Frequency and spark timing effects on thrust for pulse detonation engine

An experimental study was performed on an ethylene/oxygen/air pulse detonation engine to examine the effect of frequency and spark delay time on the thrust output and efficiency. Reactants were mixed in a stainless-steel combustion chamber at frequencies ranging from 1 to 40 Hz. Dynamic pressure measurements were recorded throughout the system over the testing interval to determine exhaust velocities. Efficiency was evaluated based on the experimental average frequency and the experimental average velocity. Results on experimental thrust, detonation frequency, and Chapman-Jouguet velocities were analyzed. It was observed that average thrust increased exponentially with the increase of detonation frequency. For a spark delay time of 2 ms, maximum efficiency and thrust were achieved for given frequencies. As spark delay time increased beyond 6 ms, testing became erratic, with pulses misfiring, and a decrease in efficiency and thrust was observed until no combustion occurred beyond a spark delay time of 8 ms.