A numerical assessment of two geometries for reducing elbow erosion

Abstract

Elbows in pneumatic conveying systems are normally prone to the erosive effects of conveyed particles. There are a number of solutions available to reduce such damage. A widely used geometric alternative for replacing the 90° elbow and reducing erosive wear is the plugged tee. Another option, although less commonly used, is the vortex-chamber elbow. In both cases, the effective reduction in erosion brought about is unclear, as it strongly depends on the operating conditions. The present study assesses relative erosion among the plugged tee, vortex-chamber elbow, and standard elbow for a dilute gas–solid multiphase flow. A numerical model is employed to predict the penetration ratio and validated using experimental data for the plugged tee. Simulations are run for the standard and vortex-chamber elbows and plugged tee under the same conditions to compare the mechanics involved and the relative erosion reduction. The analysis uses variables relating to particle–wall interactions (impact angle, impact velocity, impact frequency) to illustrate the nature of the erosive process in each pipe fitting. In general, the geometric configurations of both the plugged tee and vortex-chamber elbow promote changes in particle dynamics that reduce the rate of erosion. On the basis of the relative erosion of the standard elbow, the plugged tee proves to be an interesting option in cases of a low mass loading, while the vortex-chamber elbow demonstrates its erosion reduction potential for higher mass loading conditions. Furthermore, the advantages and disadvantages of each fitting are highlighted.