Numerical and Analytical Examinations of Diffusion Flames Attached to Solid Fuel Surfaces in Weak Convective Flows

摘要

Diffusion flames near solid fuel surfaces are investigated numerically and analytically in a 2-D planer domain. To construct an analytical model of surface-attached solid fuel flames, a segment of fuel adjacent to an insulated, non-reactive binder material is considered. The mixture fraction equation is {nabla}{sup}2 Z=0 when convective terms are negligible. An exact analytical solution is derived for this equation. To take into account the role of weak convective terms, a simple mathematical model is solved both numerically and analytically. Comparisons are made with the results of numerical modeling of a similar problem with commercially available software. Since the gas phase is of principal interest, various inlet fuel and air velocities are considered. Results of analytical and numerical models demonstrate strong agreement near the flame upstream leading edge (attachment region). Near the trailing edge, where the flame can reattach to the surface, the agreement ranges widely and is often poor. The ultimate purpose of this study is to establish an analytical model to examine heat transfer, flame structure and reaction rate in flames attached to solid fuel surfaces, particularly surfaces with complex structure and conditions in which multiple flames may exist.