Passive Control of Flutter and Forced Response in Bladed Disks via Mistuning

Benjamin Shapiro
PhD Dissertation

Mistuning or blade to blade variation in jet-engine bladed-disks can lead to large changes in engine performance. Even the small random mistuning associated with manufacturing tolerances can significantly change both stability boundaries and forced response. This thesis addresses two questions. Analysis: given any mistuning (random or intentional), what is the resulting change in performance? And passive control: can intentiona l mistuning be used to improve stability and forced response in a robust manner?

A general framework based on symmetry arguments and eigenvalue/vector perturbations is presented to answer both questions. Symmetry constrains all facets of mistuning behaviour and provides simplifications for both the analysis and control problems. This is combined with the eigenvalue/vector perturbation which captures the nonlinear mistuning dependence and solves the analysis problem. It is shown that intentional mistuning can provide robust damping and so guarantee improved stability and forced response under fixed manufacturing tolerances. Results are demonstrated on a high-fidelity low-order model derived from computational-fluid-dynamic data.

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Richard Murray (murray@cds. caltech.edu)