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分析了均匀水平燃料床从一个点火源的着火过程 ,建立了林火蔓延初期的增长模型 ,采用数值法计算了蔓延初期的加速度与速度的变化趋势。并通过室内模拟实验 ,在燃料床上测取了林火初期蔓延速度。通过对着火后1 0 0 s的实验数据与计算结果的比较 ,说明所使用的初期蔓延过程的增长模型在物理上是合理的。从实验结果分析看出 ,在着火后 2 0 s以内 ,及在着火后 80 s～ 1 0 0 s锥形火焰向环形火焰转化时 ,火蔓延速度与加速度剧烈地波动。由理论模型计算得到 ,森林火灾从一个点火源着火以后 ,大约需要 0 .5h才能达到稳定的蔓延速度 ,由于受实验条件所限 ,在室内模拟这个过程是困难的。
The ignition process of a homogeneous fuel bed from an ignition source was analyzed, and the growth model of initial stage of forest fire spread was established. The changing trend of acceleration and velocity in the early stage of propagation was calculated by numerical method. Through indoor simulation experiments, the initial spread of forest fire was measured on the fuel bed. The comparison between the experimental data and the calculated results after 1 000 s after the fire shows that the growth model of the initial propagation process used is physically reasonable. From the experimental results, it is found that the flame spread and acceleration fluctuate violently within 20 s after ignition and 80 s ~ 100 s after the ignition. Calculated from the theoretical model, after a forest fire has been ignited from an ignition source, it takes about 0.5 h to achieve a steady propagation rate. Due to the limited experimental conditions, it is difficult to simulate this process indoors.