Value of closed-cycle gas turbines with design assessment

Abstract

Currently, there is considerable interest in the design and development of closed-cycle gas turbines to exploit its various advantages like heat source adaptability, fuel flexibility, compactness, etc. In the current context of depleting fossil fuels, there is an inevitable need to make use of renewable energy sources like solar energy. A detailed review of closed-cycle gas turbines is carried out in this paper. Three research gaps have been identified on closed-cycle gas turbines and are addressed. A thermodynamic analysis of a recuperated closed Brayton cycle with and without intercooling has been carried out with different working fluids to study their effect on cycle efficiency and net specific power. The analysis shows that supercritical carbon dioxide gives considerably higher efficiencies at mild turbine inlet temperatures of 400–700 °C. Helium can be considered at higher temperatures. The main objective of the current study is to survey closed-cycle gas turbine designs from literature and bring those designs with multiple fluids on to one platform: in the form of two unique charts which can be used as turbomachinery design assessment tools for different closed-cycle gas turbine working fluids. Enthalpy-mass flow rate-diameter chart is created for the compressors and turbines, clearly showing the zones of various working fluids at a glance. The specific speed and specific diameter values are calculated for the turbomachinery designs of different working fluids, and the selected values are superimposed on the Balje’s specific speed- specific diameter charts to see their regimes.