Experimental study of the effectiveness of air curtains of variable width and injection angle to block fire-induced smoke in a tunnel configuration

Abstract

Small-scale experiments have been conducted to study the sealing effect of an air curtain for fire-induced smoke confinement in a tunnel configuration. The processed data confirmed the results obtained earlier from blind Computational Fluid Dynamics (CFD) simulations [1] using the Fire Dynamics Simulator (FDS) 6.5.3 [2, 3]. Furthermore, the CFD simulations provided complementary information on the detailed flow and temperature fields which are difficult to obtain in experiments with the available techniques. A parametric study is performed, covering a range of air curtain velocities, slot widths, injection angles and total fire heat release rates (HRRs). The momentum ratio R, defined as the ratio of the vertically downward air curtain momentum to the horizontal smoke layer momentum at the position of the air curtain, is confirmed to be a key parameter for the air curtain performance. A ratio R ≈ 10 is recommended for the optimum sealing effect in terms of smoke confinement. In addition, two other important parameters that determine the performance of air curtains for smoke confinement are presented. The first parameter is the dimensionless Preprint submitted to International Journal of Thermal Sciences https://doi.org/10.1016/j.ijthermalsci.2018.07.044 2 shape factor AR (AR=Width/Length) that characterizes the dilution effect of the air curtain jet. The second parameter is the injection angle θ that characterizes the horizontal force of the air curtain. The air curtain sealing effectiveness increases with both the increase of slot width (shape factor AR) and injection angle (θ). The air curtain width has a limited influence on the performance of the air curtain whilst the injection angle has a more significant influence on the sealing effectiveness of the air curtain for the scenarios considered in this study.An optimal injection angle of 30 o inclined to the fire source is recommended in the engineering design of the air curtain for smoke confinement for situations where the fire location can be pre-determined to be only at one side of an air curtain.

Computational fluid dynamics simulation of breathing zone of the human for air quality with a personalized air curtain

“…Sample flow configuration and coordinate system of plane twin jets. 16,20 steps of the order of 0.1 s were found to be adequate for this study.…”

“…Yu et al 20 carried out the small-scale experiments to study the sealing effect of an air curtain for fire-induced smoke confinement in a tunnel configuration. It is observed that an optimal injection angle of 30°inclined to the fire source is recommended in the engineering design of the air curtain for smoke confinement for situations where the fire location can be pre-determined to be only at one side of an air curtain.…”

Effectiveness Of Air Curtains As Thermal And Smoke Barrier Against High Gradients Of Flow Parameters

“…Use of an opposite double jet air curtain proved not only to be effective in protecting staircase, an important region during evacuation, but also drive away the fire generated smoke from the channel in case of a building fire [6]. For an air curtain with momentum ratio R=10, an injection angle of 30 o inclined to the source was reported optimum for tunnel fire [7].…”

Effects of fire location on the capacity of smoke exhaust from natural ventilation shafts in urban tunnels

“…Moreover, the toxic gases in the tunnel will seriously affect the evacuation of stranded persons and rescue work of fire department. Since injuries and deaths in the tunnel fire are basically caused by the harmful smoke, effective mechanical or natural smoke exhaust system must be installed to control its spread …”

“…Since injuries and deaths in the tunnel fire are basically caused by the harmful smoke, effective mechanical or natural smoke exhaust system must be installed to control its spread. [23][24][25][26][27][28] Although mechanical ventilation is less affected by the outside environment, its system layout is complicated, the economic investment is large, and the maintenance is difficult. In addition, the mechanical ventilation is easy to destroy the smoke layer stratification [29][30][31][32] under the tunnel ceiling, which is very unfavorable to the evacuation of stranded persons in the early stage of tunnel fire.…”