Experimental Modal Analysis of Radiator Fan Module to Predict its Influence of Structural Characteristics on Vibration and Noise Contribution

Among many accessories of a passenger car, engine cooling Radiator Fan Module (RFM) is an important source of noise and vibration. Modal parameters provide the basis for the noise generation mechanism and noise propagation phenomena. The objective of the current research work is to characterize RFM through its modal behavior to investigate the contribution of structural vibration to noise radiation during its operating state. Hence, the experimental modal analysis and the noise measurement of RFM are carried out. Additionally a finite element modal analysis of RFM is performed to validate the finite element model that can be used for vibro-acoustic and computational fluid dynamic studies. Below ۵۰۰ Hz total of eight critical modal frequencies, three for fan and five for shroud are determined and between ۵۰۰ Hz to ۲۰۰۰Hz seven modes for fan and fifteen modes for shroud are determined. From the correlation study, it is witnessed that the contribution of modal behaviour for noise radiation is observed with ۲۰ dB(A) variation below ۵۰۰ Hz, along the diagonal grid points whereas beyond ۵۰۰ Hz the variation was negligible. Importantly, blade passing frequencies corresponding to the fan speeds between ۵۰۰ to ۳۰۰۰ rpm are compared with resonance frequencies obtained and they do not coincide with modal frequencies.

Keywords:

Radiator fan module , Modal Analysis , spectral test , signature test , sound pressure level