CFD Study of Particle Concentration and Stokes Number Effect on Erosion Profile.

Abstract

A very common problem that continuously faces industrial applications involving fluid flow is solid particle erosion. This type of erosion is caused when solid particles carried by a fluid flow continuously impact a surface thus removing some of its material. It is especially notable in pipelines, oil and gas industry, and gas turbines leading to a decline in their performance, safety, and other aspects. Consequently, it is very important to be able to predict erosion in order to prevent failure of systems, protect the environment, and reduce costs. However, erosion is controlled by many parameters, which increase the complexity of the problem. Literature tends to provide sufficient information on how these parameters affect total erosion and erosion rate. On the other hand, it does not give enough analysis about the effect on the erosion profile. Therefore, this thesis aims at performing a parametric study on the effect of solid particle concentration and Stokes number on the erosion profile of a direct jet impingement slurry flow over a ductile material. A CFD (Computational Fluid Dynamics) model was developed using ANSYS CFX software to perform the needed analysis. The Stokes number was evaluated by looking at three of its defining parameters: solid particle diameter, nozzle average velocity and fluid viscosity. Additionally, the coupled effect of solid particle concentration and Stokes number was studied. It was found that as concentration increases, the erosion profile magnitude also increases but the change in its shape tends to saturate. However, it was also found that the effect of Stokes number on magnitude and shape of the erosion profile is dependent on the level of particle concentration and which defining parameter is under investigation. At low concentration, the change in profile shape saturates with increase in Stokes number when varying the nozzle average velocity and viscosity parameters; whereas, when evaluating the solid particle diameter,the shape tends to develop into a that of a high Stokes flow. However, at high concentration, the profile shape significantly grows into that of a high Stokes flow as the Stokes number increases when varying any of the three defining parameters.