Consideration on the Benefits of Intentional Blade Mistuning for the Forced Response of Turbomachinery Rotors

The intentional mistiming of blades in order to reduce the forced response amplitudes of turbomachinery rotors is considered. The statistics of the maximum blade response amplitudes for a simple model of a 12-bladed disk are investigated. It is shown that the maximum response amplitudes are appropriately modeled by a Type III Weibull distribution. Intentional mistuning is introduced into the model by varying the nominal blade stiffnesses in rotationally periodic patterns. Of the six non-zero harmonics, the first and second harmonics are shown to provide a significant decrease in the maximum amplitudes. A more practical, pseudo-harmonic-two configuration of mistuning is also considered. This pattern requires only two unique blade designs, and it results in an even larger decrease in the maximum response than that provided by the harmonic-two intentional mistuning.