Scaling laws for particle velocity in the gas-blast erosion test

Abstract

In erosion testing the wear rate of the specimen is strongly dependent on the particle impact velocity. An understanding of the factors influencing particle velocity in the test apparatus is therefore essential. In this work, precise measurements of particle velocity have been made by an optoelectronic method in a simple gas-blast erosion rig with a parallel cylindrical nozzle. The double-disc method was also used to measure velocities, and results from this technique showed good agreement with the more accurate measurements. Several commonly used erodent materials were studied, including quartz sand, silicon carbide and alumina. The particle size was varied over the range from 63 to 710 μm, with particle material densities between 2500 and 7980 kg m−3. The nozzle geometry was also varied. Measured particle velocities ranged from 16 to 85 m s−1. Computational models for the prediction of particle velocity in gas-blast erosion rigs are briefly reviewed but these exhibit various inadequacies. It is demonstrated that for cylindrical nozzles an empirical power-law expression can be used to relate particle velocity to gas pressure, particle size and particle density. It is suggested that this may provide useful scaling laws for the design of erosion experiments.