Experimental study on upward flame spread over XPS under the influence of facade openings

This study experimentally investigates the upward flame spread and combustion behavior of facade XPS boards under the coupled action of continuous and discontinuous materials. The research reveals the opening law of typical building facades, and changes the opening height (h) and ratio (α) to deeply analyze flame geometrical characteristic, such as flame shape, which is 'convex' at h < 25 cm and 'concave' at h ≥ 25 cm. The functional relationship between flame height xf and pyrolysis length xp is fitted, confirming the turbulent state of flame spread under opening influence by n < 1. The mass loss rate varies periodically with time and negatively correlates with h. The effect of the competition mechanism between oxygen supply and combustibles on the flame spread rate (vf) is studied, which shows that the vf tends to increase and then decrease with h. A new model for predicting flame spread rate related to the length of preheating zone is established, and the maximum prediction error is within 10%. The study finds that the dominance of the opening three-dimensional fire gradually changes from the top opening three-dimensional fire to the side. The interior temperature field gradually decreases with the increasing h due to the increased heat transfer distance of gas phases. This research provides a better comprehension of the combustion characteristics on building facades under different opening influence and their effects on interior spaces.