Full-scale experiments on smoke movement in a two-story detached house with two horizontal openings at the lower-floor ceiling

Abstract

This paper conducted full-scale experiments to investigate transient burning characteristics inside a two-story detached house, which had a double-pitched roof and covered an area of 14.2 m×6.5 m. Two horizontal openings, formed by a staircase and an atrium, connected the lower floor with the upper floor. By changing the heat release rates (HRRs) and locations of the fire source, as well as the opening conditions, smoke movement and filling process were addressed, and flame shapes and temperature evolutions inside the building were presented. Based on the heat transfer analysis, it was indicated that the two horizontal openings play a significant role on smoke movement and filling process. When the burner was placed between the two openings, there was a constant upward flow through the atrium opening to the upper floor due to its lower flow resistance. While gas flow inside the staircase can be both downward and upward, caused by the competition between the inertia and thermal buoyancy, as well as the air supply to the fire source. When the burner was placed under the atrium opening, there was a steady circulation of smoke with an upward flow through this opening, and a downward flow through the other. Smoke movement was accompanied by both the transverse diffusion and the settling process. An equation was derived to estimate the smoke filling time inside the building. The calculation results demonstrate that downward flow through the staircase may lead to a decrease in the smoke filling rate in the later stage of fire on the upper floor.