THE EFFECT OF DISTANCE BETWEEN TWO ELBOWS IN SERIES ON EROSION IN SINGLE AND MULTIPHASE FLOW CONDITIONS

Abstract

Solid particle erosion is an unavoidable and challenging phenomenon that occurs in elbows and leads to elbows failure. One area of interest is how erosion patterns and magnitude may change when elbows are positioned in series. One curious question is, will the erosion in a second elbow be higher, less, or equal to the first elbow? In the literature, very few investigators have examined erosion in elbows in series where the particles upstream of the second elbow are affected by the underdeveloped flow caused by the first elbow. Thus, it is advantageous to examine erosion in a second elbow with various distances between two elbows installed in series in different flow conditions. Solid particle erosion in elbows in series was investigated in large-scale flow loops experimentally in two-phase and multiphase flow conditions. In this work, sand was used as a solid particle. Before performing erosion measurements, paint removal tests using acrylic elbows were conducted to better understand the erosion pattern and the location of the maximum erosion in the elbows. In addition, the Computational Fluid Dynamics (CFD) approach was used to simulate the investigated cases with different distances between the elbows, particle sizes, and flow conditions to better represent the flow and erosion prediction using the available erosion and rebound models in the literature. The presented erosion measurements showed that the location of the maximum erosion in gas-dominated flow conditions differs from liquid-dominated flow conditions. In gas-dominated flow conditions in 3-inch elbows, the location of the maximum erosion was observed at the centerline of the exterior wall of the second elbow, for instance, from 55 degrees to 75 degrees. However, in the liquid-dominated flow conditions in 2-inch elbows, the location was observed at the end of each elbow, around 84 degrees. The presented experimental data in gas-dominated flow conditions showed that the erosion in the first elbow is higher than in the second elbow. However, for liquid-dominated flow conditions in 2-inch elbows, the experimental results showed that the erosion in the second elbow is higher than the first elbow with the 1D distance between the elbows. The maximum erosion ratio in the second elbow becomes less than the first elbow with the 5D distance between them. CFD has been used also to examine erosion magnitude of the second elbows as compared to the first. The CFD results showed good agreement compared to the experimental data in the first elbow. However, the presented CFD results overpredicted the maximum erosion ratio in the second elbow, especially with a short distance between the two elbows (1D and 2D).