Experimental research on vertical straw cleaning and soil tillage device based on Soil-Straw composite model

Strip tillage is a necessary technical means to solve blockage problems during the no-tillage sowing process under the condition of total straw return to the field. However, the large amount of straw on the surface, thick stems, and slow decomposition make it difficult for the traditional straw wheel structure to effectively clean the straw out of the operating area. Based on the distribution of straw and soil characteristics on the no-tillage surface, a Soil-Straw composite model is established using the discrete element method (DEM) for undisturbed soil under straw coverage conditions. The relative error of its bonding parameters is 7.9 %, which can accurately predict the mechanical behavior of soil contact components. A vertical rotation-based straw strip cleaning and soil tillage method is proposed, and three vertical straw strip cleaning and soil tillage devices combining spring teeth (ST) and rake teeth (RT) were designed. The reasonable operating parameters are determined through trajectory analysis, with a forward velocity of 1.67 m/s and a rotational velocity of 300 r/min. Based on the Soil-Straw composite model, the combination of three ST and RT types is studied using DEM-MFBD coupled simulation technology. Regarding the straw cleaning rate, the straw cleaning rates of STb-RTb and STc-RTc are 96.66 % and 96.99 %, respectively, meeting the operational requirements. The field test results showed that the straw cleaning and soil fragmentation rates of the STc-RTc combination were 97.7 % and 96.4 %. The bench test and field test verification show that the DEM-MFBD coupled simulation technology based on the Soil-Straw model can predict the operating quality and deformation stress of the machine. This study provides a new solution for a wide range of straw cleaning in straw-covered areas.