Thermodynamic analysis of a gas turbine cycle with direct recuperation based on a multistage compressed mass storage process

Gas turbines typically employ combined cycles owing to high exhaust temperature; however, the complex bottoming cycle often constrains system flexibility. In this study, we explored the different methods for utilizing exhaust heat in gas turbine cycles, and found that the residual heat absorption efficiency of the bottoming cycle and power consumption of the compression process were the main factors affecting heat recovery. The closer the approach to isothermal compression, the lower the power consumption of the compression process. Intercooling, a typical approach toward isothermal compression, was primarily constrained by declines in pressure. To address this constraint, we developed a new approach toward coupling the multistage compressed mass storage process, significantly reducing losses in pressure. The resultant decline in pressure during intercooling ranged from 0.01–0.1 MPa, while in this new approach, the decline during heat transfer was < 0.001 MPa. This is a theoretical breakthrough. Meanwhile, coupling the multistage compressed mass storage process increased the thermal efficiency of the cycle by 1.34–4.5 % compared to the one-stage intercooling cycle, and by 2.64–8 % compared to the two-stage intercooling cycle. This study thus provided a foundation for constructing gas turbine cycles using direct recuperation.