An investigation of erosion prediction for 15° to 90° elbows by numerical simulation of gas-solid flow

Abstract

Erosion is a common problem in various parts of the pipeline industry. In this study, computational fluid dynamics is employed for analysis of pipeline erosion due to gas transported particles. Total removed volume and maximum erosion rate in different elbow geometries from 15° to 90°elbows, for a range of mass loadings are studied. Particle tracking is achieved using combination of Eulerian and Lagrangian methods. In the first stage, gas-solid flow is validated for both straight-pipe and elbow geometries. After that, the erosion model is validated with available data for a 90°, 76.2 mm diameter standard elbow. In the final stage, simulations for a range of elbow angles are performed for two different flow orientations: horizontal inlet and outlet flow directions (H-H flow) and the cases in which inlet flows are vertical and outlet flows either lie in the horizontal plane or make some angles with it (V-H flow). In addition to erosion rate, some important particle-wall impact-related variables such as impact speed, impact angle and impact frequency are presented for elbows with different configurations and angles. Results show that, in general, for a fixed inlet condition and bend geometry, maximum erosion rate in the V-H configuration is greater than that for the H-H orientation. However, total annual eroded volume in the H-H configuration is greater than that for the V-H case. In addition, in both V-H and H-H cases, for the range of mass loadings investigated, the maximum erosion rate increases steadily when the elbow angle increases from 15° to 90° but the rate of total eroded volume remains relatively constant for each value of sand rate. Results of this study are helpful in optimal selection of pipeline elbows for erosion protection.