Aeraulic and Aeroacoustic Experimental Characterization of Academic and Industrial HVAC Flaps

The noise radiated inside the car cabin depends on many sources such as the embedded equipments like the Heating, Ventilation and Air Conditioning (HVAC) module. An HVAC is a compact and complex system composed of several elements: blower, flaps, thermal exchangers, ducts… Air provided by an HVAC is blown by a blower passing through different components and then distributed to car cabin areas. Interactions between airflow and the HVAC fixed components generate noises that emerge in the car cabin. CEVAS project, managed by the automotive equipment manufacturer Valeo, is aiming to develop a prediction tool which will provide HVAC noise spectrum and sound quality data. The tool is based, in particular, on aeroacoustic characterization of individual elements and associations of elements. An experimental test bench was therefore developed by the acoustic laboratory of the University of Technology of Compiegne (UTC) based on the assumption that an HVAC component is described as a 2N-port source (N cut-on modes) represented by its scattering matrix and its upstream and downstream modal acoustic pressure vectors. In addition measurements of mean flow velocities around the elements are performed by Particle Image Velocimetry (PIV) equipment. In this paper, results of the fluid and aeroacoustic qualification of a flap for different opening angles without and with a wall located upstream the flap are presented. Analysis is conducted based on the noise prediction model for aerodynamic sound production in low speed flow ducts suggested by Nelson and Morfey in 1981.