Abstract
This paper describes the noise generation mechanism of axial-flow fans built for heat exchangers and having 4-equally spaced blades. Generated sound power levels are observed in a field which approximates a semi free space test environment. The power levels are analyzed by means of an analytical function of flow coefficients for various blade tip configurations, tip clearances and blade pitch angles, and impeller position at inlet-bell. As a result, it is found that the proper choices of set-up position of impeller and blade tip configuration reduce the noise.
