ANALYSIS OF 2-PHASE FLOW IN CRYOGENIC DAMPER SEALS - PART II - MODEL VALIDATION AND PREDICTIONS

Cryogenic fluid damper seals operating close to the liquid-vapor regio n (near the critical point or slightly sub-cooled) are likely to devel op a two-phase flow region which affects the seal performance and reli ability. An all-liquid, liquid-vapor, and all-vapor, i.e., a ''continu ous vaporization'' bulk flow model for prediction of the seal dynamic forced response is given in Part I. The numerical method of the soluti on of the flow equations is detailed here. Computed predictions for st atic seal characteristics, leakage and axial pressure drop, correlate well with existing measurements for a gaseous nitrogen seal and a liqu id nitrogen seal with two-phase at the seal exit plane. The effects of two-phase flow regimes on the dynamic force coefficients and stabilit y of an oxygen damper seal are discussed. Fluid compressibility effect s, particularly for mixtures with low mass content of vapor, are of ut most importance. Under these conditions, an increase on seal direct st iffness and reduction of whirl frequency ratio are shown to occur.