Scale modelling experiments on the effect of longitudinal ventilation on fire spread and fire properties in tunnel

Fire spread between vehicles is of a great concern in a tunnel fire. Longitudinal ventilation, which is commonly used for the smoke control in tunnel fire, would inevitably affect fire properties and fire spread in tunnel at the same time. Such effects were studied using model-scale experiments in this paper. The results show that fire spread mostly occur due to the flame touching arising from flame tilting under longitudinal flow. Safety spacing should be kept for preventing fire spread between vehicles. The effect of longitudinal ventilation on the temperature distribution in the downstream area of the fire source is found mainly limited to the vicinity of the fire source. Maximum ceiling temperature, flame tilt angle and downwind flame temperature under longitudinal ventilation are found to be heavily dependent on Fr (Froude number) and dimensionless Q* (Dimensionless heat release rate). The formulas of flame tilt angle and mean downwind flame temperature were developed and predicted results were compared with those in modelling experiments.