HVAC Noise Prediction Using Lighthill Wave Method

Automotive Heating Ventilation and Air Conditioning (HVAC) system is essential in providing the thermal comfort to the cabin occupants. The HVAC noise which is typically not the main noise source in IC engine vehicles, is considered to be one of the dominant sources inside the electric vehicle cabin. As air is delivered through ducts and registers into the cabin, it will create an air-rush/broadband noise and in addition to that, any sharp edges or gaps in flow path can generate monotone/tonal noise. Noise emanating from the HVAC system can be reduced by optimizing the airflow path using virtual tools during the development stage. This paper mainly focuses on predicting the noise from the HVAC ducts and registers.

In this study, noise simulations were carried-out with ducts and registers. A Finite Volume Method (FVM) based 3-dimensional (3D) Computational Fluid Dynamics (CFD) solver was used for flow as well as acoustic simulations. Large Eddy Simulation (LES) was used for flow field generation and noise characteristics were studied using a hybrid Lighthill Wave Model (LWM). The frequency response of the aeroacoustic noise from the ducts and registers were predicted using the simulations and the models were compared in terms of Overall Average Sound Pressure Level (OASPL). The simulated spectra exhibit good correlation with the test data.