Ha-rok Bae (Committee Member), Jeffrey Brown (Committee Member), Richard Cobb (Committee Member), Charles Cross (Committee Member), Ramana Grandhi (Committee Member), Joseph Slater (Advisor)
Doctor of Philosophy (PhD)
This effort seeks to increase the reduced-order model fidelity for mistuned Integrally Bladed Rotor (IBR) and Dual Flow-path Integrally Bladed Rotor (DFIBR) response prediction by explicitly accounting for blade geometric and material property deviations. These methods are formulated in a component mode synthesis (CMS) framework utilizing secondary modal reductions in a cyclic symmetry format. The resulting reduced-order models (ROMs) capture perturbations to both blade natural frequencies and mode shapes resulting from geometric deviations. Furthermore, the secondary modal reductions and cyclic symmetry format offer significant computational savings over traditional component mode synthesis methods that give a further reduction in model size. The first formulation for IBRs assumes a tuned disk-blade connection and presents two methods that explicitly model blade geometry surface deviations by performing a modal analysis on different degrees of freedom of a parent reduced-order model. The parent ROM is formulated with Craig-Bampton component mode synthesis (CB-CMS) in cyclic symmetry coordinates for an IBR with a tuned disk and blade geometric deviations. The first method performs an eigen-analysis on the constraint-mode degrees of freedom (DOFs) that provides a truncated set of Interface modes while the second method includes the disk fixed-interface normal modes in the eigen-analysis to yield a truncated set of Ancillary modes. Both methods can utilize tuned or mistuned modes, where the tuned modes have the computational benefit of being computed in cyclic symmetry coordinates. Furthermore, the tuned modes only need to be calculated once, which offers significant computational savings for subsequent mistuning studies. Each geometric mistuning method relies upon the use of geometrically mistuned blade modes in the component mode framework to provide a very accurate ROM. Free and forced response results are compared to both the full finite element model (FEM) solutions and a traditional frequency-based approach used widely in academia and the gas turbine industry. It is shown that the developed methods provide highly accurate results with a significant reduction in solution time compared to the full FEM and parent ROM. An investigation into the assumed tuned disk-blade connection is then performed. Two types of disk-blade connection mistuning are investigated: as-measured principal component deviations and random perturbations to the inter-blade spacing. Finally, these methods are extended to ROM methodologies for DFIBRs to assess the susceptibility of these new designs to mistuning and to be able to efficiently and effectively predict response amplification. Two main approaches are presented: first, a frequency-based method that is analogous to traditional mistuning approaches for IBRs, and second, geometric approaches that explicitly model blade geometry surface deviations. These methods help characterize DFIBR dynamic response and investigate the unique aspects that differentiate these advanced components from IBRs. In all methods, free and forced response results are compared to both the full FEM solutions and the traditional frequency-based approaches. It is shown that the developed methods provide highly accurate results with a significant reduction in solution time compared to the full FEM and parent ROM.
Department or Program
Ph.D. in Engineering
Year Degree Awarded
Copyright 2013, all rights reserved. This open access ETD is published by Wright State University and OhioLINK.