Downsizing in combination with turbocharging represents the main technology trend for meeting climate relevant CO_2 emission standards in gasoline engine applications. Extended levels of downsizing involve increasing degrees of pulse charging. Separation of cylinder blow downs, either with double entry turbines or valve train variability, is key for achieving enhanced rated power and low-end-torque targets in highly boosted fourcylinder engines. However, double entry turbines feature specific development challenges: The aerodynamic design via 3D CFD calculations presents a difficult task as well as the engine performance modeling and matching process in 1D gas exchange simulations. From a manufacturing standpoint, casting of the turbine housing is complex especially for small displacement applications below 1.6 l due to e.g. thermo-mechanical boundaries. This paper demonstrates how to design and model double entry turbine performance characteristics within 1D gas exchange simulations, requiring special measured and processed turbine data, which is experimentally assessed on a hot gas test bench using a double burner setup. It is shown how the collective of the described development strategies can be used in assessing the potential of different turbine design concepts. This allows the turbocharger to be designed exactly to specific engine requirements.
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