Critical velocity and range of a fire-gas plume in a ventilated tunnel

To protect passengers, personnel and equipment in a tunnel fire, it is important to understand and predict the movements of the hot-gas plume. To estimate the range of a fire plume propagating under the ceiling, a model is presented, that depends on two important parameters, i.e. the energy release rate of the fire and the velocity of the ventilation flow. The theoretical results, concerning the upwind range of the plume, agree favourably with experimental data obtained from eight tunnel fire tests. The theoretical value of the critical ventilation velocity, required to arrest the upwind movement of the fire-gas, agrees well with the corresponding experimental results for a wide range of energy release rates. The influences of air entrainment, friction at the ceiling and the associated heat loss are analysed and the results discussed