Dynamics of fractional composition of grain-and-straw mass being threshed in the threshing mechanism of a combine harvester

Introduction. The article presents the results of theoretical and experimental studies of threshing and separation processes in the threshing mechanism of the combine harvester with a digital assessment of the fractional composition of the grain-and-straw material being threshed. The obtained data will allow detecting dynamics of fractional composition of grain-and-straw mass being threshed in the threshing gap of the threshing mechanism depending on its supply. Materials and Methods. The research was carried out on a special stand in the form of a separate unit of the combine threshing mechanism. Grain-and-straw samplers were installed under each threshing section. The mass feed was changed from 1.0 to 6.0 kg/s at a straw ratio of 1:1. The obtained data were approximated using a standard procedure. Results. There was determined the amount of grain and straw passed through the threshing section screen and the rest of grain and straw entering the straw separator depending on their initial amount. For each fraction, there were determined the ratio of straw mass to grain mass, the density and thickness of the grain-and-straw heap layer on the shaking board ahead of the grates and at the beginning of the straw separator keys. The dynamics of grain-and-straw separation was identified by scanning the length of the grains with the determination of the density and compression degree of the grain-and-straw mixture layer in the threshing gap. Discussion and Conclusion. It was found that in the heap of grain-and-straw passed through a threshing section, the ratio of straw mass to grain mass decreases from 0.46 to 0.27 and density increases from 60.1 to 84.0 kg/m3. In the heap of grain-and-straw that fell on the straw separator, the ratio of the straw mass to the grain mass decreases from 11.2 to 2.0, the density increases within a small range from 21.7 to 26.4 kg/m3. Thickness of the heap layer on the shaking board in front of the cleaning sieves varies in the range 0.25-10.20 cm, and on the straw walker - 2.2-19.8 cm when changing the supply of the total mass for threshing from 1 to 6 kg/s.