A Low Order Model for Predicting Turbocharger Turbine Unsteady Performance

Abstract

In this paper, a loworder model for predicting performance of radial turbocharger turbines is presented. The model combines an unsteady quasithreedimensional (Q3D) computational fluid dynamics (CFD) method with multiple onedimensional (1D) meanline impeller solvers. The new model preserves the critical volute geometry features, which is crucial for the accurate prediction of the wave dynamics and retains effects of the rotor inlet circumferential nonuniformity. It also still maintains the desirable properties of being easy to setup and fast to run. The model has been validated against a experimentally validated full 3D unsteady Reynoldsaveraged Navier–Stokes (URANS) solver. The loss model in the meanline model is calibrated by the full 3D RANS solver under the steady flow states. The unsteady turbine performance under different inlet pulsating flow conditions predicted by the model was compared with the results of the full 3D URANS solver. Good agreement between the two was obtained with a speedup ratio of about 4 orders of magnitude (∼104) for the loworder model. The loworder model was then used to investigate the effect of different pulse wave amplitudes and frequencies on the turbine cycle averaged performance. For the cases tested, it was found that compared with quasisteady performance, the unsteady effect of the pulsating flow has a relatively small impact on the cycleaveraged turbine power output and the cycleaveraged mass flow capacity, while it has a large influence on the cycleaveraged ideal power output and cycleaveraged efficiency. This is related to the wave dynamics inside the volute, and the detailed mechanisms responsible are discussed in this paper.