Quantitative experiment and numerical simulation on sub-critical and supercritical CO2-N2 multiphase jet flows

Supercritical fluid jets have found widespread applications in industrial fields such as aerospace propulsion and fuel mixing enhancement. Due to the complex property variations of fluids in these practical applications, accurately capturing the flow characteristics in multiphase jet processes has become a significant challenge. In this study, the high-precision non-contact measurement technique is combined with numerical simulation to realize quantitative measurement and analysis under sub/supercritical conditions. The study shows that the simulation accurately depicts the jet characteristics and verifies the feasibility of the numerical simulation method. Under subcritical conditions, the jet interface is clearer, and the mixing is dependent on the entrainment of the turbulent shear layer, with large instability and local oscillations. Under subcritical conditions, the jet interface appears clearer, and mixing is influenced by the entrainment of the turbulent shear layer, characterized by significant instabilities and local oscillations. Under supercritical conditions, the density distribution becomes smoother, leading to enhanced mixing and diffusion of fluids. This phenomenon is closely associated with the higher diffusivity and lower surface tension of supercritical fluids. Jets in this state are governed by a diffusion mechanism involving high-density CO₂ and low-density N₂, resulting in more ambiguous interfaces between the fluids due to the solubility of supercritical CO₂. This study aims to elucidate the flow behavior of supercritical multiphase jets, thereby providing a theoretical foundation and experimental support for related industrial applications.