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research-article

Effects of Downstream Vane Bowing and Asymmetry on Unsteadiness in a Transonic Turbine

[+] Author and Article Information
John Clark

ASME Member, Turbomachinery Branch, Turbine Engine Division, Aerospace Systems Directorate, Air Force Research Laboratory, 1950 5th Street, WPAFB, OH 45433
john.clark.38@us.af.mil

Richard Anthony

ASME Member, AFRL/RQTT, Wright-Patterson AFB, OH USA
richard.anthony.4@us.af.mil

Michael Ooten

ASME Member, AFRL/RQTT, Wright-Patterson AFB, OH USA
michael.ooten@us.af.mil

John Finnegan

ASME Member, AFRL/RQTT, Wright-Patterson AFB, OH USA
john.finnegan@us.af.mil

P. Dean Johnson

ASME Member, FTT America, Jupiter, FL USA
djohnson@fttamerica.com

Ron-Ho (Bob) Ni

ASME Member, AeroDynamic Solutions, Inc., Danville, CA USA
nirr@aerodynamic-solutions.com

1Corresponding author.

ASME doi:10.1115/1.4040998 History: Received July 16, 2018; Revised July 20, 2018

Abstract

Accurate predictions of unsteady forcing on turbine blades are essential for the avoidance of high-cycle-fatigue issues during turbine engine development. Further, if one can demonstrate that predictions of unsteady interaction in a turbine are accurate, then it becomes possible to anticipate resonant-stress problems and mitigate them through aerodynamic design changes during the development cycle. A successful reduction in unsteady forcing for a transonic turbine with significant shock interactions due to downstream components is presented here. A pair of methods to reduce the unsteadiness was considered and rigorously analyzed using a three-dimensional, time resolved Reynolds-Averaged Navier Stokes solver. The first method relied on the physics of shock reflections itself and involved altering the stacking of downstream components to achieve a bowed airfoil. The second method considered was circumferentially-asymmetric vane spacing which is well known to spread the unsteadiness due to vane-blade interaction over a range of frequencies. Both methods of forcing reduction were analyzed separately and predicted to reduce unsteady pressures on the blade. Then, both design changes were implemented together in a transonic turbine experiment and successfully shown to manipulate the blade unsteadiness in keeping with predictions. This demonstration was accomplished through comparisons of measured time-resolved pressures on the turbine blade to others obtained in a baseline experiment that included neither vane asymmetric spacing nor bowing. The measured data were further compared to rigorous post-test simulations of the complete turbine annulus including a bowed downstream vane of non-uniform pitch.

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