Interrelation between the straw chopping length and the design of straw chopper

Abstract

The article deals with the process of straw chopping in straw chopper of a combine harvester. It shows the influence of straw chopper design on the straw chopping length; in particular the influence of spatial position of straw at the moment of its cutting, and of spacing of knives setting, on the chopping length. The possible variations of straw motion with chopping rotor knives after its chopping on the shearbar are described. The nature of motion of uncut straw with the chopping rotor, and the forces acting on the straw that slides over the rotor knives, are also described. The dead zone in the straw chopper is determined; it is an area between the body of chopper and the working surface of chopping rotor knives. Motion of straw in the dead zone does not lead to its chopping, because of the lack of possibility of its contact with rotor knives. The necessity of introducing of complementary units on the low wall of straw chopper body is substantiated; it leads to the intensification of straw chopping process by means of removing the straw flow from dead zone and increasing the probability of straw contact with rotor knives. The location of such units is determined. Reorientation of straw flow before and during its chopping not only reduces the straw chopping length, but also leads to the reduction of power consumed by straw chopper. This is due to both the reduction in cutting area, and the reduction in inertia of chopping rotor, because of decrease in number of knives.