Experimental and numerical assessments on solid particle erosion in upward vertical-horizontal and horizontal-vertical downward elbows for multiphase and gas-sand flows

Solid particle erosion is unavoidable in the pipeline fitting components in different engineering applications, such as in the oil and gas industry. Elbows have been used as an efficient fitting component to change the flow direction in pipeline systems. They are commonly fitted in series. Thus, it is valuable to examine the effect of distance between two elbows in series on solid particle erosion of elbows. In the presented work, flow visualizations, paint removal tests, and erosion measurements were conducted on two test configurations of standard 50.8 mm elbows in vertical-horizontal flow. The distance between the two elbows to the pipe diameter ratio (L/D) are 1 and 5 to investigate the distance effect on erosion on the elbows. The multiphase flow regime is churn/annular flow with superficial gas and liquid velocity of 16 m/s and 0.5 m/s, respectively, and 300 μm sand size. The results of the flow visualizations showed a thin liquid film covering the inside wall of the elbows. Liquid patches or portions were flowing and covering the outer wall of the first and second elbows for the L/D = 1 test configuration. The paint removal experiment results showed that the paint started to remove at around 45° in the first elbow and about 60° in the second elbow of both test configurations with the 1D and 5D distance between the two elbows. The erosion measurement results showed a good agreement concerning the location of the maximum erosion compared to the paint removal tests. In addition, the erosion measurement results showed that the maximum erosion magnitude in the first elbow with the L/D = 1 and L/D = 5 test configurations is higher than the second elbow by a factor of 1.35 and 3.14, respectively. In addition, Computational Fluid Dynamics (CFD) approach was used to study the effect of distance between two standard 76.2 mm elbows in series with 31 m/s gas velocity and 300 and 75 μm sand sizes. The CFD results showed agreements with the available experimental data. The CFD results showed that the maximum erosion ratio in the second elbow is lower than the first elbow in the gas-solid flow condition.