Axial up-flow fan design for aerodynamic and drainage performance improvements

• Develops an axial fan with improved aerodynamic and drainage performance. • Removing the hub and constructing the fan solely with blades improves fan efficiency. • Incorporating drainage channels into the blades improves drainage performance. • Free-surface flow simulations predict the icicle formation locations on the fan. • The fan starts safely because icicles form only within the drainage channels. A design method for axial up-flow fans has been developed to improve both aerodynamic and drainage performance. The hub protects the motor positioned directly below it from rain. However, it does not contribute to airflow. In cold regions, rainwater draining from the fan can form icicles when the fan is stationary. Reducing the hub size without modifications may lead to icicles forming in the area starting from the lower edge, potentially restricting the motor and preventing safe fan startup. To address this issue, the behavior of rainwater on the fan was predicted, and potential icicle formation locations were identified using numerical simulations based on the lattice Boltzmann method for free-surface flow. Although the hub is removed and the fan consists solely of blades, the incorporation of drainage channels into the blades significantly reduces the water volume affecting the motor. Furthermore, experiments recreating the icicles formed by the fan show that the icicle formation locations match the predicted drainage points at the leading edges of the blades. This indicates that icicles affecting the motor are formed solely in the areas of the drainage channels. Consequently, the force created by the icicles restraining the motor was reduced, allowing for safe fan startup. In terms of aerodynamic performance, experiments have confirmed the occurrence of efficiency improvements across the entire operational range. Aerodynamic simulations reveal that removing the hub enables the blades to work up to the rotation axis, eliminating the hub vortex that causes energy loss.