SPECIMEN DIAMETER, IMPACT VELOCITY, EROSION RATE AND PARTICLE DENSITY IN A SLURRY POT EROSION TESTER

Using the technique of measuring impact crater size, stagnation line impact velocities of glass spheres (mean diameter 666 mum) suspended in diesel oil at 40-degrees-C on cylindrical copper erosion test specimens ranging in diameter from 3.2 mm to 9.5 mm tested at a nominal speed of 18.7 m s-1 in a slurry pot tester have been measured. Similarly, the variation in normal impact velocity of the same glass spheres as a function of angular location about the specimen has been measured for a 4.7 mm diameter specimen. Erosion rates for 1020HR steel specimens in the diameter range 3.2 mm to 9.1 mm were determined using a 1.2 wt.% suspension in diesel oil of silicon carbide particles, mean size 136 mum. Stagnation line impact velocities have been measured for spherical particles ranging in density between 2420 kg m-3 and 7830 kg m-3 suspended in diesel oil. The changes in impact conditions and erosion rates were analyzed using a model of suspension flow about, and particle impact on, a cylindrical target. It is shown that changes in erosion rate can be well accounted for by the changes in mean kinetic energy dissipated in collision and the frequency of particle impact, themselves controlled by the conditions of two-phase flow. It was also found that while the dispersion of solid particles in a slurry pot tester is very fast, the test method is subject to uncertainty in the value of the free-stream velocity. This effect is thought to be caused by rotation of the suspension in the test apparatus. A method of estimating its magnitude is given.