Energy sources in heat engine cycles

Thermal energy is, by definition, the source of useful energy (work) in a heat engine. The source of thermal energy is a heat-producing chemical reaction between the substances comprising the working mass of a heat engine, or between additional substances introduced. Heat-producing chemical reaction is called combustion reaction. A combustion reaction involves two types of substances: fuels and oxidants. The products of combustion reaction comprise the working mass of the thermodynamic cycle on its expansion stage, yielding useful energy (work). Energetic characteristics of combustion product generation processes are available for engineering and scientific purposes. There is a system of equations developed in chemical thermodynamics that determine the resulting products and energetic parameters of a reaction. To calculate heat engine cycles, it is necessary to obtain the characteristics of combustion products (thermodynamic properties - heat capacity, specific gas constant) and the maximum temperature levels of reaction products. The article provides an overview of approaches to determine the thermodynamic properties of combustion products and lists the values of these parameters for the most widespread fuels when combusted in air.