狭长空间火灾烟气传输的准稳态时间模型
收稿日期: 2021-02-23
网络出版日期: 2022-07-04
基金资助
国家自然科学基金(50909058);上海市自然科学基金(16ZR1414600)
Quasi-Steady State Time Model of Fire Smoke Transmission in Long-Narrow Spaces
Received date: 2021-02-23
Online published: 2022-07-04
火灾烟气传输延滞行为是火灾早期烟气传输过程中的重要特性之一,直接影响到火灾探测器动作响应时间.为了研究狭长空间中火灾烟气传输延滞行为与准稳态之间的定量关系,根据弱羽流理论和狭长空间火羽流研究现有成果,从理论上提出了火灾烟气传输延滞时间计算的时间链表法,依据准稳态假设成立的判别条件,建立了狭长空间非稳态火准稳态假设成立的临界时间模型,并给出了临界时间计算方法.案例分析表明: 在相同工况条件下,狭长空间中顶棚给定纵向距离处烟气传输达到准稳态的临界时间比在开放空间中的长.而对于开放空间羽流,由于贴顶棚羽流较薄,卷吸空气量较小,保持了相对较高的流速,导致相同工况条件下狭长空间中的烟气传输延滞时间比开放空间中的更长.
汪金辉, 黄意钧, 崔欣, 张少刚, 张睿卿 . 狭长空间火灾烟气传输的准稳态时间模型[J]. 上海交通大学学报, 2022 , 56(6) : 746 -753 . DOI: 10.16183/j.cnki.jsjtu.2021.062
Transport time lag is a crucial characteristic of fire spreading in fire early stage, which determines the activation time of the fire detector. To clarify the quantitative relationship between the delay behavior and the quasi-steady state of smoke transmission in a long-narrow space, a time-varying spreadsheet is theoretically proposed to calculate the delay time of fire smoke transmission based on the theory of weak plume and the existing achievements concerned. Moreover, a theoretical model concerning the critical time for quasi-steady state assumption applicability is developed, where the method of calculating the critical time is also presented. The results of the case study show that due to the difference of smoke spreading velocity in long-narrow spaces and unconfined spaces for a case with the same conditions, the critical time for the smoke transmission to reach the quasi-steady state at a given radial distance on the ceiling in a long-narrow space is larger than that in the open space. For the open case, the thin ceiling plume, the small volume of entrained air, and the relatively high velocity of smoke lead to the longer delay time of smoke transmission in a long-narrow space than that in the open space under the same situations.
Key words： fire smoke; long-narrow space; lag; quasi-steady state model; critical time
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