A Deep Insight to Secondary Flows

Abstract

Flow through turbine stages is three-dimensional and highly complex due to secondary flows, axial and tip clearances, 3D blades, rotational effects, varying fluid properties, turbulence effects, boundary layer development, etc. Secondary flows presence in turbines is identified as one of the main reason for losses and less efficiency performance. Hence in turbines, the need for understanding of secondary flows mechanisms and application of methods for their reduction is significant. This study is targeted to the discussion of secondary flows, аs follows: analysis of reasons for their development in turbine stages; influence on flow parameters distribution, efficiency of energy conversion and the overall aerodynamic performance of the turbo aggregate and ways to reduce their presence in the flow structure. As a result of the fulfilled intensive research works, a methodology for numerical modeling and mechanisms identification of secondary flows, through turbine channels, is attained also. Flow structures, specifics in aerodynamics, flow parameters distribution; interaction effects among vortices, core flow, endwalls and tip leaks, and many other flow features are discussed. An innovative approach to overcome reasons for secondary flows to appear and how to increase efficiency, have been studied and discussed.