Active control of combustors after twenty years' efforts

Abstract

Active control of combustion was proposed by Bollay [1]. Following that idea, Tsien [2] worked out an analysis of controlling low-frequency oscillations in a liquid rocket but no successful experimental results followed. More than thirty years passed before the first laboratory demonstrations were performed at Cambridge University. Interest grew rapidly in the 1990s due to potentially wonderful applications to practical combustion systems including liquid and solid rockets, gas turbines, and thrust augmentors. Dreams have not materialized: There are presently no operational control systems, despite considerable efforts, and examples of partially controlled phenomena. Only one practical installation for control of oscillations has been documented, for a large Siemens machine [3]. Its use has been rendered unnecessary by further experimental work leading to development of successful passive control with modifications of hardware [4]. The purpose of this paper is to examine briefly some of the reasons that active control of combustion has failed to become the panacea widely anticipated two decades ago. The authors' view is that the subject is far from exhausted, but rather requires carefully planned research to understand the basis of successful applications.