受限距离影响下竖向顺流火蔓延规律研究

以长45.0cm、宽5.0cm、厚2.0mm的广告画布作为研究对象，开展了受限距离为3.0~9.0cm的竖向顺流火蔓延实验，定量分析受限距离对火焰长度、火蔓延速度、点燃时间等参数的影响。结果表明：受限距离3.0~8.0cm时，受限侧火焰长度明显大于未受限侧火焰长度；受限距离超过8.0cm时，两侧火焰长度基本一致。随受限距离增加，火焰长度与火蔓延速度均表现为先增加后减小，最终趋于稳定，而点燃时间则表现为先减小后增加，最终趋于稳定值。建立了材料表面接收热流与点燃时间的关系式，分析了材料表面接收热流随受限距离的变化趋势，阐释了火蔓延速度随受限距离非单调变化的原因。

Experimental studies on upward flame spread underlimited distance effects

Using 45 cm tall, 5.0 cm wide and 2.0 mm thickadvertising canvas，the effects of limited distance with the range of3.0~9.0 cm between wall and fuel surface on flame length, spread rate andignition time are quantitatively analyzed. The major conclusions are summarizedas follows: When the limited distance is 3.0~8.0 cm，the flame length onlimited side is larger than that on unlimited side, whereas when limiteddistance is beyond 8.0 cm, the flame lengths on both sides are basically thesame. Both the flame length and spread rate first increase and then decreasewith limited distance, and finally reach a constant value, while the ignitiontime decreases first and then rises with limited distance, and ultimatelyachieves a stable value. The relationship between the heat flux received byvirgin surface and ignition time is established. Moreover, the variation trendof the heat flux received by virgin surface with the limited distance isanalyzed, which can be used to explain the cause of the non-monotonic trend inspread rate.