Flutter and Forced Response of Turbomachinery with Frequency Mistuning and Aerodynamic Asymmetry
Abstract
This dissertation provides numerical studies to improve bladed disk assembly design
for preventing blade high cycle fatigue failures. The analyses are divided into two
major subjects. For the first subject presented in Chapter 2, the mechanisms of transonic
fan flutter for tuned systems are studied to improve the shortcoming of traditional
method for modern fans using a 3D time-linearized Navier-Stokes solver. Steady and
unsteady flow parameters including local work on the blade surfaces are investigated.
It was found that global local work monotonically became more unstable on the pressure
side due to the flow rollback effect. The local work on the suction side significantly
varied due to nodal diameter and flow rollback effect. Thus, the total local work
for the least stable mode is dominant by the suction side. Local work on the pressure
side appears to be affected by the shock on the suction side. For the second subject
presented in Chapter 3, sensitivity studies are conducted on flutter and forced response
due to frequency mistuning and aerodynamic asymmetry using the single family of modes
approach by assuming manufacturing tolerance. The unsteady aerodynamic forces are
computed using CFD methods assuming aerodynamic symmetry. The aerodynamic asymmetry
is applied by perturbing the influence coefficient matrix. These aerodynamic perturbations
influence both stiffness and damping while traditional frequency mistuning analysis
only perturbs the stiffness. Flutter results from random aerodynamic perturbations
of all blades showed that manufacturing variations that effect blade unsteady aerodynamics
may cause a stable, perfectly symmetric engine to flutter. For forced response, maximum
blade amplitudes are significantly influenced by the aerodynamic perturbation of the
imaginary part (damping) of unsteady aerodynamic modal forces. This is contrary to
blade frequency mistuning where the stiffness perturbation dominates.
Type
DissertationSubject
Engineering, MechanicalEngineering, Aerospace
Aerodynamic Asymmetry
Mistuning
Transonic Fan Flutter
Forced Response
Turbomachinery
CFD
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https://hdl.handle.net/10161/610Citation
Miyakozawa, Tomokazu (2008). Flutter and Forced Response of Turbomachinery with Frequency Mistuning and Aerodynamic
Asymmetry. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/610.Collections
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