Experimental study of dynamics of flames from discrete methanol fuel wicks in ullages

Abstract

The paper presents an experimental study of the burning characteristics of discrete methanol wicks in ullages, where the burning occurs at distances much lower than the lip of the burner. Burning configurations consisting of two methanol wicks burning in varying ullages (from zero to 24 cm at intervals of 6 cm) have been considered in the experiments. At zero and 6 cm ullages, flame shapes resemble that of a general buoyant pool flame. As the ullage is increased to 12 cm or higher, a plume-induced instability triggers in the ullage and the flame bends towards one side over the wicks, resembling a boundary layer type of flame. The transition from a pool flame to a boundary layer-type flame has been illustrated with direct flame photographs. At deeper ullages, as the flame leans over the fuel wicks, the mass burning rates are enhanced from 9% to 35% for different ullages. The resulting air flow inside the ullage and flame shape affects the mass burning rate and has been visualized using smoke flow in the ullage. This study opens further research on the coupling effect of burning of heterogeneous materials in ullages with the flow field induced by the buoyant plume.