Double choking characteristics of three-dimensional steam ejector with non-equilibrium condensing

The phenomenology of double choking in a supersonic steam ejector which plays an influential role in the performance is not fully understood because the non-equilibrium condensing and three-dimensional effects are neglected in most numerical simulations. In this paper, a non-equilibrium condensation model was combined with the k-omega SST turbulence model to simulate three-dimensional supersonic steam ejectors with different working conditions and different structures. The internal relationship between the ejector performance and the double choking characteristics was revealed. The influence of the characteristics of double choking on the shock waves in the ejector was also investigated. Results show that when the minimum distance between the sonic velocity line in the diffuser and the wall is equal to the critical minimum distance which is 0.21 mm, the steam ejector is in a double choking mode. 4 mm downstream of the diffuser entrance is the critical second choking position. The deviations between discharge pressure and critical discharge pressure are getting greater with the increase of the second choking length. The intensity and number of shock waves in the diffuser are positively related to the second choking length with certain working conditions. Three-dimensional effects bring non negligible differences to both the flow field and the ejector performance.

Automated summary

This study investigated the influence of double choking phenomenon on the performance of a supersonic steam ejector through numerical simulations. It revealed the internal relationship between double choking characteristics and shock waves, as well as the critical choking position and its impact on performance. Additionally, the study found that three-dimensional effects lead to significant differences in both flow field and ejector performance.