Effect of nozzle inclination on jet attrition

The effect of nozzle inclination for a supersonic nozzle in the attrition process is investigated in this study. The aim is to determine the optimal nozzle inclination angle to give the highest grinding efficiency. A high velocity Laval-type nozzle was used and the nozzle was adjusted from 0 degrees to 90 degrees. Particle size analysis was also conducted to monitor the generation of fine particles, and the grinding of coarse particles. It is found that more new particle surface was generated at nozzle inclinations over 45 degrees. The optimal nozzle inclination is determined to be 60 degrees, as it not only created the most new particle surface, but also ground more coarse particles without generating more unwanted fines. A baffle was inserted downstream of the jet tip for the nozzle inclination of 60 degrees to test its effect. The experimental result has shown that more new particle surface area was obtained with the baffle, as the baffle was able to densify the local bed region near the jet tip and enhance particle attrition. (c) 2013 Elsevier B.V. All rights reserved.