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Coupled-Mode Flutter for Advanced Turbofans

dc.contributor.advisor Kielb, Robert E Clark, Stephen Thomas 2010-05-13T17:52:22Z 2010-05-13T17:52:22Z 2010
dc.description.abstract <p>In the vast majority of measured turbomachinery blade flutter occurrences, the response occurs predominately in a single mode. The primary reason for this single-mode flutter is that for turbomachinery applications the combination of high mass ratio, high solidity, and large natural frequency separation results in only slight mode coupling. </p> <p> The increased importance of fuel efficiency is driving the development of improved turbofans and open-rotor fans. These new designs use fewer blades and will incorporate composite materials or hollowed airfoils in their fan blade designs. Both of these design changes result in lower mass ratio, lower solidity fan blades that may cause multi-mode flutter, rather than single-mode flutter as seen on traditional fan blades. Thus, a single mode flutter design analysis technique may not be adequate. The purpose of this study is to determine initial guidelines for deciding when a coupled-mode analysis is necessary. </p> <p> The results of this research indicate that mass ratio, frequency separation, and solidity have an effect on critical rotor speed. Further, guidelines were developed for when a multi-mode flutter analysis is required. These guidelines define a critical mass ratio that is a function of frequency separation and solidity. For blade mass ratios lower than this critical value, a multi-mode flutter analysis is required. Finally, the limitations of aerodynamic strip-theory have been revealed in a three-dimensional coupled-mode flutter analysis.</p>
dc.format.extent 5774693 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Engineering, Aerospace
dc.subject Engineering, Mechanical
dc.subject Coupled-Mode
dc.subject Fan
dc.subject Flutter
dc.subject mass ratio
dc.subject open-rotor
dc.subject solidity
dc.title Coupled-Mode Flutter for Advanced Turbofans
dc.type Master's thesis
dc.department Mechanical Engineering and Materials Science

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