An energetic analysis of a gas turbine with regenerative heating using turbine extraction at intermediate pressure - Brayton cycle advanced according to Szewalski's idea

Highlights: • The gas turbine cycle with regenerative heating using turbine extraction at intermediate pressure is modeled and calculated. • Constant TIT and varied intermediate pressure or extraction mass flow rate have been compared and discussed. • Two thermodynamically performance estimation tools for GT cycles are comprised. • The implementation of mathematical model in the in-house 0D code termed COM-GAS is presented. -- Abstract: In this paper, a modification of a simple gas turbine into the Brayton cycle with regenerative heating, using turbine extraction at intermediate pressure, is presented. The main concept of the retrofitting is based on the transfer of heat from the turbine exhaust gases to the air entering the combustion chamber. The extracted gas transfers heat to air via the divided regenerative heat exchanger and after that is compressed and mixed with additional air. The efficiency gain is dependent on the extraction intermediate pressure and the extraction mass flow rate. The mathematical model of the proposed cycle and its implementation in an in-house code termed COM-GAS is presented. This zero-dimensional robust model allows the prediction of basic parameters such as temperatures, combustion composition, efficiency, and other related factors. Numerical simulations of both basic models with either semi-perfect or real gases based on thermodynamic tables were compared with available exploited data, and differences between this study and others did not exceed 5%. Contrarily, differences between gas turbine cycle with regenerative heating are visible between the two models. In particular, when using the coupled classical regeneration with regeneration according to Szewalski's idea, the integrated cycle efficiency could be significantly increased up to 39.5%.