Flow Measurements and Analysis for Automotive Blower Noise

The climate control air handling system is one of the major contributors to automobile interior noise. The most annoying features can be characterized as low frequency (<= 400 Hz) “rumble”, and “blade passing frequency, BPF tone” noise. This study presents an experimental investigation for two blower scroll assemblies, namely ‘baseline’ and ‘modified’. The baseline assembly is the original scroll which exhibited both tone and rumble noise problems. This assembly was modified to significantly reduce the tone and rumble noise. The velocity power spectral density plots of flow velocity show areas within the blower scroll where the turbulence fluctuations are relatively high for the tone and rumble frequencies, and are lower in magnitude for the modified case. A detailed CFD analysis was performed to compare the mean flow velocity components for the two assemblies. The results are in good agreement with the measurements. CFD analyses, which have been confirmed by experimental data, can be used to predict beneficial geometric alterations to minimize the tonal and rumble noise sources in climate control flow systems.