A systematic experiment has been conducted to obtain the ignition delay of fine fuel droplets in a hot and pressurized gas stream to examine the effects of ambient pressure and additional oxygen on the ignition delay and moreover the relationship between the evaporation rate and the ignition delay. An array of free fine droplets of paraffin hydrocarbon, whose mean diameter is close to that of droplets in a fuel spray, was discharged into a high temperature and high pressure gas flow. It was confirmed from the results that the ignition delay reduces with the increase in ambient pressure and additional oxygen and, moreover the more the number of carbon atom in the hydro-carbon are, the longer the delay becomes. In the case of multiple composition droplets of n-heptane and n-hexadecane, the evaporation rate constant increases and the ignition delay reduces as the proportion of n-heptane increases, and also the trend changes at the point of 50% in the proportion.
