Performance enhancements on a pulsed detonation rocket

A major problem applying detonations, into aero-propulsive devices is the deflagration to detonation transition, or DDT. The longer the DDT, the longer the physical length of the engine must be to facilitate the propagation of the flame as it transitions into a detonation. However, lengthening of the detonation chamber can significantly increase weight, rendering the reduction of DDT length of great importance. One of the most common means of shortening DDT lengths is with the aid of a Shchelkin spiral. A simple helical apparatus, it was used in early single-shot detonation investigations to over-exaggerate wall roughness effects. It was through empirical investigations that the reduced DDT phenomenon was observed. The present investigation explored the possibility of applying such an apparatus into an intermittent pulsed detonation device. Results show significant improvements in comparison to cases without the spiral. Tests through a range of cycle frequencies up to 20Hz in oxygen-propane mixtures at 1atm demonstrated the feasibility of the Shchelkin spiral in a pulsed mode.