Study on the smoke movement characteristics in large scale interchange tunnel fire

Abstract For the interchange tunnel fire, the structural features of bifurcation and convergence will make the smoke movement characteristics different from the traditional single tube tunnel fire. This paper carried out numerical simulations by ANSYS Fluent to study the smoke movement characteristics in large scale interchange tunnel fire. Different heat release rates, ventilation velocities and bifurcation angles were considered to analyze the carbon monoxide concentration distribution and critical velocity. Results showed that the CO concentration decreased as the ventilation velocity increased and the variation gradient of CO concentration decreased as the distance away from the fire increased. The CO concentration distribution was symmetrical about the longitudinal centerline of the tunnel when the fire located far away from the bifurcation point, and the asymmetric distribution phenomenon disappeared while the fire located at the bifurcation point. In addition, the critical velocity increased as the bifurcation angle increased while the fire located at the bifurcation point. However, the bifurcation angle had no direct impact on the critical velocity when the fire located far away from the bifurcation point.