Full scale measurements of the operation of fire ventilation in a road tunnel

The main aim of the research performed was to check the operation of a ventilation system in a conventionally operated road tunnel in Southern Poland. The length of the examined tunnel is 678 m and it has a gradient of 4%. It includes longitudinal ventilation. The measurements of normal and reversed velocity of air flows (which were forced by the fans) were conducted at two cross-sectional profiles inside the tunnel. A set of fourteen thermal anemometers was applied there. In addition, at the intake and exit portals the wind direction, wind velocity and temperature were recorded during the tests. The fans worked according to the emergency operation pattern. The results were compared to estimated critical velocity and the correct functioning of the ventilation system was confirmed. The results showed a significant influence of the naturally caused airflows. Numerical simulations were performed to determine the air velocity resulting from this effect. CFD Ansys Fluent was used to solve the simplified model of the tunnel. The results confirmed that the combination of the stack effect and wind influence is crucial.