Mechanics-Based Design and Performance Optimisation of a Feeding–Chopping Device for Direct Alfalfa Silage Harvesting

Abstract

Feeding and chopping are key operations in alfalfa harvesting, directly affecting silage quality and operational energy consumption. To address the problems of insufficient feeding stability, poor chopped length uniformity, and high specific energy consumption during direct alfalfa harvesting, a fi ve-roller feeding–chopping device was designed. Based on the mechanical analyses of the feeding and chopping processes, the key structural parameters of the device were determined. Feeding speed, preload force, and rotational speed of chopping cylinder were selected as experimental factors, while standard grass length ratio, specific feeding, and chopping energy consumption were used as evaluation indices. Single-factor experiments and a three-factor quadratic orthogonal rotatable combination experiment were conducted, and the operating mechanism was further analysed using high-speed photography and torque sensor data. The single-factor experiments determined that the ranges of feeding speed, preload force, and rotational speed of chopping cylinder were 1–3 m/s, 900–1300 N, and 800–1200 r/min, respectively. The optimal parameter combination obtained from the quadratic regression equation was a feeding speed of 2 m/s, a preload force of 1090 N, and a rotational speed of chopping cylinder of 1010 r/min. Validation experiments were carried out under the optimal parameter combination, and the results were 90.34%, 0.86 kJ/kg, and 2.58 kJ/kg, respectively. The relative errors between the experimental results and the software-predicted values were all less than 10%. The results provide a theoretical basis and experimental support for parameter matching and low-energy optimization design of feeding–chopping devices for direct alfalfa harvesting.