HIGH-VELOCITY IMPACT OF PARTICLES ON A TARGET - AN EXPERIMENTAL-STUDY

In order to study communition in a jet mill, an experimental rig was b uilt to investigate the breakage phenomena. Particles were accelerated with air in a nozzle to velocities ranging from 120 to 250 m/s and co llided with a target. Energy loss during impact was evaluated by measu ring particle velocities before and after impact. Two different system s for measuring particle velocities were implemented, ?The first one w as designed to work at very low loading (particles are considered to h it the target individually). The velocities are measured by a high shu tter speed video camera (up to 1 mu s) The particle traces on a frame were analysed by an image analyser. The second method, used for medium to high solid loading, consists of two sets of emitter-receptor optic fibres. Signals, collected by a 500kHz acquisition card, are cross-co rrelated in order to obtain the velocity. Influence of solid loading a nd initial air flowrate on characteristics of broken particles were ev aluated, The influence of target nature and orientation were establish ed.