Effect of extending tip chord on the performance and noise of an axial flow fan

In this paper, the leakage flow in the blade tip clearance of an axial flow fan is studied, and an improved strategy for increasing the chord length of the blade tip toward the inflow direction is proposed. It has been proved that extending the tip chord can move the flow leakage backward. This results in an attenuation of the leakage vortex intensity and a mitigation of flow losses. Through comparative unsteady simulations, it is observed that a reduction in the amplitude of pressure pulsations surrounding the tip clearance and trailing edge leads to a corresponding decrease in the intensity of the noise source. The experiment results show that, under the target operating condition, the static pressure efficiency is increased by 1.02%. The amplitudes of both discrete and broadband noise are reduced, resulting in a decrease in the total sound power level at the outlet by 1.7 dB(A).