Diffusion flame extinction in slow convenctive flow under microgravity environment
Abstract
A theoretical analysis is presented to study the extinction characteristics of a diffusion flame near the leading edge of a thin fuel plate in slow, forced convective flows in a microgravity environment. The mathematical model includes twodimensional NavierStokes momentum, energy and species equations with onestep overall chemical reaction using secondorder finite rate Arrhenius kinetics. Radiant heat loss on the fuel plate is applied in the model as it is the dominant mechanism for flame extinguishment in the small convective flow regime. A parametric study based on the variation of convective flow velocity, which varies the Damkohler number (Da), and the surface radiant heat loss parameter (S) simultaneously, is given. An extinction limit is found in the regime of slow convective flow when the rate of radiant heat loss from fuel surface outweighs the rate of heat generation due to combustion. The transition from existent envelope flame to extinguishment consists of gradual flame contraction in the opposed flow direction together with flame temperature reduction as the convective flow velocity decreases continuously until the extinction limit is reached. A case of flame structure subjected to surface radiant heat loss is also presented and discussed.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 August 1986
 Bibcode:
 1986STIN...8628378C
 Keywords:

 Convective Flow;
 Diffusion Flames;
 Extinguishing;
 NavierStokes Equation;
 Reaction Kinetics;
 Reduced Gravity;
 Aerospace Safety;
 Damkohler Number;
 Flame Temperature;
 Flow Velocity;
 Fuel Combustion;
 Mathematical Models;
 Microgravity Applications;
 Radiative Heat Transfer;
 Space Commercialization;
 Fluid Mechanics and Heat Transfer