LOCALIZATION OF AEROELASTIC MODES IN MISTUNED HIGH-ENERGY TURBINES

The effects of blade mistuning on the aeroelastic vibration characteri stics of high-energy turbines are investigated, using the first stage of the oxidizer turbopump in the Space Shuttle main rocket engine as a n example. A modal aeroelastic analysis procedure is used in concert w ith a linearized unsteady aerodynamic theory that accounts for the eff ects of blade thickness, camber, and steady loading. High sensitivity of the dynamic characteristics of mistuned rotors is demonstrated. In particular, the aeroelastic free vibration modes become localized to a few blades, possibly leading to rogue blade failure, and the locus of the aeroelastic eigenvalues loses its regular structure when small mi stuning (of the order usually present in actual rotors) is introduced. Perturbation analyses that yield physical insights into these phenome na are presented. A powerful but easily calculated stochastic sensitiv ity measure that allows the global prediction of mistuning effects is developed.