Abstract
The working mediums in the gas turbine systems are: atmospheric air, natural gas and exhaust gases. For the detailed analysis of thermodynamic performance and values at characteristic points of the cycle it is necessary to know the relations defining: specific volume, specific isobaric and isochoric heat capacity, isentropic exponent, specific enthalpy and specific entropy. Mathematical models of thermodynamic parameters for the mentioned mediums were developed based on dependencies for mixtures of ideal and semi-ideal gases. The functions obtained for semi-ideal gas mixtures were extended by pressure correction factors derived from the Redlich-Kwong and Peng-Robinson equations of state. The thermodynamic parameters of the working mediums were dependent on the mass fractions of the components, temperature and pressure. Developed models approximated the behaviour and parameters of real gas mixtures. All calculation algorithms were implemented and optimized using appropriate numerical methods in the Python programming environment. As a result, mathematical models of working mediums for the gas part of the combined cycle gas turbine system were obtained.
Highlights
Modelling thermal-flow systems should be started with precise identification of working mediums of the cycle
Mathematical models of all working mediums were implemented in such a way that thermodynamic parameters were a function of: mass/molar fractions of components, temperature and pressure
Individual computational modules were developed for each working medium. They consisted of functions and calculation algorithms, which on the basis of input data determined the values of thermodynamic parameters
Summary
Modelling thermal-flow systems should be started with precise identification of working mediums of the cycle. More advanced and complex physical models for working mediums should be used to achieve better accuracy and more precise results These models are usually based on the real gas equations of state [2,3,4]. In this work the Redlich-Kwong and Peng-Robinson equations of state were used This required the determination of additional physic-chemical parameters for pure compounds (critical conditions and acentric factors [3, 5,6,7,8], binary interaction parameters [9, 10]), properties of mixtures [2, 3, 9, 10] and analytical or numerical dependencies resulting from the mentioned equations [1, 4]
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