Modeling Flame Spread and Extinction of Solids in Space Exploration Atmospheres 2009-01-2492
Two detailed numerical models for flame growth and spread over solid surfaces are solved. For the three-dimensional model of steady spread over thin solids, the computations have included the variations of pressure, oxygen percentage and gravity in buoyant flows and pressure, oxygen percentage and flow velocity in purely forced flow in zero gravity. The overall comparisons of spread rates with experiments are reasonable but there is not enough data to perform a thorough comparison on the extinction limits. The computed results provide detailed flame structures in these different conditions that also reveal the difference between flames in a buoyant flow and in a forced flow.
The ignition and flame growth processes along a thick solid surface are studied by a two-dimensional transient model which has a quasi-steady gas phase and an unsteady solid phase. Gas-phase ignition limit, ignition delay time, and critical fuel mass burning rate at ignition have been determined as functions of free-stream flow velocity, oxygen mole fraction and ignition source parameters. The transient history of flame growth or decay normally observed in experiment is also reproduced.