Operating characteristics of a hydrogen-argon plasma torch for supersonic combustion applications
01 Apr 1989-Journal of Propulsion and Power (American Institute of Aeronautics and Astronautics (AIAA))-Vol. 5, Iss: 2, pp 129-133
TL;DR: In this article, a low-power, uncooled hydrogen plasma torch has been built and tested to evaluate its potential as a possible flame holder for supersonic combustion, and the stability limits of the torch are delineated and its electrical and thermal behavior documented.
Abstract: The residence time of the combustible mixture in the combustion chamber of a scramjet engine is much less than the time normally required for complete combustion. Hydrogen and hydrocarbon fuels require an ignition source under conditions typically found in a scramjet combustor. Analytical studies indicate that the presence of hydrogen atoms should greatly reduce the ignition delay in this environment. Because hydrogen plasmas are prolific sources of hydrogen atoms, a low-power, uncooled hydrogen plasma torch has been built and tested to evaluate its potential as a possible flame holder for supersonic combustion. The torch was found to be unstable when operated on pure hydrogen; however, stable operation could be obtained by using argon as a body gas and mixing in the desired amount of hydrogen. The stability limits of the torch are delineated and its electrical and thermal behavior documented. An average torch thermal efficiency of around 88 percent is demonstrated.
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TL;DR: A comprehensive overview of the progress and the gap in the knowledge of plasma assisted combustion in applications, chemistry, ignition and flame dynamics, experimental methods, diagnostics, kinetic modeling, and discharge control is provided in this paper.
812 citations
TL;DR: In this article, the thermal and kinetic effects of O(sub 3) on flame propagation were investigated experimentally and numerically by using C{sub 3}H{sub 8}/O(sub 2}/N{sub 2}) laminar lifted flames.
332 citations
TL;DR: In this paper, a counterflow system for CH 4 -air and H 2 -air diffusion flames by a nonequilibrium plasma discharge of air was studied experimentally and numerically through the development of a well-defined counter flow system.
Abstract: Kinetic ignition enhancement of CH 4 -air and H 2 -air diffusion flames by a nonequilibrium plasma discharge of air was studied experimentally and numerically through the development of a well-defined counterflow system. Measurements of ignition temperatures and major species, as well as computations of rates of production and sensitivity analyses, were performed to understand the kinetic enhancement pathways for ignition by plasma discharge of air. It was found that plasma discharge of air led to significant kinetic ignition enhancement illustrated by large decreases in the ignition temperatures for a broad range of strain rates. Examination of the radical and NO x production in the plasma showed that the enhancement was caused primarily by the catalytic effect of NO x . The results of numerical simulations of the counterflow burner with preheated air and NO, addition showed the existence of different ignition regimes, which appeared due to the competition between radical production by NO x and other pathways, as well as heat release. There were two ignition regimes for small concentrations of NO, and three ignition regimes for large concentrations of NO,. Numerical simulations agreed well with the experimental measurements and suggested a new strategy for plasma-assisted ignition in supersonic flow, where a combination of thermal and nonthermal plasma would work more efficiently for ignition enhancement.
100 citations
TL;DR: A review of fundamental research in combustion stabilization for hypersonic airbreathing propulsion is presented in this paper, which outlines both experimental and numerical research progress made towards combustion stabilization over the entire hypheratic regime, and intended to lay the groundwork for further studies which can provide optimized design guidelines for the next generation of high-speed air-to-air propulsion systems.
88 citations
TL;DR: A comprehensive overview of the progress and the gap of knowledge of plasma assisted combustion in applications, chemistry, ignition and flame dynamics, experimental methods, diagnostics, kinetic modeling, and discharge control can be found in this paper.
71 citations
References
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TL;DR: In this article, the radicals are generated in the igniting plasma, rather than by using chemical energy, and the volume of the "pre-chamber" of the stratified charge or torch ignition concept is shrunk to a very small space within the plug, where a very high temperature, resulting in high ejection velocity, is produced by means of a small amount of electrical energy.
Abstract: IN order to improve the emission characteristics and efficiency of internal combustion engines, the trend is to leaner mixtures. Successful combustion at lower fuel : air ratios requires increased rates of flame propagation and, in spark-ignited engines, more effective and reliable ignition sources. Various avenues of research are being pursued towards these aims. One which shares the philosophy of radical injection with the present work is the stratified charge or torch-ignition concept (see ref. 1 for review). This is based on burning a rich mixture in a cavity small by comparison with the cylinder volume so that the free radicals generated therein are ejected into the main charge, there to increase the propagation rate in a leaner mixture. In the work described here the radicals are generated in the igniting plasma, rather than by using chemical energy, and the volume of the ‘pre-chamber’ of the stratified charge or torch ignition concept is shrunk to a very small space within the plug, where a very high temperature, resulting in high ejection velocity, is produced by means of a small amount of electrical energy.
101 citations
01 Jun 1984
TL;DR: In this article, the authors explored the use of a continuous operation plasma torch as an ignitor and flameholder for scramjet combustion and found that it was a good flameholder in that both hydrogen and hydrocarbon fuels could be stabilized by the torch.
Abstract: The objective of the work reported herein was to explore the use of a continuous operation plasma torch as an ignitor and flameholder for scramjet combustion. This research was motivated by the desire to eliminate the use of pyrophoric or toxic ignition and/or combustion enhancement materials in operational aircraft or shipboard systems. The total temperatures and torch powers used to ignite/flamehold Mach 2 combustion with hydrogen, ethylene, ethane, and methane were determined. The minimum ignition total temperatures for the fuels tested were hydrogen - 1065 R (lowest test temperature); ethylene - 1500 R; ethane - 2000 R; methane - 2700 R. These temperatures were obtained while operating the torch at a nominal 2 kw net power. The torch was shown to be a good ignitor and flameholder in that both hydrogen and hydrocarbon fuels could be stabilized by the torch and would 'blow off' when the torch was extinguished. The effectiveness of the torch was very sensitive to relative fuel injection location. Best combustion resulted when fuel was injected both upstream and downstream of the torch. These results indicated that an adiabatic plasma torch operating at about 2 kw could be an effective ignitor and flameholder for high-speed combustion.
41 citations
01 Jan 1985
TL;DR: Pulsed and continuous flow plasma jets are used to achieve ignition and flame holding in fast flowing lean hydrocarbon/air streams in this article, where they demonstrate the contribution of radicals to successful ignition of sub-limit propane air streams.
Abstract: Pulsed and continuous flow plasma jets are used to achieve ignition and flame holding in fast flowing lean hydrocarbon/air streams. Small, steady-flow nitrogen plasma jets with electrical inputs of the order of 1 kW and sonic flow through their nozzles stabilize flames well below the lean limit of flammability for propane, in complete contrast to argon plasmas. Pulsed plasma jets of the surface discharge type also demonstrate the contribution of radicals to successful ignition of sub-limit propane air streams. This is achieved with plasma media ioncluding water and hydrocarbon fuel. The variation of the limit of incendividity with repeated discharges following a single wetting of the plug with the plasma medium shows very long lasting effects and contributes to the understanding of mechahisms. The potential practical applications of these observations are discussed.
32 citations
01 Jan 1985
TL;DR: In this paper, the potential utility of the low power dc arcjet in auxiliary propulsion was investigated and it was indicated that improvements in the areas of stability, energy efficiency, reliability, and electrode erosion are necessary to obtain a useful device.
Abstract: The potential utility of the low power dc arcjet in auxiliary propulsion was investigated. It was indicated that improvements in the areas of stability, energy efficiency, reliability, and electrode erosion are necessary to obtain a useful device. A water-cooled arcjet simulator was tested to investigate both the energy loss mechanisms at the electrodes and the stability of different conventional arcjet configurations in the presence of a vortex flow field. It is shown that in certain configurations only 25 to 30% of the input energy is lost to the electrodes. It is also shown that vortex stabilization is not difficult to obtain in many cases at the flow rates used and that a careful starting procedure is effective in minimizing electrode damage.
11 citations
01 Sep 1985
TL;DR: In this paper, an experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster, and the electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW.
Abstract: An experimental investigation was performed in an effort to measure and increase lifetime of electrodes in an arcjet thruster. The electrode erosion of various anode and cathode materials was measured after tests in an atmospheric pressure nitrogen arc discharge at powers less than 1 kW. A free-burning arc configuration and a constricted arc configuration were used to test the materials. Lanthanum hexaboride and thoriated tungsten had low cathode erosion rates while thoriated tungsten and pure tungsten had the lowest anode erosion rates of the materials tested. Anode cooling, reverse gas flow, and external magnetic fields were all found to reduce electrode mass loss.
4 citations