This work stems directly from a manufacturing company's need to improve the quality of its product and increase competitiveness in an industry where a physical understanding of its production process, known as centrifugal spinning, is lacking. Centrifugal spinning is the principal method of producing mineral wool; a product that is predominantly used for thermal and acoustic insulation. The production technique generates wool fibres from a molten jet that is directed to impinge onto four rotating wheels. However, it sometimes, and quite often produces mineral wool fibres of poor quality due to the presence of nonfibrous material or shots; a problem that has so far received little attention. This inquiry was undertaken with a VIew to providing insights into the physical mechanisms governing the formation of fibres and shots. Theoretical analyses and an experiment were conducted to investigate the important non-dimensional groups that govern fibre and shot formation, but concentrating mainly on understanding the mechanics of shot formation. It was established that fibres are formed from the break-up of the thin layer around the rotating wheels. It was also established that shots are formed from droplets produced as a result of jet splashing. Jet splashing is temperature independent since it occurs in a short time-scale from jet impingement with little melt cooling; it is largely governed by force balance and geometrical parameters. Such an observation led to an impinging water jet experiment that was conducted at ambient temperature and its image processed by computer software. From this, it was determined that the significant non-dimensional group that governs jet splashing on a rotating wheel or drum was that due to the jet impact position. The least liquid splashing was found to occur when the jet impinged in the forward position (relative to the direction of rotation) because the depth of fluid underneath the impingement position was always at its minimum. The speed of drum rotation affected jet splashing only up to a critical value, beyond which it had little influence.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:302422 |
| Date | January 1999 |
| Creators | Angwafo, Ade Vincent |
| Publisher | University of Hertfordshire |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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