Two-phase flow in floating-ring seals for cryogenic turbopumps

A flow visualization study on the two-phase flow in floating-ring seals for cryogenic fluid was carried out to identify the two-phase flow area (A(2)) inside the seating clearance induced by viscous frictional heating and the pressure drop. The effect of the two-phase flow area on leakage was invest igated by comparing leakage measurements (Q) and the values of A(2) obtaine d from observed results. A(2) increased with increasing rotational speed; i n the mass leakage rate. Moreover the effect of the two-phase flow on the r eduction of leakage was discussed by comparing the measurements of e with t he computational results (Q(liquid)) obtained from the incompressible flow equation. It was-confirmed that the effect of the two-phase state on the re duction in leakage can be broadly classified into the following two effects : effect of the all-liquid choked flow and effect of the two-phase flow are a (A(2)) inside the sealing clearance. In a high degree of subcooling condi tions, the increase in A(2) tends to depress the reduction effect on the le akage rate.