Feasibility of a Direct Coupled Turbine-Compressor Power Block for S-CO2 Brayton Cycles

This paper explores the feasibility of a direct coupled turbo-compressor power block for a simple recuperated S-CO2 Brayton cycle. The turbine inlet temperature is fixed at 600°C and the maximum working pressure is restricted to 300 bar due to material constraints to enable use of conventional steel alloys. Analysis is performed for a single stage radial flow turbine and a centrifugal compressor configuration. Mean-line flow is individually analyzed for the turbine and compressor to generate contour maps of optimum operating speeds for a range of power levels at various isentropic efficiencies. While performing the mean-line analysis real gas properties and friction coefficients of S-CO2 have been considered. The mean-line flow code is coupled with thermodynamic model of the simple recuperated S-CO2 Brayton cycle for generating a range of optimum operating conditions where direct coupled power blocks can be used.