Effect of coolant on wall heat flux in premixed turbulent combustion

Inside the engine combustor, addition of the coolant from the wall makes the physics of flame-wall interaction (FWI) even more complex. Considering the application relevance, wall heat flux is analyzed and modeled. Under various flow conditions, the model predictions satisfactorily match the direct numerical simulation (DNS) results. The effects of coolant on the entrained flame and head-on flame are clearly different. Statistics of the near-wall flame orientation and curvature are sensitive to the coolant blowing ratio (BR). The entrained flame is more likely to be swept away, while the head-on flame is more stable. Both the model and simulation indicate consistently that an increase in BR, although quantitatively small, will greatly reduce the wall heat flux induced by the head-on flame. In contrast, the change of wall heat flux induced by the entrained flame is much smaller. Since most of the near-wall flame is head-on, the BR effect is significant. Additionally, in an a priori large eddy simulation (LES) study, the model predictions show better consistency with DNS, in comparison with the most commonly used turbulence sub-grid models.