Effect of Entrance Shape on Erosion in the Throat of Chokes

Abstract

Erosion is a complex phenomenon that depends on many factors such as fluid properties, solid particle properties, flow stream velocity, flow geometry, and type of metal. Flow modeling and particle tracking are important tools for predicting erosion. In erosion modeling, it is important to account not only for the factors that influence erosion, but also for changes in some of these factors that occur as the erosion process continues. For example, the change in the geometry resulting can have a significant impact on the erosion results. Geometry changes result when corners, found in couplings and chokes, are eroded with time. This change in geometry due to erosion can drastically change the flow field, especially the turbulent kinetic energy and dissipation rate. Recognizing this change is imperative, since the prediction of particle behavior is heavily dependent on the turbulent kinetic energy. Furthermore, more particle impingements occur in regions with higher turbulent kinetic energy. This paper shows that neglecting the change in the flow field solution resulting from the change in geometry can cause erroneous erosion predictions. A computational study was performed on a choke geometry to demonstrate the importance of incorporating the change in geometry resulting from erosion. Predicted turbulent kinetic energy contours are presented as a function of the changing choke geometry. The predicted erosion rates along the choke are also examined for the various scenarios, and these results are compared to experimental results. Additionally, experimental results obtained from laser doppler velocimeter (LDV) measurements also demonstrate the change in fluctuating velocity (turbulent kinetic energy) as a result of rounding of the entrance of the choke. Results from this study show that it is necessary to update the flow geometry and flow model based on the changing geometry due to erosion. [S0195-0738(00)01004-9]