Bulletin of the American Physical Society
64th Annual Gaseous Electronics Conference
Volume 56, Number 15
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session TF1: Plasma Propulsion and Aerodynamics |
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Chair: Jean-Pierre Boeuf, LAPLACE and Universite Paul Sabatier Room: 255D |
Friday, November 18, 2011 9:30AM - 10:00AM |
TF1.00001: Alternating acceleration of positive and negative ions for space propulsion applications Invited Speaker: Classical electric propulsion systems accelerate positive ions for thrust and neutralize the ion beam by electrons downstream of the acceleration stage. The distinctive feature of the PEGASES thruster concept is that both positive and negative ions are accelerated to provide thrust, such that an additional neutralization system is redundant. The key to generate fluxes of both types of ions is the formation of an ion-ion plasma where the electron density is negligible compared to the negative ion density. The basic principles of ion-ion plasma formation are relatively well known. On the contrary, the extraction and acceleration of oppositely charged ions in alternating phases is the current challenge in the development of this new thruster. In this presentation we will focus on the physics of gridded ion acceleration, where the grid in contact with the ion-ion plasma is alternately biased with the aim of generating consecutive bursts of positive and negative ions. In the experimental investigation different bias waveforms and frequencies are applied to the grid, and the extracted ion beam velocities and ion beam fluxes are monitored by time resolved retarding field ion energy analyzers and planar probes. [Preview Abstract] |
Friday, November 18, 2011 10:00AM - 10:30AM |
TF1.00002: Mission Enabling: The Plasma Sources of Electric Propulsion---challenges and prospects for the future Invited Speaker: Plasma propulsion has literally been mission enabling for a wide array of space applications ranging from satellite operational lifetime extension to multi-destination voyages to the asteroids. The success of plasma propulsion, otherwise known as electric propulsion, in many respects is owed to the development of clever plasma sources that bolster both high efficiency and long life. Incidentally, these attributes are also coveted in the broad area of plasma processing and manufacturing and thus are of general applicability from a technological standpoint. Indeed, there is significant cross-fertilization and application of such plasma sources not only in plasma processing but also in fusion as well. Here, a sampling of the plasma sources that enable the practical application of electric propulsion devices will be discussed with commentary on discharge physics, implementation, and technical challenges levied by mission requirements. [Preview Abstract] |
Friday, November 18, 2011 10:30AM - 10:45AM |
TF1.00003: Picosecond CARS Measurements of Vibrational Distribution Functions in a High Pressure Non-Self-Sustained Discharge Walter Lempert, Aaron Montello, Munetake Nishihara, Joeseph Rich, Igor Adamovich Picosecond Coherent Anti-Stokes Raman Scattering (CARS) is used for measurement of nitrogen Vibrational Distribution Function (VDF) in the plenum of a highly nonequilibrium Mach 5 wind tunnel incorporating a high pressure pulser-sustainer discharge. First level vibrational temperatures of the order of 2000 K are achieved in the 300 Torr non-self-sustained plasma discharge, generated by a high E/n ($\sim $300 Td) nanosecond pulsed discharge, which provides ionization, in combination with an orthogonal low E/n ($\sim $10 Td) DC sustainer discharge, which efficiently loads the nitrogen vibrational mode. It is also shown that operation with the nanosecond pulsed plasma alone results in significant vibrational energy loading, with T$_{v}$(N$_{2})$ of the order of 1100 K. Downstream injection of CO$_{2}$, NO, and H$_{2}$ results in vibrational relaxation, demonstrating the ability to further tailor the vibrational energy content of the flow. N$_{2}$ -- NO V-V and N$_{2}$ -- H$_{2}$ V-T rates inferred from this data agree well with previous literature results, to within the uncertainty in rotational-translational temperature. [Preview Abstract] |
Friday, November 18, 2011 10:45AM - 11:00AM |
TF1.00004: The potential distribution in the Radial Plasma Source Amnon Fruchtman, Gennady Makrinich The Radial Plasma Source (RPS) is based on plasma acceleration by an applied voltage across a magnetic field. Here we report the recent progress in understanding the mechanism of plasma acceleration in the RPS. The RPS has a cylindrical symmetry. The accelerating electric field is radial and the magnetic field is axial. Most of the potential drop between the inner anode and the outer cathode is expected to be located where the magnetic field intensity is large. We employ an emissive probe and a Langmuir probe in order to evaluate the radial dependence of the potential. For inferring the plasma potential from the measured emissive probe potential, we employ our recently developed theory for a cylindrical emissive probe. Using the theory and the probe measurements, we plot the radial profiles in the RPS of the plasma potential as well as of the electron density and temperature. The possible modification of the geometry for propulsion applications will be discussed. [Preview Abstract] |
Friday, November 18, 2011 11:00AM - 11:15AM |
TF1.00005: The relationship between DBD performance in ambient and flowing air Mohammed Siddiqui, Ali Gulec, Lutfi Oksuz, Riccardo Bonazza, Noah Hershkowitz Dielectric barrier discharges (DBDs) have been shown to reduce flow separation on airfoils in flowing air [1], as well as impart momentum into ambient air [2]. The relationship between DBD performance in both regimes is not well understood. We previously investigated a novel DBD discharge regime in ambient air first discovered by Hoskinson et. al.[3], where for cylindrical exposed electrodes, as the electrode diameter was reduced below 50 $\mu$m, the force divided by power dissipated in ambient air increased exponentially. We now investigate the ability of these DBDs to reduce flow separation in flowing air of Re $\sim $ 5E5 and how it relates to their discharge characteristics in ambient air. The results are presented here for the first time. \\[4pt] [1] T. C. Corke, C. Lon Enloe, and S. P. Wilkinson, Annu. Rev. Fluid Mech, 42, 505-529 (2010).\\[0pt] [2] M. Forte et. al. Exp. Fluids, 43, 917-928 (2007).\\[0pt] [3] A. R. Hoskinson, N. Hershkowitz, and D. E. Ashpis, J. Phys. D: Appl. Phys., 41, 245209 (2008). [Preview Abstract] |
Friday, November 18, 2011 11:15AM - 11:30AM |
TF1.00006: Numerical investigation of pulsed-driven DBD plasma actuator Alexandre Likhanskii, Mikhail Shneider, Richard Miles, Sergey Macheret Dielectric barrier discharge (DBD) plasma actuators are promising devices for flow separation control. The operation of conventional DBDs, driven by AC or pulses+bias voltage, is based on direct induction of momentum into boundary layer by transferring momenta from charged particles to neutrals. However, the maximum DBD induced flow velocity for the conventional DBD is limited to $\sim $10-20 m/s, since conventional DBD operates in corona regime. The way to overcome this limitation is to use ns pulses, which transfer much more momentum to the flow during discharge propagation (forward breakdown), as driving voltage. However, on the back slope of the ns pulse, the backward breakdown induces strong negative force on the gas, significantly decreasing to effect of forward pushing. The second problem is the surface charge accumulation, which is reported to be one of the major limiting factors for pulsed DBDs. In this talk, we will present numerical simulations of both forward and backward breakdowns for DBD plasma actuators using 2D/3D hybrid plasma simulation tool VORPAL. We will also discuss potential solutions for the backward breakdown elimination. [Preview Abstract] |
Friday, November 18, 2011 11:30AM - 11:45AM |
TF1.00007: Detonation Initiation by Gradient Mechanism in Propane--Oxygen and Propane--Air Mixtures Aleksandr Rakitin, Ilya Popov, Andrey Starikovskiy An experimental study of detonation initiation by high--voltage nanosecond gas discharge has been performed in smooth detonation tubes. A gradient mechanism was used to initiate detonations in stoichiometric propane--oxygen mixtures with different nitrogen dilution and in propane--air mixtures. Initial pressures from 0.2 to 1bar have been tested. Detonation was formed within 4 transverse tube sizes at initial pressures higher than 0.2 bar for the propane--oxygen mixture and higher than 0.8 bar for the diluted mixture with 40{\%} of nitrogen. The discharge energy inputs were 0.2---0.3 J. The gradient mechanism of detonation formation similar to the one suggested by Zeldovich has been shown to be the governing process. For the mixture with air, a detonation tube with an annular discharge chamber has been designed and tested. [Preview Abstract] |
Friday, November 18, 2011 11:45AM - 12:00PM |
TF1.00008: Experimental study and numerical simulation of flow separation control with pulsed nanosecond discharge actuator Guiseppe Correale, Ilya Popov, Andrey Nikipelov, Sergey Pancheshnyi, Seo Hulshoff, Leo Veldhuis, Andrey Starikovskiy Active flow separation control with a nanosecond pulse plasma actuator, which is essentially a simple electrode system on the surface of an airfoil, introducing low-energy gas discharge into the boundary layer, with little extra weight and no mechanical parts, was performed in wind-tunnel experiments on various airfoil models. In stall conditions the significant lift increase up to 30{\%} accompanied by drag reduction (up to 3 times) was observed. The critical angle of attack shifted up to 5\{7 degrees. Schlieren imaging shown the shock wave propagation and formation of large-scale vortex structure in the separation zone, which led to separation elimination. The experimental work is supported by numerical simulations of the phenomena. The formation of vortex similar to that observed in experiments was simulated in the case of laminar leading edge separation. Model simulations of free shear layer shown intensification of shear layer instabilities due to shock wave to shear layer interaction. [Preview Abstract] |
Friday, November 18, 2011 12:00PM - 12:15PM |
TF1.00009: Ignition of hydrocarbon--air mixtures with non--equilibrium plasma at elevated pressures up to 40 bar Aleksanrd Rakitin, Gueseppe Correale, Andrey Starikovskiy The possibility to control ignition of gaseous combustible mixtures under high pressures (20---40 bar) by (nonequilibrium) SDBD discharge has been shown experimentally in RCM tests. Discharge at high pressure developed as a streamer or as a spark, depending on the conditions and the geometry. SDBD--geometries enabled propagation of long sparks, up to 20 mm, even at high gas densities. The efficiency of nonequilibrium ignition increases towards the range of conditions close to the autoignition threshold. Under the threshold, higher energy input density is required. Under low temperature and low pressure conditions, the nonequilibrium discharge leads to the partial conversion of fuel--air mixture into stable intermediary species which facilitate ignition during the compression afterwards. [Preview Abstract] |
Friday, November 18, 2011 12:15PM - 12:30PM |
TF1.00010: A strategy to obtain the glow regime of a nanosecond repetitively pulsed discharge in air at atmospheric pressure and ambient temperature Fabien Tholin, Anne Bourdon For many current applications of atmospheric pressure plasmas, the challenge is to generate a glow discharge with a low gas temperature and a high chemical reactivity. Recent experiments have shown that the use of nanosecond repetitively pulsed (NRP) discharges was an efficient way for producing glow discharges in air at atmospheric pressure. However, so far, for a 10ns voltage pulse with a repetition frequency of 30kHz, a 5mm gap between point electrodes with a radius of curvature of about 200$\mu$m, it was possible to generate the NRP glow discharge regime only for temperatures higher than 750K. In this work, we have carried out numerical simulations using a 2D-axisymmetric fluid model of the discharge generated by a single voltage pulse in a point-to-point geometry to study the dynamics of the NRP discharge. Then, we have studied the influence of the electrode geometry, the applied voltage, the pulse duration, and the gas temperature on the discharge characteristics and regimes. The obtained simulation results have been compared to the available experimental results. Finally, we propose a set of conditions to obtain a glow regime of NRP discharges in air at atmospheric pressure and 300K. The authors thank the Agence Nationale de la Recherche for its support of the PREPA project. [Preview Abstract] |
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