Theoretical Analysis And Experimental Study On Smoke Control In Long Highway Tunnels

The advantages of longitudinal ventilation and semi-transverse ventilation in smoke control are provided by the combined system. In comparison with other ventilation systems, it has more bright engineering application. According to physical meaning, it can be analyzed as the complex propagation and smoke control of the fire plume affected by the upstream vertical airflow and inclined airflow induced by smoke extraction. The present thesis is the result of the efforts devoted to developing the coupling influence of the above disturbing variables.Based on two-layer zone model of reversed flow, critical velocity is introduced into the smoke control solo influenced by the upstream vertical airflow. By use of CFD model, the concerning factors are systematically discussed. And there is a good agreement between CFD analysis and tunnel fire tests in previous study. According to CFD results, the shortcomings and the amending method of the Kennedy model is given out. Furthormore, the stack effect of the long inclined tunnel is developed in the light of heat propagation model downstream the fire.Secondly on the basis of chemical reactions and classic fire test data of the fuels, the fundamental combustion parameters corresponding to heat release rate is givn out. And in terms of Fr number revised by density, the study builds up a 1/14 geometry scale, 1/8 temperature diffence scale, and 0.145 velocity scale model tunnel. In all, 16 sets of tests are comared to fully think over 2 kinds of special upstream air velocity, 4 kinds of extraction volumes and 2 kinds of tunnel height. Detailed temperature and velocity distribution in the tunnel is measured and further validates the CFD model. Moreover the thesis gives out the mass allotment, smoke temperature, extraction effeiciecy between vents and propagation distance along tunnel axial predicted by CFD analysis. Thirdly the dimensionless optimum smoke control parameters are obtained corresponding to heat release rate, tunnel gradient and vent space.In the finality, the problems requiring further studies are discussed.