Effects of different blended blade tip and winglets on aerodynamic and aeroacoustic performances of diagonal fans

Three types of blended blade tip and winglets (BBTWs) are proposed to control leakage flow: the BBTW of the pressure and suction surface (BBTW-ps), the BBTW of the pressure surface (BBTW-p), and the BBTW of the suction surface (BBTW-s). The effects of different BBTW approaches on the aerodynamic and aeroacoustic performances of a diagonal fan are studied numerically. The calculation results show that the three BBTW blade types can effectively reduce the intensity of the main, secondary, and reverse leakage flows at the blade tip. Among these blades, the BBTW-s has the most significant effect. Additionally, these BBTW blades can reduce both the tip leakage vortex noise and the near-field noise, where the BBTW-s has the most significant effect. Furthermore, the BBTW-s blade effectively reduces the middle- and low-frequency band noise, which results in a significantly reduced far-field noise. The BBTW-p blade had an increased second-order single-tone peak, which results in a deteriorated far-field noise at some azimuth angles. The effect of the BBTW-ps blade on the far-field noise is between those of the BBTW-p and BBTW-s blades.