The suitability of hydrocarbon fuels for plasma ignition in high-speed flow was numerically and experimentally investigated. Numerical analysis of ignition delay time showed that the effects of additions of radicals and NO x on ignition delay times of C 3 H 8 and dimethyl ether were very slight in comparison with those for C 2 H 4 . Ignition tests of C 3 H 8 and dimethyl ether fuels by a plasma jet torch in a supersonic flow confirmed such a low sensitivity to additions of radicals and NO x . The amounts of combustion of C 3 H 8 ignited by the plasma jet were smaller than that of C 2 H 4 , though ignition delay times of those fuels without radical addition were almost the same as that of C 2 H 4 . In the case of fuel injection upstream of the plasma jet, the amounts of combustion of C 3 H 8 and dimethyl ether fuels increased with the mole fraction of O 2 in the feedstock gas to the plasma jet torch, the same as with CH 4 and C 2 H 4 . This result indicates that the local O 2 concentration around the igniter is very important for success in attainment of strong combustion and flameholding in a high-speed flow.Nomenclature E.R. = equivalence ratio C = mole fraction P in = electric power input p t0 = total pressure of main flow p w = wall pressure p 0 = system pressure or initial pressure T 0 = initial temperature x i = position of fuel injector

No abstract