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Theoretical Prediction of the Thermal Parameters of a Roof Close to a Fire Source in a Tunnel with a Concentred Smoke Extraction System
1 Shandong Jianzhu University 2 Key Laboratory of Renewable Energy Utilization, Ministry of Education 3 Shandong Provincial Key Laboratory of Renewable Energy Utilization in Buildings
Abstract Because a concentred smoke extraction system enables the diffusion range of upstream and downstream smoke to be better controlled, it is widely used in the design of long tunnels. In this paper, a theoretical model of defined diffusion of a fire plume in a tunnel with a concentred smoke extraction system is established for a small-scale fire scenario, and these theoretical results are compared with experimental results to verify the theoretical model and predict such thermal parameters as the maximum temperature rise and the offset distance of smoke underneath the tunnel roof. The prediction results show that: 1) the maximum temperature rise of smoke drops sharply with an increase of equivalent wind velocity when the fire intensity is unchanged, and the fire intensity has a remarkable effect on the temperature rise; 2) when the equivalent wind velocity is over 1.5 m/s, the rising temperature will slow down until it becomes constant; 3) however, the plume has no obvious offset when the wind velocity is small, as its offset increases with an increase of wind velocity but its change rate decreases with an increase of fire intensity. Based on the regression method, a dimensionless criterion correlation is obtained regarding the maximum temperature rise and offset distance of smoke underneath the tunnel roof.
Abstract：
Because a concentred smoke extraction system enables the diffusion range of upstream and downstream smoke to be better controlled, it is widely used in the design of long tunnels. In this paper, a theoretical model of defined diffusion of a fire plume in a tunnel with a concentred smoke extraction system is established for a small-scale fire scenario, and these theoretical results are compared with experimental results to verify the theoretical model and predict such thermal parameters as the maximum temperature rise and the offset distance of smoke underneath the tunnel roof. The prediction results show that: 1) the maximum temperature rise of smoke drops sharply with an increase of equivalent wind velocity when the fire intensity is unchanged, and the fire intensity has a remarkable effect on the temperature rise; 2) when the equivalent wind velocity is over 1.5 m/s, the rising temperature will slow down until it becomes constant; 3) however, the plume has no obvious offset when the wind velocity is small, as its offset increases with an increase of wind velocity but its change rate decreases with an increase of fire intensity. Based on the regression method, a dimensionless criterion correlation is obtained regarding the maximum temperature rise and offset distance of smoke underneath the tunnel roof.
.Theoretical Prediction of the Thermal Parameters of a Roof Close to a Fire Source in a Tunnel with a Concentred Smoke Extraction System[J] MODERN TUNNELLING TECHNOLOGY, 2015,V52(2): 115-119
2015, Vol. 52 