Title: Towards a Quiet Vehicle Cabin Through Digitalization of HVAC Systems and Subsystems Aeroacoustics Testing and Design
text: With the rise of electric autonomous vehicles, it has become clear that the cabin of tomorrow will drastically evolve to both improve ride experience and reduce energy consumption. In addition, autonomy will change the transportation paradigm, leading to a reinvention of the cabin seating layout which will offer the opportunity to climate systems team to design quiet and even more energy efficient systems. Consequently, Heat and Ventilation Air Conditioning (HVAC) systems designers have to deliver products which perform acoustically better than before, but often with less development time. To success under such constraints, designers need access to methods providing both assessment of the system (or subsystems) acoustic performance, and identification of where the designs need to be improved to reduce noise levels. Such methods are often needed before a physical prototype is requested, and thus can only be achieved in a timely manner through digital testing. Previous studies have demonstrated the ability of a CFD/CAA approach based on the Lattice Boltzmann Method (LBM) to predict HVAC system noise including real and complex ducts, registers, mixing unit and blower geometries. This LBM low dissipative numerical approach has indeed been shown to accurately capture turbulent and convective mechanisms and to propagate acoustic waves in ducted systems and in free-field. Combined with a noise source identification strategy, these methods provide the ability to visualize the noise sources inside the system, as well as to identify and rank noise-generating design features - a unique design methodology not available with physical testing. In this paper, such an approach is presented based on two HVAC systems layout, targeting two different vehicles. To answer the need for systems and subsystems predictions, simulation results are correlated to experiment for configurations with blower alone, blower + air intake, and for full HVAC system (blower + air intake + mixing unit). Finally, an in-depth analysis of the flow noise sources contributions to a microphone location is performed, and countermeasures are discussed.