Development of high-frequency pulse detonation combustor without purging material

A novel method for the operation of a pulse detonation combustor (PDC) was proposed and demonstrated for realizing pure fuel-oxygen combustion at high frequencies without using a purging material. In the developed operation method, a gaseous oxidizer (oxygen) is supplied to the PDC in the valveless mode. Fuel, which is supercritical ethylene, is injected into the PDC at a suitable timing using an automotive fuel injector. flowing to an irreversible isenthalpic change, which is called 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 PDC having an inner diameter of 10 mm, a total length of 190 mm, and an inner volume of 14.5 mL was used, and the operation frequency was varied between 100 and 500 Hz. The measured flame propagation speeds were 107 ± 6% of the Chapman–Jouguet detonation speed. In addition, the operation frequency of 500 Hz was 41% of the gas-dynamic upper limit, which was obtained using the one-dimensional model proposed by Endo et al. [AIAA J., Vol. 42, No. 9, 2004, pp. 1921-1930].