If properties of the particle and casing material are considered to be known, erosion prediction can be divided into the computation of the multiphase flow field in the relevant component and determination of erosion coefficients. Usually, erosion is predicted via erosion mechanisms including the characteristic of multiphase flow, properties of particle and casing together with certain empirical constants. In dilute solid-liquid flow, erosion is likely to be more due to particle impact. It is widely found in many engineering fields such as hydraulic engineering, chemical engineering and marine engineering, etc.Įrosion in hydraulic machine occurs due to the particle impact and sliding (scouring) action. Flow separation, reattachment and re-development of sediment-laden water often appear in the two typical flow patterns, which can result in serious erosive damage of the guide vane and shaft as shown in Figure 1. The clearance flow between the seal surface of the guide vane and the bottom ring (or the head cover) of the hydraulic turbine can be simplified as a flow around circular cylinder (rotating shaft of guide vane) with a backward facing step. The guide vane of hydraulic turbine is often subjected to serious abrasion under the condition of sediment-laden flow in the Yellow River of China. 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. Relative wear rate of numerical estimation agrees well with the practical one under the same working condition. ISVF and particle diameter play different roles on the impact erosion index parameter ( ) on the different wetted walls. 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. 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 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-ε turbulence model.
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