Energy and exergy analysis of gas turbine combined cycle with exhaust gas recirculation under part-load conditions

This paper presents the energy and exergy analysis of the gas turbine combined cycle during part-load operation under the exhaust gas recirculation - inlet/variable guide vane control (EGR-IGVC) strategy. The exergy destruction across each component and the energy and exergy efficiency of the topping, bottoming, and combined cycle are determined. Results show that EGR-IGVC and IGVC both effectively enhance the part-load efficiency of the combined cycle compared to fuel flow control (FFC) because higher turbine exhaust temperature allows more exergy to enter the bottoming cycle and increases bottoming cycle power output. However, EGR-IGVC decreases the bottoming cycle energy and exergy efficiency compared with IGVC. Even so, EGR-IGVC increases the topping cycle energy and exergy efficiency and can obtain a higher bottoming cycle power output. The combined cycle efficiency is enhanced by 0.97–1.21 percentage points over IGVC at 40 %–90 % loads. Exergy analysis has important guiding significance for further improving the part-load performance of the combined cycle.