A Method to Develop Radial Inflow Turbine Performance Maps for Off-Design and Dynamic Simulation Studies of sCO2 Cycles

Abstract There is a growing interest in the use of supercritical carbon dioxide (sCO2) Brayton cycles for power generation applications. Consequently, many researchers have developed cycle-only models, or plant models at various levels of detail to study the feasibility of such technologies. In these studies, the turbine model used has a significant effect on the results obtained. Despite this, researchers typically specify a constant isentropic efficiency, or adopt one of the efficiency correlations presented by Dyreby. The former approach is only suitable for steady state design point studies, and the use of Dyreby’s efficiency correlations are limiting. Furthermore, Dyreby’s correlations may be employed without considering the velocities of the fluid, which is critical for the determination of fluid properties throughout the turbomachine. Therefore, neither approach is suitable for off-design or dynamic studies but are applied regardless because of the limited public data available on sCO2 turbomachinery. In this paper, a method is presented that may be used to size a single stage radial inflow turbine for given nominal boundary conditions, and to develop performance maps for the same turbine at off-design conditions. These maps may then be employed to perform off-design and dynamic studies. The method employs a one-dimensional mean-line analysis approach with enthalpy loss correlations and is verified using the performance map of an existing turbine at Sandia National Laboratories. Additionally, case studies are presented where the method is used to produce conceptual designs for turbines for a proposed 50 MWe concentrated solar power plant.