Investigation of fluid motion in valveless pulse detonation combustor with high-frequency operation

The motion of a fluid in a valveless pulse detonation combustor (PDC) at an operating frequency of 500 Hz was investigated using a novel PDC, in which the inner diameter of the oxidizer feed line was equal to that of the combustor (inner diameter = 10 mm). Gaseous oxygen was supplied to the PDC in a valveless mode. In contrast, supercritical ethylene was injected into the PDC in a direction perpendicular to its axis. The flame propagation speed and backflow of the burned gas were measured using 12 ion probes in-stalled on the side wall. The measured flame propagation speeds in all the combustion tests were 107 +/- 4% of the Chapman-Jouguet detonation speed. In addition, the experimental results were compared with those of a one-dimensional numerical calculation. Under the condition that the stop time of the fuel injection was equal to the spark time, the trajectory of the backflowing burned gas was identical to the experimental results, within 7%. Shortening the burned-gas backflow process was found to be essential to achieve a higher operating frequency. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.