| An analysis of erosion caused by sand & clay particles entrained in a hydrocarbon flow through a high pressure letdown valve is discussed.; In order to model the erosion of the valve surfaces, the flow field and particle trajectories were obtained in the complex valve geometry. The commercial package CFDS-FLOW3D was used for this purpose. FLOW3D uses a finite volume formulation with a non-orthogonal body-fitted structured grid, and a pressure correction method. The turbulence was modelled with a k-{dollar}epsilon{dollar} turbulence model. The simulation assumed a dilute fluid-particle flow. The particle phase was modelled with a Lagrangian approach. Having obtained particle impingement locations, velocities, and angles, the erosion caused by impinging particles was modelled by empirical wear models. For ductile materials we use Finnie's cutting erosion model and Hutchings fatigue erosion model, while for the brittle materials of the valve we use Evans, Gulden and Rosenblatt's Elastic-Plastic erosion model.; When compared to the wear patterns of the operational valve, the results show that the erosion can be predicted qualitatively. Quantitative agreement was not possible because of the many assumptions needed to make the problem tractable. The assumptions of no fluid-particle, particle-particle interactions, and the lack of understanding of the particle-material wear interactions are the most severe assumptions. Experimental verification of the flow field and particle trajectories was not possible and with such a complex geometry inaccuracies are certain to occur. |
