%0 Journal Article
%T Effect of Gas Phase Heat Sink on Suppression of Opposed Flow Flame Spread over Thin Solid Fuels in Microgravity Environment
%A Vinayak Malhotra
%A Chenthil Kumar
%A Amit Kumar
%J Journal of Combustion
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/837019
%X A two-dimensional numerical model of opposed flow flame spread over thin solid fuel is formulated and modeled to study the effect of gas phase heat sink (a wire mesh placed parallel to the fuel surface) on the flame-spread rate and flame extinction. The work focuses on the performance of the wire mesh in microgravity environment at an oxygen concentration 21%. The simulations were carried out for various mesh parameters (wire diameter, ¡° ¡± and number of wires per unit length, ¡° ¡±) and mesh distance perpendicular to fuel surface ¡° ¡±. Simulations show that wire mesh is effective in reducing flame-spread rate when placed at distance less than flame width (which is about 1£¿cm). Mesh wire diameter is determined not to have major influence on heat transfer. However, smaller wire diameter is preferred for better aerodynamics and for increasing heat transfer surface area (here prescribed by parameter ¡° ¡±). Flame suppression exhibits stronger dependence on number of wires per unit length; however, it is relatively insensitive to number of wires per unit length beyond certain value (here 20£¿cm£¿1). 1. Introduction Diffusion flames formed over condensed fuels are well known to spread along the surface of the fuel by heat transfer from flame to fuel surface ahead of the flame. The heat transferred from the flame to the fuel pyrolyzes it to vapors which upon mixing with surrounding air form a combustible mixture. This combustible mixture is ignited by the flame behind and hence advances forward over the surface of the fuel. The study of flame spread phenomena is primarily driven by the need to have better fire safety, by means of enhanced understanding of the mechanisms that control the spread rates and extinction. Traditionally, the flame spread phenomena over solid fuels are studied under two basic categories: opposed flow flame spread and concurrent flow flame spread. This classification is based on the relative direction of flame spread with respect to the ambient gas velocity vector. In opposed flow flame spread, the flame spreads against the flow direction and in concurrent flow flame spread, the flame spreads in the direction of flow. Present work relates to the study of opposed flow spreading flame on thin solid fuel (cellulose sheets with area density 57£¿g/cm2) in zero gravity. Following the classical work of De Ris [1] on opposed flow spreading flames in 1969, over the last four decades research works have contributed significantly to the improvement in the understanding of the flame spread phenomena. The works [2¨C7] provide an excellent review on the
%U http://www.hindawi.com/journals/jc/2012/837019/