Influence of relative location of two openings on fire and smoke behaviors in stairwell with a compartment

Opening conditions in stairwells will affect the fire and smoke behaviors in connected compartments and stairwells in high-rise buildings. A series of experiments was conducted to investigate the influences of relative location of two openings on fire behaviors in the adjacent compartment and smoke flow characteristics in the stairwell. In the experiments either the lowest (1st floor) or the highest (12th floor) vent in the stairwell was maintained open while one of the other vents was opened to create different ventilation conditions. The results show that when the 12th floor vent was opened the large pool fires might lead to ghosting flames. The burning rate per unit area in these experiments can be divided into four stages which are the early steady burning, the boiling burning, the ghosting flame and the decaying stages. Thus the experiments without ghosting flame involve only three stages. The burning rates at the boiling burning stage are 3.7 ∼ 9.7 times of the burning rates at the early steady burning stage. A parameter λ taking into account the burning rate in open space is introduced to determine the control mechanism of combustion. The smoke flow pattern in the stairwell is dominated by respective the stack effect when the 1st floor vent was opened and the turbulent mixing when the 12th floor vent was opened. Although the maximum temperature distributions at the stairwell centerline decline exponentially with height, different smoke flow patterns result in different distribution trends.