Experimental study of the downward flame spreading characteristics of building facade flexible polyurethane with a lateral environment wind effect

Abstract

This work looks into the relationship between the downward burning behavior of flexible polyurethane (FPU) and horizontal wind speed. The flame geometry, burning rate, flame radiation, and temperature field under different wind speeds were studied experimentally. The results showed that the flame front on the windward side inclined obviously, and the flame front on the leeward side shrank gradually with the increase of wind speed and disappeared when the wind speed increased to a critical value. The burning rate and fuel melting/dripping increased first and then decreased because of the reduced flame radiation angle coefficient and the cooling and flame stripping effects induced by increased wind speed. Froude number and flame angle are positively correlated with the wind speed. The relationship between the flame angle and dimensionless velocity index is significantly lower than that of pool fire due to the inference of backplane on airflow field. The temperature at leeward side is higher than that on windward side. The peak of radiant heat flux decreases with the increase of wind speed because the inclination of the flame surface reduces the radiation area. The results of this study will permit assessments of high-rise building fire safety issues in actual windy environments.