Combustion enhancement in a supersonic flow by simultaneous operation of DBD and plasma jet

A new strong ignition system combining a plasma jet (PJ) torch and a Dielectric Barrier Discharge (DBD) device in a supersonic flow was developed in this study. The DBD device, which generates nonequilibrium plasma and the PJ torch, which injects equilibrium plasma jet were installed straight on the bottom wall of the combustor. Nonequilibrium plasma was successfully generated in a supersonic flow by DBD. Discharge power of DBD was at most 10 W, and it was considerably smaller than that for the PJ. Ignition test of hydrogen fuel perpendicularly injected into a supersonic airflow was conducted under simultaneous operation of the DBD device and the PJ torch. Although ignition never occurred by single operation of the DBD device in a non-heated supersonic flow, combustion enhancement effect by DBD on relatively weak and unstable flame was detected by simultaneous operation of it with the PJ torch. However, the combustion enhancement did not occur in a flow field where strong combustion occurred with only the PJ. The main mechanism of combustion enhancement by the DBD plasma was considered to be existence of O-3. The O-3 has a much longer lifetime than the other species and it accelerates ignition reaction of a H-2/air mixture as almost the same as O radical. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.