Effect of linetype of convergent section on supersonic condensation characteristics of CH4-CO2 mixture gas in Laval nozzle

The Laval nozzle is an important part of the supersonic separator, which structure determines the separation efficiency of supersonic separator. In order to study the flow and condensation process in Laval nozzle with different convergent section, convergent section is designed by Bicubic parametric curve, Quintic polynomial curve, Witoszynski curve and Translation of Witoszynski curve, respectively. The numerical model for the supersonic condensing flow process of CH4-CO2 mixture gas is established and the User Define Function is invoked for numerical simulation. The effects of different linetypes of convergent section on the flow and condensation parameters in nozzle were investigated. The results confirm the Laval nozzle designed by Translation of Witoszynski curve has strengths such as the most stable pressure change, the best refrigeration effect, the most intense spontaneous condensation, and the nucleation rate is 1.610×1022m−3s−1, the number of droplets is as high as 2.023×1015m−3 at the nozzle outlet far better than the other nozzles. Therefore, Translation of Witoszynski curve is recommended to design the convergent section of Laval nozzle in supersonic separator.