Investigation of High-Frequency Pulse Detonation Cycle with Fuel Phase Transition

To achieve the pulse detonation (PD) operation at high frequency, it is essential to shorten deflagration-to-detonation transition (DDT). Increasing the initial pressure of detonable mixture is a valid way to solve this problem. Then, we carried out the PD operation at 1010 Hz with the total pressure of supplied oxidizer changed. A combustor having the length of 100 mm and the inner diameter of 10 mm was used, and pure oxygen and supercritical ethylene were used as propellant. The PD operations at 1010 Hz were successful, and the decrease of DDT distance by approximately 50% was confirmed by increasing the initial pressure of detonable mixture by 242%. In addition, PD operation at higher frequency was demonstrated. With a combustor which has the length of 60 mm and the inner diameter of 10 mm, seven-cycle PD operation at 1916 Hz was carried out, and the average of measured flame propagation speed was in good agreement with the estimated detonation speed.