Abstract
The usage of splitter blades to enhance the performances of low specific speed pumps is common practice. Based on experimental and numerical studies, the influence of the addition of one and two splitter blades is investigated on a very low specific speed pump to assess their impact not only on the performance characteristics but also on the losses in all pump domains. First, the main characteristic curves are discussed and it is shown that the usage of splitter blades enhances the head of the pump while not impairing its efficiency. Secondly, a detailed analysis of the losses in the pump reveals that splitter blades improve the flow in all parts of the pumps, but the volute. The flow at the impeller outlet shows that splitter blades largely benefit the slip factor and discharges a more blade-congruent flow in the volute. However, higher absolute velocity at the outlet of the impeller with splitter blades increases friction at the volute wall, as confirmed by the average wall shear stress in the different tested cases.
Highlights
Performances of a Very Low SpecificPumps with a specific speed nq < 20 are called low specific speed (LSS) pumps
The numerical simulation of low specific speed pumps can be problematic as thoroughly presented by Juckelandt [21] when using eddy-viscosity turbulence models
The study focuses on the influence of added splitter blades in the flow passages of a very low specific speed impeller
Summary
Pumps with a specific speed nq < 20 are called low specific speed (LSS) pumps. Their design presents many challenges. Pumps provide high pressure at low flow rate To achieve these performances, impellers have large diameters, causing an important part of the shaft power to be dissipated in the sidewall gaps of the pump due to disk friction [1,2]. Impellers have large diameters, causing an important part of the shaft power to be dissipated in the sidewall gaps of the pump due to disk friction [1,2] These pumps are prone to low-flow head instability, where a positive head slope at low-flow can be observed (dH/dQ > 0). The motivation of this study is the detailed analysis of the influence of splitter blades on the performances of a very low specific speed pump. Thanks to a detailed CFD analysis, the study focuses on the influence of splitter blades on the power losses in each domain of the pump, on the flow at the outlet of the impeller and in the volute
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