Experimental observations of the effect of gravity changes on smoldering combustion

Abstract

The effects of gravity changes on the natural convection smolder characteristics of flexible polyurethane foam were determined in order to provide information on the potential onset of a smolder-initiated fire in a space-based facility. Experiments were conducted in an aircraft following parabolic trajectories providing up to 25 seconds of low gravity. Temperature histories of polyurethane foam were measured at several locations along the fuel sample interior. Results are presented and discussed for both upward and downward smoldering. Results indicate that gravity significantly effects the competition between supply of oxidizer to, and the transfer of heat to and from the reaction zone. This competition determines the characteristics of the smolder reaction. Within the reaction zone the reduction in oxygen supply in low gravity is dominant and the reaction weakens. Away from the reaction zone the reduction in convective cooling at low gravity tends to increase the material temperature. The opposite was observed at high gravity.