Simulation analysis and experimental validation of conveying device in uniform rrushed straw throwing and seed-sowing Machines using CFD-DEM coupled approach

In agricultural fields with full straw retention, shredded straw tends to be thrown unevenly. To achieve uniform crushed straw throwing in dense fields of rice stubble, and high-quality straw mulching in dense fields, the conveying device of a no-till planter to perform uniform throwing of crushed straw stubble on fields and determine the device operation mechanism was analyzed. Using kinematics and dynamics analyses of particles of crushed rice straw during lifting and dispersion, a flexible-body model of rod-shaped and agglomerate-shaped crushed straw and a coupling model that included the mechanical structure of the device were developed. By integrating computational fluid dynamics and the discrete element method, the gas–solid coupling theory in numerical simulations and motion analysis of crushed straw particles was used to determine the flow field and motion characteristics under different parameters. The simulation focused on the conveying performance of different pipelines under four scenarios with varying throwing blade speed, conveying volume, pipeline diameter, and initial feeding velocity. The influence of these parameters on both the conveying device performance and their own variation was determined. Actual operations that are then compared with test results to achieve optimal operation were demonstrated. By adopting the Box-Behnken design, the throwing speed of crushed straw was set to the evaluation index a response surface test was performed on the throwing blade speed, conveying volume of crushed straw, and pipeline diameter. The optimization results showed that the predicted optimal parameters were 2300 rpm throwing blade speed, 1.4 kg/s conveying volume, and 220 mm pipeline diameter. The simulated planter achieved an optimized throwing speed of 14.6 m/s. Then, a field test verification was conducted, and the results were averaged. The planter achieved a throwing speed of 14.8 m/s with the same optimal parameters. The straw lifting and throwing device provides high conveying performance and satisfies requirements for real-time operation. This study provides a theoretical basis and supporting data for innovating seeding technologies and optimizing equipment to achieve uniform crushed straw-throwing in dense fields of rice stubble.