Study on Operation Limit of the Supersonic Steam Injector

Steam injector is a passive jet pump which operates without power source or rotating machinery and it has high heat transfer performance due to the direct-contact condensation of supersonic steam flow onto subcooled water jet, and it has been considered to be applied to the passive safety system for the Next-generation nuclear power plants. The objective of the present study is to clarify operating mechanisms of the injector and to determine the operating ranges. In this study, temperature and velocity distribution in the mixing nozzle as well as flow directional pressure distribution were measured. In addition, flow structure in whole of the injector was observed with high-speed video camera. It was confirmed that there were unsteady interfacial behavior in mixing nozzle which advances heat transfer between steam flow and water jet with calculation of heat transfer coefficient. Discharged pressure at diffuser was also estimated with a one-dimensional model proposed previously. Furthermore, it was clarified that steam flow did not condense completely in mixing nozzle and it became two-phase flow in throat and diffuser, which seemed to induce shock wave. From those results, several discussions and suggestions to develop a physics model which predicts the injectors operating characteristics are described in this paper.