Movement of chopped material in the discharge spout of forage harvester with a flywheel chopping unit: Measurements using maize and numerical simulation

Air and chopped material movement in the discharge spout of a forage harvester was characterised, and velocity determined, with changes in the shape, the cutterhead rotational speed, the number of knives and the quantity of maize plant material fed into the flywheel cutting unit. A computational fluid dynamic (CFD) simulation of the airflow in a spout configuration was carried out using Fluent v. 6.2 software. A mathematical model for particle movement in the discharge spout of forage harvester with low throughput 3.75 kg s−1 or 13.5 t h−1 was developed. An ultra-fast digital camera recorded the particle movement at the rate of 2000 frames per second was used to provide data for validation of the mathematical model. The experiments conducted showed that the particle movement in the discharge spout has two phases. In the first phase the particles move in a dispersed manner but in the second stage, after collision with the upper spout wall, the chopped material stream became dense. An abrupt change in particle velocity occurred at the boundary of the stages; velocity then decreased more slowly in further sections of the spout.

► A mathematical model was developed for forage particle movement in the discharge spout.
► Particle movement in the discharge spout has two phases.
► In the first phase the particles move in a dispersed way.
► The second phase, after hitting the spout wall, the particles move in a dense stream.
► The model satisfactorily described the studied processes as validated by experimental results.