Shapes of nonbuoyant round luminous laminar-jet diffusion flames in coflowing air

The shapes (luminous flame boundaries) of steady nonbuoyant round luminous hydrocarbon-fueled laminar-jet diffusion flames burning in coflowing air we re studied both experimentally and theoretically, Flame shapes were measure d from photographs of flames burning at low pressures in order to minimize the effects of buoyancy, Test conditions involved acetylene-, propylene- an d 1,3-butadiene-fueled flames having initial reactant temperatures of 300 K , ambient pressures of 19-50 kPa, jet-exit Reynolds numbers of 18-121, and initial air/fuel velocity ratios of 0.22-32.45 to yield luminous flame leng ths of 21-108 mm, The present flames were close to the laminar smoke point but were not soot emitting. Simple expressions to estimate the shapes of no nbuoyant laminar-jet diffusion flames in coflow were found by extending an earlier analysis of Mahalingam et al, (Mahalingam, S,. Ferziger, J. H., and Cantwell, B. J., "Self-Similar Diffusion Flames," Combustion and Flame, Vo l. 82, No. 2, 1990, pp, 231-234), These formulas provided a good correlatio n of present measurements except near the burner exit where self-similar ap proximations used in the simplified analysis are no longer appropriate.