Abstract
Heat transfer by flame jet impingement is widely used in many of the industrial and domestic applications like heating metal bars, scrap melting, shaping the glass, metal slab cutting, domestic cooking and others. Aim of the present experimental work is to study an effect of swirl on a local heat flux distribution of an inverse diffusion flame (IDF) jet impinging on a flat target surface in a coaxial tube burner. The twisted tape of twist ratio 3 (corresponding to the swirl number, S = 0.52) is used to create a swirl in the central air jet of the burner. The flame shapes and heat flux distributions are compared for the with and without swirling IDF under the different air jet Reynolds number (Rea) of 1000 to 2500, equivalence ratio (ϕ) of 0.4 to 1.3 and a burner-to-impingement plate distance (H) of 10 to 100mm. The distributions of heat fluxes are studied within a radius of 75 mm from the point of stagnation on an impingement plate. Results show that the swirling IDF helps in clean combustion of the fuel with much shorter flame height. Swirling in the flame jet enhances the peak heat flux for the higher air jet Reynolds number for slightly fuel rich conditions of ϕ = 1.1 at the optimal burner-to-target plate distance of 40 mm.
Highlights
Gaseous combustion is used in industries for many of the applications due their better convective heat transfer
The distribution of heat flux along the radius on the target surface is studied for a different air jet Reynolds number
Impinging Flame Shapes The photos of an impinging flames of an inverse diffusion flame coaxial tube burner at varying Rea, varying φ, and varying H are shown in the figs. 3 to 5 respectively for the swirl and non-swirling conditions
Summary
Gaseous combustion is used in industries for many of the applications due their better convective heat transfer. By considering the safety and wide range of flame stability limits in comparison to premixed combustion, the diffusion flames are used in industries. The inverse diffusion flame is obtained in a co-axial tube burner having a central air jet with annular space of fuel jet surrounding the air jet. The entrainment of fuel into the air jet results in better mixing and burning. Sze et al [1] studied flame shapes, thermal and emission characteristics of two different IDF burners. Mikofski et al [2] investigated the flame heights for varying air flow rates.
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