Ignition by Combustion Jets under Supersonic Methane/Air Streams

Abstract

Ignition tests of methane fuel under supersonic air streams were conducted with the methane/oxygen combustion jets as an ignition source. The ignition capability of the combustion jets differed with their equivalence ratio φ; ignition at Mach 2 was successful at 2.4kW calorific input power with φ=0.3 jets while 6.5kW power was needed at stoichiometry (φ=1.0). Numerical calculations revealed the relative effectiveness on shortening the ignition delay times for methane/air mixture between active radicals such as H, O, and OH and ordinary oxygen gas O₂ abundantly contained in the lean combustion jets. These results overall suggest that ignition by the methane/oxygen combustion jets has an advantage in simplicity from the practical viewpoint over the plasma jet method which needs a heavy electrical power source.