Numerical simulation on liquid-solid two-phase erosion characteristics of pipe bends with different bend angles

Abstract

Pipeline transportation is a very common mode of transportation in the energy and chemical industries. Pipeline structure has an important effect on liquid-solid two-phase flow characteristics, which is vital to reduce the erosion wear of pipe bend. In this paper, an Eulerian-Lagrangian approach with liquid-solid two-phase coupling is performed to investigate the erosion characteristics of pipe bends with different bend angles of 60°, 90°, 120°, 135°, 150° and 165°. The computation domain is a pipeline segment comprising of two straight pipe sections of 250 mm in length, and a pipe bend with an inner diameter of 25 mm, a bend radius of 37.5 mm. The inlet boundary condition is set as “velocity-inlet”, and the material of the wall is aluminium with a density of 2702 kg/m³. The outlet boundary condition is set as “outflow”, The wall boundary condition is set as “reflect”, and the outlet boundary condition is set as “escape”. The influences of bend angle, solid particle size, solid-phase mass flow rate and liquid-phase inlet velocity on erosion rate distribution, velocity distribution, particle trajectory, and pressure distribution have been analyzed with CFD simulation combined with Discrete Phase Model (DPM). Results show that erosion mainly occurs on the external side of inner wall in the bend pipe section, with the 165° pipe bend exhibiting the lowest erosion rate and the erosion rate decreases with the increase of the bend angle. Meanwhile, the increase of solid particle size, solid-phase mass flow rate and liquid-phase inlet velocity will all aggravate the bend erosion. The flow field inside the pipe bend is significantly affected by the bend angle and the liquid-phase inlet velocity, while the particle characteristic parameters, including solid particle size and solid-phase mass flow rate have less effect. Furthermore, the flow field in the pipe bend shows the characteristics of secondary flow, with the increase of pipe bend angle, the high-pressure area on the inner outer wall of the pipe bend decreases gradually. The research results can provide some theoretical support for the optimal design of pipe bends in related industrial fields.