A dynamic combustion model for supersonic turbulent combustion

Supersonic combustion plays a vital role in various applications, including scramjets, dual-mode ramjets, and pulse detonation engines. However, the flame characteristics can vary significantly, depending on the application. To model supersonic combustion, large eddy simulation coupled with a partially stirred reactor (PaSR) is commonly used. This method assumes that reactions occur at turbulent fine flame structure in a computational cell, making it less effective for flames governed by not only turbulent mixing but also homogenous autoignition, which is common under supersonic flow. To address this limitation, this study proposes a novel dynamic combustion model to enable more versatile modeling of supersonic flames. The model utilizes a two-delta probability density function, which represents the sub-grid composition variation and models the filtered sub-grid reaction rate. The corresponding weights are dynamically modeled based on the level of cell composition inhomogeneity. The new dynamic model is tested in a supersonic combustion case study with a strut-cavity flame holder. Results demonstrate that the new dynamic model can properly recover the limits of supersonic flames that are primarily governed by homogenous autoignition and turbulent mixing.