Analysis of Two-Phase Flow in Cryogenic Damper Seals—Part I: Theoretical Model

Cryogenic fluid damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two-phase flow region which affects the seal performance and reliability. An all-liquid, liquid-vapor, and all-vapor, i.e., a “continuous vaporization” bulk flow model is presented for prediction of the seal dynamic forced response. Continuity, momentum, and energy (enthalpy) transport equations govern the two-phase flow of a homogeneous saturated mixture in thermodynamic equilibrium. Static and dynamic force performance characteristics for the seal are obtained from a perturbation analysis of the governing equations. Theoretical predictions and comparisons to experimental measurements in a liquid and gaseous nitrogen seal are presented in Part II. The effects of two-phase flow regimes on the dynamic force coefficients and stability of an oxygen damper seal are also discussed.