An investigation of a coaxial spark igniter with emphasis on its practical use

Abstract The dynamics and properties of a small jet of plasma produced by allowing a pulsed discharge to expand from a cylindrical cavity have been investigated. A model has been developed, which is based on the premise that the spark heats the gas within the cylinder and produces a supersonic, strongly asymmetric pressure wave propagating, essentially in one direction only, into the cold surrounding gas. Quantitative measurements of the properties of this plasma jet agree reasonably well with the model. Experimental measurements on a propane-air flame and a gasoline internal combustion engine indicate that this device may, in a practical sense, be useful for igniting fuel lean combustion.