A comprehensive preliminary design methodology and an optimization workflow for single-stage radial-outflow turbines and application for 10 MW sCO₂ turbines

Development of efficient turbines for sCO₂ power cycles is crucial to increase the efficiency, economic feasibility, and competitiveness of future thermal power plants. Radial-outflow turbines are recently considered as a viable power block option for sCO₂ power cycles for several applications. This research aims at presenting a detailed and replicable design procedure for radial-outflow turbines. A detailed one-dimensional design method was first developed and validated, then an optimization design workflow was developed using this one-dimensional design method. Utilizing this workflow, the impact of some key design parameters on turbine performance was studied. It was found that the velocity ratio, specific speed, and flow coefficient have significant impact on turbine performance, the reaction degree has moderate impact, and the diameter ratio has the lowest impact. The criterion of selecting the design variables was given and its applicability to different boundary conditions and constraints has also been illustrated. Furthermore, a test case turbine of 10 MW power scale was designed using the developed method, and 3D CFD simulations were performed to study the on-design and off-design performance of the designed turbine. Results show that high efficiency (above 90.0 %) and overall good off-design performance can be obtained from sCO₂ radial-outflow turbines in the 10 MW power scale using the developed design methodology when the design parameters are properly selected. The developed 1D design and optimization method is directly applicable to other working fluids and can be easily extended to design multistage radial-outflow turbines.