The experimental study was conducted to explore the flow behaviour of particulate solids in silos and to provide the experimental data for the theoretical work. Silo discharge tests using polypropylene pellets in a half cylindrical model silo were conducted under different discharge eccentricities. In addition, some experimental data from a research project on a full scale silo at the University of Edinburgh were also analysed and used in this thesis. In these tests, the main observations relating to flow were the residence times of the markers seeded in the solid during filling (residence time is the time a particle takes to move from its initial position to the outlet). The top surface profile was also measured at regular intervals during discharge. The residence time measurements are analysed using several approaches to infer the approximate location of the flow channel boundary in both silos. These techniques demonstrate how residence time measurements can be used to infer the flow patterns in silo discharge. In addition to the above, the transparent front wall in the half cylindrical model silo enabled a record to be made of the development of the flow channel boundary and the trajectories of individual particles. This data provided further insight into the complex flow patterns. The direct measurements of the changing flow channel boundary are also used in the thesis to evaluate the dilation of the solid which occurred in the flowing material. The dilation, or decrease in the bulk density, is believed to play a significant role in determining the solids flow pattern. The theoretical work presented starts with the development of a simple engineering model to predict solids flow in funnel flow silos. This model uses the kinematic theory for steady state flow, subject to simple assumptions concerning the top surface profile, top surface flow geometry and particle trajectory. The flow of iron ore pellets in the full scale silo and polypropylene pellets in the model silo during concentric emptying are predicted using the simple engineering model. The predictions for both silos are plausible and are in good agreement with the experimental observations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:664224 |
| Date | January 1997 |
| Creators | Zhang, Kefeng |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13254 |
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