Feasibility of Pulsed Microwave Plasma Ignition for Use in SI-Engines

Ignition of the fuel-air mixture through compression and spark ignition are the two basic methods for igniting combustion mixtures in modern internal combustion (IC) engines. A significant environmental and economic benefit could be obtained if spark ignited (SI) engines were to be made more efficient. Higher thermal efficiencies could be obtained through operation with leaner fuel-air mixtures and through operations at higher power densities and pressures. These types of mixtures are often more difficult to ignite with traditional spark plugs. In pursuit of better ignition sources, this paper investigates a microwave plasma alternative to the traditional spark plug. Additionally, measurements of a novel pulsed microwave induced plasma ignition concept are presented. Measurements at atmospheric pressures show promising results with respect to energy and plasma formation delay. With some refinement, it is possible to produce sufficiently energetic microwave discharges, in a short enough time frame to make them feasible for ignition of SI engines in an automotive setting. These results justify further investigation to quantify the advantages such an ignition source may have to offer.