The quantification of airflows generated by rotating rollers in wool carding machines.
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
The properties of fibres make them easily manipulated by aerodynamic forces. The carding machine, used in cotton and wool processing, is an example of equipment that creates aerodynamic forces due to fast rotating cylinders with rough surfaces. These forces are generally seen as an undesirable side effect in fibre processing machinery, exacerbated with modern equipment using faster rotating components. This work attempts to quantify these aerodynamic forces on carding machines used in the wool industry. A combination of boundary layer theory, experiments using hot wire anemometry and flow visualisation, and Computational Fluid Dynamics (CFD) software (Fluent) was used to build up an understanding of aerodynamics in the example of wool carding machines. The theoretical and experimental work progressed along the following topics to determine each effect on carding machine aerodynamics: rough surfaces, centrifugal forces, three-dimensional edge effects, and interactions between rotating cylinders. Examples from each section were modelled using CFD, which was found to accurately simulate theoretical and experimental results in most cases. It could also accurately predict the complex two-dimensional airflow patterns occurring in carding machines. The CFD simulations underestimated the degree of turbulence generated by interactions between rotating cylinders. Three-dimensional effects were overestimated, due in part to attempting to apply the results of an oversimplified model to a full-scale carding machine. In undertaking this work, it was found the universal velocity distribution equations describing flow over flat plates (for both smooth and rough surfaces) could also be used for flow induced by rotating cylinders by compensating for curvature effects.