Performance Evaluation of Liquorice Harvester with Novel Oscillating Shovel-Rod Components Using the Discrete Element Method

Abstract

Liquorice harvesting is the key process in the development of the liquorice industry. For harvesting liquorice with about 400 mm growth depth, a lightweight harvester with novel oscillating shovel-rod components was developed. Draft force, total torque, specific energy consumption, separation proportion, and soil structure maintenance were used to evaluate harvester performance under varied working conditions, and throw intensity and total torque were analyzed. A DEM model was developed to simulate the excavation and separation of soil. Three sets of single-factor simulation tests and one set of field tests were conducted. The results indicated that: Each 1 mm increase in amplitude decreased draft force by 463.35 N and increased total torque and specific energy consumption by 35.03 Nm and 4.3 kJ/m3, respectively. Each 1 Hz increase in vibration frequency increased specific energy consumption by 3.12 kJ/m3, while draft force and total torque decreased by 375.75 N and 28.44 Nm, respectively. Each 0.1 m/s increase in forwarding speed increased the draft force, total torque and specific energy consumption by 1302.72 N, 13.26 Nm and 3.82 kJ/m3, respectively. The main separation areas of the shovel-rod were front areas, where the soil separation proportion is greater than 60%, and the soil was completely separated at the end areas. The soils after harvesting had a relatively minimal disturbance in all layers, with soil structure maintenance greater than 0.61, and soil structure was well maintained. The liquorice plants were separated from the soil after passing smoothly through the oscillating shovel-rod components, during which the soil at different layers fell in sequence. This study revealed the interactive relationship between working components and soil, specifically the potential to maintain soil structure after harvesting. This new finding will assist in developing harvest techniques for rhizome crops with deep growth depth.