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Building Simulation 2021年第4期14卷 1311-1323页

作者： Longxing Yu Huaxian Wan Jie Ji State Key Laboratory of fire Science University of Science and Technology of ChinaJinZhai Road 96HefeiAnhui230026China College of Environment and Resources Fuzhou UniversityXueyuan Road 2FuzhouFujian350116China

This paper has analyzed the asymmetric flow effect of fire-induced thermal flow in a horizontal tunnel under the natural ventilation condition by conducting large eddy simulations (LES). The key objective is to reveal and to have a better understanding of the asymmetric flow effect caused by the upstream and downstream tunnel length difference. The mechanism behind it can be explained based on the conservation of mass and dynamic force analysis on the smoke and fresh air. The strength of the asymmetric flow effect is characterized by the mass flow rate of the induced longitudinal flow (net mass flow rate of a cross-section). An empirical correlation to predict the induced longitudinal mass flow rate is proposed. Furthermore, the law of smoke and air flow distribution within a horizontal tunnel is established. The proportion of smoke (or air) flowing out (or coming in) through the opening increase (or decrease) linearly with the increasing distance between that opening to the fire location. The variation of the air flow with the longitudinal fire location in a tunnel is more sensitive than the smoke flow. Results have shown that as the fire approaches the tunnel exit from the middle of the tunnel, the smoke spilling out through this opening is reduced from 50% to 40%, while the fresh air incoming from this opening is increased from 50% to 100% and vice versa.

关键词： asymmetric flow effect fire location thermal flow smoke tunnel fire CFD

A numerical study on smoke behaviors in inclined tunnel fires under natural ventilation

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Journal of Safety Science and Resilience 2022年第2期3卷 169-178页

作者： Jie Kong Wenjiao You Zhisheng Xu Hui Liu Haihang Li College of Quality&Safety Engineering China Jiliang UniversityHangzhou 310018China Zhejiang Police College Hangzhou 310053China School of Civil Engineering Central South UniversityChangsha 410075China

To investigate the effect of tunnel slope on hot gas movement and smoke distribution in a slopping tunnel fire,a series of tunnel fire models are built by fire dynamics simulator(FDS),with a slope varies from 0 to 10%.Parameters such as ceiling temperature and airflow velocity are measured.The results indicate that the relationship between smoke back-layering length and tunnel slope can be described as an exponential function.The smoke temperature at the downstream exit first increased and then decreased with a higher slope.The airflow velocity at downstream outlet increased nonlinearity when tunnel slope was less than 8%.In the slope tunnel,the fire smoke spread process can be divided into three stages.fire smoke spreads upstream to the peak distance,subsequently,the upstream smoke layer decreases gradually,the tunnel fire reaches a quasi-steady state.The backflow characteristics of smoke in sloped tunnels are coupled with the downstream length and outlet smoke temperature.In the initial stage of a slope tunnel fire,smoke spreads upstream for a long distance,endangering human health.

关键词： tunnel fire Slope Stack effect Smoke movement Back-layering length

Numerical and experimental study on the critical velocity and smoke maximum temperature in the connected area of branch tunnel

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Building Simulation 2022年第4期15卷 525-536页

作者： Haihang Li Fei Tang Safety Engineering Institute College of Quality and Safety EngineeringChina Jiliang UniversityHangzhouChina State Key Laboratory of fire Science University of Science and Technology of ChinaHefei230026China

The objective of this study is to investigate critical velocity and smoke maximum temperature beneath the ceiling in the connected area of branch tunnel with varying fire locations.The fire sources were located in the divergent connected area of the branch tunnel,to imitate traffic accidents near the branch point.A 1/20 scale model branch tunnel was built including main line before branch,main line after branch,and ramp.Experimental tests and numerical simulations were performed to explore smoke movement characteristics with longitudinal ventilation.The results showed that the enlarged cross-sectional area in branch tunnel caused the shortening of the back-layering length,and a modified model of back-layering length was proposed.The higher tunnel height in this work affected the critical condition of large fire;it caused a larger transition point of dimensionless critical velocity.A revised model was proposed for the maximum temperature rise of tunnel fires in the connected area of branch tunnel.The critical velocity kept unchanged when the branch angle increased from 0°to 20°because there is little change in the longitudinal smoke temperature.As the local tunnel width of fire source was increased,the required critical velocity was increased while the local effective velocity kept nearly the same.

关键词： tunnel fire critical velocity maximum temperature dimensionless back-layering length branch tunnel

A multi-purpose prototype test system for mechanical behavior of tunnel supporting structure: Development and application

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第2期15卷 467-476页

作者： Hongbin Chen Xinhua You Dajun Yuan Yang Ping China State Construction Engineering Corporation Ltd. Beijing100029China tunnel and Underground Engineering Research Center of Ministry of Education Beijing Jiaotong UniversityBeijing100044China

A multi-purpose prototype test system is developed to study the mechanical behavior of tunnel sup-porting structure,including a modular counterforce device,a powerful loading equipment,an advanced intelligent management system and an efficient noncontact deformation measurement system.The functions of the prototype test system are adjustable size and shape of the modular counterforce structure,sufficient load reserve and accurate loading,multi-connection linkage intelligent management,and high-precision and continuously positioned noncontact deformation measurement.The modular counterforce structure is currently the largest in the world,with an outer diameter of 20.5 m,an inner diameter of 16.5 m and a height of 6 m.The case application proves that the prototype test system can reproduce the mechanical behavior of the tunnel lining during load-bearing,deformation and failure processes in detail.

关键词： Prototype test system tunnel supporting structure tunnel fire Lining Mechanical behavior

Optimization of smoke exhaust efficiency under a lateral central exhaust ventilation mode in an extra-wide immersed tunnel

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2021年第5期22卷 396-406页

作者： Song-lin LIU Liang WANG Ming-gao YU Yong-dong JIANG State Key Lab of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China

This study focused on increasing the efficiency of the smoke exhaust system of an extra-wide(eight-lane,dual-directional)immersed tunnel with a specific quantity of exhaust.The Shenzhen-Zhongshan immersed tunnel was selected as the application example.A numerical simulation based on fire dynamics simulator was conducted.In the model,the concrete structure of the main body of the immersed tubes was not altered.The adoption of supplementary exhaust ducts increased the efficiency from 73%to 98%under the condition of no longitudinal wind.When a 50-MW fire occurred between two adjacent ducts,with a longitudinal wind velocity of 2 m/s,the efficiency reached 88%or more when the two ducts were opened.Furthermore,a safety evacuation path was developed.The results suggest that the addition of supplementary exhaust ducts combined with a rational longitudinal wind velocity is necessary for an extra-wide immersed tunnel.

关键词： tunnel fire Lateral central smoke exhaust Supplementary exhaust duct Large eddy simulation

Numerical simulation of smoke stratification in tunnel fires under longitudinal velocities

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Underground Space 2021年第2期6卷 163-172页

作者： Yuhao Guo Zhongyuan Yuan Yanping Yuan Xiaoling Cao Peng Zhao School of Mechanical Engineering Southwest Jiaotong University111Second Ring RoadChengdu CitySichuan Province 610031PR China

Use of the longitudinal critical velocity in tunnel fires may destroy the stratification of smoke downstream,which is not conducive to the evacuation of downstream tunnel users.Reducing the longitudinal velocity can maintain stratification,but the appropriate longitudinal velocity range is unknown.Stratification of smoke under the longitudinal velocity is studied using fire Dynamics Simulator(FDS).The aims of this paper are to explore the relationship between the longitudinal velocity and smoke stratification and to obtain a proper velocity range that can maintain clear downstream stratification.Based on Newman's theory,the"stratification velocity"is proposed,which is the maximum velocity that maintains downstream smoke stratification.A good correspondence between the average Froude number within 200 m downstream and the longitudinal velocity and heat release rate(HRR)is found.The correlation between the temperature stratification and Froude number is obtained.Fr=0.49 can be used to distinguish whether the stratification is clear.The relationship between the critical velocity and the stratification velocity is also discussed.

关键词： tunnel fire Longitudinal ventilation Smoke stratification

NUMERICAL SIMULATION ON EMERGENCY tunnel fireS WITH TRANSVERSE VENTILATION

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Journal of Hydrodynamics 1999年第3期11卷 111-126页

作者： Wang Qian, Nobuyoshi Kawabata, Motoyoshi Tachibana Fukui University, 3 9 1 Bunkyo, Fukui 910 8507, Japan Fumio Watanabe Echo Plan Co. Ltd, 1 1 11 1207 Ishimachi, Chuo ku, Osaka 540 0033, Japan (Received Feb.2, 1999)

In case of an emergency fire in vehicle tunnel, the ventilation system should be operated effectively to control the thermal fume and smoke inside tunnel. However, it is quite difficult to predict every kind of emergency fire by fire tests because the actual movement of thermal fume and smoke is affected by many factors such as ventilation system, structure of the tunnel, etc., especially for tunnels equipped with transverse ventilation system on which rare experimental and numerical studies have been found so far. In this paper, a three dimensional numerical simulator using LES turbulence model is developed to simulate the movement of thermal fume induced by emergency fire in vehicle tunnel. The SMAC method is employed to calculate the pressure and velocity fields. The upwind differnece scheme with the third order accuracy is applied for the discretization of convection terms of the governmental equations. As the applications of the present simulator, the behavior of thermal fume induced by emergency fire in a vehicle tunnel with two direction traffic is analyzed. It is confirmed that the partial transverse ventilation system is more effective than the longitudinal ventilation system under large and small velocities of longitudinal bulk flow inside tunnel. Simulation result also shows that remaining the velocity of longitudinal bulk flow near zero around fire source can provide the best working condition for partial transverse ventilation system.

关键词： tunnel fire transverse ventilation exhaust duct thermal fume longitudinal velocity backflow numerical simulation two direction traffic