Studies on the Three-Dimensional Flow Field in a Turbine Scroll (2nd Report, Analysis of Secondary Flows)

The behavior of secondary flows in a turbine scroll has been investigated experimentally. Detailed flow measurements, using a five-hole probe, were made at sixteen cross sections. Considering the effect of nozzle sink flows, the secondary flows were defined by the velocity components perpendicular to the local flow directions of the axisymmetric potential flow solutions in each measuring plane. This secondary flow field was found to correspond well to the distribution of streamwise vorticity and to be dominated by two passage vortices. The secondary flows associated with the passage vortices increase rapidly downstream of the scroll inlet section. As the secondary flows increase, inward radial flows of low energy fluids on the walls are so strong that the low energy fluids flow out into the nozzle. The discharge of low energy fluids results in the decrease in the secondary flows at the downstream part in the scroll.