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dc.contributor.advisor Kielb, Robert E en_US
dc.contributor.author Spiker, Meredith Anne en_US
dc.date.accessioned 2008-05-14T16:28:48Z
dc.date.available 2008-05-14T16:28:48Z
dc.date.issued 2008-04-24 en_US
dc.identifier.uri http://hdl.handle.net/10161/585
dc.description Dissertation en_US
dc.description.abstract This research presents a detailed study of non-synchronous vibration (NSV) and the development of an efficient design method for NSV. NSV occurs as a result of the complex interaction of an aerodynamic instability with blade vibrations. Two NSV design methods are considered and applied to three test cases: 2-D circular cylinder, 2-D airfoil cascade tip section of a modern compressor, and 3-D high pressure compressor cascade that encountered NSV in rig testing. The current industry analysis method is to search directly for the frequency of the instability using CFD analysis and then compare it with a fundamental blade mode frequency computed from a structural analysis code. The main disadvantage of this method is that the blades' motion is not considered and therefore, the maximum response is assumed to be when the blade natural frequency and fluid frequency are coincident. An alternate approach, the enforced motion method, is also presented. In this case, enforced blade motion is used to promote lock-in of the blade frequency to the fluid natural frequency at a specified critical amplitude for a range of interblade phase angles (IBPAs). For the IBPAs that are locked-on, the unsteady modal forces are determined. This mode is acceptable if the equivalent damping is greater than zero for all IBPAs. A method for blade re-design is also proposed to determine the maximum blade response by finding the limit cycle oscillation (LCO) amplitude. It is assumed that outside of the lock-in region is an off-resonant, low amplitude condition. A significant result of this research is that for all cases studied herein, the maximum blade response is not at the natural fluid frequency as is assumed by the direct frequency search approach. This has significant implications for NSV design analysis because it demonstrates the requirement to include blade motion. Hence, an enforced motion design method is recommended for industry and the current approach is of little value. en_US
dc.format.extent 1687153 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Engineering, Mechanical en_US
dc.subject Engineering, Aerospace en_US
dc.subject Non-sychronous Vibration en_US
dc.subject Aeromechanics en_US
dc.subject Vortex Shedding en_US
dc.subject Turbomachinery en_US
dc.subject Computational Fluid Dynamics en_US
dc.subject Unsteady Aerodynamics en_US
dc.title Development of an Efficient Design Method for Non-synchronous Vibrations en_US
dc.type Dissertation en_US
dc.department Mechanical Engineering and Materials Science en_US

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