Science and civilisation in China by Joseph Needham. Vol. V, part I. Paper and printing: By Tsien Tsuen-Hsuin. Pp. xxv + 485. Cambridge University Press, 1985. £45.00

Abstract

Pipe erosion caused by solid particles is an important cause of pipeline damage, for example, parts such as elbows are particularly prone to erosion problems. In this work, the insertion of a twisted tape on different working conditions upstream of an elbow is investigated numerically in order to study the mechanism of the swirling flow reducing the erosion of the elbow. In order to ensure the reliability of numerical calculations, experimental data are used to verify the CFD simulation model of the standard elbow. The influence of the twist ratio of the twisted tape, the insertion position of the twisted tape and the gas velocity on the erosion of the elbow was studied. It was found that the swirling flow induced by the twisted tape make the solid particles suspended and more evenly distributed in the pipeline, which reduces the focusing effect and the impact frequency of particles on the same position of the elbow wall. The insertion of the twisted tape results in a reduction in the area of the maximum erosion zone of the elbow and a significant decrease in the erosion rate along the elbow curvature angle, indicating that the swirling flow can significantly reduce the erosion of the elbow. The smaller the twist ratio of the twisted tape, the closer to the elbow, the more obvious the erosion mitigation effect is. In addition, swirling flow can interfere and inhibits the Dean Vortex on the cross section of the elbow. Under the condition of swirling flow, as the gas velocity increases, the influence range of the Dean vortex increases, the kinetic energy of particle impact increases, and the type of collision changes from sliding collision to direct collision. The erosion rate of the elbow with a twisted tape insert also increases with the increase of the gas velocity, but the swirling flow reduces the velocity index of the erosion rate to a certain extent.