Acoustical Modeling and Test Correlation of an Intake Manifold and Charge Air Cooler Assembly for a 4-Cylinder Turbocharged Engine

The charge air cooler (CAC), which is placed between the compressor and the engine intake manifold (IM), is an important component in a turbocharged engine. It is essential to capture the temperature change, the pressure drop or the acoustical wave behavior of the charge air cooler in the one-dimensional(1D) simulation model for the predictive accuracy of engine performance and intake noise. In this paper, the emphasis is on the acoustic modeling of an intake manifold and charge air cooler assembly for the low frequency engine intake order noise. In this assembly, the core of the charge air cooler is embedded in the plenum of the intake manifold. The modeling and correlation process is comprised of three steps. First, the charge air cooler core is removed from the intake manifold and put into a rectangular box matching its envelope with a single air inlet and outlet, thereby simplifying the complex shape of the manifold with the different runner components. The acoustic transmission loss across the charge air cooler core in this box is simulated using different modeling parameters in the 1D simulation model and compared with the transmission loss test bench results. Next, once models are established for the core itself, it is reinstalled into the plenum and the full intake manifold and charge air cooler assembly is tested and modeled. Transmission loss from the different runner paths to the zip-tube of the intake manifold are simulated and correlated to the test bench data. Finally, the transmission loss correlated model of the assembly is incorporated with the full engine performance calibrated model. The in-duct engine order sound pressure levels at the compressor outlet and inlet are simulated at full load condition across the RPM range. The simulation results are compared with the in-duct measurement data from the engine dyno test. The correlation of the firing order and its first harmonic order of the in-duct sound pressure level is evaluated. Good correlation is observed at these orders. In conclusion, the best practices of acoustic modeling of a similar assembly using the developed process are recommended.