## 3 Results and Discussion
### Comparative Analysis of Internal Flow Characteristics Inside Steam Ejectors  
Compared with the ideal gas model, the nonequilibrium phase change of steam was considered in the wet steam model. Therefore, the difference in pressure, temperature and Mach number distribution between the wet steam model and the ideal gas model under different \(P_{m}\) was compared and analyzed in this paper. The shock wave was formed in the mixing chamber after the high-temperature and high-pressure primary flow accelerated through the Laval nozzle, which caused the pressure of the primary flow to change dramatically. Therefore, the distribution of pressure could reflect the characteristics of the shock wave well. Figure 6 shows the pressure contours of the steam ejector for the wet steam model and the ideal gas model under different \(P_{m}\). By comparing the two figures, it could be seen that the shape of the shock wave train changed when the \(P_{m}\) increased. The first shock wave of the shock wave train changed from the compression shock wave to the expansion shock wave. For the wet steam model, the first shock wave changed from the compression shock wave to the expansion shock wave when the \(P_{m}\) was 55,000 Pa. For the ideal gas model, the compression shock wave changed to the expansion shock wave when the \(P_{m}\) was 75,000 Pa. The \(P_{m}\) for the wet steam model was significantly lower than that for the ideal gas model, by 27%. In addition, the number of shock wave trains for the wet steam model was seven, while the number of shock wave trains for the ideal gas model was nine. With the increase in the \(P_{m}\), the length of the shock wave train in the mixing chamber increased. Comparing the results of the wet steam model and the ideal gas model, it was found that the change in the shock wave train length of the wet steam model was shorter than that of the ideal gas model. The pressure at the nozzle exit had an important effect on the shape of the shock wave train in the mixing chamber. When the pressure at the nozzle exit was lower than the mixing chamber pressure, the primary flow was in a state of overexpression, resulting in an expansion shock wave. When the pressure at the nozzle exit was higher than the mixing chamber pressure, the primary flow was in the underexpansion state, resulting in an expansion shock wave. In order to quantitatively analyze the difference in the pressure at the nozzle exit between the two models, the pressure distribution along the steam ejector axis under different \(P_{m}\) is shown in Figure 7. It was found that the pressure at the nozzle  
Figure 5: Wetness fraction distribution along the steam ejector axis under different \(P_{m}\). exit for the wet steam model was 5320 Pa and the pressure at the nozzle exit for the ideal gas model was 3933 Pa, while the \(P_{m}\) was 50,000 Pa. The pressure at the nozzle exit for the wet steam model was 35.2% higher than that for the ideal gas model. According to the analysis of the nonequilibrium phase change characteristics, it could be seen that the primary flow was in the supercooled nonequilibrium state during the expansion in the nozzle, and a large number of condensation nuclei formed at this time. The droplets grew and released latent heat of condensation, which caused the \(P_{m}\) to rise. Therefore, there were differences in the shape of the shock wave train between the wet steam model and the ideal gas model under different \(P_{m}\). Compared with the ideal gas model, the condensation phase change was also considered in the wet vapor model. The latent heat of condensation released by the condensation phase change process caused the temperature field inside the steam ejector calculated with the two models to be very different. The temperature distribution for the wet steam model and the ideal gas model under different \(P_{m}\) is shown in Figure 8. It can be seen from the figure that the temperature in the nozzle divergence section for the wet steam model was significantly higher than that for the ideal gas model.