Supercritical CO2 Radial Turbine Design Performance as a Function of Turbine Size Parameters

Abstract

Supercritical CO2 (sCO2) radial inflow turbine are an enabling technology for small scale concentrated solar thermal power. They are a research direction of the Australian Solar Thermal Research Initiative (ASTRI). This study uses the 1D meanline design code TOPGEN, to explore the radial turbine design space under consideration of sCO2 real gas properties. TOPGEN maps a parametric design space defined by flow and head coefficient. The preliminary design code is used explore the feasibility, geometry and performance of sCO2 turbines in the 100kW to 200kW range in order to assess feasible design spaces and to investigate turbine scaling. Turbines are scaled with respect to power, while maintaining specific speed constant and with respect to speed. This analysis shows that both scaling approaches change the feasible design space and that both geometric constraints such as blade height or operational constraints such as blade natural frequency can significantly limit the design space. Detailed analysis of four shortlisted designs shows that turbine efficiencies close to 85% can be attained for 100kW and 200kW output powers, even when operating at reduced rotor speeds. This work provides new insight towards the design of small scale radial turbines for operation with sCO2 and highlights scaling issues that may arise when testing sub-scale turbine prototypes.