Understanding the physics properties of pulsating flow inside radial turbocharger turbines is fundamental to enhance efficiency in modern internal combustion engines (ICE). Under on-engine operating conditions, a turbocharger turbine is subject to pulsating flow, so that the turbine, essentially designed to operate under steady conditions, works in a non-optimum scenario. &nbsp;In this work, the computational model is firstly validated by comparing numerical and experimental results under steady operating conditions. Then, a Large Eddy Simulation (LES) is performed under pulsating flow conditions inside a single scroll radial turbocharger turbine in order to characterize and categorize the complex aerodynamics behavior of the turbine.&nbsp;Preliminary results has identified four different flow conditions, which are determined by the distribution of the relative inflow angle around the turbine over the entire pulse cycle. In the first conditions, characterized by low mass flow rate, the low values of the relative inflow angle (between -90 and -70) cause the flow to separate at the leading edge on the blade pressure side, forcing the development of a couple of counter-rotating vortices. A free-wheeling condition is achieved during the phase, so that the transfer of momentum occurs from the turbine to the fluid. As the relative inflow angle increases during the acceleration phase, two other characteristic flow fields can be identified. At a relative inflow angle between -60 and -30, the flow field in the second configuration is characterized by a smaller separation compared to the first one, and no counter-rotating vortices appear. Then, as the relative inflow angle assumes small values close to zero, the flow is perfectly aligned with the turbine blade and no secondary flows arise. In the end, the fourth condition occurs near the pulse peak. At this stage the relative angle is characterized by large positive values so that the separation occurs on the suction side of the turbine blade. At really high values, the separation is stronger enough that the separated flow merges with the boundary layer developing on the pressure side of the nearby blade.The performed study, besides giving a characterization of the flow field in a radial turbine under pulsating flow conditions, demonstrated the importance of accounting pulsating flow conditions in the blade design and optimization processes due to the wide range of conditions the turbine is subject to. &nbsp;&nbsp;

Large Eddy Simulations of a Turbocharger Radial Turbine Under Pulsating Flow Conditions

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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