Abstract
The effect of clearance flow on the erosion characteristics of a circular cylinder with a backward facing step in sediment-laden water flow is analyzed numerically with the mixture model and the re-normalization group (RNG) k-e turbulence model. Thirty-six monitoring points are set up on different stream surfaces to collect information on the impact erosion under different flow conditions, where the Initial Sediment Volume Fraction (ISVF) is set to 0.05, 0.075, 0.1, 0.125, and 0.15; particle diameter is set to 0.05 mm, 0.15 mm, 0.25 mm, 0.35 mm, and 0.45 mm respectively. The distribution of particle velocity and Local Solid-Phase Volume Fraction (LSVF) along different stream surfaces are calculated, based on which the trend of erosion is qualitatively evaluated. ISVF and particle diameter play different roles on the impact erosion index parameter () on the different wetted walls. Relative wear rate of numerical estimation agrees well with the practical one under the same working condition. Numerical analysis demonstrates that guide vane with a negative curvature end surface (concave surface) can decrease erosion damage effectively, which may provide a reference for optimal design and maintenance of hydraulic turbine.
Highlights
The velocity distribution and the Local Solid-Phase Volume Fraction (LSVF) of particles are investigated under different particle diameters (0.05 mm, 0.15 mm, 0.25 mm, 0.35 mm, and 0.45 mm) when the Initial Sediment Volume Fraction (ISVF) is set to 0.05 and the results are shown in Figure 8 and Figure 9, respectively
The flow structure, the particle velocity distribution and LSVF in guide vane end clearance of hydraulic turbine have been investigated in this paper
The impact wear index of a circular cylinder with backward facing step in sediment-laden water flow is predicted under different ISVF and particle diameters
Summary
It is widely found in many engineering fields such as hydraulic engineering, chemical engineering and marine engineering, etc. The clearance flow between end surface of guide vane and head cover of the hydraulic turbine is simplified to a flow around circular cylinder with a backward step. Three redesign models with positive, zero and negative curvature are proposed to evaluate the effects of end-surface shape on erosion damage
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