Experimental and computational modelling of solid particle erosion in a pipe annular cavity

Abstract

Pipe annular cavities are present in equipment related to the oil and gas and other process industries. The flow in a pipe initially expands into an annular cavity of a given length with a larger pipe diameter before suddenly contracting into a smaller pipe. In this work, air-suspended sands flow through an aluminium pipe annular cavity (diameter ratios, 1.25 and 0.8; cavity length, 10.25 step-heights) in which multi-layer paint erosion and parent material loss information were obtained. It was found that:•the highest erosion rate occurs on the leading edge of the forward-facing step;•the forward-facing step shoulder erodes more than the backward-facing step;•the maximum depth of erosion per unit mass on the curved cavity surface is approximately one third that of the material loss on the pipe surface;•more material is removed in the downstream half of the cavity than in the upstream half;•negligible erosion occurs up to 1.7 step-heights downstream from the backward-facing step;•198μm-sized particles remove twice as much material from the pipe surface as 38μm-sized particles, and value of the particle size exponent is 0.36.A complementary computational fluid dynamics study using a Lagrangian approach predicted erosion rate at the forward-facing step by the 198μm-sized particles to within ±30% of experimental values, while that for 38μm-sized particles are over predicted by up to 100%. It was observed that erosion rate is most accurately predicted on surfaces that experience direct impact with particles compared to erosion predictions on surfaces where erosion is caused by secondary or higher order impacts.