Design and Experiment of Axial Flow Threshing and Cleaning Device for Roller Brush Type Castor Harvesting Machine

In order to alleviate the problems of lack of research on threshing and cleaning equipment and poor operational performance of castor harvester, an axial-flow threshing and cleaning device was designed and evaluated for a roller brush type castor harvester. This paper introduces the overall machine structure and elaborates on the working principles of the castor threshing and cleaning device. It clarifies the design and analysis of key components such as the conveyor design, rod-tooth structure design, collision force analysis between the fruit and rod-tooth, concave sieve design, and guide plate design. The main indicators for evaluating the castor threshing and cleaning device include the impurity rate, damage rate, and separation loss rate. Based on the previous experimental research, the working parameters of castor threshing and cleaning device are tested and studied by using the Box–Behnken central combined test method. The three-factor three-level quadratic regression orthogonal test design is carried out based on the forward speed, roller rotational speed, and threshing gap of concave sieve. A response surface mathematical model was established, analyzing the impact of various factors on work quality and conducting comprehensive optimization of influencing factors. The experimental results indicate that the significance order of factors affecting the impurity rate was forward speed > roller rotational speed > threshing gap of concave sieve; the significance order for damage rate was roller rotational speed > threshing gap of concave sieve > forward speed; and the significance order for separation loss rate was roller rotational speed > forward speed > threshing gap of concave sieve. The field test results show that the optimal working parameter combination is forward speed of 0.87 m∙s−1, roller rotational speed of 462 r∙min−1, and threshing gap of concave sieve of 30 mm, with an impurity rate of 2.95%, a damage rate of 1.75%, and a separation loss rate of 0.49%. The research findings can provide references for the structural improvement and operational parameter optimization of the castor harvester’s threshing and cleaning device.