Effects of inlet parameters on the supersonic condensation and swirling characteristics of binary natural gas mixture

Highlights: • A mathematical model for supersonic condensation of binary gas was established. • Supersonic spontaneous condensation process of binary gas was investigated. • Influence of inlet parameters on the swirling capacity of the nozzle was studied. -- Abstract: This paper aims at clarifying the characteristics of spontaneous condensation of natural gas under the swirl condition and obtaining the influence mechanism of the inlet parameters on the condensation and swirling characteristics. A swirl nozzle with a central body was designed, and the condensation characteristics of a methane-ethane binary mixture under supersonic swirling conditions were numerically studied by using the gas-liquid governing equations, internally consistent classical nucleation theory, Gyarmathy's droplet growth model, and Reynolds stress turbulence model. The results show that with the decrease of the inlet temperature and the increase of the inlet pressure, the condensation position moves toward the nozzle inlet, the maximum nucleation rate, droplet radius and outlet humidity of methane-ethane binary mixture increase. When the temperature rises from 250 K to 270 K, the speed increases about 2 m/s, which indicates that the increase of the inlet temperature can increase the tangential velocity in the nozzle and promote the separation of the droplets from the dry natural gas. At the same time, it is found that with the increase of the inlet pressure, the tangential velocity remains unchanged.