In the case of a tunnel fire, it is likely that the evacuation path of some of the tunnel users will be obstructed by the cloud of smoke that falls to the road surface of the tunnel. It is important to be able to predict the falling point of the ceiling jet smoke resulting from the fire for improving evacuation strategy. However, a considerably long tunnel is required for examining the distance traveled by the smoke generated in full and model scales fire experiments. It is often difficult to satisfy this requirement while performing fire experiments at laboratory scale. The objective of this study was to develop a new technique for examining the smoke falling phenomenon by using a model scale tunnel with insufficient length. In the new technique, a cooling apparatus was introduced to simulate heat transfer from smoke to tunnel walls. If the amount of convective heat absorbed by the cooling apparatus with length L_c is equivalent to the amount of convective heat lost by the heat transfer to the tunnel walls while the smoke flowed through the distance L_s under a tunnel ceiling, the cooling apparatus with length L_c can be equivalent of a tunnel length L_s. We denote the tunnel length simulated by the cooling apparatus by a pseudo tunnel length. A series of fire experiments were conducted using a 1:10 scale model tunnel with a length of 12 m. In this study, we assessed the effectiveness of the technique for simulating a pseudo tunnel. Experimental results showed that a tunnel with a length of 18.6 m can be simulated by a 12 m tunnel using the new technique proposed.

在发生隧道火灾的情况下，一些隧道用户的疏散路径可能会受到掉落到隧道路面上的烟雾云的阻碍。重要的是要能够预测火灾引起的天花板喷射烟气的下降点，以改善疏散策略。但是，需要一个相当长的隧道来检查在全尺寸和模型规模的火灾实验中产生的烟雾所经过的距离。在实验室规模进行火灾实验时，通常很难满足这一要求。这项研究的目的是开发一种新技术，通过使用长度不足的模型规模隧道来检查烟雾下降现象。在新技术中，引入了一种冷却装置来模拟热量从烟雾传递到隧道壁的过程。L _c等于当烟雾流过隧道顶棚下的距离L _s时，热量传递到隧道壁所损失的对流热量，长度为L _c的冷却设备可以等于隧道长度L _s。我们用伪隧道长度来表示由冷却装置模拟的隧道长度。使用长度为12 m的1:10比例模型隧道进行了一系列火灾实验。在这项研究中，我们评估了模拟伪隧道技术的有效性。实验结果表明，使用该新技术可以通过一条12 m的隧道模拟一条长度为18.6 m的隧道。