Study on Secondary Flow within Low Aspect Ratio Steam Turbine Cascade (2nd Report, Flow Control Technology)

Abstract

In order to develop the performance improving technology for low aspect ratio cascade of the steam turbine, mechanism of the secondary loss generation has been investigated using the smoke visualization and detailed internal flow measurement in phase I. Next in phase 2, flow control technologies such as the blade fillet, endwall convergence and negative curving are introduced. This paper presents the loss reduction mechanism of these flow control technologies by applying the computational fluid dynamics (CFD) and the test results of air model turbine to verify the effects of endwall convergence and negative curving in rotating flow field. In conclusion, the technologies greatly contribute to improving the performance of the actual steam turbine with low aspect ratio cascade.