Design and performance analysis of a supercritical CO₂ radial inflow turbine

Due to the high efficiency and compactness, the supercritical carbon dioxide (S-CO₂) Brayton cycle recently emerged as a promising power cycle for the power plant economics. The turbine is the key power unit of the cycle, but relevant investigations are still lacking. In this paper, the design study of an S-CO₂ radial inflow turbine based on system optimization is conducted. The CFD simulation of the turbine under design and off-design conditions is performed, and tip clearance analysis is conducted to evaluate the turbine performance. The properties of CO₂ in the CFD analysis are calculated using the NIST database. Results show that the power output and total-to-static efficiency of the turbine are 1.16 MW and 85.36%, respectively. The largest deviation of design results and simulation results under the nominal condition is 3.73%, indicating that the design model is reliable. Numerical simulations reveal that the turbine maintains great performance at design and off-design conditions. Furthermore, tip clearance analysis shows that a 6% increase of tip clearance results in a 3.84% reduction of turbine efficiency and a 4.16% reduction of turbine power output.