The influence of the geometry of the leading edge of diffuser vanes on the noise generated by a centrifugal fan

Abstract

An experimental study is described to investigate the influence of diffuser vane leading edge on the noise behaviour of a centrifugal fan. The geometric shapes of the diffuser vane leading edge refer to the diffuser inlet radius, and the broken and inclined leading edges. The sound pressure level and pressure rise of the centrifugal fan were measured in a semianechoic chamber. The rotational speed of the test fan varied from 20 000 to 35 000 r/min; the flow coefficient was in the range of 0.02–0.14. The results show that: (a) by using the inclined leading edge vaned diffuser (ILEVD) with proper inclined angle, the overall fan noise is reduced by 3.6 dB(A), and the fan performance is improved; (b) when the diffuser leading edge radius R₃/R₂ increases from 1.03 to 1.07, the tones are reduced whereas the broadband noise is almost unchanged; and (c) the influence of the broken leading edge diffuser on the overall fan noise and performance is negligible, although the tonal noise is reduced by 4 dB(A). In order to better understand the behaviour of the ILEVDs, a numerical simulation has been carried out on steady three-dimensional flows. The results indicate that the flow condition improves by the application of the ILEVD.