Numerical analysis of a centrifugal fan for performance enhancement using boundary layer suction slots

Abstract

Flow in centrifugal fans tends to be in a state of instability with flow separation zones on both the suction surface and the front shroud. The overall efficiency of the diffusion process in a centrifugal fan could be enhanced by judiciously introducing the boundary layer suction slots. With easy accessibility of computational fluid dynamics (CFD) as an analytical tool, an extensive numerical whole field analysis of the effect of boundary layer suction slots in discrete regions of suspected separation points is possible. This article attempts to explore the effect of boundary layer suction slots corresponding to various geometrical locations on the impeller as well as on the diffuser. The analysis shows that the suction slots located on the impeller blade near to its trailing edge appreciably improves the static pressure recovery across the fan. Slots provided at a radial distance of 30 per cent from the leading edge of the diffuser vane also significantly contribute to the static pressure recovery across the fan.