超高“Z型”中庭高度对自燃排烟特性影响的数值模拟研究

超过12m的超高中庭发生火灾时,常规排烟方法不能完全满足实际需求。通过FDS软件对某超高"Z型"中庭进行数值模拟,研究中庭高度对自然排烟特性的影响。该"Z型"中庭底层南面是自然进风口,顶层北面是自然排烟口,以烟气最先到达指定楼层人员危险时间值为到达危险时间。实验条件下模拟结果表明:无风情况下,中庭高度增加,到达危险时间增加,自然排烟效果增强。到达危险时间t与中庭高度h之间满足一定指数增长关系:t=y0+Aexp(h/α),中庭火源位置和中庭宽度对y0、A和α有一定影响。有风情况下,外界风向与进风口方向一致时,中庭自然排烟效果优于无风状况,中庭越高效果越强。在外界风向与排烟口方向相反时,烟气倒灌进中庭,自然排烟效果较弱。

Numerical simulation on the impact of ultra-high Z-shaped atrium height upon characteristics of natural smoke extraction

Conventional fire smoke extraction methods do not fully meet the actual demands for ultra-high atrium over 12 meters. The paper aims to study the impact of atrium height based on the characteristics of natural smoke extraction, by numerical simulation on a ultra-high Z-shaped atrium using FDS software. The ground floor air inlet is located in the south and the top floor air outlet is located in the north of ultra-high Z-shape atrium. The hazard occurrence time is defined as the time when the designated floor smoke emerges which causes people in danger. The simulation results showed that: under no-wind conditions, a higher atrium height results in longer hazard occurrence time and better effect of natural smoke extraction. The hazard occurrence time and the atrium height meet certain exponential growth. Meanwhile, under wind conditions, when the wind is consistent with the air inlet direction, the natural smoke extraction of atrium works better than no-wind conditions. When the wind and the external air outlet are in the opposite direction, smoke will flow backward into the atrium, leading to worse natural smoke extraction.