Effects of Fuel Volatility on Flame Spread along Fuel Droplet Arrays in Microgravity

Abstract

Microgravity combustion experiments of fuel droplet arrays were conducted with different fuel volatilities. N-octane, n-decane and n-hexadecane were used to examine effects of volatility. Experimental results showed that the flame spread rate took a maximum value at a specific inter-droplet distance for all the fuels and increased with fuel volatility. Effects of inter-droplet distance on flame spread behavior at room temperature were discussed based on positional relation between the leading flame and an unburned droplet. Effects of fuel volatility were discussed based on the droplet heating time. Simple formulas to estimate flame spread rates were proposed considering rate-controlling processes. Flame spread behavior were explained based on the droplet heating process for small inter-droplet distance and on the droplet heating process and the development of the flammable mixture layer around the next droplet for large inter-droplet distance.