Abstract
In a radial turbine for automotive turbocharger, variable nozzle guide vane is an indispensable component to achieve high aerodynamic performance over the wide operating range. By changing the nozzle throat area, it is enabled to ensure optimum operation of the engine. However, aerodynamic excitation forces caused by wakes behind the nozzle vanes have become issue as High Cycle Fatigue. In this paper, three-dimensional numerical simulations were performed for three types of nozzle opening angle accompanied with the turbine impeller, in order to estimate the unsteady aerodynamic forces acting on the impeller blades. It was verified that excitation forces could become large around the leading edge of the blade, especially in the case of middle nozzle opening condition. Besides, pressure distributions were highly distorted near shroud and hub sides due to nozzle tip clearance flows. It was confirmed that large-scale and complicated pressure fluctuations were produced on the impeller blade by the wakes depending on the nozzle opening angle.
