Droplet combustion in a reactive environment

The transient processes of evaporation, ignition, and combustion of a fuel droplet in a hot, reactive fuel-oxidizer environment simulating the spray interior are studied numerically, with emphasis on the relative importance of diffusional burning in the droplet vicinity and premixed burning in the ambience. It is shown that for a fuel-lean environment diffusional burning is generally possible and is initiated rapidly, whereas for a fuel-rich environment only premixed burning is possible. For a sufficiently reactive environment one of the reactants is rapidly depleted such that during most of the droplet lifetime the environment is really nonreactive. The present numerical study yields much physical insight useful for further analytical modeling efforts. A new transient process, involving the need to build up the fuel vapor concentration in the droplet vicinity from an initial state of low concentration, has also been identified to be important during droplet combustion and warrants further study.