A fast and efficiency numerical simulation method for supersonic gas processing

Supersonic swirling separation technology is an innovative gas conditioning technology to separate heavy hydrocarbon and water vapor from the natural gas. The Laval nozzle, where the condensation occurs, is used to generate supersonic flow and achieved a high degree of supersaturation in natural gas dehydration unit. Therefore, the nozzle shape has a strong impact on the non-equilibrium phase transition and plays a decisive role to the distribution of the nucleation and the growth rate. To optimize the structure of the Laval nozzle and achieve higher separation efficiency, numerical simulation plays an important role in accelerating development cycles and cutting down the cost of experiment. In this paper, to avert the complexity of using the multiphase models and real gas model, a quick and efficiency method is validated and used to determine the location of the nucleation zone and the droplet growth zone. The corrected Internally Consistent Classical Theory (ICCT) model and Gyarmathy model (gya82) were employed to the numerical simulation of a condensing Laval nozzle flow by coupling the N-S equation and condensate mass equation at different nozzle pressure ratios (NPR) and initial supersaturations. The results show that, in a supersonic expansion Laval nozzle flow, high cooling rate results in a high value of supersaturation and nucleation rate. When condensation occurs, the flow is affected by the latent heat released and the total temperature is increased. This method can accurately predict the distribution of the condensing flow parameters, find an optimized flow state to obtain larger droplet, and assure the latent heat released is moderate to maintain a steady flow. Finally, this method is applied to the numerical simulation of a full-scale supersonic swirling separator flow field under different work conditions.