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A study of the formation of vortices within a multiple pump sump Spurr, Kerrin J. W.

Abstract

A literature survey was undertaken to collect information on multiple pump-sump design, the problems involved and solutions offered by various authors. This led to a study of the vortex forming mechanisms and a detailed examination of their significance to the design of a particular multiple pump-sump. An 'in-line' sump layout was selected because it was considered that such an arrangement may give the smallest sump volume, which often proves the cheapest. Though this layout is known to give rise to severe vortex formations, a better understanding of the vortex forming mechanisms might permit the development of a satisfactorily operating 'in-line' sump. Hot film anemometry techniques were used to monitor the turbulence levels within the sump and provide an index of the condition of the flow entering the bellmouth intakes. Considerable practical difficulties were experienced in making the anemometer probe function reliably. Because of the inherent inaccuracy of any unidirectional sensor within a fluid, the normal turbulence intensity parameter [formula omitted] was replaced by measurements of the main stream velocity fluctuations (dU), which offered a better representation of the comparative state of the flows within the sump. It was found that the introduction of various flow guides about the bellmouth intakes to physically suppress eddy shedding from the adjacent upstream pumps, significantly improved the sump performance. The tapering of the sump by varying the angle between the channel walls to reduce the deceleration of the flow along the channel, also added to the flow stability. It was concluded that the present study indicated the feasibility of constructing a workable 'in-line' sump configuration, and that further investigations encorporatlng direct pump efficiency tests in conjunction with turbulence measurements would be worth while.

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