Passive Pulsing Air‐Classifier Theory

Abstract

A mathematical model based on a fluid‐mechanical force balance has been used to study the behavior of spheres in the positionvarying airflow in idealized passive pulsing air classifiers. The movement of spheres whose terminal velocities prevent their being separated by density is modeled. Earlier work showed that pulsing airflow could achieve density‐dominant separation. Passive pulsing air classifiers use a varying cross‐sectional throat area to cause regions of high and low velocity in the airstream. Laboratory tests have shown passive pulsing classifiers are superior to standard air classifiers. Modeling and experimental results show that theory does not explain how passive pulsers achieve superior efficiency, but passive pulsing can reverse the falling order of these spheres.