Impact of the Secondary Air System Compressor on the Performance of a Pressure Gain Combustion Gas Turbine

Detonation-based combustion systems for application in gas turbines (GTs) have received growing attention in recent decades. Such a technology leads to higher thermodynamic cycle efficiency compared to the conventional deflagrative solution as a result of pressure rise occurring during the heat addition process. This study aims to implement pressure gain combustion (PGC) into a thermodynamic cycle where the main compressor is operated at a lower pressure ratio compared to the Brayton–Joule cycle. In detail, this study focuses on the impact of the secondary air system (SAS) compressor, which is necessary to correctly feed the blade cooling circuits with adequate pressure as well as to deliver high-pressure air for cooling the PGC system. A parametric analysis based on different amounts of cooling air to the PGC system is proposed and discussed. In detail, the power demand by the SAS compressor can be as high as 5–6% of the net PGC GT power output, with maximum demands calculated in the range from 16 to 22 MW for a 335 MW F-class gas turbine. These figures are significant because the higher they are, the greater the risk of reducing the performance advantage introduced by the pressure gain combustion. In addition, the effects of SAS compressor efficiency are investigated and a preliminary assessment of both size and rotational speed of the SAS compressor is proposed as well.