Combustion and extinction of PMMA cylinders during depressurization in low-gravity

Abstract

Combustion and extinction behavior of a diffusion flame over polymethyl methacrylate (PMMA) cylinders during depressurization in low gravity are examined experimentally and via numerical simulations. Low-gravity conditions were obtained using the NASA Lewis Research Center's reduced-gravity aircraft. Effects of reduced pressure and transient depressurization on the visible flame are examined. The flammability of the burning solid is determined as a function of pressure and solid phase center temperature at constant velocity; as the solid-phase temperature increases, the extinction pressure decreases. The numerical model assumes a two-dimensional model with a quasi-steady gas phase and an unsteady solid phase. A parametric study is conducted to examine the effects of forced flow, heating of the solid phase, and depressurization rates on the extinction boundary. One case with conditions similar to the low-gravity aircraft experiments is presented in detail. The predicted extinction boundaries from the parametric study are quasi-steady in nature and could be relevant to the International Space Station's fire fighting scenario.