Experimental study of the trailing edge noise generated by axial flow fans

An experimental rotor has been expressly realized to study the trailing edge noise generated by axial flow fans and has then been tested in a hemi-anechoic chamber. The rotor blades have has radially stacked profiles based on a NACA 0012 airfoil, resulting in a simple geometry, which prevents complex flows and eases comparisons with noise predictions. Several working points and rotational speeds have been considered yielding a complete data base. The SPL spectra have been scaled according to the similarity rules and then analyzed resulting in typical trends: a broad peak at low blade loading, which grows and moves towards low frequency as the blade loading increases. Finally, the experimental SPL spectra have been compared with those predicted by the Brooks, Pope and Marcolini (BPM) method. The comparisons show a good agreement at the lower blade loadings and rotational speeds but the agreement becomes poorer as both parameters increase. The effect of the rotational speed was unexpected and seems to indicate that, for the present application, some of the BPM correlations should be modified.