Investigation of the Loss Generation in a Turning Vane Frame at Different Inlet Turbulence Conditions

Abstract

Abstract The integrated concept of a turning vane frame (TVF) located between the high pressure turbine (HPT) and the low pressure turbine (LPT) can consist of structural vanes and aerodynamically assisting splitters, thus offering insight into the behavior of mixed blade cascades. In order to judge the sensitivity of the flow through a TVF to different turbulence conditions, the presented investigation focuses on the effects of different turbulence intensities and integral turbulent length scales. It is based on steady state RANS simulations validated against results from steady five hole probe measurements and static profile pressure distributions. The flow and loss behavior of the TVF under varying incoming turbulence conditions is investigated using a second law analysis of the loss generation, combined with a secondary flow field analysis relying on the established Q-criterion and the recently presented vortex visualization parameter (VVP)-method. The secondary flows were identified as key loss drivers at all turbulence conditions and changes in secondary flow patterns, as well as loss generation effects for the different passages were identified and discussed. The vortex structures in the upper half of the passage were found to be most sensitive to an increase in turbulence level. Increases in loss generation per passage were found to be most pronounced for the pressure side splitter to vane passage and the suction side splitter to pressure side splitter passage. Changes in profile boundary layer thickness and entropy production rate were found to contribute to alterations in loss generation only on a minor level.