Acoustical Modeling and Test Correlation of an Intake Manifold and Charge Air Cooler Assembly for a 4-Cylinder Turbo Charged Engine 2023-01-1076

The charge air cooler, which is placed between the compressor and the engine intake manifold, is an important component in a turbocharged engine. Air, already hot and under high pressure from the compressor, passes through many small fin tubes in the core of the charge air cooler which decreases the temperature of the air before it enters the engine cylinder. This process increases both engine power and efficiency. To improve the predictive accuracy of engine performance and intake noise using a 1-D GT-power model, it is essential for the charge air cooler model to capture all the parameters of the component, whether it is temperature change, pressure drop or the acoustical wave behavior. Although there may be flow-induced high frequency noise content present from the compressor, low frequency engine intake order noise is more dominant of the overall intake noise level for a turbocharged engine. In this paper, the emphasis is on the acoustic modeling of the charge air cooler to improve the predictive accuracy of the low frequency engine intake order noise. The scope of this paper was an intake manifold with a water charge air cooler assembly from a 2 liter 4-cylinder turbo-charged engine. The core of the charge air cooler with all the small fin tubes is embedded in the plenum of the intake manifold. Normally when acoustic modeling in 1D-GT Power, the charger air cooler and intake manifold are created as individual components and then put sequentially, but because the charge air cooler is embedded, several extra steps had to be taken and verified by means of a transmission loss bench test and engine dyno test. First, the charger 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 then simulated using different modeling parameters and then compared with the transmission loss test bench. Next, once models were established for the core itself, it was reinstalled into the plenum and then steps were taken to model the full manifold. Transmission loss from the zip-tube of the intake manifold to the different runner paths were simulated and correlated again to the bench data. Finally, the modified models of the assembly were incorporated with the engine performance calibrated model. The in-duct low frequency order sound pressure level at the compressor outlet and inlet were simulated in this project at full load condition across the RPM range. The simulation result was compared with the in-duct measurement data from the engine dyno test. Good correlation was observed at these low frequencies using this detailed 1D GT-Power model. In conclusion, the best practices of acoustic modeling a similar assembly using 1D GT-Power was recommended.