SUMMARY

The supercritical carbon dioxide power cycle has gained attention for its high cycle efficiency, wide operating conditions, and low footprint. Despite these merits, one of the bottlenecks in the power cycle is the utilization of supercritical fluids near the critical point, a region with drastic nonlinear property variations. More experimental and computational analysis requires to be performed to fully understand the effect of the nonlinear property variations to flow behaviors, which ultimately influences the cycle component performances. The main motivation of this study stems from two parts: providing an experimental basis of supercritical conditions near the critical point and filling a gap in classical mixing layer research with mixing fluids experiencing drastic property variations. The objectives of this thesis are to build an experimental platform that can conduct mixing parameter exploration of supercritical fluids shear layer mixing, set up laser-based diagnostics for flow visualization, and investigate supercritical regime mixing to assess the impact of nonlinear property variations on the turbulent shear-driven mixing behavior. A high-pressure test chamber and supporting closed-loop cycle facilities with flow visualizations using the Schlieren technique and spontaneous Raman scattering are constructed to extract turbulent shear layer mixing characteristics. Through these two visualization techniques, experimental studies explored the impacts of thermodynamic conditions and mixing parameters through a range of density ratio and velocity ratios at multiple isobars. The change of thermodynamic conditions has a significant impact on altering the overall mixing behavior due to the nonlinear property variations and the position of the pseudocritical point. Though the density ratio did not have much influence due to the logarithmic law, the entrainment ratio of two flows contributed to the difference in the overall mixed composition of supercritical fluids.