Session: 40-07 Turbine Secondary Flows and Interactions

Paper Number: 125408

125408 - Unsteady Loss Mechanisms in Low-Pressure Turbines With Diverging End-Walls Studied via High-Fidelity Simulation 

High-fidelity simulations are used to conduct controlled, numerical experiments to investigate the effect of periodically incoming wakes on three-dimensional loss mechanisms. The present work considers the MTU-T161 cascade with spanwise-diverging end-walls, representative of a high-lift, low-pressure turbine blade. All simulations are carried out at engine-relevant conditions, with exit Reynolds number of 90,000 and exit Mach number of 0.6. Upstream moving bars are used to generate rotor-like wakes which impinge on the blade and potentially alter its aerodynamic performance. In the mid-span, the incoming wakes are subjected to an additional axial pressure gradient when convecting through the passage, due to the divergence of the spanwise end-walls. The present engine-realistic configuration cannot be reproduced with previously considered spanwise periodic studies. Additionally, the end-wall region upstream of the blade is moving at the same relative speed as the bars. As a result, the evolving secondary vortex systems around the bars periodically disturb the free-stream end-wall boundary layer facing the blade leading edge. This ultimately influences the end-wall related losses downstream of the blade and governs the overall aerodynamic performance of the blade.

Following validation against available experimental data, a systematic variation of flow coefficient and reduced frequency extends the parametric space studied to encompass engine-realistic operating conditions. The high-fidelity simulations reveal the impact of incoming wakes on blade boundary layer losses and wake-induced losses both at the mid-span and within the end-wall regions. Furthermore, the data-rich results shed light on the underlying physical mechanisms driving unsteady losses by performing an entropy loss analysis. The loss breakdown applied to phase- and time-averaged flow fields separates wake-free and wake-ingestion-related losses over a range of bar passing conditions. The broad numerical data base establishes a clear understanding of wake-induced unsteadiness in low-pressure turbines with diverging end-walls. 

Presenting Author: Marco Rosenzweig The University of Melbourne

Presenting Author Biography: Marco Rosenzweig is a Ph.D student at the University of Melbourne. In 2022, he obtained his M.Sc. degree in Aerospace at the Technical University of Munich and has two years of industrial work experience at MTU Aero Engines AG. Marco’s current research expertise is in turbomachinery flows with a focus on low-pressure turbines. To date his research interests have included modeling of multi-stage components, the evaluation of standard industrial design methods and scale resolving, numerical methods. His most recent work focuses on performing high-fidelity simulations of low-pressure turbine cascades on the latest high-performance-computing architectures.

Authors:

Marco Rosenzweig The University of Melbourne
Melissa Kozul The University of Melbourne
Richard Sandberg The University of Melbourne