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

Using the technique of measuring impact crater size, stagnation line i mpact velocities of glass spheres (mean diameter 666 mum) suspended in diesel oil at 40-degrees-C on cylindrical copper erosion test specime ns 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, t he 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 i n 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 spherica l particles ranging in density between 2420 kg m-3 and 7830 kg m-3 sus pended in diesel oil. The changes in impact conditions and erosion rat es were analyzed using a model of suspension flow about, and particle impact on, a cylindrical target. It is shown that changes in erosion r ate can be well accounted for by the changes in mean kinetic energy di ssipated in collision and the frequency of particle impact, themselves controlled by the conditions of two-phase flow. It was also found tha t while the dispersion of solid particles in a slurry pot tester is ve ry 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 m agnitude is given.