Numerical Simulation of Open Active Control of Low Frequency Combustion Instability Related to Vortex Shedding in Model Ramjet Dump Combustor

Abstract

Ramjet dump combustors exhibit undesirable low frequency combustion instabilities related to vortex shedding under certain operating conditions. A lot of control methods are devoted to suppress combustion instabilities. This paper provides numerical investigations to basic mechanism of low frequency instabilities and open active control approaches that prevent low frequency combustion instabilities, which include air injection and gas suction. Large-eddy simulation (LES) and reduced kinetic mechanism combustion model have been efficiently implemented to study these open active control strategies. The results show large vortex structures propagating play a key role in low frequency unsteady combustion. Air injection and gas suction methods are both effective to suppress pressure oscillations, 34% and 55% reduction of pressure oscillations respectively, through change reactant mixing process and prevent large vortex form.