Numerical analysis of the effects brought by a twisted tape insert in elbow erosion

Abstract

Due to the ongoing problem related to erosion caused by the impingement of solid particles in many engineering fields, parts such elbows, for instance, are particularly prone to erosion issues. In this work, the insertion of a twisted tape at different positions upstream of a bend is investigated numerically with the intent of reducing the elbow erosion. To ensure the reliability of the numerical calculations, experimental data were used to validate the CFD model for the standard elbow. Subsequently, simulations considering one, two and four-way coupling were evaluated for both the standard and the twisted tape-equipped elbows. Simulations were run to evaluate the average particle impact angle, impact frequency and impact velocity and the penetration ratio for each geometry. The present work used the finite-volume, unstructured code UNSCYFL3D, which solves the gas flow using the fully coupled Euler-Lagrange approach. The two-layer k-epsilon was used to model turbulence effects. Interestingly, it was found that the swirling motion imparted to the particles by the twisted tape reduces the maximum penetration ratio in the bend. Another important finding is that the farther the insert is placed upstream of the elbow, the lower the erosion in the elbow, although the tape itself becomes more prone to erosion. In general, it was noticed that the fluid-particle and particle-particle interactions are very important and cannot be neglected. Consequently, depending on the mass loading and geometry configuration, elbow erosion can be dramatically reduced.