Published: 30 June 2012

Investigation of straw layer movement over the walker surface

D. Steponavicius1
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Abstract

Straw layer movement over the walker surface has been examined by measuring characteristics of elasticity and viscosity of the straw layer. For this purpose a visco-elastic model has been introduced. The examined process is represented by two stages: the first one is associated with the elastic deformation of the straw while the walker section moves upwards, and the straw layer laying on its surface is subjected to compression. Whereas the second stage involves a free throw of straw after the takeoff from the walker surface, and after the free throw, their contact onto the walker surface. The method of successive steps was used for the analysis of the movement process. The proposed model can be applied for modeling complex nonlinear characteristics of the straw layer movement by employing linear elastic and viscous elements through selection of their equivalent coefficients. Measurement of the elastic and viscous characteristics of the straw layer by their equivalent coefficients enabled to calculate rational rotation angles of the walker crankshaft at the takeoff ωt1 of the layer from the walker surface and contact ωt3 to the surface provided that during each period of crankshaft rotation a straw layer undergoes an impact. It was determined that straw movement is mainly dependent on the thickness, moisture content and viscosity of the straw layer. The takeoff of the thicker straw layer from the walker surface is delayed, since after the impact duration of its deformation is longer, resulting in a shorter time of free throw. Wet straw layer is less elastic, resulting in its longer movement jointly with the walker section, and the height of the free throw is smaller resulting in less favorable conditions for grain penetration when compared to the dry straw.

About this article

Received
27 March 2012
Accepted
14 May 2012
Published
30 June 2012
Keywords
straw walker
grain separation
straw properties
crankshafts rotation