Study on detachment mechanism of rice wet extruded mixtures adhering to cleaning sieve for combine harvester

Wet extruded mixtures of rice tend to adhere to the cleaning sieve of combine harvesters, leading to a high grain loss rate during cleaning. In this study, the surface morphology of rice wet extruded mixtures was studied. Models for the liquid-bridge force and detachment between the mixtures and the cleaning sieve were established. The results showed that the surface morphology of the mixtures was complex and there was liquid film, resulting in it easy to adhere to cleaning sieve. The liquid bridge force can significantly affect the collision process between the mixture (the light impurity and the stem with a small length-diameter ratio) and cleaning sieve. The liquid bridge force between the mixtures and the cleaning sieve decreased and increased with the increase of separation distance and the surface moisture content of the mixtures, respectively. The critical shear velocity of stem and light impurity detaching cleaning sieve decreased with the increase of its diameter, indicating that the smaller diameter of mixtures was easy to adhere to the cleaning sieve. The method of reducing the relative air humidity of cleaning room by heating was proposed to improve the cleaning performance, and the method was verified by experiments.