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

Richard Anthony

ASME Member, AFRL/RQTT, Wright-Patterson AFB, OH USA

Michael Ooten

ASME Member, AFRL/RQTT, Wright-Patterson AFB, OH USA

John Finnegan

ASME Member, AFRL/RQTT, Wright-Patterson AFB, OH USA

P. Dean Johnson

ASME Member, FTT America, Jupiter, FL USA

Ron-Ho (Bob) Ni

ASME Member, AeroDynamic Solutions, Inc., Danville, CA USA

1Corresponding author.

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


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.

Section 4: U.S. Gov Employees + Reg Authors
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