Structure and properties of diffusion flame spreading over thermally thin fuel/inert sheet

An analytical theory for the steady-state flame spread over a thermally thin fuel/inert sheet is developed in this study. The model considers a laminar diffusion flame in a uniform opposed flow and is based on the solution of the two-dimensional gas phase species and energy equations carried out early by the author. The solid phase energy equation is one-dimensional and coupled to the gas phase. Under some standard assumptions, the solution of this problem has been derived, from which it follows that the analytical dependence of non-dimensional flame-spread rate on the properties of components when the heat transfers via the solid phase is considerable. Main tendencies of the flame-spread process have been discovered and analyzed for two limiting cases. In the first one, when the flame size is large and due to this there is the strong heat flow going through the solid phase into a longitudinal direction, the spread rate rises considerably with the thermal conductivity of solid phase. In the second case, when the flame size and the heat flow from the flame into the solid phase are relatively small, the spread rate decreases with the thermal conductivity of solid phase due to the convective heat loss from the preheating zone into the gas flow. On the achievement of the critical conditions, the flame spread ceases. On the basis of the theory developed some explanations of the main feature of the flame-spread process over thin fuel/inert sheet are given and the generalization of available experimental data of the flame-spread rate has been carried out.