Bulletin of the American Physical Society
2005 58th Gaseous Electronics Conference
Sunday–Thursday, October 16–20, 2005; San Jose, California
Session BM1: Plasma Propulsion and Combustion I |
Hide Abstracts |
Chair: L. Vuskovic, Old Dominion University Room: Doubletree Hotel Pine |
Monday, October 17, 2005 8:00AM - 8:30AM |
BM1.00001: Micro plasma thruster for small spacecraft Invited Speaker: A microplasma thruster of electrothermal type has been proposed using azimuthally symmetric microwave-excited plasmas, which consists of a microplasma source and a micronozzle. The microplasma source is made of a dielectric chamber 2 mm in inner diameter and 10 mm long covered with a metal grounded, producing high temperature plasmas at around atmospheric pressures. The micronozzle has a throat 0.2 mm in diameter, converting high thermal energy of plasmas into directional kinetic energy of supersonic plasma flows. First, we have developed a numerical model for microwave-excited microplasmas in Ar and plasma flows in the micronozzle. The model consists of three modules: a volume-averaged global model and an electromagnetic model for microplasma sources, and a two-temperature fluid model for micronozzle flows. Numerical results indicated that the microwave power absorbed in plasmas increases with increasing microwave frequency $f$ and relative permittivity \textit{$\varepsilon $}$_{d}$ of dielectrics, and that a certain combination of frequency and permittivity significantly increases the power absorption. The micronozzle flow was found to be heavily affected by viscous dissipation in thick boundary layers, indicating that shortening the nozzle length with increasing half-cone angles suppresses the effects of viscous loss and thus enhances the thrust performances. A thrust of 2.5-3.5 mN and a specific impulse of 130-180 s were obtained for a given microwave power range ($P_{t}<$10 W), which is applicable to a station-keeping maneuver for microspacecraft less than 10 kg. Moreover, we have developed a microwave-excited microplasma source, based on the model analysis, with mullite (\textit{$\varepsilon $}$_{d}\approx $6) and zirconia (\textit{$\varepsilon $}$_{d}\approx $12-25) being employed for dielectrics. Experiments were performed at $f$=2 and 4 GHz,$ P_{t}<$10 W, Ar flow rate of 50 sccm, and microplasma chamber pressure of 10 kPa. Optical emission spectroscopy and Langmuir probe measurement were employed for diagnostics of microplasmas, indicating that the ArI emission intensity and plasma density $n_{e}$ increase with increasing $f$ and \textit{$\varepsilon $}$_{d}$, and that the $n_{e}$ is in the range 10$^{12}-$10$^{13}$ cm$^{-3}$. Moreover, the rotational temperature $T_{rot}$ of N$_{2}$ added was in the range 1100-1500 K, and the specific impulse estimated was about 70s. [Preview Abstract] |
Monday, October 17, 2005 8:30AM - 9:00AM |
BM1.00002: Diode Laser Diagnostics for Combustion Environments Invited Speaker: The current state-of-the-art in hypersonic air-breathing propulsion system development relies heavily on a combination of ground tests and numerical simulations. Generally, wall measurements (e.g., pressure, temperature, and heat flux) dominate the instrumentation suite available in most ground test facilities. If in-stream information (usually pitot pressure) is available, it is usually sparse and is generally available only at the inflow and outflow planes of the test article. While valuable for various analyses, these types of information provide little or no detailed descriptions of the mean and turbulent velocity fields, the turbulence-chemistry interactions, or the local state properties within the device. Advanced laser-based techniques can provide this information but impose significant challenges on test article design which are not practical for flight systems. The aim is to develop simpler diode laser based techniques which are practical in terms of weight, power, and optical access requirements. The presentation will outline some of the key issues relating to the development and application of these techniques to plasma and combustion environments. [Preview Abstract] |
Monday, October 17, 2005 9:00AM - 9:15AM |
BM1.00003: Development of Micro Hall Thruster Tsuyohito Ito, Nicolas Gascon, Mark Cappelli There is a growing need for advanced propulsion options for small spacecraft. Hall plasma thrusters have intrinsic properties that are attractive for potential Micropropulsion applications -- high thrust densities; minimal space charge effects; the discharge is stable over a wide range of input parameters; and the thrust and specific impulse is throttled by varying the discharge voltage. In this study, we are developing a micro-Hall plasma thruster with an operating power of less than 50W. The channel has a 4 mm outer diameter and a Sm-Co magnet is employed for generating the nearly 1T magnetic field strength required for the scaling of these thrusters to low power. I-V curves with the discharge operating on Xe propellant have been measured and the characteristic breathing-mode oscillations have been observed, as expected, at higher frequency in comparison to higher power thrusters. The first prototype studied is actively cooled, and no detrimental damage to thruster components was observed in the operating conditions explored. Ongoing studies include the measurements of near-field ion energy distribution using a retarding potential analyzer. [Preview Abstract] |
Monday, October 17, 2005 9:15AM - 9:30AM |
BM1.00004: Fuel Oxidation and Ignition in Premixed Hydrocarbon-Air Flows by Nonequilibrium Plasmas Igor Adamovich, Ainan Bao, Guofeng Lou, Munetake Nishihara, J.William Rich, Walter Lempert We present nonequilibrium RF plasma assisted combustion experiments in ethylene-air and methane-air flows using FTIR absorption and visible emission spectroscopy. Results show highest oxidation efficiency ($\sim $100{\%} of ethylene and $\sim $70{\%} of methane) under conditions which do not produce a flame (T=250-300$^{\circ}$ C). Under these conditions, oxidation occurs by plasma chemical reactions which differ from those leading to ordinary thermal combustion. These results, combined with previous measurements demonstrating very low temperature ignition, suggests the following nonequilibrium plasma ignition mechanism: (i) plasma generation of active radical species, (ii) plasma fuel oxidation with participation of these radicals, (iii) heating by net exothermal fuel oxidation, and (iv) ordinary thermal ignition and combustion. Emission spectroscopy shows that O, H, and OH emission intensities are highest in lean fuel-air mixtures, when a significant fraction of fuel is oxidized by plasma chemical reactions without producing ignition. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700