Effect of Burner Geometry on Heat Transfer Characteristics of an Impinging Inverse Diffusion Flame Jet with Swirl

Abstract

An experimental investigation is carried out on an inverse diffusion flame (IDF) burners having central air jet and being surrounded by fuel jets for an impingement heat transfer. A thorough investigation has been performed to study the effects of the diameter of air jet, orientation of fuel jets and swirl in the central air jet on an inverse diffusion flame shapes, mainly on heat transfer characteristics. The twisted tapes of twist ratios (TR) 2.5 and 3.75 (corresponding to the swirl numbers of 0.62 and 0.41) are used for two different IDF burners to create a swirling flame jet. A comparison is made between the two IDF burners for with and without swirl conditions operating at a fixed air jet Reynolds number (Rea) of 2000 and equivalence ratio (ϕ) varying from 0.4 to 1.4 for a fixed burner surface to impingement plate distance of 20 mm. It is observed that for the same operating conditions, diameter of an air jet and orientation of fuel jets impart a substantial change in an inverse diffusion flame behavior by enhancing air–fuel mixing intensity. The experimental results show that the burner with smaller air jet diameter along with swirl produces a higher heat transfer rate to an impingement plate. An experimental work provides a contribution to improve a combustion characteristic of IDF for impingement heating on a flat surface.