Ho Joon Yoon

Design Methodology of Supercritical CO2 Brayton Cycle Turbomachineries

The supercritical CO2(S-CO2) Brayton Cycle is gaining attention due to its high thermal efficiency at relatively low turbine inlet temperature and compactness of turbomachineries. For designing turbomachineries of the S-CO2 Cycle, however, most of existing codes based on ideal gas assumption are not proven yet to be accurate near the supercritical condition. Furthermore, many of existing design computer programs usually focuses on a specific type of turbomachinery, e.g. axial or radial, which makes hard to compare performance of both types at the same design condition. Since both axial and radial types of turbomachineries were pointed out as an equally possible candidate for the S-CO2 Brayton cycle, in order to compare and determine the best effective type of turbomachinery requires considering both types under the same design conditions. Taking into consideration of these facts, some modifications to the conventional design methodology of gas cycle turbomachinery are necessary to design a turbomachinery for the S-CO2 cycle. Especially, a modified design method should consider non-linear property variation of CO2 near the critical point to obtain an accurate result. Thus, the modified design method for the S-CO2 Brayton cycle turbomachineries is suggested in this paper and the method was implemented in the in-house code. In addition, some preliminary results will be discussed with the plan for validation and verification of the code.© 2012 ASME

HORIZON EXPANSION OF THERMAL-HYDRAULIC ACTIVITIES INTO HTGR SAFETY ANALYSIS INCLUDING GAS-TURBINE CYCLE AND HYDROGEN PLANT

We present three nuclear/hydrogen-related R&D activities being performed at KAIST: air-ingressed LOCA analysis code development, gas turbine analysis tool development, and hydrogen-production system analysis model development. The ICE numerical technique widely used for the safety analysis of water-reactors is successfully implemented into GAMMA, with which we solve the basic equations for continuity, momentum conservation, energy conservation of the gas mixture, and mass conservation of 6 species (He, N2, O2, CO, CO2, and H2O). GAMMA has been extensively validated using data from 14 test facilities. We developed a tool to predict the characteristics of HTGR helium turbines based on the throughflow calculation with a Newton- Raphson method that overcomes the weakness of the conventional method based on the successive iteration scheme. It is found that the current method reaches stable and quick convergence even under the off-normal condition with the same degree of accuracy. The dynamic equations for the distillation column of HI process are described with 4 material components involved in the HI process: H2O, HI, I2, H2. For the HI process we improved the Neumann model based on the NRTL (Non-Random Two-Liquid) model. The improved Neumann model predicted a total pressure with 8.6% maximum relative deviation from the data and 2.5% mean relative deviation, and liquid-liquid-separation with 9.52% maximum relative deviation from the data.