An investigation of secondary flow in a turbine blade with end wall profiling

Abstract

Secondary flows have been long recognised as a significant form of loss mechanism in turbomachinery. They have a major influence over the performance of the blade rows since they cause unsteadiness in the mainstream flow. This consequently affects not only the mechanical integrity of the blades but also causes extra loss. This research is aimed to reduce secondary flows using a novel method; end wall profiling. Profile 2 end wall was designed by Rolls Royce pic. with improved design features compared to its predecessor, Profile 1 end wall. Profile 2 end wall was manufactured and tested using the test facility available at the University of Durham. The flow was measured at two different axial positions, together with end wall static measurements and flow visualisation. The inlet flow conditions were also checked for consistency. These results were analysed and compared to Profile 1 and Planar end wall profile results, which have been studied previously by Hartland [1999]. Profile 2 end wall achieved better secondary flow reduction compared to the Planar end wall. However Profile 1 end wall still proved to be better compared to both Profile 2 and the Planar end wall. This project has provided a thorough understanding of the various flow mechanisms in turbines and the available techniques in eliminating secondary flows. The application of end wall profiling has still shown potential in being a reliable method. It is also important that the flow physics is understood in detail to determine the shape of the end wall profile that will be effective.