Active Combustion Control for a Low-Emissions Aircraft Engine Combustor Prototype: Experimental Results

Abstract

Lean combustion concepts for aircraft engines are more susceptible to combustion instabilities. Prior activity has demonstrated active control to suppress combustion instabilities with a conventional rich-front-end combustor. The current effort is developing further understanding of the problem specifically as applied to future lean-burning, very low-emissions aircraft engine combustors. A prototype low-emissions aircraft engine combustor with a combustion instability has been identified and previous work has characterized the combustor’s dynamic behavior. The combustor exhibits thermoacoustic instabilities related to increasing fuel flow that prevent full-power operation. Active combustion instability suppression using the adaptive sliding phasor average control method has been demonstrated experimentally with this combustor prototype in a combustion test cell operating at engine pressures, temperatures, and flows. A high-frequency fuel valve perturbed the combustor fuel flow. Successful instability suppression was shown using a dynamic pressure sensor in the combustor for controller feedback. Instability control was also shown with a pressure feedback sensor in the lower temperature region, upstream of the combustor. It was also demonstrated that the controller can prevent the instability from occurring while combustor operation was transitioning from a stable low-power condition to a normally unstable high-power condition, thus enabling the high-power condition.