Investigation of Secondary Flow Behavior in a Radial Turbine Nozzle

Abstract

Fundamental investigation of secondary flow phenomena in a radial turbine nozzle are presented. Laser two focus (L2F) measurements have been used for validation of numerical computational fluid dynamics (CFD) calculations. Having a good agreement by using the Reynolds stress turbulence model (RSM), the numerical results have been further used to analyze the structure of secondary vortices. Contour plots of the flow angle with typical isoline pattern, as well as the vorticity, have been evaluated. It is shown that the channel of the radial nozzle similar secondary vorticity systems generates as known from the axial turbine nozzles. The formation and the development of the horseshoe vortex and the corner vortex are discussed. The well known passage vortex of the axial turbines could not been found because of the small curvature of the streamlines. Instead of these, an additional single vortex can be observed, called the “inflow” vortex caused by the unsymmetrical flow into the radial cascade from the upstream scroll.