MEASUREMENT OF LEAKAGE AND FORCE COEFFICIENTS IN A SHORT LENGTH ANNULAR SEAL OPERATING WITH A GAS IN OIL MIXTURE
Deep sea compression systems must work under strenuous conditions with either gas in liquid or liquid in gas mixtures, mostly inhomogeneous. Off-design operation does affect the mechanical system overall efficiency and reliability, with penalties in leakage and rotordynamic performance of secondary flow components, namely seals. The paper introduces a test facility to characterize the leakage and dynamic force coefficients of a short length annular seal operating under various flow regimes ranging from pure gas, to mixture, to pure liquid. The paper shows flow rate measurements with a seal supplied with an ISO VG 10 oil in gas mixture whose liquid volume fraction (LVF) at the inlet plane varies from 0 to 1. Wet seal stiffness, mass and damping coefficients follow for a seal operating with pure air and also with an oil in air mixture with inlet LVF=2% and 4%. The experimental results reveal a small amount of liquid increases ten-fold (or more) the damping coefficients of the wet seal.