Experiments and analysis of the differential threshing cylinder for soybean with different maturities

The threshing cylinder of the combine was used for soybean threshing and auxiliary soybean separation. However, soybean in Southern China has a high ratio of grass to grain and immature pods during harvest. The existing nondifferential speed threshing cylinder has poor adaptability to this feature, resulting in low threshing quality, low operating efficiency and high fuel consumption in the harvesting process. Therefore, this study aims to improve the adaptability and comprehensive performance of the threshing cylinder of soybean combine harvester in Southern China. Aims at the high ratio of grass to grain and the proportion of immature pods in soybean harvest in Southern China, a longitudinal axial flow differential threshing cylinder with adjustable cylinder speed difference was designed, it's front cylinder threshes the pods that are easy to thresh at a lower rotating speed, while the rear cylinder threshes the pods that are difficult to thresh at a higher rotating speed. And two types of threshing teeth were made, the full rod tooth threshing teeth was the front and rear cylinders were adopt rod teeth, and the rasp-rod combined threshing teeth was the front cylinder adopts the rasp bar, and the rear cylinder adopts the rod teeth. At the same time, in order to study the impact of the structure and parameters of the threshing cylinder on the threshing quality, the type of the threshing teeth, front cylinder speed and cylinder speed difference related to the threshing cylinder are selected as factors, and the Epicit Dnamics module of ANSYS software was used to analyze the impact of different factors on material changes from the perspective of energy and shape variables. It can be speculated that the cylinder with the rasp-rod combined threshing teeth has lower the percentage of broken, the percentage of unthreshed and the percentage of separation loss grains. In the end, the optimal parameter combination of the differential threshing cylinder and the traditional nondifferential threshing cylinder was obtained through experimental analysis, and the threshing quality, operating oil consumption and maximum operating efficiency of the two threshing cylinders are compared under the optimal parameter combination, evaluated the comprehensive working quality of the threshing cylinder, which provides a reference for the research of soybean harvester threshing device in many aspects. In the field test, due to the limitation of test cycle and safety, it is impossible to measure the fuel consumption and maximum operating efficiency in each group of tests. Therefore, the percentage of broken, the percentage of unthreshed and the percentage of separation loss that reflect threshing quality are taken as evaluation indicators, and a single factor comparative test was conducted, and the fuzzy comprehensive evaluation method was adopted, It was determined that the threshing cylinder most suitable for soybean characteristics in the Southern China was the differential speed threshing cylinder, and the threshing teeth type was the rasp-rod combined threshing teeth. The optimal parameter combination was: the speed of the front cylinder was 450 r/min, the speed difference of the cylinder was 150 r/min, and the optimal rotational speed of the traditional nondifferential speed threshing cylinder with rod tooth was 500 r/min. Under the optimal parameter combination, the comprehensive performance comparison test of two threshing cylinders was carried out. The results showed that the threshing quality of the differential threshing cylinder was higher, its fuzzy comprehensive evaluation value was 0.4 higher than that of the traditional rod tooth threshing cylinder, the fuel consumption was 2.7 L/hm2 lower, and the working efficiency was 10.35% higher, It was proved that the differential speed threshing cylinder with the rasp-rod combined threshing teeth can improve the adaptability and comprehensive working performance of the harvester to soybeans. This discovery provides a favorable technical support for mechanized soybean harvesting in Southern China.