Session: 28-02: Dynamic response of engine components

Paper Number: 152970

Forced Response of an Unstable LPT Bladed-Disk: New States With Different Blade Vibration Amplitude 

In the forcing of an LPT bladed disk, the final amplitude of the vibration state that sets in is determined by the dissipation produced by the friction forces at the blade-disk contact surfaces. The friction effect is small but strongly nonlinear, and, therefore, it can couple different vibration modes that, in a purely linear description, would be completely independent.  In this work, we present a vibration state that appears for a single travelling wave forcing (resembling the aerodynamic unsteady loads coming from the upstream stator wakes) of an unstable LPT rotor, and that produces a response with different blade vibration levels. The surprising result is that the blade vibration amplitude is not uniform along the rotor, and blades show different vibration amplitudes despite of the fact that this a perfectly tuned bladed-disk. This vibration state is basically composed of the forcing travelling wave coupled with an unstable travelling wave through the nonlinear mode interaction induced by the nonlinear friction. This vibration state was previously found in a reduced order model of the problem, and now we find these states using a high-fidelity FEM description of a realistic unstable LPT bladed disk with 144 blades that was developed and tested in the context of the European Project ARIAS. These states are found to be quite robust against perturbations, and show a quite extended range of existence for different forcing engine orders.     

Presenting Author: Carlos Martel Universidad Politécnica de Madrid

Presenting Author Biography: Carlos Martel is Professor of Aerospace Engineering at Universidad Politécnica de Madrid (Spain) since 2009, where he also completed his PhD in Applied Mathematics in 1995. His research activity started in the field of nonlinear dynamics and pattern formation applied to basic fluid mechanics problems (convection, water waves, boundary layer). In the past 20 years he has been involved in the study of different aeroelastic problems in turbomachinery in close collaboration with the industry, mostly related to the analysis and description of mistuning and nonlinear friction effects in the flutter and forced response vibration of rotors. He has authored more than 70 scientific and technical papers on peer reviewed journals, conferences, and technical reports.

Authors:

Carlos Martel Universidad Politécnica de Madrid
Salvador Rodríguez Universidad Politécnica de Madrid
Javier González Universidad Politécnica de Madrid