Heat Release Dynamics Modeling for Combustion Instability Analysis of Kinetically Controlled Combustion

We present a heat release dynamics model which utilizes a well-stirred reactor (WSR) model and one-step kinetics to describe the unsteady combustion process. The model incorporates the linearized mass and energy equations to describe the response of the reactor to external perturbations, and is cast in the form of a first order filter. The model is able to predict the phase between the mass flow rate oscillations and the resulting heat release fluctuations, as function of the operating conditions, e.g., the mean equivalence ratio and mean mass flow rate. The model predicts a sudden shift in phase in the region between the maximum reaction rate and the blow-out limit. We show that this phase change may trigger combustion instability. We use this novel model to predict combustion instability conditions in high swirl combustion, and demonstrate that these predictions agree qualitatively with experimental studies.