Session: 32-04 Low Pressure Turbines 1

Paper Number: 128691

128691 - RANS Prediction of Low-Pressure Turbine Tip Shroud Flows 

In low-pressure turbines, an attached tip shroud is often used to mitigate rotor tip leakage. The interaction between the tip shroud's bypass flow and the primary flow leads to mixing losses and amplifies vortex structures, which contribute to aerodynamic losses. Accurately predicting these losses remains a challenge with RANS approach, especially for engine manufacturers aiming to design an efficient tip shroud geometry that ensures proper sealing while minimizing losses. The Boussinesq linear turbulence approximation often fails in such flows, where turbulence anisotropy is present. Therefore, in RANS, the use of two-equation linear eddy-viscosity turbulence models based on this approximation is questionable. This study aims to evaluate the capability of RANS simulations in tracking loss evolution with changes in tip shroud geometry. To do so, the present work assesses a second order Reynolds Stress Model (RSM), as well as an eddy-viscosity model, in a two stage low-pressure turbine with attached tip shrouds. Two different geometries (axisymmetric and non-axisymmetric) of the off-chanel components have been simulated and compared to relevant experimental measurements. The RANS simulations capture the correct trend in the isentropic efficiency: the non-axisymmetric tip shroud increases entropy production, resulting in poorer aerodynamic performance. The RSM simulations align better with the measurements and predict secondary structures that differ from those predicted by the linear model.

Presenting Author: Fatih Uncu Safran Aircraft Engines

Presenting Author Biography: I hold a Ph.D. in "RANS prediction of low-pressure turbine cavity flows" and currently work as a Turbine Aerodynamics Engineer at Safran Aircraft Engines.

Authors:

Fatih Uncu Safran Aircraft Engines
Benjamin François ONERA
Nicolas Buffaz Safran Helicopter Engines
Sébastien Le Guyader Safran Helicopter Engines