Effect of Atomization Quality on Lean Blow-Out Limits and Acoustic Oscillations in a Swirl Stabilized Burner

The present experimental work highlights the influence of atomization quality on lean blow-out (LBO) limits and acoustic oscillations in a swirl stabilized burner with simplex atomizer. With decrease in the initial spray droplet diameter, the LBO limit shifts toward lower equivalence ratios. Reduction in droplet size also strongly influences the mode of LBO from diffusion flame to premixed lifted flame. Correlations have been developed for the LBO limit, involving mainly the time scales for evaporation, reaction and residence times for the fuel drops, as well as the gas flow. Delay in evaporation causes vapor accumulation before combustion and hence it influences both acoustic oscillations and LBO limit. The frequency of acoustic oscillations locks-in with the quarter wave frequency of the combustor duct for all initial droplet diameters considered. The amplitude of acoustic oscillations decreases with decrease in the initial droplet size.