Experiments of two-phase flow dynamics of marine reactor behavior under heaving motion

Two-phase flow dynamics of a marine propulsion reactor - of the steam generator in particular - subjected to heaving acceleration were studied on a small-scale rig simulating the primary and secondary circuits of those of N.S. Mutsu. To impart the heaving acceleration, the rig was mounted on a suspended platform oscillated in vertical direction by hydraulic device. Heaving acceleration applied to this rig proved the responding variations of circulating flow, of evaporator steam void fraction and of downcomer water level to be proportional in amplitude to that of the acceleration. The circulating flow was found to pulsate with phase lag behind the heaving acceleration indicative of a second order lag function. Constriction of flow channel downstream of the evaporator - producing resistance against flow amounting to 1.15 times that of the entire loop - proved to amplify significantly the responding pulsation of circulating flow. The pulsations were conversely appreciably diminished by the insertion of a second channel constriction upstream of evaporator - producing 2.7 times loop resistance. When devoid of heaving acceleration, with insertion of flow constriction downstream of evaporator, circulating flow was indicated to be controlled by density wave oscillation, whereas upon application of heaving acceleration, the flow came to be controlled by the external acceleration. (author)