This paper presents the work on part-speed fan flutter due to acoustic reflections from the intake, commonly called “flutter bite.” A simple model for the prediction of the flutter bite is presented. In a previous work by the authors, it was shown that the acoustic effects of the intake are very important and need to be considered during the design of a fan blade. It was also shown that the contribution to blade aerodamping due to blade motion (for the isolated rotor in an infinitely long duct) and intake acoustics is independent and can be analyzed separately. The acoustic reflections from the intake change the damping of the blade by modifying the phase and amplitude of the unsteady pressure at the leading edge of the fan. It will be shown in the paper that, for a given intake, the phase and amplitude of the reflected acoustic waves can be evaluated analytically based on established theories independent of the fan design. The proposed model requires only the design intent of the fan blade and the geometry of the intake, which are available in the early design stages of a new engine, and can predict the operating conditions at which fan flutter is likely to occur.
A Simple Model for Identifying the Flutter Bite of Fan Blades
Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 23, 2016; final manuscript received October 25, 2016; published online February 23, 2017. Editor: Kenneth Hall.
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Zhao, F., Smith, N., and Vahdati, M. (February 23, 2017). "A Simple Model for Identifying the Flutter Bite of Fan Blades." ASME. J. Turbomach. July 2017; 139(7): 071003. https://doi.org/10.1115/1.4035567
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