Deflagration-to-Detonation Transition in Nitrous Oxide-Ethylene Mixtures and its Application to Pulsed Propulsion Systems

摘要

In the past several years nitrous oxide has been more widely considered as a "safe", clean oxidizer for rocket propulsion systems, that was useable as both a monopropellant or as a bipropellant. Therefore, the present work investigated the use of nitrous oxide and ethylene as a bi-propellant mixture at elevated pressures. Earlier work with this bipropellant mixture suggested that a steady detonation can be established in a combustion tube of larger L/d ratio and the associated flame acceleration prior to DDT could be studied more accurately. In order to use this bi-propellant mixture in a pulsed detonation engine quick flame acceleration is essential and this leads to a transition to detonation in a short duration of time. To study the flame acceleration and DDT behavior, tests were carried out in a combustion tube with L/d = 68 and detonation pressures were recorded using high pressure (100,000 psia) transducers. The detonation velocities were determined based on the time instances of measured pressure peaks and the distances between the transducers. Additionally, the pre compression observed in the combustible mixture before transitioning to a detonation was also studied and described in this paper. Finally, the run-up distances from these tests were determined and compared with values for different fuel-oxidizer mixtures from literature.