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Wet natural gas widely exists in the natural gas industry, and the selection of throttling devices plays an important role in wet natural gas transportation. In order to study the flow field characteristics of different throttling devices in wet natural gas pipelines, a set of Laval nozzles, orifice plates, and plate valves have been designed. The standard k-ε model was selected for numerical simulation. By changing inlet pressure, inlet temperature or volume fraction of water-liquid, the pressure field and temperature fields of different throttling devices were obtained, and the influence of the presence of a shockwave on the flow fields of the throttling devices was analyzed. Different throttling devices have significantly different operating characteristics. Therefore, appropriate throttling devices should be selected in different conditions in order to control the pressure of wet natural gas transportation and reduce gas hydrate formation. The present simulation results show that under identical conditions, the throat pressure and temperature of the Laval nozzle are the lowest, the throat pressure of the orifice plate is the highest, and the throat temperature of the plate valve is the highest.

In order to reveal the supersonic condensation characteristics of carbon dioxide (CO 2 ) in natural gas under low temperature condition, the mathematical models and numerical schemes for the CH 4 -CO 2 mixture gas under supersonic flow condition were established, and the influence of inlet CO 2 concentration on the CO 2 removal efficiency of Laval nozzle was investigated. The results show that with the increase of CO 2 concentration at nozzle inlet, the initial nucleation position is closer to nozzle throat, the maximum nucleation rate and the droplet number decrease but the droplet radius increases significantly, which eventually leads to an increase in liquefaction rate. When the inlet CO 2 mole fraction is lower (less than 10%), the CO 2 fraction in gas phase is almost 0, which indicates that low-temperature separation technology is practicable for the removal of CO 2 from natural gas.