Erosion of a multistage orifice due to liquid-solid flow

Liquid-solid impact erosion represents one of the major problems affecting systems reliability in many industries including oil and gas and power generation industries. The presence of solid particles, which cannot be avoided in these systems, is the main cause of erosion failure of piping and equipment, especially downstream complex pipe fittings. The present study aims at numerically investigating the effects of flow parameters and particle size on the solid particle impact erosion in a two-stage orifice arrangement with different spacing in a carbon steel pipe. The impact erosion occurs as a result of the presence of sand particles in the water stream. Inlet flow velocity ranges from 1 to 4m/s (Re ≈ 2.5 × 104 to 105) and solid particles in the range 50–400µm are used in this study. Also, the two orifices diameter ratios ranging from 0.5 to 0.77 with a spacing of 1D and 2D are used. The numerical analysis was performed using the k-ε eddy viscosity model integrated with a discrete phase model (DPM) along with solid impact erosion correlations to predict the impact erosion features in the piping system. The results show a strong dependence of erosion rates on the orifice diameter ratio, solid particle size and bulk liquid flow velocity. The two critical erosion locations were found downstream the second orifice; namely in the recirculation and reattachment zones. The least erosion rate was found in the case of double-orifice configuration with 1D spacing. Although a high-velocity region exists in the spacing between the two orifices, very small rate of erosion was found in this region for small particles and negligible erosion for large particles Dp≥100μm. Moreover, the erosion rates were found to increase with the increase of flow velocity and with the decrease of orifice diameter ratio and solid particle size.