Experimental and Numerical Study of Cross-flow Fan in Air-conditioner Indoor Unit

The cross-flow fan is an essential component of an air-conditioner indoor unit, and its aerodynamic performance seriously affects the performance and heat exchange efficiency of air-conditioning. The internal flow of the crossflow fan is studied by PIV measurements combined with the three-dimensional unsteady simulation. It is observed that the internal flow of the cross-flow fan is unevenly distributed along the axial direction, and it presents prominent three-dimensional characteristics. Due to the influence of the end-wall, the eccentric vortex is strong in the middle and weak at both ends. Therefore, a pressure gradient along the axial direction in the eccentric vortex area, resulting in axial fluid transport inside the eccentric vortex. At the exit of the impeller, there is a small recirculation zone near the end-wall, which grows continually as it moves downstream in the diffuser section, thereby blocking the outlet. This paper further proposes a structure optimization, which effectively enhances the eccentric vortex near the end-wall and reduces the recirculation zone in the diffuser section, resulting in a 2.1% increase in the flow rate of air-conditioner indoor unit and a 0.8dB reduction in noise level. It is indicated that the structure optimization strategy based on the understanding of three-dimensional flow is beneficial to the internal flow and effectively improves the aerodynamic performance and the aeroacoustics performance of the whole air-conditioner indoor unit.