Session: 27-04 Methods and Modeling in Rotordynamics

Paper Number: 125865

125865 - Damping Phenomena in Rotating Machines: A Focus on Rotor Damping With Synchronous and Asynchronous Excitation 

Accurate modeling of damping in rotors is critical for rotor dynamic analysis of turbo machinery such as aircraft engines.  This paper documents the recent work of the ‘Rotordynamics consortium’ with the cooperation of Safran Aircraft Engines, General Electric Aerospace and Hexagon (MSC.Software) demonstrating best practice for rotor damping across the solution disciplines of both frequency and transient response as well as complex eigenvalue analysis.

Any rotating machine is subject to out of balance loading due to the imperfections associated with manufacturing processes.  Out of balance or unbalance loading is always present and is known as a synchronous phenomenon as the frequency of the unbalance excitation is synchronous with the rotation speed of the rotor, leading to vibration causing noise and fatigue issues.  In contrast, the frequencies of asynchronous vibrations are unrelated to the rotation speed of the rotor and are typically caused by external aerodynamic loads, bearing properties such as squeeze film dampers and other nonlinearities to name a few.

Synchronous excitation tends only to excite forward whirl modes of rotating machines that are axisymmetric, whereas asynchronous excitation may excite any whirl modes of the structure, even those with a rotor that is axisymmetric.  With the deep differences in these two families of excitation, it is essential to adapt the simulation procedure to the type of excitation and especially important to represent the frequency dependent damping affecting rotating parts in a faithful manner.

Viscous and structural (hysteretic) damping are studied numerically in a rotating shaft under synchronous and asynchronous excitation using the MSC Nastran finite element software.  A simplified dual-rotor finite element model is used to demonstrate the non-synchronous response of one rotor on the other one, representative of a whole aircraft engine.  Credible values of stiffness, damping and mass properties are adopted to give integrity to the work and pave the way to an industrial scale problem.

Presenting Author: Francesco D'alessandro SAFRAN AIRCRAFT ENGINES

Presenting Author Biography: Francesco D'Alessandro obtained his Bachelor degree in mechanical engineering at the "Univ. of Naples-FEDERICO II" in 2016. He began a double master degree between the "Univ. of Naples-FEDERICO II" and the "Inst. Superieur de mécanique de Pairs (SUPMECA-Paris)" in 2017, obtaining his double Master degree in September 2019. He began his PhD in 2020 at the "Univ. of Bourgogne and Franche-Comté"(FR), collaborating with SAFRAN AIRCRAFT ENGINES, FEMTO-ST Institute and with the research centre CENAERO. He obtained his PhD with honours in early 2023.

He is now a permanent research engineer at SAFRAN AIRCRAFT ENGINES (FR), interested in anything concerning aircraft engines dynamics, from the experimental to the numerical points of view.

Authors:

Francesco D'alessandro SAFRAN AIRCRAFT ENGINES
Florian Garnier SAFRAN AIRCRAFT ENGINES
Damien Guivarch SAFRAN AIRCRAFT ENGINES
Amit Zutshi General Electric Aerospace
Weize Kang General Electric Aerospace
Manoj Kunnil General Electric Aerospace
Payyoor Narayanan General Electric Aerospace
Mark Robinson Hexagon
j.s. Kumar Hexagon
Jianming Cao Hexagon
Ted Rose Hexagon