Movement rules and screening characteristics of rice-threshed mixture separation through a cylinder sieve

摘要

The rice-threshed mixture presents the phenomenon of axial flow and radial stratification under the impact of airflow field, gravitational field, and sieve. We used the method that couples computational fluid dynamics (CFD) with the discrete element method (DEM) to numerically calculate the process described above, and investigated the influence of inlet airflow velocity, diameter and rotating speed of cylindrical sieve on the movement rules and screening characteristics of rice-threshed mixture components (grains, shriveled grains, and short stalks). The nonlinear fitting curve showed that inlet airflow velocity had a significant influence on the axial average velocity of mixture components, the sifting grain mass distribution, and screening loss rate. The greatest screening efficiency give with an inlet airflow velocity of 9.67 m/s. The diameter of cylindrical sieve has a large influence on the axial average velocity of grains and short stalks. Cylindrical sieve rotating speed has a great influence on the axial average velocity of the short stalks, screening loss rate, and screening efficiency. Validation test for one of parameters shown that the error for the screening cleaning rate of each collection area is below 5%, while the screening loss rate and screening efficiency error are 8.11% and 3.3%, respectively. The research result indicates that the CFD-DEM coupling method has scientific and practical value in calculating the movement rules and screening characteristics of rice-threshed mixture in a cylindrical sieve.