A Unique Test Facility to Measure Particle Restitution and Fragmentation

This paper describes an experimental test facility for measuring particle restitution ratio and particle fragmentation where the turbulent effect of air has been minimised. The restitution ratios, which relate the particle rebound characteristics to the impact velocity (and angle), are used in a trajectory code so that rebound conditions can be calculated after a particle has collided with a wall surface. Trajectory calculations are often used to predict the separation performance of inertial particle separators in a design cycle without resorting to the expensive ‘cut and try’ method. A ‘coanda’ particle injector is used to separate particles from the airstream which then relies on its own inertia to collide with a target plate. Particle rebound occurred in an quiescent condition in a target chamber which has been isolated from the surroundings. The particle rebound velocity (and angle) is measured with a two-spot transit anemometer operating in the backscattered mode. Measurements are taken at about 1.0–1.5 mm from the target plate surface. The overall dimension of the test facility is relatively small (1.0 × 0.5 × 0.5 m) compared to a windtunnel facility due to the absence of an airflow. Some results are presented for certain materials showings the effect of impact velocity, angle and particle size.