Large-eddy simulation of a lean-premixed hydrogen flame in a low-swirl combustor under combustion instability

Large-eddy simulation (LES) of a lean-premixed hydrogen turbulent jet flame with combustion instability (CI) in a low-swirl combustor (LSC) is performed by employing a dynamically thickened flame model with a detailed chemical reaction model with 9 chemical species and 20 reactions, and the LES validity and the CI characteristics are investigated in detail. The results show that the present LES can accurately reproduce the experimentally observed characteristics of the CI such as intensity, frequency, sporadic decay of pressure oscillations, and a flame-flow interaction inducing the periodic transitions of an inverted conical flame structure and a flat flame structure in the LSC. The sporadic decay of pressure oscillations and the flame-flow interaction are caused by the temporal decoupling of pressure and heat release rate and the periodic outward and inward deflections of the inflow, which is associated with the flow behavior in the upstream injector channel, respectively.