Forced Response of Bladed Disks With Excitation Variability

The prediction of forced vibration of mistuned bladed disks remains an important topic in turbomachinery design. The investigation of mistuning usually focuses on the blades in terms of their different structural properties. The excitation mechanism is considered to be mainly caused e.g. by the wakes from an upstream and the potential field from a downstream blade row. In recent years, it has been demonstrated that the Tyler-Sofrin modes (scattered or spinning modes) may affect blade forcing significantly and cause variable forcing amplitudes on individual blades in multistage turbomachinery. As a result, the vibration is localized at some of the blades forced by greater amplitudes, which leads to a higher risk damage for those blades. In this paper, the generation mechanism of TSMs is demonstrated and the effect of TSMs on blade forced responses is studied. Depending on the configuration of turbomachinery, excitation arising from Tyler-Sofrin modes may consist of different frequency components, which requires multiharmonic balance method (MHBM) to find the periodic solutions in presence of nonlinear blade couplings1. The methodologies for calculating linear and nonlinear FRFs are presented here on an academic bladed disk with shroud coupling, while TSMs is taken as part of the blade excitation.