An experimental and numerical analysis of erosion caused by sand pneumatically conveyed through a standard pipe elbow

Abstract

Erosion of surfaces is an on-going industrial problem wherever solid particles are conveyed. The literature reveals very limited data reported for elbow erosion. Almost all data that is available only relates to the elbow extrados, or else provides an overall mass loss of surface material with no information on erosion distribution. A detailed surface map of erosion depth in a standard elbow (90° bend, with bend radius to pipe diameter ratio equal to 1.5) is presented using measurements taken with a surface profiler. The full erosion data map is reported on a 40×20 point grid for erosion caused by the passage of 200kg and 300kg of sand through the elbow. The sand had a median diameter of 184μm, and was conveyed by room temperature air travelling at 80ms−1.Numerical modelling of the erosion distribution is then performed using the conventional Euler–Lagrange approach to erosion prediction. It is found that the use of this approach, in combination with a smooth wall assumption for particle–wall collisions, leads to inaccurate prediction of maximum erosion depth together with a characteristic “vee”-shaped erosion scar that is not present in the experimental data. By adopting a suitable rough wall collision model the erosion depth and distribution are much more accurately predicted. However, particle shape, surface profile development and surface roughness development are all factors that may also affect the erosion pattern.The numerical modelling demonstrates the importance of accurately incorporating particle–wall collisions, as well as other more complex flow behaviour, into the simulation if a true prediction of the erosion distribution is to be captured.