Pressure Scaling Effects on Ignition and Detonation Initiation in a Pulse Detonation Engine

Abstract

An experimental study was done to examine the effects of elevated initial tube pressure in the Pulse Detonation Engine (PDE). Measured parameters were the ignition time, deflagration to detonation transition (DDT) run-up distance, DDT times, and ChapmanJouguet (C-J) velocity. Mixed with air, three fuels, i.e., aviation gasoline, ethylene, and hydrogen, were tested at various initial pressures and equivalence ratios. An aftermarket automotive ignition system was employed, along with two plasma ignition systems to quantify the benefits of each. Measured results show a reduction in the ignition time of roughly 50% and in the DDT distance of roughly 30%, for all three fuels at an initial tube pressure of 3 atmospheres. With atmospheric initial tube pressure, the transient plasma ignition system yielded the shortest ignition times, followed by the thermal plasma ignition system, and lastly the aftermarket automotive ignition system. At roughly 2 atmospheres of initial pressure the thermal plasma ignition system showed no benefit over the aftermarket automotive ignition system. C-J wave speeds have shown to increase with elevated initial pressure, and agree with numerical results. In addition to the experimental results, a brief Chemkin analysis was done to model the aftermarket automotive ignition system to estimate ignition times of the mixtures at pressures that were not tested.