Abstract
The steam injector, which attains higher discharge pressure than the supply steam pressure, is a passive jet pump that has no movable part and drives feedwater by supersonic jet. Applying the multistage steam injector to a feedwater heating system of a nuclear power plant could be of great advantage for simplification of the feedwater heating system and reduction of the volume of the turbine building. It is remarkably important to improve the thermal-hydraulic performance of the first-stage steam injector to enhance the thermal efficiency of the plant, since it utilizes low-pressure steam of 0.05MPa, extracted from the turbines. The analytical simulation for the four-stage steam injector system by CFD could realize the enhancement of the thermal-hydraulic performance of the multistage steam injector by its design improvement. Further issues exist in the application of reduced-scale experimental and analytical results for the design of equipment as large as an actual plant. A-fifth-scaled test facility, consisting of the three-stage steam injectors and the last stage steam injector with the jet deaerator, enlarges by two times in a flow rate as large as a-seventh-scaled test facility. The test results and analyses exhibited the similarity in the performance of both facilities. With this in view, we developed a four-stage simplified feedwater system using the steam injectors as shown below and proved its viability by a-seventh-scaled and a-fifth-scaled model tests in a bid to significantly rationalize the BOP for the turbine feedwater and condensation system. The CFD code was applied to the multistage SI system to analyze the whole performance from the first-stage SI through the third-stage SI. A-fifth-scaled test facility, consisting of the three-stage steam injectors and the last stage SI with the jet deaerator, enlarges by two times in a flow rate as large as a-seventh-scaled test facility. The test results and analyses exhibited the similarity in the performance of both facilities. The predicted discharge pressure and temperature of the SI by the CFD analyses for a full-size model showed almost same values as those of scaled models. The similarity could be valid in the large scaled-up multistage SI system.
