Pulse Combustion: Demonstration of the Characteristic Mixing Time in a Commercial Burner

Abstract

The response of a prototype Helmholtz-type commercial pulse combustor to changes in two fundamental characteristic times has been investigated both experimentally and numerically. The natural resonant frequency and the fluid dynamic mixing geometry were modified separately. The response of the combustor to these changes was determined by measurements of pressure, frequency, and OH· chemiluminescence. The combustion chamber volume was modified to change the resonant frequency of the combustor. Changes in the fluid dynamic mixing time were obtained by injecting premixed reactants axially and then temporally and spatially modifying the injection profile by varying the geometry of a novel injection system. A wide dynamic range in pressure amplitude and frequency was obtainable by changing the characteristic fluid dynamic mixing time. Results from systematic changes in these two parameters compare well with the results from the numerical model of a pulse combustor that has been developed at Sandia National Laboratories.