Effect of Ambient Gas on Flammability Limit of Flat Materials in Microgravity

Abstract

The flammability map of a thin PMMA sheet with an opposed flow in microgravity environment was investigated with varying the thermal properties of the ambient gas. We also developed a new model to predict the limiting oxygen concentration (LOC) in 1g, minimum limiting oxygen concentration (MLOC) and critical opposed flow velocity, Vcr, at which MLOC was observed. We compared the predicted results with the experiment results by changing the gas-phase properties to validate the model. As the balance gas, nitrogen, carbon dioxide, and argon were used. It was found by experiment that LOC, MLOC, and Vcr significantly changed for each balance gas. These differences were reasonably predicted by the scale analysis which included the effects of radiation and kinetics on the suppression of the flame spread.