Numerical Simulation Study On The Combined Fire Ventilation In Crossing-River Tunnel

The combined ventilation system is a late-model ventilation system .In the paper, tunnel space feature, the existing combined ventilation system, tunnel fire study method and existing condition are recommended. Especially when the fire happens in the tunnel center, commercial numerical simulation soft is used and 3D mathematic physics model is build according to the conservation laws are obeyed by the state parameters in the tunnel fire. The differential equation of model is discretised by using the finite volume method, and then it is solved by using SIMPLEC method.The cross-river tunnel is from Wu chang to Han kou. Because of its particularity, the combined longitudinal and semi-transverse ventilation system is used. The existing problems are uncertainty of space length of draft tuyeres and multiplicity of the ventilation schemes .When the fire happen, the hot smoke must be discharge in time.Different ventilation systems greatly influent fire momentum of development and smoke control. In the paper, the left cavern is subject investigated and CFD method is adopted. When the fires happen in different positions, many work conditions are numerical simulated and investigated.Opening upstream draft tuyeres, different modes of blowing-in and discharge air of the shafts, longitunal blow-in velocity, number of opening draft tuyeres and space length of draft tuyeres are combined and simulated. The influences from them on the velocity field and the temperature field are gotten. According to the safety escape requirement of person in tunnel, structure of tunnel, equipment, and the working environment requirement of axial flow fan, the proper mode of opening draft tuyeres, the proper mode of blowing-in and discharge air of the shafts, the best longitudinal blow-in velocity and space length of draft tuyeres are defined. The optimum ventilation scheme is defined finally when the fire happens in the tunnel center.On the base, the fire condition of other positions in the tunnel are simulated and the proper ventilation schemes are defined.