Design and experiment of spiral step cleaning device for ratooning rice based on CFD-DEM coupling

In order to solve the problem of increased impurity rate and loss rate during the cleaning of ratooning rice using traditional cleaning devices, a spiral step cleaning device with vortex blockage removal function was designed. The structural parameters of the spiral step cleaning device were determined, and the motion law of the mixture inside the device was studied. First, the global flow state was analyzed and the rationality of the design of the cleaning separation core structure was confirmed verified through the vortex inside the slot. Meanwhile, the variation patterns of penetration velocity, shear velocity, and rising velocity were obtained through the analysis of screen surface flow velocity. Subsequently, the simulation of the movement of rice grains and impurities under the influence of vortices was carried out. The results showed that after the ratooning rice were screened out, the impurities are transferred from the surface of the screen to the connection between the skeleton and the screen under the action of shear flow, without blocking the screen. The proportion of impurities on the overflow screen was between 10.1 % and 13.7 %, which was significantly lower than that on the front and rear screen. The vortex had a significant effect on the blockage removal of the screen. Finally, the test platform of the spiral step cleaning device was built to test the cleaning performance. The results showed that the average grain impurity rate was 1.35 %, the average grain loss rate was 1.62 %, and the average screen plugging rate was less than 0.1 %. Compared with traditional cleaning devices, the grain impurity rate was decreased by 2.5-3.4 %, the grain loss rate was reduced by 2.3-3.5 %. Therefore, it is feasible to use spiral step cleaning device to clean ratooning rice, and this study can provide a basis for the design and research of ratooning rice harvester.