火灾节流过程参数变化时序及其影响因素的研究

巷道火灾节流过程中各物理参数变化时序是正确模拟非稳态火灾过程和救灾决策的基础。通过实际规模的火灾试验,三维布点,自动采集数据。研究揭示:节流发生的时段为着火初期燃料挥发分的快速释放和燃烧的数分钟以内;此时,烟温小于330℃,升温速率为138℃/min,耗氧速率为3.4%/min,阻力的响应速率为8.5Pa/min;着火分支节流函数的最小值为0.83,其入口风速滞后下降速率为1.67×10-3m/s2;温度峰滞后于氧气浓度谷点、节流函数最小点和阻力峰的时间分别为1.6min,4.2min和5.6min,使用温度峰值计算最大阻力的传统方法是错误的。提出了描述节流度的定量方法,并导出了影响节流效应的因素为系统和风机特性参数、火灾发生的位置、比燃料消耗速率、火风压和热阻的方向及增长速率。

Study on Parameter Variation Time-sequence in Fire-throttling Process and Its Influence Factors

In the process of tunnel fire throttling, the variation time sequence of various physical parameters is the bases for accurately modeling the unsteady fire process and fire fighting decision-making. Through full scale tunnel fire test with 3-dimensional automatic data collection, it is shown that the occurrence period of fire throttling or within several minutes when combustion occurs corresponds to the primary fire stage of rapid devolatilization of the fuel. At this point, the temperature of the smoke is below 330℃, the rate of temperature elevation is 138℃/min,the rate of oxygen consumption is 3.4%/min,and the response rate of resistance is 8.5 Pa/min. The minimum value of throttling function in fire zone is 0.83, the in-let wind speed lag declining rate is 1.67×10 -3 ?m/s 2. The temperature peak usually lags behind the trough of oxygen concentration,the minimum point of throttling function,and the resistance peak,the time-lag are 1.6 min, 4.2 min and 5.6 min respectively, from which it could be seen that the traditional method for calculating the maximum resistance from the temperature peak is not correct. The quantifying method for describing the extent of throttling is put forward, and the factors influencing throttling efficacy are derived, i.e. characteristic parameters of ventilation network and the fan, the location of fire occurred, the ratio of fuel consumption rate, and the direction and its increasing rate of heat potential and heat resistance.