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.