Influence of Geometric Parameters for a 100 kW Inward Flow Radial Supercritical CO2 Turbine

Abstract

Abstract As an emerging technology, supercritical CO2 (sCO2) power generation systems currently focus on small-scale power generation. Inward flow radial (IFR) turbine is preferred for small-scale power generation due to its efficient and compact design. The influence of design parameters on sCO2 turbine performance can be different from gas turbines due to small size, high rotational speed, and low viscous losses. This paper presents a CFD study to find the optimal value of four geometric design parameters — axial length, outlet-to-inlet radius ratio, number of rotor blades, and velocity ratio for a 100 kW IFR turbine and their effect on the turbine’s performance. The results are compared against well-established gas turbine correlations in the 0.2 to 0.8 specific speed range to review their applicability on sCO2 turbines. The results show significant differences in the optimal value of design parameters compared to gas turbines. sCO2 turbines require fewer blades and a higher velocity ratio for optimal performance. The maximum turbine efficiencies (∼ 82%) are achieved at a lower specific speed of ∼0.4 than gas turbine results ∼ 0.55 to 0.65. Also, high incidence angles ∼ −50° to −55° are required at high specific speeds to counter the Coriolis effect in rotor passage. The results also show the variation of stator, rotor, and exit kinetic energy losses with specific speeds, which shows the cumulative losses are minimum at the specific speed of ∼ 0.4.