Control of Low-Pressure Turbine Separation Using Vortex-Generator Jets

Abstract

The application of vortex-generator jets to control separation on the suction surface of a low-pressure turbine blade is reported. Blade Reynolds numbers in the experimental, linear turbine cascade match those for high-altitude operation of many aircraft gas-turbine engines, as well as the last stages of industrial ground-based gas turbines. Results are presented for steady blowing at jet blowing ratios from zero to four and at several chordwise positions and two freestream turbulence levels. Findings show that above a minimum blowing ratio, which is dependant on the injection location, the pressure loss in the modified blade's wake is reduced by a factor of between two and three. Boundary-layer traverses show that separation is almost completely eliminated with the application of blowing. No significant deleterious effects of vortex-generator jets are observed at higher (nonseparating) Reynolds numbers. The addition of 4% freestream turbulence to the cascade freestream lowers the separation Reynolds number of the turbine blade studied, but does not eliminate the effectiveness of the control technique. The vortex-generator jet control strategy is demonstrated to be a viable technique for low-pressure turbine separation control.