Analyzing mixing behavior in a paddle mixer with two types of non-spherical particles through DEM simulation and bench test

The discrete element method (DEM) and bench test were used to study the movement process and mixing performance in a paddle mixer by two types of total mixed ration (TMR) components (corn stalk silage and crushed corn grain). The DEM models of particles were established using muti-sphere method, and the validated models were utilized to investigate the effect of impeller rotational speed and vessel wrapped angle on the motion characteristics of particles, velocity variation of particles, thickness of dynamic flow layer and mixing performance in the paddle mixer, respectively. The simulation results revealed that the axial motion of particles was promoted by the cross-zone flowing of particles along the surface of particle bed. The circumferential and axial motions of particles were enhanced with the increase of rotational speed, and the superior mixing performance was attained at 28 rpm. The axial motion of particles was enhanced with the increase of wrapped angle from 0° to 40°, the circumferential motion of particles was the most intense at 30°, and the superior mixing performance was attained at 30°. The bench test was carried out based on the simulation results, the central composite design (CCD) was applied to establish a binary quadratic regression model of the effects of rotational speed and vessel wrapped angle on the relative standard deviation (RSD). The optimal rotational speed and wrapped angle were determined as 26.2 rpm and 26.6°.