Acoustic Characterization of a Centrifugal Fan in an Automotive Ventilation Unit Sound Predicting Model

E1 - Noise of Cooling Fans in Automotive Applications

The acoustical model used to predict the sound generated by the centrifugal fan of automotive HVAC systems is described in this paper. It is one of the ventilation unit components, considered as main noise sources, that were modelled in an approach for automotive HVAC sound prediction based on virtual prototyping and noise synthesis. The other noise sources studied are the heat exchanger and the butterfly flap.

A correlation found in the ASHRAE Handbook was used for the centrifugal fan model. It relates the sound power level at the nominal working point of a fan to its aerodynamic flow rate and its pressure rise. Our correlation was developed in order to calculate the sound power at the actual working point. Results obtained by the ventilation unit sound prediction model has allowed to define the ranges of frequencies and flows, related to the flap opening, where the fan is the dominant source.

Sound power measurements were performed on a prototype of an automotive ventilation unit , containing only the investigated components. These measurements were done under the same hypothesis applied to the prediction model. They show that when the fan is the dominant source, the predicted and the measured values are very similar.


This work was performed within the REVA/CESAM project. Involved Partners are Valeo Thermique Habitacle, Université de Technologie de Compiègne, ESI Group and CETIM.