Development of multilevel cascade layouts to improve performance of SCO2 Brayton power cycles: Design, simulation, and optimization

Abstract

The multilevel cascade SCO2 Brayton cycles are developed based on the conventional recompression-reheat cycle to enhance thermodynamic performances using the multilevel cascade scheme. Mathematical models are proposed to characterize their thermal cycle efficiency. The results show that for three typical cases, the proposed multilevel cascade cycle with 3 compressors × 3 reheats × 2 turbines improve cycle efficiency by 2.56 %, 3.17 %, and 3.44 % in absolute change, while the other with 3 compressors × 3 reheats × 3 turbines further enhance by 3.17 %, 4.19 %, and 4.17 % in absolute change over the conventional cycle. The latter cycle as the optimal layout is chosen to perform the key parametric analysis. The cycle efficiency increases with increasing high-pressure turbine inlet temperature, while the main compressor inlet temperature has the opposite effect. It increases and then decreases with the high-pressure turbine inlet pressure, the main compressor inlet pressure, and the split ratio of the recompressor, respectively. Finally, the parametric global optimization is conducted to improve the cycle performance more deeply. It is demonstrated that the absolute efficiency can be further increased by 2.62 %, 1.81 %, and 1.09 % for the responding cases. The integrated configurations are also suggested for power generation systems with different applications.