Non-equilibrium condensation of water vapor in sonic nozzle

The non-equilibrium condensation phenomenon during the operation of sonic nozzle is very complicated, and will affect the flow measurement and control of sonic nozzle. Two-dimensional multi-fluid k-epsilon turbulence models for both homogeneous and heterogeneous nucleation of condensation were constructed to investigate the effect of vapor condensation on mass flow-rate of sonic nozzle. These models were validated by experimental data of homogeneous nucleation in the moist nitrogen flow through a convergent-divergent nozzle by Wyslouzil and the numerical solutions of heterogeneous nucleation in wet steam flow by Dykas respectively. Finally, both models above were applied to study the condensation flow in sonic nozzle. It was showed that the discharge coefficient of sonic nozzle is affected by both homogeneous and heterogeneous nucleation. When the flow is homogeneous, there is significant influence on discharge coefficient with high inlet relative humidity, which agrees with the thermal choking theory. The discharge coefficient deviation reaches 0.275% when the inlet relative humidity is 95%, which is close to the Lim's experimental data with accuracy of 0.15%. However, under low relative humidity condition, the experimental discharge coefficient deviation is larger, which is explained by the heterogeneous nucleation fortunately. (C) 2014 Elsevier Ltd. All rights reserved.