Shredder windage investigation

Air flow through a shredder is complex. There are many examples where relatively small design changes to the shredder and surrounding conveyors can cause quite large changes to air flow. Windage is the term used to describe undesirable air flow. Windage that is counter current to the flow of cane into the shredder is particularly undesirable because it can cause feeding problems. Windage can limit the transfer of energy from the shredder hammers to the cane billets by reducing the relative velocity at impact which can reduce preparation. Shredder windage is also a source of dust, trash and billet emissions. A computational fluid dynamics model of a shredder has been developed to model the air flow through a shredder and its surrounding conveyors. A subsequent investigation, carried out on two factory shredders that suffered from significant windage, is described. Computational fluid dynamics was used to investigate the windage problem and evaluate potential design solutions. Modifications were made to both shredders. Measurements were carried out on these shredders before and after the modification to validate the model predictions, understand the factors that cause windage and reduce the detrimental effects. Key words Shredder, computational fluid dynamics, windage, flow measurements