Variable Injection Active‐Pulse Air Classification

Abstract

The effect of varying the time of particle injection within pulse periods, called the pulse injection time, in active‐pulse air classification is examined. A mathematical model based on a fluid mechanical force balance is used to study the behavior of spheres injected at different pulse times into a periodic, time‐varying, incompressible air flow, and the results are related to laboratory results of active‐pulse air classification experiments. Pulse injection time is found to affect the forces governing particle movement and particle separation. The results of theoretical modeling suggest that synchronizing feed inputs with pulse time can result in increased separation efficiency. A sawtoothed wave form airflow with a decay fraction equal to 0.1 is found to separate the particles studied most effectively over the full range of varying pulse injection times. Laboratory results, confined only to the measurement of particle drop times, are consistent with the mathematical predictions.