CFD–DEM Analysis and Field Evaluation of a Dual-Roller Fresh-Safflower Filament Harvester with Pneumatic-Assisted Separation

Abstract

To achieve the efficient mechanized harvesting of fresh safflower filaments, this paper proposes a harvesting device using dual-roller gripping and pneumatic-assisted separation. According to the mechanical properties of fresh filaments, the meta-particle method is employed to construct a flexible geometric model, and the Edinburgh elasto-plastic adhesion (EEPA) contact model is used to calculate the contact forces. It is found that, as the dual-roller gap decreases, the maximum normal contact force and adhesive force increase according to power law relationships. The increased adhesion can cause filaments to remain on the roller surfaces, resulting in adhesion-induced carry-back. Then, CFD–DEM coupling simulations are carried out to analyze filament gripping and transportation. The results reveal that two air jets at a pressure difference of 1.0 kPa assist filament separation from the roller surfaces. Finally, a harvesting machine is developed, and comparative field tests are carried out. At a dual-roller gap of 0.8 mm, a rotational speed of 800 rpm and a pressure difference of 1.0 kPa, the filament pulling-out rate and effective collection rate are 91.4 ± 0.6% and 84.3 ± 0.2%, respectively (mean ± standard deviation across three spatial sampling sections within one field pass). These results support pneumatic-assisted separation under the tested conditions.