Flow mapping using 3D full-scale CFD simulation and hydrodynamic experiments of an ultra-supercritical turbine’s combined valve for nuclear power plant

Abstract

In a typical steam turbine generator system, electrical power output is related to the steam flow regulated by a control valve. Hence, to ensure adequate electrical load as well as the proper stability of the turbine, a linear operation of the control valve is desired. However, in reality, the control valve exhibits different flow characteristics (FCs), both linear and nonlinear, which stem from its complex shape of plug and stem lift. Therefore, precise estimation of FCs is of utmost importance for better controllability, reliability, and safety of the turbine system. In this study, experiments and CFD simulations were carried out to evaluate the hydrodynamic FCs of a combined emergency stop and control valve to be employed in an ultra-supercritical (USC) turbine system for power plant. A full-scale prototype valve was designed, fabricated, and tested for a vendor company. Experiments were performed in the so-called VELO (Valve Engineering Layout Operation) test bench, and CFD simulations were conducted using a commercial code STAR CCM+. Air was used for experiments and simulations for simple economic and safe operation. Hydrodynamic characteristics were analyzed, and the theoretical mass flow rate of the valve was estimated. Finally, the valve coefficient of the turbine system was determined from the obtained FC curves. The simulation and test data showed a scale deviation of 15–16% for the original model valve and the simplified test valve. The test valve required such scaled modification to match with the test bench and fabrication. The prospective future research and improvement were recommended. This study's findings would support improving the turbine system performance to ensure safer, reliable, and modular power conversion systems for nuclear and conventional fossil fuel-based power plants.