Einfluss der mechanischen und pneumatischen Anregung auf die Entmischung und Abscheidung in der Mähdrescherreinigungsanlage

Abstract

Due to the legal limitation of the maximum machine width the throughput increase is realized by further developing of the process technology. This requires precise knowledge of the ongoing processes. The aim of this work is the metrological investigation of the combine cleaning system according to the white-box model by analyzing the process sequence of the sub-processes.This enhances process understanding and enables the validation and verification of DEM-CFDsimulations. The evaluation of the segregation and separation process is based on the movement behavior of grain and straw. For this purpose, 2D high-speed x-ray images, static 3D reconstructions and 2D high-speed camera images are analyzed. The segregation in the lower layers is limited by the compression of the material layer due to its own weight. Due to the higher porosity the segregation of the grain near the wall is slightly faster. Additional relative movements of the material based on the superimposed conveying process. The resulting voids are used for a faster segregation. The influence decreases with increasing mechanical and pneumatic excitation in vertical direction. The influencing factors on the movement behavior of the material in the cleaning system is investigated with a test-rig. In the unloaded state the airflow decreases along the sieve. Due to higher sieve loads the airflow is flatter. Therefore the maximum air speed under the lower sieve is shifted to larger sieve lengths. The front area of the upper sieve is less loaded. The air passes by these areas and causes an increase of the air speed. High air speeds in the winnowing steps result in a high grain separation. A high component of the air velocity in the conveying direction between the sieves causes a shift of the separation on the lower sieve to longer lengths. The air throughput must be within the limits between a sufficient material fluidisation and a low conveying process on the sieves. In addition to identifying development potential, the results are used to verify DEM-CFDsimulations. There are deviations of movement behavior between grain and straw. Nevertheless,the influencing factors can also be examined qualitatively on the basis of the simulations.

In dieser Arbeit erfolgt die messtechnische Untersuchung der Mähdrescherreinigungsanlage nach dem White-Box-Modell, indem das genaue Wirken der Teilprozesse herausgestellt wird. Dies erhöht das Prozessverständnis und ermöglicht die Validierung und Verifizierung von DEM-CFD-Simulationen. Die Entmischung und Abscheidung wird anhand des Bewegungsverhaltens von Korn und Stroh bewertet. Dazu werden 2D-Hochgeschwindigkeitsröntgen-Aufnahmen, statische 3D-Rekonstruktionen und 2D-Hochgeschwindigkeitskamera-Aufnahmen analysiert. Die Untersuchung der Einflussgrößen auf das Bewegungsverhalten der Gutbestandteile erfolgt an einem Reinigungsprüfstand. Neben der Identifikation von Entwicklungspotential werden die Erkenntnisse zur Verifizierung von DEM-CFD-Simulationen genutzt.