Investigation of CO2 condensation characteristics in nozzle based on Witoszynski curve equivalent centrosome model

Supersonic separation technology enables efficient carbon capture, incorporating supersonic fluid dynamics, swirling flow, and enhanced gas-liquid heat and mass transfer processes. The nozzle is the key place to realize the above method, and its structure greatly affects the gas flow and condensation characteristics. To solve the problems of difficulty, accuracy, and high cost of traditional nozzle inner surface machining, a nozzle structure with centroid and straight pipe segment was proposed. Based on droplet growth and classical nucleation theory, a spontaneous condensation model of CH₄-CO₂ mixture gas was established and the spontaneous condensation process of CO₂ was analyzed. The findings indicated that the CO₂ liquefaction efficiency in this structure can reach 42.5 %. A swirling condensation model is established, and the influences of swirling and inlet parameters on condensation parameters are considered. The findings indicate that: compared with the increase in inlet CO₂ concentration and reduced inlet temperature, the increase in inlet pressure has a more obvious effect on improving the liquefaction effect. When the pressure is increased from 4 MPa to 7 MPa, the liquefaction efficiency is increased from 26.1 % to 60.1 %, which is increased by 1.30 times. The above research helps promote the application of supersonic swirl separation technology.