Frequency control in unstable and pulse combustors

Abstract

The main objective of the experimental and theoretical investigations reported in this paper has been to develop capabilities for controlling the behavior of unstable and pulse combustors. In pursuit of this objective, the dependence of an unsteady combustor behavior upon the phase difference between the heat release rate and pressure oscillations has been investigated. Propane-air mixtures were burned in a two dimensional combustor and the phase of the heat release rate oscillations was varied by changing the relative positions of two circular flame holders which stabilized the combustion process. The combustor performance was determined from CH radiation and acoustic pressure measurements. Simultaneously, a theoretical model of the investigated combustor has been developed and used to predict the dependence of the excited combustor pressure oscillations upon the unsteady heat release rate. Trends predicted by the model are in qualitative agreement with measured data. The results of this study are consistent with existing approaches for controlling the oscillations in unstable and pulse combustors.