RANS Prediction of Low-Pressure Turbine Tip Shroud Flows

Abstract In low-pressure turbines, an attached tip shroud is often used to mitigate rotor tip leakage. The interaction between 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 approaches, especially for engine manufacturers aiming to design an efficient tip shroud geometry that ensures proper sealing while minimizing losses. 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-channel components have been simulated and their performance have been compared to relevant experimental measurements to understand the loss sources. 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.