Control of combustion instability with a high-momentum air-jet

摘要

An improved strategy for controlling combustion oscillations using a high-momentum air-jet that changes the reactant mixing process is presented in this paper. The oscillations in the swirl-stabilized spray combustor of interest are dominated by an acoustic mode (235 Hz) with a low-frequency (13 Hz) bulk mode (of the upstream cavity) oscillation superimposed. The bulk mode gives rise to an axial movement of the flame and leads to cyclic variations of the dominant mode time period. These cyclic variations lead to phase jitter and make control more difficult. The most effective strategy for maintaining control is shown to be achieved through the use of a new concept which utilizes a high-momentum air-jet injected directly into the regions of positive Rayleigh Index from where the instability originates. Improvements with this new strategy relative to the traditional fuel-modulation-based control are demonstrated.