Simulation Study on Critical Velocity of Longitudinal Ventilation Tunnel Fire

The critical velocity of tunnel fire of ten groups power from 10 to 100 MW were simulated using FDS. The critical velocities under different fire power were determined. For example 50MW tunnel fire. The inside the tunnel temperature, speed and visibility distribution at Y = 5m under the critical velocity were studied. Through the comparison of the gas average temperature of fire source upstream and downstream, and the average visibility of 0-195m,195-250m, 250-300m, 300-350m, 350-400m. The effects of the critical velocity to rescue and evacuation during tunnel fire were analyzed. The relationship curve between critical velocity and heat release rate was fitted out, and obtained that the simulation curve is closer to the results of Bettis by contrast with the empirical formula of Bettis and Thomas.