Free convection diffusion flames from burning solid fuels

A general analysis for free convection diffusion flames is presented for the burning of solid fuels having surface geometries which give rise to boundary layer flows. The combustion chemistry is treated at the level of a single global reaction. Thermal radiation from the flame and the burning fuel surface is included in the formulation of the problem as well as the possibility of radiation from an external source. Allowance is also made for the case in which the gaseous products of pyrolysis include an inert component in addition to the combustible fuel. Solutions are presented for a variety of cases which show the effects of varying the chemical reaction rate, the radiation parameters, the Lewis number and the inert component in the fuel. Extinction phenomena are discussed, and results are given which show how extinction limits are affected by ambient oxygen concentration, water droplet sprays and chemically active fire suppressants. A discussion of some of the numerical techniques developed to obtain and verify the solutions is included.