The vibration amplitude that sets in for an aerodynamically unstable bladed disk is a quantity of crucial importance to correctly estimate the blade fatigue life. This amplitude is basically the result of the balance between two small effects: the energy pumped into the blades by the gas flow, and the dissipation at the blade-disk friction interfaces. For the case of a perfectly tuned configuration, one can assume that the blade displacements take the form of a single (nonlinear) travelling wave with a given number of nodal diameters. The problem can be accordingly reduced to the computation of a time periodic (and multi-harmonic) solution in a single sector with phase-lagged boundary conditions. This simplification is no longer valid for a mistuned bladed disk. The mistuned system output consists of a nonlinear combination of several travelling waves with different number of nodal diameters coupled through mistuning. In this case, the complete bladed disk has to be considered, together with a large number of random mistuning patterns in order to have a statistically relevant prediction. This has an extremely high computational cost, and, for this reason, reduced order models (ROM) are normally used to analyze this situation. ROMs usually focus on the purely linear case of computing the mistuned flutter stability characteristics. In this work, we use a 3 DOF/sector ROM to analyze the nonlinear friction saturation of the flutter vibration amplitude of a mistuned bladed disk. From this ROM some asymptotic results will be derived taking into account the fact that both the aerodynamic instability growth rate and the mistuning are small effects compared to the purely elastic vibration. The results will be then compared with the experimental measurements obtained in the european project FUTURE, where an aerodynamically unstable LPT bladed disk was tested with different intentional mistuning patterns. 


Mistuning Effects on the Nonlinear Friction Saturation of Flutter Vibration Amplitude

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

Turbo Expo - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.