Cycle Thermal Efficiency of Supercritical CO2 Gas Turbine Dependent on Recuperator Performance

Copyright © 2013 by JSME Abstract The supercritical CO2 gas turbine cycle can achieve high cycle thermal efficiency by reducing compressor work near the critical point. The achievable cycle thermal efficiency value is strongly dependent on the recuperator performance. Values of the achievable cycle thermal efficiency are calculated by assuming a value of average recuperator temperature-effectiveness of 91%. The turbine inlet pressure is 20 MPa. The effects of turbine inlet temperature are examined. The calculations are conducted both for the non-intercooling cycle and the intercooling cycle. Results show that the non-intercooling cycle is preferred to the intercooling cycle up to 600°C because of its simplicity. However, the latter is preferred to the former at temperatures greater than 600°C attributable to its approximately 2% higher efficiency. For the typical temperature of 527°C and also 650°C, the diagrams of mass and heat balance are given. The maximum cycle thermal efficiencies are, respectively, 43.4% and 48.9% for 527°C and 650°C. The effects of pressure are examined and 20 MPa is justified as an optimal value. Finally, the effects of recuperator effectiveness on the cycle thermal efficiency are examined, which are revealed to be linear and the cycle thermal efficiency increases about 0.5% for a 1% increase of the recuperator effectiveness.