Experimental studies on combustion of fuel droplets in flowing air under zero- and high-gravity conditions

Abstract

To examine in detail the gas-flow effects in the combustion of fuel droplets, the individual effects of forced and natural convection on their burning characteristics such as the evaporation constant and flame shape were observed and analysed by using two kinds of experimental technique, i) a freely falling chamber, which is provided with a wind tunnel, and ii) a rising chamber, in which an increased acceleration of fall is established. The results were compared with those previously obtained under normal- and zero-gravityconditions. Especially, about the evaporation constant k , simple formulas, k = k o [1+const.Re 1/2 ] for forced convection and k = k o [1+const. (α/g) 0.52 ] for natural convection, were found to hold, where k o is the evaporation constant in the spherical combustion, and Re, α and g denote Reynolds number based on initial droplet diameter, acceleration of fall and gravitational acceleration, respectively.