Swirl number effect on the flame dynamics and combustion instabilities; computational studies using LES

Swirl combustion presents the advantages of enhanced turbulent mixing and thus, it enhances the combustion efficiency. However, the swirl combustion poses significant challenges associated with the flame instability. Over decades, extensive experimental and computational studies of swirl combustion have been performed. The experimental studies of swirl combustion are quite challenging due to the unsteady nature of the combustion process. To overcome these challenges, computational studies have been used in the study of turbulent combustion. The present study concerns the effect of the swirl number on the combustion efficiency and flame stability. The combustion efficiency is assessed based on the temperature developed inside the combustion chamber and NOx levels. The effect of air/fuel blowing ratio on the combustion efficiency and instability is also investigated in this research. The computations are carried out using the large-eddy simulation (LES) approach along with the flamelet combustion model. The analysis reveals the unsteady nature of the flame and thus, its departure from the core of the combustor. The analysis also reveals the presence of a region of high level of temperature, NO and CO₂, inside the combustor.