A novel air-suction classifier for fresh sphere fruits in pneumatic bulk grading

To improve the harvesting efficiency of the sphere fruits and reduce the workload of post-harvest classification, an air-suction sphere fruit classifier was designed in this paper, which can achieve the separation of high-quality fruit and common fruit through a pneumatic device according to the size and quality of the fruit when the cones are picked. First, three fruit pickers with various shapes are proposed, and the characteristics of the external flow field are analyzed, and a fruit picker that can maximize the classification efficiency is obtained. Then, the internal flow field of the classification pipeline was analyzed, the pressure and velocity changes in the classification pipeline were studied, and the displacement changes and classification of high-quality and common fruits in the classification pipeline were analyzed by particle simulation. According to the three influencing factors of pressure divider tube inner diameter, inclination angle, and outlet volume flow rate, an orthogonal test is designed, and the regression equation of fruit classification accuracy is fitted by the Box-Behnken method. The optimal factor parameters are obtained through response surface optimization: pressure divider tube inner diameter D3 = 48 mm, inclination angle = 60°, outlet volume flow = 0.01 m3/s. Research content provides a basis for the application of gas–solid separation technology in fruit classification.