Window ejected flame width and depth evolution along facade from under-ventilated enclosure fires

• Flame base position of different opening conditions revealed.
• Evolution of width and depth of ejected fire clarified.
• Non-dimensional model proposed well collapsing experimental data.

This paper investigates window ejected flame width and depth evolutions along facade from under-ventilated enclosure fires. Experiments are carried out by 1:4 scale model. Two CCD cameras are employed to record the evolutions of flame depth and width. The flame base position (vertical height above the bottom of the opening), flame depth (width) along with their maximum values and corresponding positions (vertical height above the flame base position) are measured and analyzed by non-dimensional scaling. It is found that the flame base position is independent of fire heat release rate and its ratio to opening height is nearly the same. The flame depth for all heat release rates and the flame width for openings with aspect ratio in the range of 0.5≤W/H≤1.50.5≤W/H≤1.5 (the “(semi-) axi-symmetrical flame type”) first increases, reaching a maximum value and then decreases with height. However, for the opening with a relative larger aspect ratio (W/H=2W/H=2) (“wall flame type”), the flame width decreases monotonously with height. The maximum flame width and its corresponding vertical position for “(semi-) axi-symmetrical flame type” are found to be well correlated by characteristic length scale ℓ1ℓ1 [=(AH)2/5] non-dimensionally after normalized by the flame height. Meanwhile, the maximum flame depth for all conditions is found to be well correlated by characteristic length scale ℓ2ℓ2 [=(AH2)1/4(AH2)1/4] non-dimensionally after normalized by the flame height.