Reducing Secondary Flow Losses in Low-Pressure Turbines: The “Snaked” Blade

This paper presents an innovative design for reducing the impact of secondary flows on
the aerodynamics of low-pressure turbine (LPT) stages.
Starting from a state-of-the-art LPT stage, a local reshaping of the stator blade was in-
troduced in the endwall region in order to contrast the flow turning deviation. This re-
sulted in an optimal stator shape, able to provide a more uniform exit flow angle. The
detailed comparison between the baseline stator and the redesigned one allowed to point
out that the rotor row performance increased thanks to the more uniform inlet flow, while
the stator losses were not significantly affected. Moreover, it was possible to derive some
design rules and to devise a general blade shape, named ‘snaked’, able to ensure such re-
sults. This generalization translated in an effective parametric description of the ‘snaked’
shape, in which few parameters are sufficient to describe the optimal shape modification
starting from a conventional design.
The stator redesign was then applied to a whole LPT module in order to evaluate the
potential benefit of the ‘snaked’ design on the overall turbine performance.
Finally, the design was validated by means of an experimental campaign concerning the
stator blade. The span-wise distributions of the flow angle and pressure loss coefficient at
the stator exit proved the effectiveness of the redesign in providing a more uniform flow to
the successive row, while preserving the original stator losses.