Computational analysis on the stability and characteristics of partially premixed butane-air open flames in tubular burner

Abstract

Partially premixed combustion is one of the developing areas of combustion research that has the advantages of both premixed and diffusion mode of combustion. The present work involves a computational study on the stability and characteristics of partially premixed butane-air flames. The effect of operating parameters like fuel-air ratio, primary aeration, and the presence of co-flow and co-swirl on the stability and flame characteristics has been studied. The simulation results show that the height of the flame decreases with an increase in primary aeration and also in the presence of a co-swirl stream. It has also been found that the stability of flames increases with co-swirl air but deteriorates with the presence of the co-flow air. The flame temperature increases with primary aeration and it has been observed that the peak flame temperature shifts away from the burner mouth for lower primary aeration. It has been observed that the flame stability improves with co-swirl air which is attributed to the re-circulation zone created due to the swirl motion which acts as a heat source. The poor stability in the presence of co-flow air is attributed to flame stretching and aerodynamic quenching of the stretched flamelets. The lift-off velocity and the stable operating range increases with equivalence ratio and also with co-swirl air.