Estimating the fire growth potential in corridors and tunnels

An experimental study is presented in which the influence of ventilation on the heat release rate in a long and narrow room, such as a corridor or a tunnel, has been investigated. The experimental rig that was used measured 6.4 metres long and with a cross-section of 1x1 m2 and a wood-crib was used as fuel source. Radiation is shown to be of major importance and the classical laws of scaling may not be fully applicable. It is found that there is an almost linear relationship between the ventilation factor and the maximum heat release rate in the enclosure. Furthermore, it is noted that not all of the incoming oxygen is consumed by the fire. A number of blind simulations using the CFD code FDS were carried out in advance of the actual testing. The stand-alone heat release of the free-burning wooden crib was used as input to the program. The results show good or fair agreement during the initial stages of burning but diverge greatly, producing non-physical results, when the oxygen concentration drops within the enclosure and ventilation becomes a factor. The implication of this being that the combustion models that are currently favoured in fire modelling are inadequate in several scenarios relating to vulnerability studies.