This paper addresses a noise comparison of centrifugal fans, with backward-curved blade and backward-inclined airfoil blade, by using computational aeroacoustics. Flow fields over simplified models are examined under specific system resistance and sound pressure levels are calculated with Ffowcs Williams-Hawkings acoustic analogy. For backward-curved blade, flow separation occurs at the leading edge; strong vortex sheets are generated and propagated downstream; and pressure fluctuation is increased. To attenuate unsteady acoustic sources, airfoil blade based on four-digit NACA has been implemented and then vortex shedding is suppressed and sound pressure level is decreased significantly. Over the actual experiment, air flow rates and sound pressure levels are measured, validating the analysis accuracy.
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