Limiting Factor of Flame Propagation in Mono-Sized Sprays of Low-Volatility Fuels

摘要

The propagation limits in monosized sprays have been measured for n decane over the droplet size range from 40 to 140 micro m and n dodecane from 40 to 160 micro m. The limits are expressed in terms of the number density or spacing of droplets as well as the fuel concentration. With increasing droplet size, the critical value for flame propagation of number density decreases sharply but that of spacing increases at a very small rate. It is found that the critical fuel concentration decreases drastically as droplet size changes from a few microns to about 40 micro m, then decreases moderately towards less than half of the limit of inflammability of a premixed gas mixture of the same fuel. This reduction is attributed to the transition, of the mechanism of ignition from the normal continuous ignition to the relay ignition of the neighboring droplets. The effect of fuel volatility is detected.