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Abstract
Blade passing frequency (BPF) noise is the dominating component of the flow induced noise of centrifugal fans. The numerical methods for BPF noise prediction, based on the computational aeroacoustics (CAA), have been published for decades. However, there are a couple of challenges for accurately predicting noise for industrial centrifugal fans. The first arises from the fact that the free field hypothesis, adopted in the numerical model, has not yet been carefully studied. The second challenge stems from the current criteria for which the prediction results are compared to the measurement data. Because the test conditions do not always satisfy the requirements of the numerical model, inaccurate predictions occasionally resulted. Therefore, since the prediction results may deviate largely from the test data, the applicability of these methods is severely limited.
Nomenclature
| B | = | blade number |
| H | = | total pressure (Pa) |
| L | = | total sound pressure level (dB) |
| Ls | = | specific sound pressure level (dB) |
| N | = | rotating speed (rpm) |
| Q | = | flow rate (m3/min) |
| Δt | = | time step size (s) |