Energetic and Exergetic Investigation of Regenerative Gas Turbine Air-Bottoming/Steam -Bottoming Combined Cycle

Abstract

The present study is a thermodynamic analysis of a Regenerative Air-Bottoming combined (RABC) cycle /Steam bottoming combined (RABC) cycle operated by the exhaust gases the topping gas turbine cycle. The fractional mass of exhaust gases passes through the first heat exchanger where it exchanges heat with the compressed air from the air compressor of topping cycle and remaining amount of exhaust gasses passes through a second heat exchanger where it uses to supply heat to RABC cycle or third heat exchanger where it uses to supply heat to RSBC cycle. The energetic and exergetic performance of RABC cycle and RSBC cycle is investigated using turbine inlet temperature (1000 K⩽ TIT⩽1500 K) and mass fraction of exhaust gas (0⩽x⩽1) of the topping cycle as the input variables.  The work net output attained its peak value at x=0 which is 22.1 % to 27.3 % for RABC cycle and 22.7 % to 21.5 % for RSBC cycle whereas the maximum thermal efficiency and minimum specific fuel consumption is observed at x=1. Also exergy loss by exhaust gases is minimum at x=0 for both RABC cycle and RSBC cycle. Finally, it is concluded that for the maximum work net output and minimum exergy loss by exhaust gases, RABC cycle is the best option followed by RSBC cycle but for optimum thermal efficiency and minimum specific fuel consumption purely regenerative gas turbine cycle have no comparison with RABC cycle and RSBC cycle.