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Non-equilibrium condensation can result in thermodynamic losses within turbine stages and potentially cause blade erosion. During turbine operation, steam frequently carries foreign particles, which can influence non-equilibrium condensation. However, there is a lack of systematic research on the specific effects of these particles on the condensation processes. This paper firstly utilizes OpenFOAM to establish a homogeneous-heterogeneous condensation coupling model, which is validated for accuracy through experimental data. Secondly, it investigates the effects of NaCl particle concentration and radius on the heterogeneous condensation process in Laval nozzles and Dykas cascades. Finally, it examines the relationship between the kinetic energy ratio, condensation loss ratio, wetness fraction ratio, and particle concentration and radius in turbine cascades to explore the optimal method for reducing the impact of condensation phase change in steam turbines. The results indicate that nucleation rate decreases as particle radius decreases and concentration increases in Laval nozzle. However, the effect of concentration on wetness is non-linear; as concentration increases, wetness initially decreases before increasing. In comparison to homogeneous condensation within Dykas cascades, when the introduced particle radius is 1 × 10−9 m and the concentration is 1014kg−1, the kinetic energy increases by 2.93%, condensation loss decreases by 22.91%, and wetness fraction decreases by 23.64%. • The homogeneous-heterogeneous condensation coupling model was developed utilizing OpenFOAM. • The research explored the impact of NaCl particle concentration and radius on heterogeneous condensation flow. • Optimal concentration and radius to mitigate the effects of wet steam condensation in turbine cascade were identified. • In the optimal scenario, wetness decreased by 23.64%, and condensation loss decreased by 22.91%. [ABSTRACT FROM AUTHOR]

• The nucleation and growth pathways of CO 2 clusters are illustrated at the molecular level. • The thermodynamic and kinetic characteristics of the CO 2 condensation are obtained. • High pressure and low temperature increase nucleation rate and accelerate cluster growth. • The differences between the simulated and theoretical values of nucleation rates are compared. The potential of supersonic separators to remove CO 2 from natural gas has received extensive attention. However, microscopic understanding of the condensation mechanism of CO 2 in natural gas and the applicability of classical nucleation theory (CNT) is unclear. In this study, we investigated the condensation characteristics of CO 2 gas by using computational fluid dynamics (CFD) and molecular dynamics (MD) simulations with a CH 4 -CO 2 mixture gas. The nucleation and growth pathways of CO 2 are elucidated from the molecular scale. The results show that the Laval nozzle creates low-temperature conditions for CO 2 liquefaction, and that reducing the inlet temperature and increasing the inlet pressure will create more favorable conditions for condensation. In the nucleation stage, CO 2 gas molecules collide to form clusters, releasing large amounts of latent heat, leading to repeated condensation and evaporation of CO 2 gas, and the stability of the clusters depends on the energy interactions with surrounding molecules. With higher initial pressure and lower cooling temperature, the nucleation phase duration is shortened, the nucleation rate increases, and the cluster growth is accelerated. In addition, CNT deviates from the MD simulation results by 3 ∼ 4 orders of magnitude, and reasonable corrections to the CNT will be made subsequently by combining the results of many MD simulations. [ABSTRACT FROM AUTHOR]

Due to the cooling effect of natural gas throttling, spontaneous condensation will occur in the throttle valve, which may affect pipeline system efficiency. However, the condensation characteristics (such as nucleation rate and condensation rate) remain unclear, and the traditional method based on the isenthalpic hypothesis can hardly solve this non-equilibrium issue. Based on the geometry differences between the throttle valve and the Laval nozzle, this paper explored the condensation parameters of the CH 4 –C 2 H 6 binary mixture in the throttle valve and the Laval nozzle using CFD techniques (solving non-equilibrium condensation at a lower cost). This paper discussed the influence of the inlet pressure and inlet temperature on the spontaneous condensation process in the throttle valve as well. The findings are that the nucleation and droplet growth regions in the throttle valve are closer to the throat but narrower than that of the Laval nozzle, and the liquid mass fraction decreases after reaching the peak value. The onset of droplet nucleation and droplet growth is closer to the throat when increases inlet pressure or decreases inlet temperature. The condensation rate of ethane in the throttle valve is lower than that in the Laval nozzle, and the sensitivity of the nucleation rate and the Wilson point to the inlet parameters is higher and lower than that in the Laval nozzle, respectively.. The main innovation of the paper lies in revealing the differences in the condensation between the throttle valve and the Laval nozzle using the non-equilibrium method. • A 2D transient CFD model of condensation of the CH 4 –C 2 H 6 mixture in the throttle valve was developed. • The condensation regions in the throttle valve are earlier than those in the Laval nozzle under the same conditions. • The condensation in the throttle valve occurs in a narrow region behind the throat unlike the Laval nozzle. • The condensation rate of C 2 H 6 positively and negatively correlates to the inlet pressure and temperature, respectively. [ABSTRACT FROM AUTHOR]