Off-Design Aerodynamics of a High-Speed Low-Pressure Turbine Linear Cascade

High-speed low-pressure turbines in geared turbofans operate at transonic exit Mach numbers and low Reynolds numbers. Engine-relevant data remain scarce. The SPLEEN C1 linear cascade is investigated at Mout=0.70--0.95 and Reout=65,000--120,000 under steady inlet flow. Experiments are combined with 2D RANS and MISES, including transition modelling and inlet-turbulence decay calibrated to measurements. Results are consistent with conventional LPT behaviour: losses decrease with increasing Mach and Reynolds numbers, except when shocks interact with the blade boundary layer (M≈0.95). Profile loss drops by 23% from M=0.70 to 0.95 at Re=70,000, and by 19% at M=0.80 when open separation is suppressed. Secondary loss decreases by up to 25% at Re=70,000 and shows weak sensitivity to Reynolds number. A coupled loss model predicts profile loss with RMSE=4.7%. Secondary-loss modelling reproduces global trends: separating endwall dissipation from mixing keeps errors within ±10% for most cases, but accuracy degrades near the shock–boundary layer interaction case and at the highest Reynolds number. Mixing dominates endwall loss (∼75%), with the passage vortex contributing ∼50% (±10%) of the mixing component. This article is a revised and expanded version of “An Experimental Test Case for Transonic Low-Pressure Turbines—Part 2: Cascade Aerodynamics at On- and Off-Design Reynolds and Mach Numbers” presented at ASME Turbo Expo 2022, Rotterdam, June 13–17, 2022. All data and documentation are openly available at https://doi.org/10.5281/zenodo.7264761.