Commercially available gas turbines have been mostly designed based on the simple Brayton cycle and despite the enormous advancements made in their components design, materials technology, blade cooling methods, etc., thermodynamic performance achievable for this simple cycle is limited. Numerous variants to the basic Brayton cycle viz., Recuperated (REC), Inter-Cooled (IC), Re-Heat (RH), steam injected (STIG) and their combinations have been proposed, extensively discussed in the literature since the early stages of gas turbine development and few of them have been successfully implemented. New variants not yet implemented in commercial engines and still in various stages of the development with potential for additional performance improvement are: advanced Steam Injected cycle and its variants (such as Inter-cooled Steam Injected, (ISTIG)), Recuperated Water Injection cycle (RWI), Humidified Air Turbine (HAT) cycle and Cascaded Humidified Advanced Turbine (CHAT) cycle, Brayton cycle with high temperature fuel cells (Molten Carbonate Fuel Cells (MCFC) and Solid Oxide Fuel Cells (SOFC)) and their combinations with the available modified Brayton cycles. The main objective of this paper (Part 1 of the two-part paper) is to provide a comprehensive review of high performance (with most promising solutions) complex gas turbine cycles, describing their main characteristics, benefits and drawbacks in comparison with the simple Brayton cycle. Detailed parametric thermodynamic cycle analyses for the selected high efficiency cycles under development are presented in Part 2 of this paper.

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