The Effect of Lean Premixed Combustion on Thermoacoustic Instability in a Swirl Combustor

Combustion instability is a large amplitude oscillation of one or more natural acoustic modes of the combustion chamber. It is the outcome of advancement in the modern engine to reduce emission and fuel consumption by maintaining the lean equivalence ratio. It creates large amplitude pressure and velocity oscillation which results in thrust oscillation, severe vibrations, enhanced heat transfer, thermal stress, and failure of the system. In this work, a laboratory model swirl combustor with a lean mixture has been simulated to understand the mechanism of combustion instability. A 3D unsteady Reynolds-averaged Navier–Stoke numerical simulations are performed to understand the effect of lean premixed combustion on combustion instability. The results show that flame fluctuation due to lean premixed combustion leads to heat release oscillation. Heat release oscillation leads to pressure and velocity oscillation which results in combustion instabilities. The amplitude of pressure and velocity oscillation increases with time and finally become saturates. The numerical model is validated with experimental results.