Description
The ventilation systems for underground transport infrastructures are designed based on optimised solutions to ensure the safety and comfort of the users. Following these design criteria, axial fans are specified to provide required performance values such as flow, pressure, reversibility and acoustic levels, improving fan efficiencies and minimizing power consumption. However, the ventilation system design and subsequent fan specification often fall short in identifying and preventing potential issues that may lead to catastrophic fan failures, such as severe stall episodes during fan operation. It is crucial to prevent stall in fans when they operate outside the range for which they were designed. This paper analyses the two most commonly used solutions to prevent stall: fans with anti-stall devices and stall-free fans, evaluating their performance. With carefully design considerations, stall-free axial fans can achieve comparable efficiencies with standard axial fans. A minor deviation from the fan operating point induces a standard axial fan into stall. To alleviate this, standard axial fans are equipped with anti-stall devices, but their efficiency significantly decreases. Additionally, most axial fans for metros and tunnels need to be reversible, requiring the installation of two anti-stall devices, resulting in further efficiency reduction. It is in this context that an assessment on the performance of stall-free axial fans and a comparison with standard axial fans with anti-stall devices become necessary.
This paper presents the aerodynamic tests conducted in an AMCA Accredited Laboratory, along with the conclusions drawn from this comparative analysis.
