Numerical Simulation of Leaf Gathering Process of Fresh Leaf Collecting Pipeline Based on CFD-DEM

In order to reveal the airflow characteristics in the leaf collecting pipe of a riding tea picker, the gas-solid two-phase flow in the pipe was numerically simulated by computational fluid dynamics (CFD) and discrete element method (DEM). The numerical calculation model of machine-picked fresh leaves was established by the multi-sphere polymerization method. On the basis of analyzing the movement law of fresh leaf particles, the different changes of inlet wind speed, fresh leaf particle size and bend structure were simulated and analyzed respectively. Through the numerical model the blade collecting effect and the optimal wind speed and feeding quantity of the riser pipe could be predicted. In the optimal inlet wind speed range, the larger the fresh leaf particles were, the more residual particles were in the pipeline, which was easy to produce deposition. Fresh leaf particle flow formed a bend curve when it passed through the vertical pipe to the bend. The bend structure had a certain influence on the movement of fresh leaf particles. The average velocity of flow field was decreased firstly and then increased. A rounded elbow with a radius of 0. 04 m was selected as the blade collector elbow structure, and the transverse pipe length was reduced. The inner length was 0.03 m to avoid deposition caused by gravity action of fresh leaf particles and ensure the smoothness of blade collector. Through mathematical model simulation and experimental results, it was verified that the blade collecting pipe with rounded corner bend can meet the requirements of blade collecting by reducing the length of horizontal and straight pipe. The pipe with round corner elbow structure had a penetration rate of more than 86.8% . The fresh blade particle modeling method proposed was used for discrete element simulation analysis and structural optimization of the interaction between the leaf collecting pipe and the fresh blade flow. The research results provided a theoretical basis for the optimization of optimization design of the fresh leaf collecting pipeline. © 2022 Chinese Society of Agricultural Machinery. All rights reserved.