In this study, we performed both experimental and numerical investigations of cyclopentane sprays in a transcritical environment, aiming to explain the complex phase change and mixing of sprays. Employing three optical diagnostics techniques, shadowgraphy (SH), Mie scattering (MS), and infrared radiation (IR), we investigated the differences between subcritical and transcritical sprays. The combined SH and MS images distinctively separated the liquid-core region from other phases such as gaseous and supercritical phases. The MS results provided detailed information on droplet behavior, showing the effects of injection and chamber conditions on droplets along the axis. Furthermore, the IR results revealed differences in the spray pattern after evaporation depending on the chamber pressure, whereas the other methods did not. Complementing the experiments, large-eddy simulations (LES) based on the vapor-liquid equilibrium (VLE) assumption were conducted. Four subgrid turbulence models—WALE, Vreman, Smagorinsky, SES—were compared, which predict slightly different mixing behaviors. Despite some discrepancies, such as narrower spray widths in the numerical models, the trends in vapor mass fraction from LES well predict the two-phase region in axial direction, as observed in the experimental results. In conclusion, integration of experimental techniques and LES revealed distinct characteristics of phase transition and mixing of transcritical sprays.      «

In this study, we performed both experimental and numerical investigations of cyclopentane sprays in a transcritical environment, aiming to explain the complex phase change and mixing of sprays. Employing three optical diagnostics techniques, shadowgraphy (SH), Mie scattering (MS), and infrared radiation (IR), we investigated the differences between subcritical and transcritical sprays. The combined SH and MS images distinctively separated the liquid-core region from other phases such as gaseous...     »