纵向通风条件下隧道坡度对火灾烟气流动影响的实验研究

摘要

Vertical ventilation is the common means of tunnel smoke control.When the wind is large enough,the wind will make the smoke spread in one direction,so as to achieve longitudinal smoke evacuation.However,if the wind speed is too large,the smoke structure may be destroyed,and the smoke turbulence may endanger the human evacuation.Therefore the smoke stratification should maintain a reasonable time period.Many practical tunnels involve slope,which may produce the so-called ＂smoke stack effect＂.This paper uses bench-scale models to conduct experiments,in order to examine the slope and vertical ventilation under fire smoke.The results indicate that when the slope is increased,the air entrainment will be more significant,with more rapid smoke temperature decrease and smoke settlement.The experimental results agree well with the theoretical analysis.%纵向通风是隧道烟气控制的常用手段之一,若风速足够大,烟气会保证向一个方向蔓延,达到纵向排烟的目的,但同时过大的风速可能会破坏烟气层结构,造成烟气层紊乱,危害到地面附近疏散的人群。因此隧道排烟的策略应是在保证烟气层维持一定时间分层的前提下合理排烟。在实际中,很多隧道都是存在坡度的,这就可能产生烟囱效应,导致倾斜隧道内烟气的扩散速度会与水平隧道不同,进而影响到纵向通风排烟策略。本文采用比例模型的实验方法,对不同坡度及纵向通风风速条件下隧道内火灾烟气流动规律进行了研究。结果表明,隧道坡度越大冷空气卷吸越强烈,烟气降温越快,烟气沉降速度也越快。同时初步得到了本实验条件下的烟气分层化临界风速,并与理论分析结果吻合得较好,为研究烟气的运动情况和人员疏散方案提供重要参考依据。