Laser-induced spark flameholding in supercritical subsonic flow

Abstract

Laser-induced spark e ameholding was demonstrated, and the effect of e ow and optical parameters on the e ameholding distance was investigated. A pulsed Nd:YAG laser was used to induce electrical breakdown in a e ow and ignite a methane/air gas mixture. The laser energy, pulse frequency, and methane concentration were varied, and the e ameholding distance as a function of these parameters was determined. Results were then compared to calculated values. For a e ow speed of approximately 110 cm/s and a laser repetition rate of 15 ‐ 20 Hz, the e ameholding distance, dee ned as the downstream distance from the spark to the position where continuous combustion is achieved, was found to be on the order of a few centimeters. Experimental results were extrapolated to determine the pulse frequencies required for e ameholding at hypersonic e ow speeds. The potential application of solid-state, continuous-wave lasers to spark e ameholding is also considered.