Simulation Analysis of Straw Movement in Straw-Soil-Rotary Blade System

Abstract

The straw soil rotary tool interaction plays a pivotal role in the field of crop production. The simulation of straw soil rotary blade interaction using distinct element method (DEM) could be hypothesized to provide a better understanding of the straw movement. Firstly, DEM model of straw soil rotary blade interaction was established. Secondly, indoor soil bin experiments were conducted to verify simulation model, positions of straw particle at every moment were used to study straw displacement in simulation and tracer method was employed to measure straw displacement in experiments. Both simulation and experiment were performed with four rotational blade speeds (77r/min, 100r/min, 123r/min, 146r/min) at constant forward speed of 0.222m/s and depth of 100mm. The straw displacement both in soil bin and simulation increased with increasing rotational speed of blade. Moreover, the displacement in forward direction was larger than that of side direction at all rotational speeds in both experiment and simulation. The average error of straw displacement between simulated results and experimental results was about 40% for higher rotational speed while 70% for lower ones. The relation equation between relative error and rotational speed can be used to predict the experimental values, and the error between the predicted ones and experimental ones were 8.7% and 9.3% for forward and side displacements. Microscopic movements of straws were analyzed by tracing three specific straw particles. The movement of straw near sidelong edge or lengthwise edge was affected by cutting edges, the straw located at inner side of sidelong edge slipped off along the border of sidelong edge when rotary blade started to cut the soil while the straw near lengthwise edge was pushed to move along the lengthwise edge at the initial stage of soil cutting and later was tossed upward. The movement of straw away from cutting range was only affected by soil disturbance. The straw particles near lengthwise edge or transition edge could be buried directly during tillage. It is recommended to increase the ration of straw burial during tillage by optimizing edge curve and improve dispersed homogeneous degree by selecting the optimal operational parameters of rotary blade.

Keywords: rotary blade, straw movement, discrete element modeling, microscopic analysis