The direct-fired supercritical CO2 (sCO2) cycle is currently considered as a zero-emission power generation concept. It is of interest to know how to optimize various components of this cycle using computational tools, however, a comprehensive effort on this area is currently lacking. In this work, the behavior of thermal properties of sCO2 combustion at various reaction stages has been investigated by coupling real gas CHEMKIN (CHEMKIN-RG) with an in-house Premixed Conditional Moment Closure (PCMC) code and the high pressure Aramco-2.0 kinetic mechanism. Also, the necessary fundamental information for sCO2 combustion modelling is reviewed.
The Soave-Redlich-Kwong equation of state (SRK EOS) is identified as the most accurate EOS to predict the thermal states at all turbulence levels. Also, an empirical model for the compression factor Z is proposed for sCO2 combustors, which is a function of mixture inlet conditions and the reaction progress variable. This empirical model is validated between the operating conditions 250–300 bar, inlet temperatures of 800–1200 K and within the current designed inlet mole fractions and the accuracy is estimated to be less than 0.5% different from the exact relation. For sCO2 operating conditions the compression factor Z always decreases as the reaction progresses and this leads to the static pressure loss between inlet and exit of the sCO2 combustor.
Further, a review of high pressure viscosity and thermal conductivity models of mixtures and pure-components are presented from the literature and suggestions are made for their adoptability in sCO2 combustor simulations. The thermal properties such as specific heats, speed of sound, pressure exponent and isothermal compressibility are accurately quantified.