Experimental study on frequency hopping of a self-excited pulse combustor

Frequency hopping phenomenon of a self-excited pulse combustor was experimentally studied and the regular of the frequency hopping with the power and equivalence ratio of this kind of combustor was measured. That is when the power of the combustor decreases to a certain critical value, the operating frequency of the combustor will hop from a fundamental frequency value to a higher harmonic frequency and if the power of the combustor is further decreased, the operating frequency of the combustor will decrease according to acoustics law at this harmonic wave, and vice versa; when equivalence ratio is higher, frequency hopping phenomenon will occur at higher power; too low in equivalence ratio may lead to unstable operation at the frequency hopping process. The mechanism of this phenomenon was analyzed by Rayleigh Criterion based on the experimental measurement results above and the effective controlling methods were presented as well.