Design scheme and experimental investigation for a 100 kW-class CO2 axial turbine-generator

Abstract

Hundred-kilowatt-scale supercritical carbon dioxide (sCO 2 ) cycles are viable solutions for distributed generation and waste heat recovery owing to their high efficiency and compactness. The sCO 2 turbine is a core component of the cycle, playing a decisive role in overall system performance. However, few turbine prototypes are available at this power scale, and their tested performance is relatively poor. This paper presents the design scheme and experimental investigation of a 100-kW sCO 2 Turbine-Generator (TG). Under the design boundary conditions, a configuration featuring two expansion stages arranged symmetrically was adopted to accommodate the high enthalpy drop while balancing most of the axial thrust; an axial architecture with a moderate design rotational speed was selected to balance aerodynamic and mechanical performance. Modal analysis for the shaft system showed a substantial safety margin, and dedicated cooling strategies were implemented for thermal management. To evaluate the TG prototype, a closed transcritical carbon dioxide (tCO 2 ) test bench was constructed. Experimental results showed that the TG could be smoothly started, accelerated, and operated. A power generation capacity of 100 kW and a peak thermal-to-electric conversion efficiency of 67% were also obtained during the test campaign. Furthermore, the relative error between simulation and experiment was as low as 6.6%, enabling reliable wide-range performance simulation. These results demonstrate the feasibility of an axial architecture at the 100-kW scale under the present aerodynamic and mechanical constraints, providing additional engineering insight into architecture selection and enriching the experimental database for this power scale.