Mechanical and mathematical justification of the operation of the upper sieve extension of the combine harvester cleaning system

The article describes the process of separating the grain pile on the extension of the upper sieve of the combine harvester cleaning system. Mathematical modeling of the extension operation process was carried out, as a result of which mathematical expressions were obtained to determine the weight of loose grain and unpolished ears in the recycling auger when it passes through the extension and when it descends from the extension into the chaff. The variables are the average values of the coefficients that affect the performance of the cleaning system and the extension of the upper sieve. Based on the results obtained, graphical dependencies are constructed. The simulation result showed that the percentage of loose grain and unpolished ears in the recycling auger was 9.9–13.5 % of the grain pile supply to the upper sieve of the cleaning system, and when it descended from the extension into the chaff – 0.86–5.05 %.