Browsing by Subject "Vorbereitungsboden"

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Förderung und Entmischung auf dem Vorbereitungsboden des Mähdreschers
(2013) Timofeev, Andrey; Böttinger, Stefan
In the last years with the increasing performance of the combine harvester capacity, the performance of the cleaning system has been the limiting factor, because the capacity of the threshing drum and the separation elements by the use of additional separation drums and rotors is not a problem anymore. The performance of the cleaning system can be greatly increased, especially through intense pre- segregation, whereas grain losses remain at a relatively low level even at high particle rates of approximately of m˙ K = 5,5 kg/(s·m). Grain- and NKB (chaff and other plant residue) -throughput affect both the conveying speed and the segregation on the grain pan. The grain throughput has a particularly strong impact on the conveyor speed, when throw occurs in the conveying process (Frv > 1). Thereby the elastic properties of the crop layer (straw and chaff rack) damps very strong the introduced mechanical agitation. This decreases the conveying speed strongly. The segregation in turn affects positively the speed of transfer from the grain pan to the material. The separation takes place substantially in the last third of the grain pan.
Grundlagenuntersuchungen am Mähdrescher-Vorbereitungsboden mit pneumatischer Unterstützung
(2017) Schwarz, Michael
Nowadays the cleaning unit in combines is often the power limiting assembly unit. There are no additional accelerating fields acting to segregate and separate grain besides gravitational acceleration. A strengthened pre separation of the material mixture acting in front of the winnowing step in the combine can increase the power of the cleaning unit without additional accelerating fields. A pneumatically supported separation process at the preparation floor is a promising measure. The target is to generate a fluidized bed. Conveying and segregation at the preparation floor are modeled following different approaches. The analytical description of the conveying at the pneumatically supported preparation floor by means of extended point mass approaches in conjunction with a stochastic description of the segregation is suitable for conventional modeling approaches for complex process engineering processes to a limited extent. For the experimental evaluation of the conveying and segregation a test rig with an additional fan at the preparation floor is developed. The test rig allows the determination of grain losses, cleanliness, return and separation characteristic in the cleaning unit. As typically handled in combines the feeding of the material is handled via the preparation floor and return pan. In order to be able to assign the grain losses to the point of delivery, the grains transported on the return pan are coloured. To evaluate the segregation at the preparation floor, the average height of the grain above the preparation floor is to be determined. This determination is done by means of a high-speed camera recording with subsequent particle tracking. The investigations at the preparation floor without pneumatically support show that the segregation at the preparation floor is restricted at high throughputs. Furthermore, it demonstrates that upon increasing throughput the proportion of the grains in the share of grain losses from the return pan increases disproportionally higher than the total grain losses. The design notes derived therefrom include the adaptation of the preparation floor length as well as the optimization of the return pan’s connectivity to the cleaning unit. By means of a pneumatic support arranged in the last third of the preparation floor, a fluidized bed is generated in the investigation, which increases the work efficiency of the cleaning unit by approximately 10%.
Simulation der Trennprozesse im Mähdrescher
(1999) Beck, Folker
Die Kosten für Versuche nehmen in der Mähdrescherentwicklung weiter zu. Außerdem ist die zur verfügung stehende Zeit während der Ernte begrenzt. Deshalb wird ein Simulationswerkzeug für die Trennprozesse im Mähdrescher entwickelt, mit dem sich der Gutfluß im Mähdrescher schon beid er Entwicklung jederzeit und kostengünstig am rechner nachvollziehen lässt. Das Simulationswerkzeug ist außerdem zur Untersuchung physikalischer Zusammenhänge bei der Korn/Stroh/Spreu-trennung geeignet, da es auf stochastischen, mathemnatisch-physikalischen Modellen für die Teilprozesse in Dreschwerk, Schüttler, Vorbereitungsboden, Fallstufe und Obersieb der Reinigungsanlage aufbaut. In laborversuchen werden sämtliche Teilprozeßmodelle einzeln experimentell bestätigt. beispielhaft durchgeführte Simulationsrechnungen für den Gesamt-mähdrescher bei Variation von Durchsatz, dreschtrommel-Drehzahl, Dreschkorblänge und Länge des Vorbereitungsbodens zeigen gute Übereinstimmung und machen Potential für zukünftige Entwicklungen deutlich.