The three major aeroelastic issues in the turbomachinery blades of jet engines and power turbines are forced response, nonsynchronous vibrations, and flutter. Flutter primarily affects high-aspect ratio blades found in the fan, fore high-pressure compressor stages, and aft low-pressure turbine (LPT) stages as low natural frequencies and high axial velocities create smaller reduced frequencies. Often with LPT flutter analyses, physical insights are lost in the exhaustive quest for determining whether the aerodynamic damping is positive or negative. This paper underlines some well-known causes of the LPT flutter in addition to one novel catalyst. In particular, an emphasis is placed on revealing how local aerodynamic damping contributions change as a function of unsteady (e.g., mode shape, reduced frequency) and steady (e.g., blade torque, pressure ratio) parameters. To this end, frequency domain Reynolds-averaged Navier–Stokes (RANS) CFD analyses are used as computational wind tunnels to investigate how aerodynamic loading variations affect flutter boundaries. Preliminary results show clear trends between the aerodynamic work influence coefficients and variations in exit Mach number and back pressure, especially for torsional mode shapes affecting the passage throat. Additionally, visualizations of qualitative bifurcations in the unsteady pressure phases around the airfoil shed light on how local damping contributions evolve with steady loading. Final results indicate a sharp drop in aeroelastic stability near specific regions of the pressure ratio, indicating a strong correlation between blade loading and flutter. Passage throat shock behavior is shown to be a controlling factor near the trailing edge, and as with critical reduced frequency, this phenomenon is shown to be highly dependent on the vibratory mode shape.
Skip Nav Destination
Article navigation
April 2016
Research-Article
The Impact of Blade Loading and Unsteady Pressure Bifurcations on Low-Pressure Turbine Flutter Boundaries
Robert E. Kielb
Robert E. Kielb
Search for other works by this author on:
Joshua J. Waite
Robert E. Kielb
1Corresponding author.
Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 1, 2015; final manuscript received November 10, 2015; published online December 29, 2015. Editor: Kenneth C. Hall.
J. Turbomach. Apr 2016, 138(4): 041002 (9 pages)
Published Online: December 29, 2015
Article history
Received:
October 1, 2015
Revised:
November 10, 2015
Citation
Waite, J. J., and Kielb, R. E. (December 29, 2015). "The Impact of Blade Loading and Unsteady Pressure Bifurcations on Low-Pressure Turbine Flutter Boundaries." ASME. J. Turbomach. April 2016; 138(4): 041002. https://doi.org/10.1115/1.4032043
Download citation file:
Get Email Alerts
Related Articles
Aeroelastic Stability of Welded-in-Pair Low Pressure Turbine Rotor Blades: A Comparative Study Using Linear Methods
J. Turbomach (January,2007)
A Method for Predicting the Aeroelastic Response of Radial Turbomachines
J. Turbomach (August,2023)
Physical Understanding and Sensitivities of Low Pressure Turbine Flutter
J. Eng. Gas Turbines Power (January,2015)
Fan Flutter Mechanisms Related to Blade Mode Shape and Acoustic Properties
J. Turbomach (September,2023)
Related Proceedings Papers
Related Chapters
Control and Operational Performance
Closed-Cycle Gas Turbines: Operating Experience and Future Potential
Introduction
Turbine Aerodynamics: Axial-Flow and Radial-Flow Turbine Design and Analysis
Hydrodynamic Mass, Natural Frequencies and Mode Shapes
Flow-Induced Vibration Handbook for Nuclear and Process Equipment