Influence of leading-edge obstacles on flow field and noise of axial flow fan for building ventilation

Axial fans are widely employed in ventilation and air-conditioning systems, yet the associated noise pollution remains a significant challenge. This study investigates the influence of leading-edge modifications on the aerodynamic performance and noise characteristics of an axial flow fan utilized in building ventilation. Three types of leading-edge obstacles, including tetrahedral, hemispherical, and semi-cylindrical, were applied to the fan blades, and their impact was assessed through numerical simulations using FLUENT, incorporating turbulence and broadband acoustic models. The results reveal that leading-edge obstacles can effectively reduce noise by mitigating trailing-edge vortex shedding, improving airflow stability, and decreasing pressure pulsations and noise frequency amplitudes near the impeller root. Among the tested configurations, attributed to the enhanced airflow uniformity and minimized aerodynamic interference, the semi-cylindrical obstacle exhibited superior performance in noise reduction, particularly at the fan outlet where the maximum sound power level is reduced by 12.4 %. Limited experimental noise measurements were performed to confirm the noise reduction. This study provides valuable insights into the design of low-noise fan blades for building ventilation systems, highlighting the potential of leading-edge modifications to achieve substantial noise reduction without compromising aerodynamic efficiency.