Two-phase flow structure and operating characteristics of supersonic steam injector

Abstract

This paper experimentally studies the influence of two-phase flow behavior on the operating limits of steam injector (SI). SI is the passive jet pump with a converging-diverging structure. SI operates without the electrical power and discharges water at high pressure. However, in regard to the operating limits of SI, it is unclear which takes into account the discharged flow structure. In this paper, the pressure distributions along the flow direction and the discharge pressure were measured by changing the inlet steam pressure and the load on the exit of the test section. Furthermore, the discharged flow at the diffuser was observed with a high-speed camera. As a result, a boundary was observed in the discharged flow at which the flow structure changed. The area from the throat to this boundary is considered as a two-phase region which steam did not condense completely in the mixing nozzle remained. This boundary moved upstream as the load on the exit increased, and a significant pressure rise occurred at the position where the boundary was reached. In addition, white propagations towards the downstream direction were observed. This propagation is considered as pressure wave propagation. The propagating speed was estimated using image processing. Assuming that the pressure wave propagates at sonic speed, the void fraction at the discharged flow was estimated by the existing model. Based on the above, the influence of the two-phase flow (in the discharged flow structure) on the operating characteristics of SI is discussed.

Keywords

• steam injector
• nuclear plant safety system
• passive jet pump
• two-phase flow
• direct contact condensation