Performance enhancement of the gas turbine combined cycle by simultaneous reheating, recuperation, and coolant inter-cooling

The simultaneous use of gas turbine reheating and recuperation is favorable for improving the efficiency of the gas turbine combined cycle (GTCC). However, less power output is obtained from the combined cycle with both reheating and recuperation than with only reheating. Three cases of coolant cooling were analyzed to compensate for the power deficit and improve the efficiency: coolant inter-cooling, coolant pre-cooling, and conventional inter-cooling. The cycle with gas turbine reheating, recuperation, and coolant inter-cooling (RCRHCC-CIC) was predicted to be the most efficient among the three cases and showed higher efficiency than the conventional simple-cycle GTCC. In addition, scenarios of both the cycle improvement and required enhancements of the design parameters of components were investigated to achieve 67% cycle efficiency. RCRHCC-CIC achieved 67% efficiency with less enhancement of the component parameters in comparison to the simple-cycle GTCC, including 2% points less compressor efficiency and a more than 10% smaller flow path diameter. In conclusion, RCRHCC-CIC could be a possible option to reach the next level of GTCC efficiency goals. •The impact of topping cycle improvements on the gas turbine combined cycle performance was investigated.•The synergistic use of reheating, recuperation, and coolant inter-cooling was investigated.•Coolant inter-cooling compensates for the power loss due to recuperation and enhances efficiency.•The proposed cycle enables 67% efficiency with mild advances in gas turbine components.•It also alleviates a large increase in blade speed required in the simple-cycle gas turbine.