The advantage of ＇＇chemical＇＇ energy is determined by the process in which the combustion is integrated as part of the process. If the gas turbine process is considered as typical example, then the conversion of the fuel energy into technical work is the primary process objective. As the combustion, as is well-known, is highly irreversible, the following question has to be clarified: How is the relevant portion of the irreversibility due to combustion to be defined? As exergetic analysis will not lead to the objective in this case, as this one does not take the existing process limitations into consideration. The thermodynamic modelling of the combustion therefore has to take place within the framework of the total process. In this way, the influence of the combustion on the ＇＇profile of the irreversibility＇＇ of the considered process can be shown.