Particle Separation in Pulsed Airflow

Abstract

A theoretical model was developed based on a fluid mechanical force balance to describe the behavior of particles in pulsing airflow. Several attributes distinguished this flow regime from those that have been widely studied: (1) The fluid was a gas; (2) the particles were much larger than aerosol; (3) the airflow was pulsed, as opposed to the more commonly studied oscillatory flow; and (4) the flow was vertical, requiring the inclusion of a body force in the expression. Much effort in the theoretical formulation and calibration was devoted to the acceleration effect, due to its importance in time‐varying flow. Computer models were developed and presented that were used in laboratory calibration of the theoretical expression and in modeling particle separation in rising, pulsing airflow. Theory showed separations based upon density that were not possible in steady rising airstreams. Experimentation with air classifier designs suggested by the model showed greatly increased separation efficiency.