1. Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing 100084, China; 2. School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China; 3. Xinjiang Vital Development and Construction (Group) Co., Ltd., Urumqi 830000, China
Abstract：[Objective] To investigate the metro interval tunnel fire under the ceiling multipoint vertical smoke exhaust, the smoke temperature distribution under the tunnel ceiling is analyzed by performing a series of field fire experiments at a scale of 0.25-1.25 MW in a subway section tunnel.[Methods] A fire dynamics simulator numerical simulation tunnel model corresponding to the actual size is established. Subsequently, by increasing the fire source heat release rate (5.00-20.00 MW) and the exhaust air volume of the ventilation tunnel (0-120 m3/s), the critical exhaust air volume and exhaust efficiency is investigated, which can help in mitigating the spread of downstream smoke.[Results] According to the experiment and simulation results, different fire source positions exhibited no effect on the range of the lateral centerline temperature increase area. The position of the smoke exhaust port enabled the suppression of the increase in the ceiling temperature due to the elevated fire source heat release rate. Thus, establishing the air inlet in the metro tunnel could suppress the reverse flow of the smoke; however, it would make the downstream smoke unstable, and the exhaust port could not completely discharge the high-temperature smoke. The smoke temperature of the exhaust port near the fire source, which was related to the fire source heat release rate, but was almost independent of the exhaust air volume. With the increase of the exhaust air volume, it almost remained unchanged. Concurrently, the smoke exhaust port near the fire source played a major role in exhausting the smoke and heat. A critical exhaust air volume completely exhausted all the smoke generated by the fire, whose value was related to the fire source heat release rate. The Fr characterized the ratio of the inertial force to the buoyancy of the smoke layer. The dimensionless Fr was used to determine whether "plug-holing" occurs in the smoke exhaust system. The critical Fr was calculated to be approximately 2.7, slightly higher than that in previous studies.[Conclusions] The exhaust efficiency is an important parameter reflecting the exhaust effect of the exhaust port in the tunnel. The smoke exhaust efficiency of the exhaust port is calculated using the ratio of the mass flow rate of CO in the smoke discharged from the exhaust port and the total downstream CO mass flow rate of the smoke. With the increase in the exhaust air volume, the mass flow of CO discharged from the exhaust port close to the fire source first increases and then gradually becomes flat primarily because the exhaust efficiency of the exhaust port reaches saturation. Therefore, for different exhaust air volumes and fire source heat release rates, the exhaust efficiency first increases and then remains constant. Thus, when the exhaust air volume reaches a certain value, the exhaust port can completely discharge all the high-temperature smoke, and the exhaust efficiency of the port becomes 1. The empirical formula among the smoke exhaust efficiency, the Fr, and the dimensionless wind speed is obtained, and the empirical formula presents a piecewise function relationship.
钟茂华, 胡鹏, 陈俊沣, 程辉航, 吴乐, 魏旋. 顶部多点竖向排烟下地铁隧道烟气控制研究[J]. 清华大学学报（自然科学版）, 2023, 63(5): 754-764.
ZHONG Maohua, HU Peng, CHEN Junfeng, CHENG Huihang, WU Le, WEI Xuan. Research for smoke control in a subway tunnel under the ceiling multi-point vertical smoke exhaust. Journal of Tsinghua University(Science and Technology), 2023, 63(5): 754-764.
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2023, Vol. 63 
