Ignition characteristics for transient plasma ignition of ethylene/air and JP-10/air mixtures in a Pulse Detonation Engine

Abstract

The inlet mass flow, fuel injection profile, igniter characteristics, ignition delay, and operational frequency all dictate the success of a Pulse Detonation Engine (PDE). An optical sensor was developed and utilized for the observation of ignition zone characteristics over varying refresh conditions that showed decreasing ignition delay times when approaching marginally fuelrich reactant mixtures. A wide range of equivalence ratios for ethylene/air mixtures were explored and a limited number of JP-10/air mixtures. The JP-10/air fuel mixtures were nearly impossible to ignite at characteristic velocities greater than 35 m/s until a porous ignition shield was installed. The porous shield, surrounding the Transient Plasma Ignition (TPI) electrode, demonstrated the successful ignition at characteristic velocities up to 100 m/s for C2H4/air and 55 m/s for JP-10/air mixtures. The ignition shield slowed down a portion of the fuel-air mixture to increase the local residence time, allowing for more reliable ignition. The resulting combustion products proceeded to ignite the remaining fuel-air mixture. The ignition shield design appears to locally prevent a complete purge of the previous cycle's products, and a transient plasma discharge was still required for subsequent ignition to occur. This effect further reduced the observed ignition delay time in ethylene/air and JP-10/air fuel mixtures.