Flow modelling of a turbocharger turbine under pulsating flow

In automotive powertrain systems, turbocharger turbines experience pulsating flow conditions due to the engine cycle. The temperature and pressure pulses originating from the engine through the exhaust manifold can exert a strong influence on the turbine flow downstream, particularly at low engine speeds and powers. The designed performance of the turbine may therefore deviates significantly from the field performance. In this paper, a computational fluid dynamic (CFD) analysis of a turbine under unsteady (pulsating) flow is presented. The full complement of nozzle vanes and rotor blades vanes was modeled to study the complexity of the flow interaction between the turbine components. The analysis was performed for a simulated 720degrees engine cycle, at 1,600 rpm engine speed. The transient calculation is compared to the steady-state calculation, with equivalent mass- and time-averaged inlet conditions at the manifold inlet. The errors in turbine performance parameters which are caused by ignoring the pulsation effect are presented and discussed.