The experimental and numerical studies have been carried out to investigate the flow and the noise characteristics of the three impellers with different blade angles in a cross-flow fan (CFF). First, the aerodynamic performances of the fan with these impellers are obtained experimentally, and the averaged flow patterns inside the impellers are measured by the three-hole probe. Second, the far-field noise generated by CFF with different impellers has been measured in a semianechoic chamber under different throttling conditions. Third, the two-dimensional unsteady CFD simulations have been performed by commercial software. The internal flow patterns influenced by the different blade angles have been summarized through the computational results. The accuracy of the calculations is validated by the corresponding experimental ones. The detail analysis has been carried out on the unsteady vortex flow properties of the three impellers, which is considered to be the main factor that influences the aerodynamic and aeroacoustic performance of the CFF. Finally, the relative far field noise generated by different impellers are evaluated by an empirical formula based on the assumption that the total sound pressure levels are proportional to the sixth power law of the relative velocity on the outer and inner circumferences of the impeller. The circumferential distributions of relative velocity are provided from the numerical solutions. The varying trends of predicted results agree well with the actual relative noise of the CFF with three different impellers.
Study of Cross-Flow-Fan Internal Flow by Flow Visualization. (Discussion of Measured Results by Particle-Tracking Velocimetry).