Experimental and Numerical Investigation of Partial Admission of a Radial Turbocharger Turbine for Improved Off-Design Operation

Abstract

A new partial admission concept for turbocharger turbine operation at off-design is designed and investigated numerically and experimentally in a turbocharger test rig. This new concept is called MEDUSA (Multiple Exhaust Duct with Source Adjustment) and is based on a partial admission turbine system consisting of several separate flow channels that connect the cylinder of the engine and individual nozzle segments of the turbine. The turbine flow is adjusted by the chosen admission rate according to the available exhaust enthalpy. In the present study, a reference turbocharger has been equipped with a four segment partial admission system instead of its conventional Waste-Gate scroll. The numerical results indicate similar loss mechanisms compared to an axial turbine stage, when partial admission is applied. Based on a stator design optimization, a design was chosen for manufacturing and testing on the turbocharger test rig. Despite the fact that the turbocharger efficiency at partial admission for the MEDUSA-system drops, a higher turbine expansion ratio can be achieved to obtain the same compressor operating point. These results indicate an enhanced use of the available exhaust enthalpy at part-load conditions, thus improving the turbocharger performance at low end torque engine speeds.