Linear acoustic multi-port modeling of automotive charge air coolers

1D linear acoustic or gas-dynamics modeling of intake and exhaust systems is typically done during the early development stages of a vehicle in order to do quick sound design assessments. One of the components in the intake system of a turbocharged IC engine is the automotive charge air cooler. The charge air cooler is positioned at the outlet of the compressor in order to cool the charged air before it enters the engine. Charge air coolers are typically modeled as a 1D system comprised of an intake tank/duct, cooling tubes and an outlet tank/duct. A problem arises when the position of the inlet/outlet ducts is not axially symmetrical, which introduces three-dimensional acoustic effects. This behavior is not included in typical 1D modeling. Finite element modeling could be used to describe this 3D effect but would need much longer time and a detailed geometrical model that could be unavailable during the early development stage. In this study an acoustic multi-port description of the charge air cooler model is presented. Such a description includes the influence of the asymmetric position of the inlet/outlet ducts on the acoustics. The multi-port description is then reduced to an equivalent acoustic two-port model for the entire charge air cooler between its inlet/outlet ports. The frequency dependent transmission loss (TL) is calculated and compared to experimental results with good agreement.