Ignition of hydrogen and hydrocarbon in a supersonic flow by simultaneous operation of DBD and PJ

Abstract

Ignition of hydrogen (H2) and hydrocarbon fuel such as ethylene (C2H4) in a supersonic flow by simultaneous operations of a dielectric barrier discharge (DBD) device and a plasma jet (PJ) torch were experimentally investigated. The DBD device generated non-equilibrium plasma while the PJ torch injected equilibrium plasma. They were in tandem arrangement installed on the bottom wall of the combustor. The main stream Mach number was 2.0, and the stagnation pressure and temperature were those of the atmospheric condition. Nitrogen was employed as feedstock gas of the PJ torch. Fuel was injected perpendicularly into the mainstream at the sonic speed from upstream of DBD device. The DBD device was discharged for generating of non-equilibrium plasma directly in the mainstream. The wall pressure on the top wall was measured for judgment of the success of ignition. For hydrogen fuel, it was clearly shown that simultaneous operation of PJ and DBD resulted in larger wall pressure increase than that without the DBD operation. Ignition and combustion of ethylene fuel occurred by the PJ with higher input power comparing with one required for hydrogen fuel. However, there was no clear difference in the wall pressure distributions by adding the DBD operation. The effect of ignition and combustion enhancement of ozone, which might be produced by the DBD operation, was numerical simulated in regard to hydrogen and ethylene. The ozone accelerates ignition reaction of a hydrogen/air and ethylene/air mixture as almost the same as O, H and N radicals. Even if the mole fraction of active species such as ozone was increased, the ignition delay time of ethylene was longer than hydrogen of it.