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Until recently, domestic and HVAC fans were designed using essentially the same methods as those used 50 years ago. These methods involved hand calculations using airfoil design methods to estimate the performance of various blade design concepts. The calculations had many simplifying assumptions that limited their accuracy in practical situations. This necessitated the building and testing of expensive prototypes that was quite time consuming. Consequently, engineers have often been forced to settle for less than ideal performance because they haven't had the tools to access a truly optimized design.
Velocity field for the propeller configurationExperimental data by Oh and Kang (1999, 1996) for the fan performance curves of a four-bladed axial flow fan were compared with CFD simulations in a recent validation study. The fan's rotational speed was 2000 rpm, with a Reynolds Number of 120,000. The FLUENT model involved a fully unstructured tetrahedral mesh created in GAMBIT. The simulation included both the rotational reference frame model and the realizable k-e turbulence model. Excellent agreement between the CFD results and the experimental wind tunnel data for fan head versus flow rate predictions was achieved.
Head coefficient vs. flow coefficient: comparison of FLUENT results with published experimental data(click image for enlarged view) This CFD study showed that the performance of this class of axial fan
could be predicted with reasonable accuracy over a wide range of flow
rates. This approach provides evidence that fan designers can rely upon
to predict the performance characteristics of new and existing fan designs,
thereby allowing systems to be optimized at much lower cost than traditional
Development of tip vortices from the propeller bladesReferences:
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