Flow-Induced Noise Prediction and Validation of a Heavy-Duty Electric Vehicle’s HVAC System Using the Lattice Boltzmann Method

Within automobiles, the HVAC is a critical system to regulate the occupants’ thermal comfort. However, at its high operating speeds, it can contribute significantly to the overall sound levels perceived by the cabin occupants, impacting their experience. This is especially true in the case of electric vehicles due to their overall quieter operation. This work has the intention to validate HVAC noise predictions using computational fluid dynamics (CFD) simulations. In addition, CFD simulations provide detailed flow field insights which are essential to identify and rank the main noise sources, and it ultimately allows a better understanding of the physical mechanisms of noise generation on similar systems. These insights are very difficult, if not impossible, to obtain with physical testing and are key to designing a quiet and efficient HVAC system. Sound levels were measured experimentally at eight different locations inside of a Class-8 Nikola TRE hydrogen fuel cell electric semi-truck cabin. In this paper, the analysis is performed with the HVAC in vent mode configuration and microphone measurements are available for different blower operational speeds, which are eventually compared against simulation results. Very Large Eddy Simulation (VLES) CFD simulations are performed with the commercial software PowerFLOW^TM. Overall good agreement was obtained, both for the absolute and relative sound levels, as well as the noise directivity inside the cabin.