Comparison of computed and measured particle velocities and erosion in water and air flows

Abstract

Erosion equations are usually obtained from controlled experimental tests for solid particles carried in a gas or liquid flow. These equations are then applied to estimate the erosion damage resulting from solid particle impacts for cases of practical interest. It is well known that the particle impact speed and impact angle affect the erosion process and are used as parameters in most erosion equations. For a simple geometry with gas as the carrier fluid, the particle impact speed and impact angle can be accurately estimated, since the particles do not deviate greatly from their initial path. However, for complex geometries, very small particles with liquid as the carrier fluid, the particle trajectories can change significantly and determining the impact velocities can be more challenging. Furthermore, a lot of work has addressed solid particle erosion in gas flows. Many important applications in the oil and gas industry are liquid flows in complex geometries. There is a need for (1) erosion equations for liquid flow with sand and (2) a methodology for predicting erosion for complex flow geometries with liquid and sand. Computational Fluid Dynamics (CFD), particle tracking programs and erosion equations are often used together as a tool to help predict erosion damage. However, the accuracy of the CFD based erosion modeling is yet to be determined. In the present work, the velocities of particles entrained in water approaching a target are measured using a laser Doppler velocimeter (LDV). CFD simulations of the experiments were then carried out and the predicted particle velocities match the data very well, implying that CFD is a practical way to estimate the particle impact information. In this work, erosion damage of flat specimens in water or air flow and 90° standard elbows in air flow is also measured using a sensitive electrical-resistance (ER) probe under varying flow conditions. An erosion equation generated from data and several other erosion equations from the literature are applied in the CFD simulations. Predicted erosion rates from the simulations were then compared with the ER probe data. Good agreement between data and CFD predictions is demonstrated by applying a newly generated erosion equation as well as another published equation.