**1. Introduction**

The danger of fire in a long and narrow space refers, mainly, to the damage to the building structure caused by high-temperature and toxic smoke [1–3]. Controlling the smoke in a certain area and discharging it out of the buildings in time will help to reduce the fire hazard [4–10]. Therefore, tunnel ventilation and smoke control are the primary issues in tunnel fire safety research. In recent years, ceiling exhaust ventilation has been widely used in tunnel fire. Ventilation data for underwater tunnels constructed by shield tunnelling machine in southern China were collected through field research, as shown in Table 1. Research on the application of point exhaust ventilation in tunnel fire smoke control has been reported extensively. Zhao et al. [11] analyzed the critical smoke exhaust rate and temperature distribution in two-point exhaust tunnels through a 1:20 model test combined with theoretical analysis and obtained the corresponding prediction model. Tang et al. [12] studied the effect of the longitudinal velocity on maximum temperature and found out a calculation model of maximum temperature in a smoke exhaust tunnel. They also explored the influence of smoke exhaust on the transverse temperature profile beneath ceiling, and established a unified temperature calculation model [13]. Tang and other colleagues [14] also studied the effects of longitudinal wind speed and exhaust rate on tunnel fires and proposed a calculation model of smoke distribution considering exhaust volume.

**Citation:** Tao, L.; Zeng, Y. Effect of Different Smoke Vent Layouts on Smoke and Temperature Distribution in Single-Side Multi-Point Exhaust Tunnel Fires: A Case Study. *Fire* **2022**, *5*, 28. https://doi.org/10.3390/ fire5010028

Academic Editors: Chuangang Fan and Dahai Qi

Received: 21 January 2022 Accepted: 16 February 2022 Published: 18 February 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). *fire*


**Table 1.** Ventilation data for underwater tunnels.

Some scholars have also studied lateral ceiling exhaust tunnel fires. Zhu et al. [15] studied the changes of critical wind speed and maximum temperature when the smoke vent is located on the side wall and put forward some calculation models of maximum temperature and critical wind speed that can guide the tunnel fire ventilation design based on the test results. Wang et al. [16] studied the effect of exhaust volume and smoke vent area on smoke back-layering length through a model test and obtained an empirical formula for calculating the length of smoke back-layering considering in a point exhaust tunnel. He et al. and Jiang et al. investigated the characteristics of smoke entrainment at the vent and found that the HRR and smoke exhaust rate have the greatest influence on smoke entrainment coefficient [17,18]. Tao et al. [19,20] studied the smoke control and temperature distribution of a two-point exhaust tunnel and obtained some conclusions and temperature calculation models that could improve tunnel ventilation design.

The factors, such as smoke and temperature distribution, related to evacuating one- or two-point exhaust tunnels have been widely reported [21–23]. A tunnel fire will quickly produce a large amount of toxic smoke. It is difficult to discharge the smoke out of the tunnel by opening only one or two smoke vents. Therefore, the design of tunnel fire ventilation allows for multiple smoke vents to be opened at the same time. More importantly, the traditional smoke exhaust tunnel will discharge the smoke from both sides of the tunnel, which will cause waste for some short tunnels. A separate fan room needs to be built for tunnel ventilation, and the cost is often very expensive. If fan rooms are designed only on one side and the exhaust duct outlet of the tunnel on the other side is closed, it will reduce not only the cost of construction but also the number of axial-flow fans. It will also greatly reduce the maintenance cost of ventilation facilities during operation. This kind of smoke extraction scheme was adopted in the Mawan Tunnel in Shenzhen, China. Unfortunately, the fire characteristics in single-side point exhaust tunnels have not been reported.

To fill this gap, this paper verified the reliability of the numerical model based on the tunnel model. The effects of different smoke vent opening modes and smoke exhaust rate on the smoke distribution, maximum temperature, temperature attenuation, and smoke exhaust efficiency in the tunnel were studied based on the numerical results.
