Abstract
One of the main problems that could be suffered by the fans installed in the definitive ventilation systems is stalling, this being one of the major causes of concem for the operation contractors in charge of the ventilation systems of tunnels.
Stalling in axial fans is a phenomenon that can be compared with the situation experienced by aircraft wings where, as the angle of incidence of the airflow is increased, the lift force increases first, but falls abruptly when a certain critica! angle is exceeded. Figures 1 and 2 show both flow conditions.