Objective Supersonic separation is a new gas purification and fuel gas processing technology based on contraction-expansion nozzle. The cyclone in the post-swirl supersonic separator is usually set in front of the diffuser section, which is easy to induce the positive shock wave and destroy the low temperature environment inside the separator. Moreover, the shock wave is difficult to control. Therefore, this study intends to reduce the impact of shock waves by optimizing the structure.

Methods Firstly, based on the principles of thermodynamics and aerodynamics, a shock wave control theory for a rear-swirl supersonic separator was proposed. Secondly, according to the theory, a trans-swirl structure which could control shock waves was designed, and a universal design formula for the structure was established. Thirdly, through numerical simulation, the effects of three important structural parameters on the shock waves control were analyzed, namely, the dip angle of the trans-swirl structure, the length of the gradually expansion section and the twist angle of the cyclone blade.

Results The separator had the best performance when the dip angle of the trans-swirl structure was set to 3.3°, the length of the gradual expansion section was set to 107 mm, and the blade torsion angle of the cyclone was set to 120°.

Conclusions Compared with the traditional cyclone post-separator, the addition of the trans-swirl structure can ensure that the fluid flow area continues to increase in the gradual expansion section, thereby achieving effective control of shock waves and improving the condensation and separation efficiency.