Plasmas, Discharges, and Electromagnetic Phenomena
10:00am - 10:20am
Plasmas and Discharges: 1
Computational study of plasma flow in arcing horns during a voltage surge
1Esgee Technologies Inc., United States of America; 2The University of Texas at Austin
Arcing horns are used to protect the insulators from high-electric stress conditions. These horns maintain a certain gap between the horn tip such that under excess voltage conditions, the air between the horns breaks down prior to any flashover event across the bushing. Subsequent to the breakdown, a conductive plasma channel forms between the arcing horns. This arc formation leads to the parallel current path which avoids the high voltage build-up across the insulator. In this study, we use VizSpark, a high-fidelity plasma flow solver, to simulate the arcing between the horns under over-voltage conditions. The horn geometry is taken from the previously reported research literature. The build-up of potential in the horns and subsequent arcing in between the electrodes is reported with detailed information on the electric field. The potential and electric field distribution inside the insulator is also reported.
10:20am - 10:40am
Plasmas and Discharges: 2
Numerical simulation of arcing during contact separation in SF6-filled high voltage circuit breaker
1Esgee Technologies Inc., United States of America; 2The University of Texas at Austin
The numerical simulation of thermal arcs in circuit breakers has been challenging, essentially due to the multi-physics involved in the process. In this work, we use VizSpark, a fully-coupled electromagnetic and fluid flow solver to simulate the arcing inside the SF6-filled circuit breaker. The two-dimensional axisymmetric mesh is created for a plug-tulip type SF6 breaker geometry widely reported in the research literature. The moving plug is simulated as an in-motion subdomain, while the tulip, auxiliary nozzle and main nozzle are considered to be static. The sinusoidal current amplitude is varied from 4 to 40 kA to simulate the arcing during the disconnection process. We discuss the temperature, velocity and pressure maps at different time instants to demonstrate the arc evolution process until it quenches.
10:40am - 11:00am
Plasmas and Discharges: 3
Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China, China, People's Republic of
To investigate the evolution of electron density of pin to plate discharge plasma at atmospheric pressure, the atomic optical emission line is processed by the interpolation to reduce the uncertainties of the Stark broadening method at first. Based on the Stark broadening method and the imaging method, the electron density of the plasma generated at different pulse frequencies, gap distances and inner diameters of the electrodes is diagnosed. The experimental results indicate that reducing the pulse frequency, shortening the gap distance of the electrodes and using thinner diameter electrode are all in favor to enhance the electron density. With the help of the global model, we perform the numerical simulation to explore the factors that influence the variation of the electron density. According to the simulations results, we find the reduced discharge volume results in the increase of electron density at low pulse frequency. When the gap distance of the electrodes is reduced, although the increased absorbed power and the reduced discharge volume both have an effect on the electron density, the reduced discharge volume plays a decisive role between these two factors. Moreover, using thinner inner diameter electrode can also reduce the discharge volume, which is beneficial to obtain the plasma with high electron density.
11:00am - 11:20am
Plasmas and Discharges: 4
Pulsed Spark Plasma Cracking Heavy Oil for Hydrogen and Acetylene Production
1Beijing International S&T Cooperation Base for Plasma Science and Energy Conversion, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China; 2University of Chinese Academy of Sciences, Beijing 100049, China
Spark discharge plasma is a promising technology for heavy hydrocarbons cracking due to its wide feedstocks adaptability and high conversion rate. Pulsed discharge can improve energy efficiency in energy conversion by its unique low energy compression and high instant power release. A combination of spark plasma and pulsed discharge has a potential for cracking the abundant but low-quality heavy oil efficiently into valuable light chemicals, such as hydrogen and acetylene. In this work, we used microsecond pulse power to crack heavy oil, and the spark discharge and conversion characteristics were studied in a gas-liquid reactor without catalyst at atmosphere pressure and room temperature. Heavy oil was injected into the plasma reaction area by a hollow needle electrode to improve contact with the plasma. Pulse voltage, pulse frequency and carrier gas sorts were evaluated for the improvement of discharge stability and conversion. Hydrogen and acetylene were the main gaseous products, and the gaseous products flow rates increased with discharge proceeding and became stable after 90 s. High voltage and high frequency can improved spark discharge stability, and with the increase of discharge power, the hydrogen and acetylene production flow rates were increased. Gaseous products flow rates were more superior than DBD (dielectric barrier discharge) and corona discharge. Conversion experiments in different carrier gases indicated that methane atmosphere was favorable for heavy oil cracking to produce more gaseous products. The spark discharge emission spectra in heavy oil mainly consisted of C2 and Hα, and the gas temperature was estimated at about 3000 K by fitting C2 spectra lines. This work provides a new idea for heavy oil utilization.
11:20am - 11:40am
Plasmas and Discharges: 5
1Nagaoka University of Technology, Japan; 2Pulsed Power Japan Laboratory Ltd.
As one of the industrial applications by pulsed power, water purification and sterilization by pulsed electric discharge with water has been investigated. Pulsed power discharge in water produces OH radical and shockwave which decompose harmful substances and kill bacteria. For these applications, it is important to study electric breakdown in water. In a previous study, we confirmed experimentally that a pre-electric field makes a main electric field required for arc-discharge decrease for a few hundred micro-second. From these results, new questions have come up, that is, how the effects of pre-fields on a streamer discharge and production of active species are. Thus, we investigated the effects experimentally. The streamer discharge was generated at a point-to-plate electrode in water, applying a pre-voltage and a main voltage using a pulse transformer source consisting of LTD boards and cores. Characteristics of the streamer discharge with various peaks of the pre-voltage and with various times between the pre-voltage and the main-voltage, were investigated from obtained voltage and current waveforms. Then, the amounts of hydrogen peroxide produced by the electric discharge with and without the pre-electric-field were measured and compared to investigate the effects on active species. In this presentation, these results are detailed, and the effects of the pre-electric field on the generation of streamer discharge and active species are discussed.
11:40am - 12:00pm
Plasmas and Discharges: 6
Underwater Electric Discharges: Experiment and Modeling
1Loughborough University, United Kingdom; 2University of Pau, France
At present, underwater electric pulsed discharges are used in a wide range of modern applications. During the development of a system for generating underwater acoustic pressure pulses, a numerical model is an essential tool for guiding the design and interpreting the data. Developing a complex 1-D numerical code, like those presented in the literature, requires a substantial dedicated effort. Unfortunately, previous work trying to use simple and elegant theoretical models developed many decades ago reported a fundamental issue, apparently related to the input data. The present work performs a detailed analysis of the real meaning of the voltage measured across an underwater discharge and clarifies the correct way the power input to a simple two-phase model should be calculated. Based on accurate measurements, a phenomenological methodology to obtain the input data is demonstrated, with theoretical predictions obtained from the simple two-phase model being successfully compared with the experimental evidence obtained from both the present work as well as from other reliable data presented in the literature.