficient were responsible for a reduction in the inception voltage, and the reduction reinforced the ground-level resultant electric field. Moreover, due to the charged water particles and the lower ion mobility with increasing relative humidity, the space charge density distribution was enhanced, which also strengthened the ground-level resultant electric field.

关键词： corona discharge humidity electric field