P. Sundararajan et Jm. Vance, A THEORETICAL AND EXPERIMENTAL INVESTIGATION OF A GAS-OPERATED BEARING DAMPER FOR TURBOMACHINERY .1. THEORETICAL-MODEL AND PREDICTIONS, Journal of engineering for gas turbines and power, 117(4), 1995, pp. 742-749
This is the first (Part I) of two papers describing recent results of
the research program directed at developing a vibration damper suitabl
e for high-temperature turbomachinery applications. It is expected tha
t such dampers will replace squeeze-film dampers, which use oil as the
working fluid and have limitations at higher temperatures. A novel ga
s-operated bearing damper has been evaluated analytically and experime
ntally for its damping characteristics. A theory based on the isentrop
ic assumptions predicts the damper performance characteristics reasona
bly well. A maximum damping level of 2311 N-m/s (13.2 lb-s/in.) at a f
requency of 100 Hz was measured with a single actuator of the gas damp
er. Since many such actuators could be placed circumferentially around
the squirrel cage, considerable damping levels can be realized. The s
tudy also shows that significantly higher damping levels can be achiev
ed by modifying the current design. Part I describes the theoretical m
odel that has been developed based on isentropic assumptions. This mod
el is an improved version of the previous theory (Vance et al., 1991)
and includes the supply groove effects, dynamic area changes of the in
let feeding holes, and the effects of flow choking on damper behavior.
The governing equations are derived and theoretical predictions using
these equations have been made for two hardware designs that were exp
erimentally investigated (see Part II for experimental results).