Droplet Array Combustion Experiments on Effect of Initial Droplet Diameter on Flame Spread Characteristic Time

Abstract

Fuel droplet array combustion experiments of a fuel droplet array were performed at microgravity to investigate the mechanism of fuel droplet group combustion. The purpose of this research is to understand the dependence of flame spread speed on droplet spacing and initial droplet diameter. Ten fuel droplets were generated using a thin glass needle and suspended at the crossing points with SiC fibers of 7.5 and 14 ®m in diameter, respectively. Sequential backlit-images of the droplet suspension fibers and the droplets were taken at the time of flame spread. n-Decane was employed as the fuel. The effect of initial droplet diameter on the normalized flame spread speed were examined with varying droplet spacing. In the case of 3.75 in nondimensional droplet spacing showed that the normalized flame spread speed increased less than 0.48 mm in initial droplet diameter and remained constant above 0.48 mm. In the case of short flame spread induction times, which is the time for a flame to travel between two droplets, the normalized flame spread speed increased as the initial droplet diameter increased. The reason for this believed to the flame spread induction time is dominated by the premixed-flame propagation time.

Crankcase Explosions in Marine Diesel Engines: A Computational Study of Unvented and Vented Explosions of Lubricating Oil Mist

“…The ignition and combustion of fuel mist is a complex physicochemical phenomenon [31][32][33]. Contrary to the ignition and combustion of an isolated fuel droplet in an unconfined oxidizing atmosphere [34][35][36], the processes of ignition and combustion of fuel mist depend on the local instantaneous droplet size, liquid vapor concentration, and distance between droplets [37]. Both experimental and computational studies indicate that evaporating fuel droplets affect differently fuel-lean and fuel-rich laminar flames: they enhance the flames under fuel-lean conditions and suppress the flames under fuel-rich conditions [38].…”