External Cluster Combustion of Binary-Fuel Drops

Abstract

A model describing external sheet combustion of a cluster of drops has been developed for clusters of binary-fuel drops. The binary-fuel is assumed to be a solvent-solute combination in which the solute is much more volatile than the solvent whose initial mass fraction within the mixture is larger than that of the solute. Both the ignition timing and location are calculated using criteria previously derived; for the range of air/fuel mass ratios considered, ignition always occurs around the cluster. Following ignition, an internal flash flame burns all the oxygen within the cluster. An external sheet flame ensues fueled by vapor released from the cluster. Results show that drop interactions are important in modifying the amount of fuel burnt. It is only for small initial cluster velocities and for large air/fuel mass ratios that the external flame behaves approximately like a classical diffusion flame in that it almost burns all the fuel released from the cluster. For all other conditions, the amount of fuel burnt is smaller than that released from the cluster. These conclusions are independent of the initial solute mass fraction and of the Arrhenius ignition parameters having assumed them identical for solvent and solute.