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

Abstract

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-ω 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.