Design and loss analysis of radial turbines for supercritical CO2 Brayton cycles

Abstract

The use of supercritical fluids has been identified as potential solution in realizing highly efficient and compact sized power systems. In this study, the effect of design power scale and specific speed on supercritical CO2 operated radial inflow turbines within the power range of 0.1 MW–3.5 MW is investigated and analyzed. A radial turbine design tool including loss distribution analysis based on loss correlations was developed. In general, the SCO2 radial turbines can be designed to have high efficiency with efficiency ranging from over 80%–87% depending on the turbine design power scale. On the other hand, the turbine dimensions are small and the required rotational speeds are significantly high even at MW scale designs. It was observed that the specific speed and mass flow rate highly affect both the geometry and the turbine loss distribution. Turbine designs with highest isentropic efficiencies were observed with specific speeds ranging from 0.50 to 0.60. With the lowest investigated turbine power outputs from 100 kW to few hundreds of kW the tip clearance loss is the most significant loss whereas the passage, stator and exit kinetic loss are the most significant loss sources at higher power levels.