Abstract: The fan wheel of the outdoor unit in air conditioning systems directly impacts the energy efficiency, stability, noise levels, and environmental performance of the system, and also a key factor to improve the overall performance of air conditioning systems. Based on the four-boundary theory of the impeller, this study systematically optimizes the outdoor unit's fan wheel through a combination of numerical simulations and experimental research. The results demonstrate that the flared design at the leading edge of the blade effectively controls the top and bottom rotating vortices, increasing the fan pressure and air volume by approximately 10% at the same rotational speed while reducing noise by 1.3 dB(A) at the same air volume. Additionally, the backward-curved design in the region of 2% of the impeller diameter at the blade tip significantly suppresses the tip vortex backflow effect and pressure pulsation, maintaining the same air volume at the same rotational speed while reducing noise by 0.5 dB(A)~1 dB(A) at the same air volume. The two optimization schemes exhibit a synergistic effect; when applied simultaneously, they achieve a noise reduction of 1.7 dB(A)~2.3 dB(A) at the same air volume, with a 3 dB(A)~4 dB(A) reduction in the peak of low-frequency rotational noise, significantly improving the acoustic quality.

Key words: Air conditioner outdoor unit, Semi-open axial flow fan, Impeller modification, Numerical simulation, Aerodynamic noise