Development of high-frequency pulse detonation combustor without purging material

A novel method for the operation of a pulse detonation combustor is proposed and demonstrated for realizing high frequencies without using a purging material. In the developed operation method, oxygen is supplied to the pulse detonation combustor in the valveless mode. Fuel, which is supercritical ethylene, is injected into the pulse detonation combustor at a suitable timing using an automotive fuel injector. Because of the Joule-Thomson effect, a phase transition of ethylene from the supercritical state to a low-temperature vapor occurs, and a detonable mixture is produced by mixing with oxygen. In demonstration experiments, a small pulse detonation combustor having an inner diameter of 10 mm, a total length of 190 mm, and an inner volume of 14.5 mL is used, and the operation frequency varies between 100 and 500 Hz. The measured flame propagation speeds are 107 ± 6% of the Chapman-Jouguet detonation speed. In addition, the operation frequency of 500 Hz is 41% of the gas-dynamic upper limit, which is obtained using the one-dimensional model proposed by Endo et al.