Thermodynamic Design Point Study of a Semi-Closed Recuperated Intercooled Gas Turbine Combined With a Rankine Bottoming Cycle

Abstract

A design point study of a semi-closed recuperated intercooled gas turbine combined with a closed, unfired, Rankine cycle is presented to demonstrate the overall thermodynamic design and efficiency tradeoffs for this type of cycle. Through its semi-closed design, having control over combustor equivalence ratio and recirculation flow exit pressure, this cycle provides improvements in emissions, specific power (net system power output divided by gas turbine inlet airflow), part power thermal efficiency, and overall system size relative to a combined cycle with an open cycle gas turbine. The relationship of design variables to cycle and component selection is discussed. Interface heat exchanger configuration, along with bottoming cycle choices of regeneration, feedwater heating, and fluid (H2O or DOWTHERM®A) are evaluated to determine their effects on mechanical design and thermal efficiency.