Influence of horizontal projection on upward flame spread over XPS thermal insulation material

摘要

Experimental methods and theoretical analysis are employed to investigate the effects of horizontal projection on upward flame spread over extruded polystyrene thermal insulation material of building fagade. The average flame height (H_f) (or area S) drops exponentially as dimensionless projection width (w*) rises, and dropping rates are more significant for wider projection. The decrease of flame area is more remarkable than that of flame height. There exists a low temperature zone which is surrounded by the horizontal projection, the flame, and the fagade. The average of maximum temperature (T_(max)) of zone below the projection first decreases and then increases as projection width (w) rises. The temperature dropping rate increases exponentially with w*.T_(max) of the zone adjoining the surface of extruded polystyrene sample above the projection decreases linearly with w*. For wider projection (w ≥ 10 cm), the average temperature above it first increases and then drops as height rises. The heat flux history could be divided into 4 stages, ie, ignition stage, smoke heat transfer stage, flame heat transfer stage, and attenuation stage. The average heat flux (q") at each stage decreases as w rises. The maximum value is observed at the third stage, where q" increases linearly with S.