Development of low power-consumption multi-helical rotavator for small vertical-shaft deep-cultivator

Small deep-cultivators with light weight and simple structure are urgently needed to satisfy the requirements of deep cultivating in hilly regions. Development of a low power-consumption rotavator is a prerequisite for the lightweight of a small deep-cultivator. In this paper, in order to reduce the power consumption of the rotavator for a small vertical-shaft deep-cultivator, a multi-helical rotavator was proposed. The multi-helical rotavator consisted of a vertical-shaft rotavator head and 3 discontinuous multi-helical cutters that are unevenly distributed along the circumference of the head. The discontinuous multi-helical cutter consisted of a cutter-shaft and 3 discontinuous helical cutter edges that are evenly distributed along the axis of the cutter-shaft. The rotavator head had a diameter of 250 mm and the rotavator had a design tillage depth of 30 cm. The cutter-shaft length was 0.35 m and the helical angle of the helical cutter edge was 53º. Based on the motion analysis of the multi-helical rotavator, the motion path and its parameters model were established. The structure and operating parameters of the discontinuous multi-helical cutter and the rotavator were designed and analysed. Then the three-dimensional models of the discontinuous multi-helical cutter and the rotavator were established for simulation analysis. Based on the SPH (smoothed particle hydrodynamics) algorithm, the motion of soil particles, cutting resistance and power consumption were simulated and analysed during the operation of the discontinuous helical cutter and the traditional vertical-shaft orthogonal cutter in ANSYS LS-DYNA. In addition, an actual multi-helical rotavator was manufactured and its tillage effect and power consumption were tested. The simulation results showed that, comparing with the traditional vertical-shaft orthogonal cutter, the performance of the discontinuous helical cutter was significantly improved. 1) The discontinuous multi-helical cutter could greatly stir the upper soil particles, and the displacement of the upper soil particles was obviously increased during the cultivation process. At the same time, the lower soil particles were only slightly disturbed, and the displacement of the lower soil particles was significantly reduced. 2) The cutting resistance of the designed discontinuous helical cutter decreased by an average of 37.5%. Besides, the fluctuation range of cutting resistance decreased by an average of 60.6%, which could reduce the rotavator vibration and make the small deep-cultivator to work more stably and more reliable. 3) The total energy consumption of the designed discontinuous helical cutter was reduced by 58.7% and the average power consumption was reduced by 47.6%, which could reduce the weight of the small deep-cultivator under the same power consumption conditions. The test results showed that the actual power consumption of the designed multi-helical rotavator was 2.86 kW, which was 11.28% higher than the simulation value of 2.57 kW. The simulated power consumption value was close to the test value, which verifies the validity of the simulation results. At the same time, the average tillage depth of the designed multi-helical rotavator was 28.7 cm with a stability coefficient of 94.64% and the average soil pulverizing rate is 76.02%. Therefore, the designed multi-helical rotavator had better crushing and throwing ability than the traditional vertical-shaft orthogonal cutter, and could improve the soil subsoiling effect while meeting the requirement of the tillage depth. The reduction in cutting resistance and the decrease in cutting resistance fluctuation could also reduce the power consumption and vibration of small deep-cultivators. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.