The study on calculation method of burning rates of discrete multiple fires

Abstract

A calculation model for dimensionless burning rates in discrete multiple fires is developed based on the quantitative relation between two dominant coupled mechanisms: the radiant heat feedback enhancement and air entrainment restriction. The radiant heat feedback enhancement among discrete fire sources is transferred as external thermal radiation to independent fire source, while the air entrainment restriction is transferred as the decrease in atmospheric pressure for an independent fire source. To reveal their relative dominance, key parameters, dimensionless burning rates ${{\dot{m}}_i}^{″\ast }$, air entrainment restriction coefficient k_p,i and separation distance $\frac{D-d}{d}$, are introduced. Fitted with the burn-out time data of discrete multiple fire arrays, a formula including these parameters is derived. Based on this formula and the theoretically derived burning rates evolution, the model is proposed, which well-predicts the experimental burning rates. The model effectively predicts burning rate trends under extreme and non-uniform conditions, verifying its feasibility in both actual and theoretical fires. The consistency between uniform and non-uniform arrays suggests that the model can be extended to more complex conditions.