Numerical simulation on the influence of ambient pressure on smoke exhaust in tunnel shafts
Through FDS numerical simulation,the influence of ambient pressure on the smoke spread law,smoke stratification characteristics,and vertical shaft smoke exhaust effect of tunnel fires was studied.Research has shown that the smoke on the tun-nel ceiling in low-pressure environments has a higher tempera-ture,and the longitudinal attenuation curves of the ceiling tem-perature of the fire source-vertical shaft and downstream area of the vertical shaft follow an exponential distribution.The tempera-ture attenuation coefficient decreases with the increase of ambient pressure;The smoke movement in the fire source vertical shaft area is dominated by thermal buoyancy,and the trend of layering curve change is not obvious.The layering curve in the down-stream area of the vertical shaft is greatly affected by ambient pres-sure.As the ambient pressure decreases,the layering curve shows a clockwise rotation trend,the layering intensity de-creases,and the stability of the smoke layer decreases;The smoke exhaust effect of a vertical shaft in a low-pressure environ-ment is better than that of a vertical shaft under normal pressure,and the critical height for the occurrence of suction penetration at the bottom of the vertical shaft has also increased.Therefore,compared with general altitude areas,when a tunnel fire occurs in higher altitude areas,the smoke exhaust effect of the higher verti-cal shaft is better,the critical height of suction is higher,and the impact on the stability of the downstream smoke layer is smaller,which is more conducive to evacuation and smoke exhaust.
tunnel firesmoke exhaust by vertical shaftambient pressuresmoke stratificationnumerical simulation
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