Active Control of Combustion Dynamics for Lean Premixed Gas Fired Systems

Abstract

The present paper describes an active control system consisting of a fast-acting actuator valve, coupled with a control algorithm capable of adaptive phase and amplitude control for pressure oscillation suppression. Experiments were conducted using two separate combustion test rigs: a small, lean premixed, tubular combustor (75 kW) and a larger premixed annular DLE system (4 MW). Active control of pressure oscillations at frequencies of approximately 90 Hz and 300 Hz was demonstrated on the 75 kW rig. Up to 90% reduction in single-frequency dynamic pressure amplitude and 70% reduction in peak-mean was achieved. Simultaneous suppression of these two distinct modes was also demonstrated. The system was also demonstrated on a full-scale 4 MW combustion rig, with peak-mean dynamic pressure reductions between 33–45%. Instability reductions were achieved by pulsing fuel supplied to either a diffusion or a premixed flame. The response of the flame was notably better for the premixed case. For the premixed flame, combustor pressure pulses were realizable up to a frequency of about 400Hz, while the diffusion flame could only induce combustor pressure pulses up to approximately 50Hz. Adaptive frequency, phase and amplitude logic were developed, allowing automatic selection of the optimal values of these parameters to maximize suppression efficacy to suit the particular operating condition.