Combine model for grain threshing

A mathematical model to simulate the threshing process in conventional and axial-flow combines was derived. The model was based on the probability of repeated impacts striking unthreshed grain and the ratio of kinetic energy received to that needed to thresh a unit mass of grain. The basic equation was expanded using dimensional analysis to include the variables of cylinder diameter, concave spacing, the concave length. The final equation was verified with data for conventional combines. An R^2 of 0.97 was obtained which was significant at the 99.9 percent level (@a = 0.001). The model is easy to use since it requires data typically considered in combine design and operation. Based on this model, some alternative combine designs are discussed.