The quantification of airflows generated by rotating rollers in wool carding machines.

摘要

The properties of fibres make them easily manipulated by aerodynamic forces. The cardingmachine, used in cotton and wool processing, is an example of equipment that createsaerodynamic forces due to fast rotating cylinders with rough surfaces. These forces aregenerally seen as an undesirable side effect in fibre processing machinery, exacerbated withmodern equipment using faster rotating components.This work attempts to quantify these aerodynamic forces on carding machines used in thewool industry. A combination of boundary layer theory, experiments using hot wireanemometry and flow visualisation, and Computational Fluid Dynamics (CFD) software(Fluent) was used to build up an understanding of aerodynamics in the example of woolcarding machines. The theoretical and experimental work progressed along the followingtopics to determine each effect on carding machine aerodynamics: rough surfaces,centrifugal forces, three-dimensional edge effects, and interactions between rotatingcylinders. Examples from each section were modelled using CFD, which was found toaccurately simulate theoretical and experimental results in most cases. It could alsoaccurately predict the complex two-dimensional airflow patterns occurring in cardingmachines. The CFD simulations underestimated the degree of turbulence generated byinteractions between rotating cylinders. Three-dimensional effects were overestimated, duein part to attempting to apply the results of an oversimplified model to a full-scale cardingmachine.In undertaking this work, it was found the universal velocity distribution equationsdescribing flow over flat plates (for both smooth and rough surfaces) could also be used forflow induced by rotating cylinders by compensating for curvature effects.