Cycle characteristics of solar gas turbines using supercritical carbon dioxide as a working fluid

摘要

Cycle characteristics of closed gas turbines using super critical carbon dioxide as a working fluid are investigated. It is found an anomalous behavior of physical properties of CO{sub}2 at quasi critical point may limit heat exchange rate of recuperator due to the onset of pinch point inside recuperator. Taking such pinch problem into consideration, the cycle efficiency of Brayton cycle is assessed and is found limited to 39%. As an alternative recompression cycle is investigated and operable range has been identified. It is revealed that the recompression cycle is a promising candidate and may achieve the cycle efficiency no less than 45% under a typical operating condition of pressure of 20MPa and temperature of 823.2K at turbine inlet, and temperature of 308K at compressor inlet and temperature effectiveness of 98% at recuperators together with an optimal choice of both parameter values, turbine expansion ratio of 2.5 and bypass ratio of 0.32. Parametric study is carried out. In neither compressor nor turbine, deteriorated adiabatic efficiency may affect cycle efficiency. However, pressure drop characteristics of heat exchangers govern the cycle efficiency.