Numerical Analysis of Bionic Inlet Nozzle Effects on Squirrel-Cage Fan Flow Characteristics

In order to improve the inlet distortion of the squirrel-cage fan, this study proposes a parametric design method for the bionic structure of the inlet nozzle generatrix, which is spliced by multiple sinusoidal curves, based on the bionic structure of the humpback whale flipper leading-edge nodule. The geometric shape of the bionic generatrix is controlled by three parameters: the number of segments n, the amplitude ratio Tm, and the amplitude of the last curve An. These parameters are optimized through orthogonal tests and numerical simulations, with the aim of improving the fan’s aerodynamic efficiency. Based on the selected solution, a comparative analysis is conducted to examine the impact of cylindrical, conical, and bionic inlet nozzles on inlet distortion and flow evolution within the centrifugal fan. Numerical calculations demonstrate that the fan’s maximum total efficiency, with a bionic inlet nozzle designed in a rational manner, is 5.46% higher than that of the original fan and is 2.01% higher than that of the fan with a conical inlet nozzle. The proposed bionic structure can create a buffer zone at the fan’s inlet, thereby reducing the region of high vorticity caused by the separated flow. Consequently, this improvement leads to enhanced uniformity at the impeller’s inlet. Furthermore, the design method proposed in this study for the inlet nozzle’s bionic structure effectively regulates the airflow angle near the impeller shroud, thereby enhancing the fan’s inlet distortion and improving its overall aerodynamic performance.