Numerical analysis of a centrifugal fan for performance enhancement using boundary layer fences on the volute casing

Flow within the centrifugal impeller and diffuser passage is a decelerating flow with an adverse pressure gradient along the stream wise path. This flow tends to be in a state of instability with flow separation zones. Several experimental attempts were made to assess the effectiveness of using boundary layer fences to realign the flow in the regions of flow separation to make the flow align itself into stream wise direction so as to minimize the loss and improve the overall efficiency of the diffusion process. With the development of CFD, a numerical whole field analysis of the effect of boundary layer fences in discrete regions of suspected separation points is possible. However it is found from the literature that there has been no significant attempt to use this tool to explore numerically, the utility of the fences on the flow field. This paper attempts to explore the effect of boundary layer fences corresponding to various geometrical configurations on the volute casing. It is shown from the analysis that the fences mounted on the initial half measured from the tongue of the volute casing surface improves the static pressure recovery across the fan. Fences provided elsewhere on the casing does not show any improvement in the performance of the fan.