Effect of Ambient Atmosphere on Flame Spread at Microgravity

The effects of atmosphere composition on the rate of opposed-flow flame spread (Sf ) over thin solid fuel beds at microgravity (μg) were measured and compared to earth gravity (lg) results and theoretical predictions. Two modifications to standard atmospheres were considered. First, the effects of sub-flammability-limit concentrations of a gaseous fuel (CO or CH4) were measured and compared to an existing theoretical model that was extended to ug conditions. The agreement between the model and experiment is reasonable considering the simplicity of the model. Notably, both model and experiment show that the effect of added gaseous fuel is greater at μg than lg. Secondly, the effect of diluent type on Sf -was studied by comparing results using He, N2, Ar, CO2 and SF6 diluents. It was found that, in agreement with prior studies in N2 diluent, for He, N2 or Ar diluents, Sf was larger at 1g than μg. In contrast, for CO2 diluent, Sf was slightly lower at 1g than at μg and for SF6 diluent, Sf was much lower at 1...