An investigation into the correlation between operating conditions and non-equilibrium condensation in supersonic nozzles: Focusing on supercooled, saturated, and superheated vapor states

Non-equilibrium condensation (NQC) is a critical process within a supersonic nozzle, leading to thermodynamic losses and significant alterations in the flow structure. The release of latent heat during NQC results in increased pressure, temperature, and a reduction in Mach number. This study investigates the influence of different input vapor types—superheated, saturated, and supercooled—on the flow structure and two-phase flow regimes within the supersonic nozzle. A compressible flow model is employed to simulate the flow behavior. Results reveal that the type of input vapor has a profound impact on the flow pattern. Supercooled vapor is associated with a gradual pressure increase in the converging section, whereas saturated and superheated vapors exhibit abrupt pressure surges at the throat and in the diverging section. Furthermore, supercooled vapor demonstrates a higher mass fraction of liquid and larger droplet radii compared to saturated and superheated vapors. Saturated vapor exhibits the highest mass flow rate, while supercooled vapor experiences the highest condensation loss. Superheated vapor, on the other hand, exhibits the highest entropy production. Compared to saturated vapor, a 10-degree supercooled vapor demonstrates a 1.33% decrease in mass flow rate, a 9.06% increase in condensation loss, and reductions in frictional and thermal entropy production by 3.61% and 2.56%, respectively.