Effects of externally applied pulsations on LPG flames at low and high fuel flow rates

Abstract

The effects of externally applied pulsations on jet diffusion flames and premixed flames of LPG have been investigated experimentally. The external pulsations were generated by providing up-down motion to a piston by a cam and follower arrangement. The characteristics of flame were studied with and without pulsations. The videos of flame were captured by a high speed digital camera and converted to digital images which were then processed to obtain flame properties such as diffusion and partially premixed flame lengths, flickering frequencies and amplitudes. The flames were observed to oscillate in ‘tip flickering’ mode for both diffusion and partially premixed flames at low fuel flow rates. At high fuel flow rates, the flames were observed to oscillate in ‘bulk flickering’ mode for both diffusion and partially premixed flames involving the detachment of a flamelet in every cycle. For the buoyancy-dominated diffusion flames at high fuel flow rate, significant interactions occur between the sinuous shear layer mode of oscillation and external pulsations, resulting in modulations of the flickering frequency as well as the amplitude of fluctuation in flame length. In the case of partially premixed flames which are inertia-dominated, flickering frequency remains invariant for the cases with and without pulsations at high fuel flow rate.