Internal group combustion of liquid droplets

Abstract

A quasi-steady internal group combustion model of a spherical droplet cloud has been developed to assess the effects of the collective behavior of fuel droplets on combustion characteristics and cloud structures. Analytical solutions are obtained for the predictions of the distributions of the temperature, concentrations of fuel vapor, and oxidizer in strongly and weakly interacting zones. Overall burning rate under internal group combustion mode at various flame penetration is also obtained. Numerical analysis is carried out to determine the combustion behavior of droplet clouds at some selected group combustion numbers. It was found that for a cloud of n-butylbenzene droplets, the group envelope flame is stabilized on the boundary of the droplet cloud for a group combustion number of 1.36. As the group combustion number decreases the envelope flame penetrates into the droplet cloud and divides the cloud into two zones; a strongly interacting zone located inside the group envelope flame and a weakly interacting zone established between the envelope flame and the boundary of the cloud. In the strongly interacting zone, the droplet vaporizes and the vapor produced is consumed at the group envelope flame. The droplets in a weakly interacting zone burn with an envelope flame surrounding each droplet. When the group combustion number decreases to 0.1, the group envelope flame degenerates into a point flame at the center of the droplet cloud.