Burning rates of liquid fuels in fire whirls

This paper presents semi-empirical investigations on the quasi-steady burning rates of laminar and turbulent fire whirls established over liquid fuel pools. The inflow boundary layer above the fuel surface consists of two regions: outer reactive region and inner non-reactive region. Based on the momentum boundary layer solutions with the applications of stagnant film model and Chilton–Colburn analogy, the burning rates are correlated with ambient circulation and pool size for laminar and turbulent fire whirls respectively. It is shown that in general pool fires the mass and heat transfers on the fuel surface are controlled by natural convection, while in fire whirls they are strongly enhanced by forced convection. Fuel evaporation rate in the outer region is relatively larger than that in the inner region. The large proportion of fuel evaporated from the outer region is mainly due to its larger area. The predictions agree well with the data from the present experiments and the literature. Furthermore, the flame height is confirmed to be proportional to the ambient circulation for both laminar and turbulent liquid fire whirls.