Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session RR2: Thermal Plasmas: Arcs, Jets, Switches, Others |
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Chair: Mark Cappelli, Stanford University Room: Classroom 203 |
Thursday, October 25, 2012 1:30PM - 1:45PM |
RR2.00001: Electrothermal Characterization of an AC Thermal Plasma Torch Alexander Zielinski, Harry Fair, Reginald Allen, Trey Gebhart, Leigh Winfrey, Joshua Nowak, Mohamed Bourham A primary component in gasification is the plasma torch. Conversion of electrical energy to a high-temperature arc is essential. The properties of this arc determines, among other things, the efficiency of converting electrical input power to heat and mass transfer in the reactor chamber. A unique, single-phase torch was acquired for gasification studies. Power for this torch is supplied from the electric mains and is stepped up to 6 kV. The torch uses gas flow to complement the electrical energy transfer. Electrical operation of the torch is characterized by the Volt-Ampere plot, which is useful in determining the power rating of the torch as well as diagnosing the dynamic behavior of the plasma. The output of the torch is a thermal source at or near local thermodynamic equilibrium (LTE). Diagnostics are employed to characterize the torch. Plasma current is obtained by using a current transformer. Measurement of the plasma voltage is via an isolated technique. Optical emission spectroscopy, with the assumption of LTE, is used to determine the plasma kinetic temperature using the relative line method. An electrothermal plasma code provides the fundamental parameters at the torch nozzle, which are needed for gasification reactor design. [Preview Abstract] |
Thursday, October 25, 2012 1:45PM - 2:00PM |
RR2.00002: Numerical modeling of deflagration mode in coaxial plasma guns Hariswaran Sitaraman, Laxminarayan Raja Pulsed coaxial plasma guns have been used in several applications in the field of space propulsion, nuclear fusion and materials processing. These devices operate in two modes based on the delay between gas injection and breakdown initiation. Larger delay led to the plasma detonation mode where a compression wave in the form of a luminous front propagates from the breech to the muzzle. Shorter delay led to the more efficient deflagration mode characterized by a relatively diffuse plasma with higher resistivity. The overall physics of the discharge in the two modes of operation and in particular the latter remain relatively unexplored. Here we perform a computational modeling study by solving the non-ideal Magneto-hydrodynamics equations for the quasi-neutral plasma in the coaxial plasma gun. A finite volume formulation on an unstructured mesh framework with an implicit scheme is used to do stable computations. The final work will present details of important species in the plasma, particle energies and Mach number at the muzzle. A comparison of the plasma parameters will be made with the experiments reported in ref. [1]. \\[4pt] [1] F. R. Poehlmann et al., Phys. Plasmas \textbf{17}, 123508 (2010) [Preview Abstract] |
Thursday, October 25, 2012 2:00PM - 2:15PM |
RR2.00003: Speckle imaging of a circuit breaker arc near current-zero Patrick Stoller, Raphael F\"arber, Emmanouil Panousis, Michael Schwinne Optical speckle imaging can be used to determine quantitatively the temperature and density distribution in an axially symmetric gas flow by measuring the gradient of the index of refraction. This technique was applied to studying the properties of a high current arc embedded in a supersonic flow as the current approaches a zero-crossing. Such conditions play an important role in high voltage gas circuit breakers, where an arc is drawn between two contacts and axially blown to interrupt a current. A simple test device designed to reproduce the key features of a circuit breaker while allowing easy access for optical measurements was used. The arc was blown axially with synthetic air. Nozzles equipped with glass windows were used to permit speckle imaging of the flow; measurements were also carried out at the exit of the nozzle. The decaying phase of the high current arc was extended artificially by injecting a low DC current. Density and temperature information calculated from speckle images was coupled with arc voltage and current measurements and compared to CFD calculations to gain a better understanding of arc dynamics during the current-zero phase. [Preview Abstract] |
Thursday, October 25, 2012 2:15PM - 2:30PM |
RR2.00004: Numerical study on the Z pinch dynamics of gas jet type discharge produced plasma (DPP) source Bin Huang, Bin Xie, Taku Tomizuka, Masato Watanabe, Feng Xiao, Eiki Hotta Z pinch DPP source is often used as an Extreme Ultra-Violet (EUV) source. It is convenient to produce high temperature and high density plasma. There are several analytical models to describe the dynamics of the plasma. The snowplow model is a simple and widely used model to analyze the motion of the plasma shell and predict the pinch time; however, it is incapable of analyzing the plasma behavior after the maximum pinch and providing detailed information of concerned plasma parameters, such as electron density and electron temperature. In this study, we present the simulation results of the Z pinch DPP dynamics obtained by a 2D MHD code. This code solves the problem based on the assumption of single fluid, two temperature approximations in the cylindrical geometry. The numerical scheme for this MHD code is Total-Variation-Diminishing scheme in Lax Friedrich formulation (TVD-LF). The evolution of electron density, electron temperature, current density, magnetic flux and some other important parameters in Z pinch dynamics are investigated with this code. The simulation results show that the maximum pinch electron density is on the order of 10$^{19}$ cm$^{-3}$, with a pinch plasma radius of about 0.1 mm. In order to optimize the radiation output, the influences of initial gas distribution and the current waveform on the Z pinch dynamics are also investigated. They affect the electron density at pinch stagnation obviously; while in term of electron temperature, the effect is slight. [Preview Abstract] |
Thursday, October 25, 2012 2:30PM - 2:45PM |
RR2.00005: Role of external magnetic field and current closure in the force balance mechanism of a magnetically stabilized plasma torch Ravi G, Vidhi Goyal Experimental investigations on the role of applied external magnetic field and return current closure in the force balance mechanism of a plasma torch are reported. The plasma torch is of low power and has wall, gas and magnetic stabilization mechanisms incorporated in it. Gas flow is divided into two parts: axial-central and peripheral-shroud, applied magnetic field is axial and return current is co-axial. Results indicate that application of large external magnetic field gives rise to not only {\bf J} $\times$ {\bf B} force but also, coupled with gas flow, to a new drag-cum-centrifugal force that acts on the plasma arc root and column. The magnetic field also plays a role in the return current closure dynamics and thus in the overall force balance mechanism. This in turn affects the electro-thermal efficiency of the plasma torch. Detailed experimental results, analytical calculations and physical model representing the processes will be presented and discussed. [Preview Abstract] |
Thursday, October 25, 2012 2:45PM - 3:00PM |
RR2.00006: Spectroscopy of multicomponent thermal plasma Anton Lebid, Anatoliy Veklich, Viacheslav Boretskij, Sergiy Fesenko, Rostislav Semenyshyn Applications of composite materials in switching devices for the electrical engineering industry stimulate the interest in studying of the arc discharge plasma between composite electrodes. As an industrial application of silver -- cadmium oxide leads to the environmental pollution, the more attention must be paid to the development of composites, which contain alternate materials, in particular, Ag-SnO$_{2}$-ZnO. Composite materials on copper base with addition of high-melting metals, like tungsten and molybdenum, are widely used as well. The plasma parameters of free burning electric arc discharge between composite electrodes Ag-SnO$_{2}$-ZnO, Cu-Mo and Cu-W were obtained by optical emission spectroscopy. The radial profiles of temperature and electron density at different arc currents were obtained by spectroscopy techniques. These experimental results were used in calculation of plasma composition in assumption of local thermodynamic equilibrium. So, electric erosion properties of such kind materials were testified. The selection of CuI, AgI, ZnI, MoI and WI spectral lines and their spectroscopic data were carried out. [Preview Abstract] |
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