Order –Tuned
Vibration Absorbers for Rotating Machinery –
From Symmetric
Bifurcations to Automotive Engines
Department of
Mechanical Engineering
Michigan State
University
East Lansing, MI
48824
Abstract
Vibrations
in rotating machinery often arise from so-called order excitation, that is,
periodic excitation with frequencies that are multiples of the machineÕs
nominal rotation rate. This
occurs, for example, in the torsional dynamics of internal combustion engines
and in the flexural vibrations of turbine blades. A proven approach to attenuate these vibrations is to employ
vibration absorbers that are tuned to given order of rotation, rather than to a
fixed frequency. This tuning
strategy is achieved by using the centrifugal field, instead of an elastic
element, to provide the absorber restoring force. In this presentation I will outline some of the historical
developments of these absorbers and describe more recent work wherein nonlinear
aspects of their response are considered.
Some of these nonlinear effects can be exploited to provide enhanced
performance, while others limit their operating range. Of particular interest are rotors
fitted with systems of identical absorbers, which are described by models with
permutation symmetry. This
symmetry leads to instabilities and subsequent responses that can be described
using the tools of symmetric bifurcation theory. It will be shown that with the proper selection of absorber
parameters, these instabilities can be avoided. The presentation will also describe experimental results
from a controlled experimental rig, and from a successful implementation of
absorbers on an experimental displacement-on-demand automotive engine. An introduction to ongoing work on the
use of absorbers for rotating flexible structures with cyclic symmetry (joint
work with Christophe Pierre from UM) will also be presented.
3:30 – 4:30
p.m.