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Title: Swirling Flow In A Straight Cone Draft Tube: Axi-Symmetric Flow Analysis And Comparison With Circumferentially Averaged PIV Measurements
Published In: Scientific Bulletin of the “Politehnica” University of Timisoara, pp. 185 – 197, Tom 52(66), Special Issue
Description: ABSTRACT The paper presents an investigation into the capability of axisymmetric swirling flow models to correctly reproduce the flow features in the draft tube cone of a pump turbine. Time averaged PIV velocity measurements for three operating points (part load, best efficiency, over load) are used to assess the accuracy of the numerical results. It is shown that the axisymmetric swirling flow model can capture both flow detachment from the cone wall, at low swirl levels, and the development of a large quasi-stagnant region in the center, at high swirl levels. A brief analysis of the accuracy of turbine flow simulations reveals the difficulties in accurately estimate the swirl level downstream the turbine runner, particularly for low specific speed machines. The numerical simulations favorably compare with experimental data at part load and best efficiency operating points. However, it is shown that the inlet boundary conditions used at the over load point significantly underestimate the swirl level. As a result, we conclude that accurate swirling flow numerical results heavily rely on the draft tube cone inlet boundary conditions corresponding to the swirling flow downstream the turbine runner blades.
ISSN:ISSN 1224-6077
Publication year: 2007
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Authors: KIRSCHNER Oliver , MUNTEAN Sebastian , SUSAN-RESIGA Romeo , RUPRECHT Albert ,
Type: National Journal Article
Laboratory: Numerical Simulation and Parallel Computing Laboratory
Institution: UPT