Summary
This study experimentally investigates the radiation heat flux distribution received on the floor due to fire plume impinging upon an inclined ceiling, which has not been quantified previously. The radiation heat fluxes were measured on the floor for 160 experimental conditions, involving various fire source heat release rates, source‐ceiling heights, angles of ceiling inclination and dimensions (aspect ratios) of the rectangular sources. The main findings include that the declining rate of the radiation heat flux along with distance received by the downstream floor decreases, while that received by the upstream floor increases, with the increasing of ceiling inclination angle. The radiation heat flux received by the floor is higher as the ceiling inclination angle is smaller for the downstream side, while it is lower as the ceiling inclination angle is smaller for the upstream side. Both of these variations can be explained by change of the flow distribution as well as flame length due to combustion and heat released in the two directions beneath the inclined ceiling. Further, a model with various fire source heat release rates, source‐ceiling height, and ceiling inclination angles is proposed, to globally describe the radiation heat flux received by both the upstream and downstream floors.
Smoke is the main cause of death in tunnel fires. It is one of the important measures to maintain smoke stratification in the early stage of tunnel fire. This article focused on experimentally studying the combined effect of lateral concentrated smoke extraction and longitudinal ventilation on the smoke stratification, which never be revealed before. The velocity of the smoke layer and air layer, vertical temperature distribution, and the flow patterns of the smoke were measured. It was found that the longitudinal ventilation and lateral concentrated smoke extraction would affect the flow of the smoke and change the shear velocity between the smoke layer and air layer, then, the patterns of the smoke layer will be affected. And the flow patterns with Froude (Fr) number can be classified into three categories: (a)Fr < 0.6, with stable smoke stratification; (b) 0.6 < Fr < 0.85, with a stable smoke stratification but the blurring interface; and (c) Fr > 0.85, the smoke layer is completely unstable. The result can provide a reference for ventilation design of immersed tube tunnels.
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