Hot Combustion Torch Jet Ignition Delay Time for Ethylene-Air Mixtures

Abstract

Ignitability and the ignition delay time of ethylene-air mixtures, ignited by a hot gas jet generated from combustion in a pre-chamber were investigated experimentally. The jet enters one end of a long combustion chamber, consistent with seeking a viable igniter method for wave rotor combustors. A numerical simulation of jet penetration and mixing in the main chamber provided guidance in testing and interpretation. The ignitability limits were established and ignition delay times were measured for a range of equivalence ratios. Chemical kinetics and mixing between the combustion torch jet and the combustible mixture both appear to be important in determining ignition delay times. This is in contrast with chemical ignition delay studies using shock-heated ignition techniques. Ethylene-air mixtures proved to be ignitable for initial premixed equivalence ratios ranging from 0.4 to 2.4, with the shortest ignition delay times of about one millisecond occurring for lean nearstoichiometric mixtures. The ethylene-air ratio of the combustion torch jet affected the ignition delay time in the main chamber combustible mixture, with the slightly rich prechamber mixtures providing the lowest delay times in igniting the main chamber ethyleneair mixtures.