Effects of ambient condition on flame spread over a thin PMMA sheet

The flame spread rates over PMMA sheets are measured throughout the thin an d the thick regimes with varying oxygen level and pressure in normal-gravit y. The prediction by Extended Simplified Theory (EST) shows good agreement with the experimental results in the thermal regime where relatively high o pposed-flow exists. In micro-gravity, the spread rate over thin PMMA sheets is measured with varying opposed-flow velocity and oxygen level. When the opposed-flow velocity is very low, the thermal regime assumption breaks dow n so that the radiative effect becomes significant. As the radiative effect appears, the mass diffusion layer grows faster than the thermal layer, and the flame spread is suppressed due to the shortage of oxygen. On the other hand, if the oxygen level is high and/or thickness of the fuel is sufficie ntly thin, the radiative effect is negligible and the steady spread is esta blished even in a quiescent environment.