点火源引燃条件下坡度和载荷对火蔓延影响的实验研究

发布时间：2018-05-11 04:43

本文选题：地表火蔓延 + 点火源引燃　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：森林地表火蔓延是森林火灾最主要的形式。本文主要研究点火源引燃条件下坡度和燃料载荷对火蔓延过程的影响。在变坡度火蔓延实验台上,用刨花丝为燃料,分别开展变化7个坡度角和3种燃料载荷的点火源引燃火蔓延实验研究。重点分析火焰几何参数(火线夹角,火焰倾斜角,火焰长度)、火线形状、全局火蔓延速率、局部火蔓延速率以及火前锋阻滞时间的变化规律。上坡火线夹角、火焰倾斜角随坡度角的增大而减小,火焰长度随坡度角的增大而增大。平坡条件下,火线呈规则的圆形,阻滞时间高于上坡火前锋的阻滞时间。坡度条件下,火线形状会呈泪滴状,当坡度角低于20°时,上坡火蔓延速率随坡度角缓慢增大;当坡度角高于20°时,上坡火蔓延速率随坡度角迅速增大。上坡火蔓延表现出整体稳定和局部波动的特征。自引燃点向下、左、右的火蔓延速率随坡度角的增大震荡变化。上坡火焰长度随着载荷的增大而增大,引燃点位置向上、下、左、右的火蔓延速率均随载荷的增大而增大。高坡度条件下(22.5～30°)上坡火蔓延速率随着载荷增大的速率,高于低坡度条件(O～20°)。除平坡外,任意坡度下4个方向上的火前锋平均阻滞时间均随载荷的增大而增大。上坡火蔓延过程中,随坡度角增加,火焰长度增长且火焰倾斜角增大,火焰对燃料的辐射传热增强,引发了火蔓延速率的增大。
[Abstract]:The spread of forest surface fire is the main form of forest fire. In this paper, the effects of slope and fuel load on the process of fire propagation are studied. In this paper, the flame propagation of ignited sources with 7 slope angles and 3 kinds of fuel loads were studied by using planed wire as fuel on the fire spread test bench with variable slope. The variation of the geometric parameters of the flame (the angle between the lines of fire, the angle of the flame inclination, the length of the flame, the shape of the line of fire, the global fire spread rate, the local fire spread rate and the fire front block time) are analyzed. The angle between the fire line and the slope angle of the fire line decreases with the increase of the slope angle, and the flame length increases with the increase of the slope angle. Under the condition of flat slope, the fire line is regular and circular, and the blocking time is higher than that of the fire front on the slope. When the slope angle is lower than 20 掳, the fire spread rate increases slowly with the slope angle, and when the slope angle is higher than 20 掳, the fire spread rate increases rapidly with the slope angle. The upslope fire spread shows the characteristics of global stability and local fluctuation. The fire spread rate varies with the increase of slope angle. The flame length of the slope increases with the increase of the load, and the fire spread rate increases with the increase of the load at the position of ignition point upward, down, left and right. Under high slope condition, the rate of fire spread on the slope is higher than that on the low slope condition by 20 掳with the increase of load. With the exception of flat slope, the average block time of fire front increases with the increase of load at any slope in four directions. In the process of slope fire spread, the length of flame increases and the angle of inclination increases with the increase of slope angle, and the radiative heat transfer between flame and fuel increases, which leads to the increase of fire spread rate.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S762

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