The ignition process of liquid fuel droplets has been studied. A laboratory flame maintained by a vertical, monosized liquid fuel droplet array surrounded by a laminar flow of a mixture of helium and oxygen represents the system investigated. A system of partial differential equations describing the ignition of a single droplet was formulated. By specifying the droplet surface position with the rfa-law, the system of partial differential equations could be solved numerically. The effects of convection and interference between the droplets in the array were lumped in the evaporation rate constant in the rfMaw. The ignition model could interpret the experimental results on the ignition of droplet arrays of pure fuel, and by extension, of residual fuel oil.