Theoretical study on sieving of potato heap elements in spiral separator

One of the principal problems in the harvesting of potatoes is the cleaning of the lifted heap from soil and plant impurities. The low quality in the performance of this harvesting work process operation is the main cause of the withdrawal from fields of considerable amounts of fertile soil. In order to facilitate choosing the optimal parameters for the new design of the spiral potato heap cleaning unit, a mathematical model of sieving the soil impurities through its cleaning spirals has been developed. The obtained analytical expressions have been solved with the use of a PC and the results have been used for plotting the graphic relations between the parameters of the examined process of a variable-mass body’s motion on the surface of a spiral, which have made it possible to select the optimal design and kinematic parameters of the spiral cleaning unit under consideration. The obtained graphic relations indicate that the rate of sieving in the spiral separator depends on many factors, including the initial mass, the design dimensions (spiral’s radius, helix angle etc.), the frictional properties of the surface, the angular parameters of the position of the potato heap elements on the spiral’s surface, and the angular velocity of the rotational motion of the spiral roll itself.