Flow noise in automotive heating, ventilation, and air conditioning systems.

Abstract

Acoustic noise generated by a typical automotive heating, ventilation, and air conditioning (HVAC) system can be dominated by unsteady flow and turbulence. A comprehensive flow field and acoustic field study has been conducted experimentally on a stand‐alone HVAC system operating in its maximum air conditioning mode. Acoustic intensity field mapping was conducted in an anechoic environment. Detailed flow visualizations were conducted underwater on an optically clear system operating at prototypical values of the Reynolds number. The blower is the dominant low‐frequency source of noise, while at higher frequencies, additional flow noise sources exist. These include high shear regions within the ducting, separated flows off of flow obstructions, and the exit flow from register vents. Flow visualizations of the blower internal flow field were also conducted on a three‐times‐larger optically clear model of the blower using underwater particle tracking techniques. The results identify significant regions of inefficient flow, such as blade passage flow separation, reentrant flow, and rotating stall. Collectively, these lead to poor aerodynamic performance as well as noise. [Work supported by Ford Motor Co. and is drawn from the thesis research of former students Timothy Brungart, George Denger, Lori Perry, and Mike Sullivan.]