Large eddy simulation of combustion instabilities in multiple combustors densely interacting with each other

Abstract

Large eddy simulation (LES) of combustion instabilities in the can-annular gas turbine combustors are performed. Naturally occurring thermoacoustic instability is simulated in the can-annular combustors for the first time, and the resulting dynamic flames are investigated. Premixed swirl flames are generated in the two combustors, and the combustor-combustor interaction of pressure wave occurs in the cross-talk connecting each combustor. Both symmetric and asymmetric conditions are considered for explaining their effects on flame perturbation and instability mode during the operation. In the symmetric inlet condition, longitudinal pressure wave induces the flame fluctuation resulting in a push-push mode in the combustion system, which indicates that the instability phases in two combustors are identical. In the asymmetric case, an inlet velocity pulsation with an opposite phase of combustion instability is applied, which results in the suppression of instability and the attenuation of acoustic energy transferred to the whole system through the cross-talk. This work expands the scope of LES together with high-fidelity turbulent combustion models for addressing the combustion instability in the can-annular combustors. The results indicate that asymmetry in flow rate oscillations provides an effective actuation for the attenuation of combustion instabilities.