Experimental and theoretical rotordynamic coefficients and leakage of straight smooth annular gas seals
and leakage of straight smooth annular gas seals. Experimental rotordynamic
coefficients were measured and trends in changes of rotordynamic coefficients with
operating variables such as rotor speed, back-pressure, fluid preswirl, and seal clearance
Experimental results show that cross-coupled stiffness coefficients are highly
influenced by fluid preswirl and only moderately influenced by other operating
parameters, whereas direct damping is nearly unaffected by changes in operating
parameters. Effective damping, a good indicator of stability, is highly affected by fluid
preswirl. Although rotordynamic coefficients of straight smooth annular gas seals are
assumed to be frequency independent, experimental results suggest a frequency
dependent nature at high back-pressures and high excitation frequencies.
Experimental results for rotordynamic coefficients and leakage are compared
with theoretical predictions of ISOTSEAL, an isothermal-flow, two-control-volume,
bulk-flow rotordynamic analysis program. All rotordynamic coefficients are underpredicted.
Direct stiffness is poorly predicted while cross-coupled stiffness and direct
damping are predicted reasonably well. Leakage is also consistently under-predicted.
Theory predicts a slight frequency dependent nature for a limited number of test
Advisor:Childs, Dara; Vance, John; Cizmas, Paul
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:rotordynamics gas seals
Date of Publication:12/01/2004