Investigation of separation control for low-pressure turbines using CFD

Separation from low-pressure turbine (LPT) blades at low operating Reynolds numbers can significantly degrade performance. We investigated separation control by steady and pulsed vortex generator jets (VGJs) as well as harmonic blowing through a spanwise slot using computational fluid dynamics (CFD). The detailed fluid dynamics were explored in fully resolved direct numerical simulations (DNS) for a flat and curved plate model geometry under LPT conditions. The most promising AFC control schemes were then validated for the full LPT blade geometry. Steady VGJs were found to generate streamwise vortices. Our simulations have shown that pulsed VGJ actuation leads to an earlier transition to turbulence and the generation of spanwise coherent structures. In both cases, separation is controlled by an increased entrainment of freestream fluid. The stunning effectiveness of pulsed VGJs is explained by a hydrodynamic instability mechanism which amplifies spanwise instability modes. The authors confirm that they, and/or their company or institution, hold copyright on all of the original material included in their paper. They also confirm they have obtained permission, from the copyright holder of any third party material included in their paper, to publish it as part of their paper. The authors grant full permission for the publication and distribution of their paper as part of the ICAS2008 proceedings or as individual off-prints from the proceedings.