Browsing by Person "Schwarz, Michael"

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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%.