Numerical study on deposition of particles in a 90° bend in the presence of swirling flow using Eulerian-Lagrangian method

Abstract

An Eulerian-Lagrangian method has been used to study deposition and penetration of particles in a 90° bend in the presence of swirling flow. Presence of bends and curved pipes is inevitable for industrial applications and deposition of particles in curved pipes is a commonplace phenomenon and may reduce system efficiency or cause erosion on the bend wall. The main objective of this study is to understand if deposition of particles is affected by imposing swirl to fluid flow. The simulations are performed using commercial CFD code Ansys Fluent and RSM turbulent model is employed for all simulations. Swirl was generated using internal spiral vanes which were placed on the inner wall of the pipe. Different heights for vanes and different swirling pitches were used to see how they affect swirl intensity and deposition efficiency. Deposition efficiency is reported as function of particle stokes number. It was found that both lowering swirling pitch and increasing vanes' heights increase swirl intensity and higher swirl intensities reduce deposition rates for wide range of stokes numbers. The results show that increasing vanes' heights have better effect on reduction of deposition efficiency than lowering swirling pitch. Another important finding of this study was that larger particles with higher stokes numbers have more predictable behavior in swirling flow and all ranges of swirl intensities reduce deposition rate of these particles.