Critical height of the vertical mechanical smoke vent
To improve the effect of smoke exhaust on subway platforms,this paper proposes a new mechanical smoke exhaust system,which is named vertical mechanical smoke exhaust.The effect of vertical mechanical smoke extraction in subway platform fire is analyzed by a numerical simulation method.The results show that the smoke exhaust effect of the vertical smoke exhaust mode is significantly better than that of the top exhaust mode,and the total heat exhausted is 14.51％higher than that of the top exhaust mode.The reason is that compared with the top exhaust,the vertical exhaust improves the height of the exhaust port,and the height and temperature of the exhaust smoke are increased.Further research shows that there is a critical height of the vertical exhaust vent(CHV).When the height of the exhaust vent is lower than the CHV,the high-temperature smoke under the ceiling cannot be discharged,but when the height of the exhaust vent exceeds the CHV,the smoke exhaust effect will decline due to the restriction of the ceiling.When the height of the exhaust port is high,the distance between the ceiling and the exhaust port is too narrow.In the process of exhaust,the smoke violently collides above the exhaust port and forms a positive pressure vortex near the center of the exhaust port.The vortex cannot exhaust smoke,resulting in a decrease in the exhaust effect.When the length of the side of the exhaust port increases,the heat discharged per unit area decreases.The height of the critical smoke exhaust vent is not affected by the exhaust velocity u,but is affected by the length of the vent side D.The distance l between the vent and the ceiling at the critical height is approximately equal to D/2.
safety engineeringsubway stationvertical mechanical exhaustcritical heightsize of smoke vent
万方数据
维普
