CFD Based Simulation Analysis On Research Of Temperature Properties Of Vehicle Fire In Large Cross-section Road Tunnel

The significant road tunnel fire which happened frequently in all the countries in recent years caused the tunnel fire protection to become the hotspot and the difficult point on the international fire research work. The high temperature and quantity of heat and the massive corrosiveness combustion gas caused by tunnel fire could often endanger personnel's safety, and lead derogation to vehicles, materials and facilities in tunnel. At the same time, the fire also could destroy the tunnel structure, and reduce the whole stability of tunnel.In this paper, taking Shanghai Yangtze tunnel as application example, the temperature properties for large cross-section road tunnel in case of vehicle fire including the maximum vault temperature, the temperature-time curve, the temperature field distribution in longitudinal direction, horizontal direction and transverse direction were studied based on CFD simulation technology. Ten fire scenarios were set synthetically considering different fire loads and ventilation velocities under longitudinal ventilation in CFD model.The main research results obtained through the CFD simulation study includes:1. The temperature field distribution in horizontal direction assumed three-section phenomena: in the initiatory scope downstream the fire source called "two-side high temperature section", the central region temperature was obviously lower than two-side region; in the followed scope downstream the fire source called "central high temperature section ", the two-side region temperature was obviously lower than central region; in the last scope downstream the fire source called "even temperature section", the temperature distributed evenly.2. The fire protection design of tunnel structure should consider its interior possibly maximum temperature, temperature elevation characteristic and structure behavior in case of fire, and ascertain the corresponding fire loads and temperature-time curve. As for the medium-size and small-size fire loads, ISO834-standard temperature time curve should be adopted in the tunnel fire protection design. Regarding the large-size fire load(50MW), two kinds of situations should be considered: (1) ventilation velocitiy 3m/s, 4m/s, the wide-open environment carbon hydrogen curve should be adopted in the tunnel fire protection design; (2) ventilation velocitiy 5m/s, ISO834-standard temperature time curve may be adopted in the tunnel fire protection design.Two fire protection design standards of structure may be divided in large-cross section road tunnel: (1) the mountain road tunnel, Heart Release Rate 20MW; (2) the seabed/river road tunnel, Heart Release Rate 50MW. The computing formula of the maximum vault temperature was proposed corresponding to different fire protection design standard.