Transportation of slurries in channels often leads to erosion caused by solid particles’ impacts on the walls. Previous analytical and experimental studies on effect of solid particle erosion have shown that impact parameters such as velocity, incident angles and physical properties of particles and specimen are known to be major determiners of erosion.
Dr. Yuri Perelstein and Professor Ephraim Gutmark from University of Cincinnati studied the erosive features of developing vortical flow formed when slurry passes from the inner to the outer annulus through a row of four identical rectangular apertures equally spaced on periphery of a tube separating the two conduits.
The authors built a test rig which allows measurement of velocity of the carrying phase flow in the aperture and the outer annulus. They used stereoscopic particle image velocimetry in measurement of velocity in the aperture and the outer annulus.
Numerical simulations of slurry flow through the aperture and outer annulus showed that small particles disperse well but the large particles concentrate near the external wall of the outer annulus. Turbulence was also observed to disperse small particles as they traverse along highly erratic trajectories. Trailing vortices formed as the fluid passed through the aperture. These vortices induced erosion.
When observing particle trajectories near the wall, trajectories of small particles were highly erratic compared to those of larger particles with successive impingements on both walls of small particles. The trajectories of large particles showed small number of secondary collisions with the walls. This result shows that erosion caused by slurry is governed by multiple subsequent impacts for certain range of particle size.
The probability density function of impingement angle and velocity gave detailed information on range of occurring impact properties. Hence, it was said that a decrease in average velocity magnitude and turbulence kinetic energy of carrying phase alleviates impact velocity.
Larger particles in the outer annulus were found to generate as much as three times maximum wear compared to smaller ones. The impact angle of large particles was also found to rely on both turbulence and velocity of carrying phase upstream where velocity magnitude decreases while that of the smaller particles mostly depends on turbulence close to the wall. The results provided will advance solid particle erosion studies, which are relevant to many industries.
Yuri Perelstein, Ephraim Gutmark. A numerical investigation of wear caused by dilute slurry injected into an annulus through rectangular apertures, Wears 364-365 (2016) 169-183.
University of Cincinnati, P.O. Box 210070, Cincinnati, OH 45221-0070, USA.
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