The Noise-Producing Characteristics of Highly Loaded, Valveless, Pulse Combustors

Abstract

An inherent problem of pulsating combustors is noise generation and the difficulty of predicting noise levels. Analytical data are presented which illustrate the transient velocity profiles prevailing at the open ends of the inlets and tailpipes of valveless pulse combustors. A comparison is made of measured sound pressure level spectra at these locations with corresponding predicted transient velocity profiles. It is shown that there is a correlation of the main characteristics of the noise spectra and velocity profiles. Consideration is also given to the problems of muffling valveless pulse combustors and the potential, from the noise suppression viewpoint, of twin-coupled units and relatively high frequency pulse combustors featuring multiple inlet passages. An indication is also given of how it may be possible to operate clusters, or arrays, of pulse combustors firing sequentially.