Session: 40-06: Turbine Secondary Flows and Interactions I

Paper Number: 153506

Hybrid Large-Eddy Simulation of Tip-Leakage Flow in a 1.5-Stage High Pressure Turbine 

Hybrid LES-RANS based on improved delayed detached eddy simulation (IDDES) was used to study the compressible flow in a 1.5-stage high-pressure turbine with geometry and operating conditions that are relevant to power-generation gas turbines.  The focus is on the flow in the tip-gap region that accounts for the flow features created by the upstream stator vanes, stator-rotor interactions, and downstream stator vanes.  Results obtained reveal the unsteady flow structures about the tip-gap region and the flow mechanisms that create them.  Highly three-dimensional vortical structures are present in the tip region due to the complex interaction between the tip leakage flow and the shear layer due to the shroud. Turbulent kinetic energy (TKE) is highest about tip leakage vortex next to the suction surface and in the wake of the stator vane, signifying regions of intense turbulent activity. Power spectral density (PSD) analysis was performed by using pressure data from probes located in the vane wake, tip gap, and tip leakage vortex to determine the dominant frequencies created by the unsteady turbulent flow. The vane wake shedding frequency was found to be an order of magnitude higher than the blade passing frequency. Furthermore, the flow inside the tip gap and tip leakage flow was found to be characterized by large spikes at both the blade passing frequency and the wake shedding frequency. Finally, a refined mean flow schematic is presented, detailing the statistically stationary vortical structures in the tip gap separation bubble, interaction of shroud shear layer with tip leakage flow, and small vortical structures induced by the tip leakage vortex. The new understanding gained on the unsteady flow mechanisms about the blade tip will guide designs that reduce tip-leakage flow and mitigate their adverse effects on aerodynamics.

Presenting Author: Adwiteey Raj Shishodia Purdue University

Presenting Author Biography: Adwiteey Shishodia just got his PhD from the School of Aeronautics and Astronautics at Purdue University. His PhD resesarch is on LES and RANS studies of the flow physics in a 1.5 stage high-pressure turbine under engine relevant conditions with focus on the blade-tip region.

Authors:

Adwiteey Raj Shishodia Purdue University
Tom Shih Purdue University
Kenneth Bryden Iowa State University
John Crane National Energy Technology Laboratory