An analytical grain flow model for a combine harvester, Part I: Design of the model

A good understanding of the way grain kernels are processed and transported through a combine harvester is not so easy. Every section of the machine has its own impact on the flow depending on geometrical dimensions and crop properties. Some work has already been performed on these individual machine parts but this study, on the contrary, connects the different sections and looks at their role in the total dynamic impact on the grain flow. Some different starting points are possible for constructing this flow model. In this work, an analytical approach is chosen in order to maintain the physical insight and the possibility of analysing the impact of parameter variations on the total dynamic influence. Another reason is the impossibility of measuring the incoming grain flow above the cutterbar of the machine which is necessary for 'black-box' identification. Simulations revealed that two parameters are dominating the process: the portion of the internal return flow of unthreshed ears in the total grain flow and the material speed across the grainpan of the machine. (C) 2001 Silsoe Research Institute.