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

Abstract

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 were carried out. Additionally a finite element modal analysis of RFM was performed to validate the finite element model that can be used for vibro-acoustic and computational fluid dynamic studies. Below 500 Hz total of eight critical modal frequencies, three for fan and five for shroud are determined and between 500 Hz to 2000Hz seven modes for fan and fifteen modes for shroud were dedermined. From the correlation study, it is witnessed that the contribution of modal behaviour for noise radiation is observed with 20 dB(A) variation below 500 Hz, along the diagonal grid points whereas beyond 500 Hz the variation was negligible. Importantly, blade passing frequencies corresponding to the fan speeds between 500 to 3000 rpm were compared with resonance frequencies obtained and they do not conicide with modal frequencies.