The individual and combined effect of a water mist system (WMS) and longitudinal ventilation (LV) on the fire HRR, smoke temperature and back-layering (BL) degree were explored in a 3 m (width)$\times$2.2 m(height)$\times$30 m (length) tunnel model. A series of 39 tests has been conducted in 6 configurations, varying the velocity, water volume flow rate and nozzles arrangement. When the WMS or LV is imposed individually, the reduction effect on the HRR gets stronger with larger water volume flow rates or higher velocities. Yet, under the combined effect, the effect of the LV velocity on the HRR is non-monotonic: the HRR first reduces more, and then rises again with higher LV velocities for given WMS settings. The reduction in temperature monotonically increases with higher LV velocities, in contrast to the HRR behavior. The above phenomenon is explained to be due to the relatively ‘low’ flame height in the present paper, as a consequence of which the interaction between the flame and the water droplets mainly occurs in the lower part of the tunnel, while the interaction between the hot smoke and the water droplets mainly happens in the upper part. The fire HRR behavior mainly relates to the interaction in the lower part, while the temperature depends on both regions. Besides, for a certain BL distance, the required ventilation velocities reduce by 13%–55% with activated WMS, compared to the same conditions without WMS. The effect of covering the fire with a shield is also discussed. For relatively small velocities, the fire HRR, smoke temperature and BL distance are larger with the shield in place.

在3 m（宽）范围内，探索了水雾系统（WMS）和纵向通风（LV）对火灾HRR，烟气温度和背层（BL）程度的单独和综合影响。$\times$2.2 m（高度）$\times$30 m（长）隧道模型。已经在6种配置中进行了39项测试，改变了速度，水体积流量和喷嘴的布置。当单独施加WMS或LV时，随着水体积流量或速度的增加，对HRR的降低效果会越来越强。然而，在综合作用下，LV速度对HRR的影响是非单调的：对于给定的WMS设置，HRR首先降低更多，然后随着更高的LV速度再次升高。与HRR行为相反，温度的降低随较高的LV速度单调增加。解释上述现象是由于本文中的火焰高度相对较低，其结果是火焰与水滴之间的相互作用主要发生在隧道的下部，而热烟与水滴之间的相互作用主要发生在上部。火灾HRR行为主要与下部的相互作用有关，而温度取决于两个区域。此外，在一定的BL距离下，与没有WMS的相同条件相比，激活的WMS所需的通风速度降低了13％-55％。还讨论了用屏蔽罩掩盖火的效果。对于相对较小的速度，在安装防护罩的情况下，火灾的HRR，烟雾温度和BL距离较大。与没有WMS的相同条件相比，激活的WMS所需的通风速度降低了13％–55％。还讨论了用屏蔽罩掩盖火的效果。对于相对较小的速度，在安装防护罩的情况下，火灾的HRR，烟雾温度和BL距离较大。与没有WMS的相同条件相比，激活的WMS所需的通风速度降低了13％–55％。还讨论了用屏蔽罩掩盖火的效果。对于相对较小的速度，在安装防护罩的情况下，火灾的HRR，烟雾温度和BL距离较大。