Semi-closed supercritical CO₂ (sCO₂) gas turbine is a promising candidate for the next generation power cycles with high efficiency and almost 100% carbon capture. In this study, the multicomponent effects on the sCO₂ systems are investigated. A real-fluid modeling framework based on the vapor-liquid equilibrium (VLE) theory is implemented to predict the phase boundary and real mixture critical point, and to capture the phase separation in computational fluid dynamics (CFD) simulations. A novel VLE-based tabulation method is developed to make the CFD solver computationally more affordable. VLE-based thermodynamic analyses show that a small amount of combustion-relevant impurities (e.g., \(\text {H}_{2}\text {O}\), \(\text {CH}_{4}\), and \(\text {O}_{2}\)) can significantly elevate the mixture critical point of the \(\text {sCO}_{2}\) systems. As a result, the so-called “supercritical” \(\text {CO}_{2}\) systems might be in the subcritical two-phase zone where phase separation occurs. At the relevant conditions in this study (100–300 bar), phase separation only has a small influence on the \(\text {CO}_2/\text {H}_{2}\text {O}/\text {CH}_{4}/\text {O}_{2}\) mixture density, but has a considerable influence on the heat capacity of the mixture. VLE-based CFD simulation of a laminar premixed \(\text {sCO}_{2}\) shock tube shows that expansion waves can trigger significant condensation in the systems and the latent heat of the condensation can change the temperature and density fields in the systems. To understand the phase separation during mixing, VLE-based large-eddy simulations (LES) of turbulent jet-in-crossflows in the \(\text {sCO}_{2}\) systems are conducted, and the results show that when two subcritical gas or supercritical gas-like streams mix, the mixture can partially condense to subcritical liquid phase. Higher pressure, lower temperature, and higher \(\text {H}_{2}\text {O}\) concentration can enhance the phase separation phenomenon in the systems.

半封闭超临界 CO ₂ (sCO ₂ ) 燃气轮机是具有高效率和几乎 100% 碳捕获的下一代动力循环的有希望的候选者。在本研究中，研究了多组分对 sCO ₂系统的影响。采用基于汽液平衡 (VLE) 理论的真实流体建模框架来预测相边界和真实混合物临界点，并在计算流体动力学 (CFD) 模拟中捕获相分离。开发了一种新的基于 VLE 的制表方法，以使 CFD 求解器在计算上更实惠。基于 VLE 的热力学分析表明，少量与燃烧相关的杂质（例如，\(\text {H}_{2}\text {O}\)，\(\text {CH}_{4}\)和\(\text {O}_{2}\) ) 可以显着提高\(\text {sCO}_{2}\的混合临界点)系统。因此，所谓的“超临界” \(\text {CO}_{2}\)系统可能处于发生相分离的亚临界两相区。在本研究的相关条件下（100-300 bar），相分离对\(\text {CO}_2/\text {H}_{2}\text {O}/\text { CH}_{4}/\text {O}_{2}\)混合物密度，但对混合物的热容量有相当大的影响。基于 VLE 的层流预混\(\text {sCO}_{2}\)的 CFD 模拟激波管表明膨胀波可以引发系统中的显着冷凝，冷凝的潜热可以改变系统中的温度和密度场。为了理解混合过程中的相分离，对\(\text {sCO}_{2}\)系统中的湍流横流射流进行了基于 VLE 的大涡模拟 (LES)，结果表明，当两种亚临界气体或超临界气体流混合，混合物可以部分冷凝为亚临界液相。较高的压力、较低的温度和较高的\(\text {H}_{2}\text {O}\)浓度可以增强系统中的相分离现象。