Wave dynamics analysis at the intake of a turbocharged engine: concept proposal of a new active inlet charge air duct for low-speed tuning and high-speed permeability

The unsteady-state gas dynamics at the intake of a turbocharged engine were analysed. The objective is to tune the intake line to low operating speeds where the exhaust gases lack the enthalpy needed to operate the turbocharger at rated speeds and to provide the boost pressure needed. The proposed methodology compensates for the lack of boost pressure by benefiting from the existing wave action at the intake. Zero-dimensional acoustic modelling is first used to investigate the geometrical parameters which have the most influnce on low-end acoustic tuning. Impedance bench and electrically driven engine tests complete the study and compare different intake configurations and two geometries of charge air coolers: an air-to-air charge air cooler and a water-cooled charge air cooler. Optimal intake configurations were found for low-end torque considerations as well as high-speed operation where a reduction in the pressure losses is most important. The findings were validated and established on an engine test bench with torque gain at different rotational speeds of the engine. The study led to the proposal of an active charge air duct which enables a solution to be found for the low-end torque where acoustic tuning is favoured and for high-speed operation where the boost pressure is readily available. The acoustic response of this part was compared with the reference solution, and conclusions and possible topics for future work were obtained from the analysis.