Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session GT54: Aerospace Plasmas |
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Chair: Carmen Guerra-Garcia, MIT Room: Virtual GEC platform |
Tuesday, October 5, 2021 3:45PM - 4:00PM |
GT54.00001: Applying Conformal Mapping to simulate the generation of species in Nanosecond Pulsed Discharges in a tip-to-tip geometry Sree Harsha N R, Allen L Garner Nanosecond pulsed plasmas (NPPs) are used to generate reactive species in many applications such as combustion, flow control and medicine1. Here, we report a new conformal transformation (CT) that maps the hyperboloids representing the electrodes in the one-dimensional tip-to-tip geometry (TTG) onto concentric circles in a plane. The map is based on the stereographic projection of the hyperboloids that forms an extended Poincaré disk. The species concentrations are obtained in the TTG by coupling the drift-diffusion model of planar geometry modified using this CT function to BOLSIG+2. Applying CT to modify the governing equations significantly reduces the computational expense3 by only requiring the simulation of the planar geometry to characterize species concentration in any electrode configuration. We demonstrate the utility of CT by applying it to a TTG and comparing to experiments and other simulations. |
Tuesday, October 5, 2021 4:00PM - 4:15PM |
GT54.00002: Dissociative recombination (DR) and associative ionization (AI) cross section calculations for the NO++ e --> N + O (2D+3P, 2P+3P, and 2D+1D) reaction for atmospheric entry modeling E Papajak, Winifred Huo, David W. Schwenke, Richard L Jaffe During entry into Earth atmosphere, the flow surrounding space craft becomes ionized leading to significant cation and free-electron production. Subsequently, electron impact excitation and dissociation form radiating excited state species that contribute to the heat load on the vehicle. While experimental data on total cross sections are available, few experiments address the need for accurate AI cross sections for metastable states at the high temperatures realized in atmospheric re-entry. In order to maintain desired safety margins during atmospheric entry of a space vehicle, chemical reaction models need to accurately account for this process. |
Tuesday, October 5, 2021 4:15PM - 4:30PM |
GT54.00003: EFISH Electric-field measurement in discharges relevant to plasma-assisted-combustion Davide Del Cont Bernard, Deanna A Lacoste We present quantitative time- and space-resolved electric-field measurements in atmospheric-pressure nanosecond repetitively pulsed (NRP) discharges. Discharges are formed in a plasma-assisted-combustion burner, developing across a flame-front, partially in a fresh lean methane-air mixture and partially in the burned gases. The electric field has a prominent role in determining the reaction rate for electron impact reactions, so the knowledge of its space and time evolution would be advantageous for numerical simulations. The Electric-Field-Induced Second-Harmonic generation (EFISH) technique was used in the measurements. Spatially resolved measurements are obtained by raster scanning. Two significant challenges are (1) the small spatial features of the electric field in this kind of discharges and (2) the presence of different gases that alter the EFISH generation. A novel deconvolution-like post-processing procedure is used to improve the spatial resolution, overcoming the limitations arising from a large interaction volume, typical in EFISH measurements. Preliminary results suggest a first ionization wave (from anode to cathode) and a return wave. Evolution of the electric field close to the anode is analyzed and discussed. |
Tuesday, October 5, 2021 4:30PM - 4:45PM |
GT54.00004: Enhancement of the detonability of hydrogen-oxygen mixture by use of nanosecond plasmas. Mhedine Ali Cherif, Alain Claverie, Pierre Vidal, Svetlana Starikovskaia This experimental work aims at highlighting the effects of a non-equilibrium, nanosecond plasma at moderate pressure on the detonability of hydrogen-oxygen mixture. Two detonability parameters were investigated, namely: (A) the detonation cell width and (B) the distance for the deflagration-detonation transition. The experiments were carried out in the stoichiometric H2:O2 composition at initial pressures ranging from 100 to 200 mbar for (A) and from 200 to 1400 mbar for (B). ICCD imaging, back current shunt technique, sooted-plate technique and schlieren imaging were used to characterize the plasma and the detonation. The effect of a nanosecond plasma ahead of a detonation front reduces significantly the detonation cell width in the region where the plasma was applied. The effect is instantaneous and reproducible at all the pressures. The experiments also bring out differences in the deflagration to detonation process between a classical spark plug igniter and a self-designed multi-channel nanosecond plasma igniter. The differences for transition length and time, flame speed and the ignition of the mixture are presented for both devices. The efficiency of the plasma igniter is underlined by schlieren imaging. Overall the work brings experimental evidences of the effect of the predissociation of a combustible mixture by nanosecond plasma on the behavior of a detonation wave. |
Tuesday, October 5, 2021 4:45PM - 5:00PM |
GT54.00005: The effect of surface charge distribution on the electrohydrodynamic force in dielectric barrier discharge plasma actuators Shintaro Sato, Kodai Mitsuhashi, Tomoki Enokido, Atsushi Komuro, Akira Ando, Naofumi Ohnishi We experimentally investigate the relationship between the charge distribution on a dielectric surface and electrohydrodynamic force produced by a dielectric-barrier-discharge (DBD) plasma actuator. The surface potential distributions are measured using the Pockels effect. We found that the saturation time of the surface potential takes hundreds of milliseconds, which shows a large difference in the time scale of the surface discharge (several nanoseconds). Also, the electric potential distribution strongly depends on a biased DC voltage and the electrode configuration of the DBD plasma actuator. In particular, an additional exposed electrode placed downstream prevents the electric field screening. As a result, the electrohydrodynamic force is significantly enhanced by adding the exposed electrode since the electric field downstream contributes to the acceleration of charged particles. In the presentation, we are going to discuss the surface charge dynamics and its effect on the mechanical performance of the DBD plasma actuators in detail. |
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