The purpose of this paper is to study and analyze the gas turbine engine and the thermodynamic cycle of a gas turbine. The article describes the processes of influence of the working fluid composition on the parameters of the main energy gas turbines, depending on the composition of the fuel gas. The calculations of the thermal scheme of a gas turbine, which were made using mathematical modeling, are given. As a result of research on the operation of the GE PG1111 6FA gas turbine installation with various gas compositions, it was established that when the gas turbine is operating on different fuel gases, the engine efficiency changes. The gas turbine efficiency indicators were determined for various operating parameters and fuel composition. The impact of fuel components on the equipment operation is revealed.