Numerical investigation of low-pressure turbine blade separation control

Laminar separation on the suction side of low-pressure turbine (LPT) blades at low operating Reynolds numbers can degrade overall engine efficiency and impose limitations on the flight envelope. In wind-tunnel experiments it was shown that laminar separation can be controlled by pulsed vortex generator jets. This active-flow-control technology could be transferred to real flight hardware with more confidence if the physical mechanisms involved in the control were better understood. Here, calculations of a linear LPT cascade at a Reynolds number based on axial chord of 2.5 × 10⁴ are presented and compared to experimental data. Good agreement was observed between numerical and experimental results, except in the separated region near the trailing edge. In two-dimensional calculations separation was controlled by pulsed blowing through a slot upstream of the flow separation location. The blade pitch was then increased by 25% to obtain a larger region of separated flow. Again, using pulsed blowing through a slot, the separation could be controlled, and an increase of 19% in the time-averaged ratio of lift and drag was achieved.