Optimization of Aerodynamic Flow in a Stripping Header for the Reduction of Grain Losses

The research was carried out in order to optimize the flows in the combing device for harvesting grain crops at different stages of ripeness, allowing to reduce grain losses and increase the proportion of threshing due to a higher air flow velocity in the ribbed deck area. The construction of the initial and upgraded geometry of the combing device and the study of flows in it were performed in the Ansys software package. The mathematical model is based on the Navier- Stokes equations of hydrodynamics. Numerical results were obtained by the volumetric element method in the Ansys CFD software package using RANS equations and turbulence models. With a constant rotation speed of the combing drum of 400 rpm, the highest air flow velocity is achieved in the area of the combing drum – from 7 to 18 m/s. Low air flow rates are observed in the milling and milling zones, which leads to grain losses of upto 4–5 % and a low proportion of free grains – 65–70 %. Increasing the rotation speed of the combing drum increases the proportion of injured grain from 0.7 % to 2.5 %. In order to reduce grain losses and optimize air flows, two casings were added – in the lower and upper parts of the working chamber of the combing device. The first one prevents air intake in the lower part of the combing drum, the second one increases the flow rate in the area of the ribbed deck. The upgraded design of the combing device distributes air flows more efficiently. The values of air flow velocities in the area of the hearth and in the area of the ribbed deck increased from 8.3 to 42 %, which helps to reduce grain losses from 0.5 to 2 % or more, as well as increase threshing in the working chamber of the device by at least 10 %.

stripping header, airflow, computational fluid dynamics, finite volume method, Navier-Stokes equations