A novel coolant cooling method for enhancing the performance of the gas turbine combined cycle

The turbine inlet temperature (TIT) has a significant effect on the performance of gas turbines, and enhanced cooling methods are being applied to the latest gas turbines to increase this temperature. The coolant pre-cooling (CPC) is also used to improve the cooling performance. In this study, coolant inter-cooling (CIC) is proposed to reduce the coolant temperature and improve the gas turbine performance further. The air required for turbine cooling is extracted from the middle of the compressor, cooled, and pressurized by a separate compressor. This decreases both the coolant temperature and the power needed to compress it. The effect of CIC on the performance of a combined cycle power plant was analyzed in comparison with the conventional CPC method using an H-class gas turbine. A heat recovery system was considered to collect the heat wasted in the coolant cooling process and generates additional steam in the bottoming cycle. Various locations of the water source for the heat recovery were compared, and the optimal ones were selected. The proposed method enables higher power output and efficiency in a combined cycle power plant than the CPC method.