Abstract
This paper establishes a mathematic model of a CO2 two-phase ejector to investigate flow distribution in the components of a mixing chamber and diffuser. The suction chamber was modeled using the characteristic line method to describe the development process of the supersonic expansion wave, and the mixing chamber, as well as diffuser models, were built based on the double-flow model. The reliability of the model was verified by experimental data. The distributions of flow parameters along the axis of the mixing chamber and diffuser were analyzed under different expansion ratios of the ejector. Structure optimizations of the mixing chamber and diffuser were conducted. The results showed that the primary flow temperature gradually increased along the axis of the mixing chamber and diffuser, but the Mach number distribution decreased for a certain ejector expansion ratio. The temperature and Mach number of the secondary flow showed the opposite trend. Moreover, at the initial stage of mixing, the fluid pressure increased rapidly, and the Mach number of the primary flow decreased rapidly. The gas-phase fraction of primary flow increased gradually in the mixing chamber and was stable in the diffuser. When the length–diameter ratio of the mixing chamber was about 10.8–12, it was beneficial to mix uniformity, and when the expansion angle of the diffuser was 4–6°, the ejector had a better ejector efficiency.
Highlights
Ejectors have been subject to great focus in energy systems, the process industry and low-grade heat use, by virtue of its advantages of saving energy and its simple structure
Palacz and Haida et al [5,6,7] conducted a series of studies to continuously perfect the delay equilibrium model (DEM) and homogeneous equilibrium model (HEM)
Though many CO2 ejector models have been established based on the thermodynamic method or gas dynamic method, the suction chamber model is usually constructed based on the zero-dimension model, given the lack of the understanding of the expansion wave and flow distribution analysis [11]
Summary
Ejectors have been subject to great focus in energy systems, the process industry and low-grade heat use, by virtue of its advantages of saving energy and its simple structure. An in-depth study of flow distribution in the mixing chamber and diffuser can provide important theoretical references for the analysis of energy and mass transfer, as well as irreversible loss. A global mathematical model of a CO2 two-phase ejector was established, in which the suction chamber model was developed using the characteristic line method, focusing on supersonic expansion of primary flow, and the mixing chamber and diffuser was molded using the double-flow model to obtain the flow distribution characteristics in the mixing process. Based on the experimental structural and thermodynamic parameters of the CO2 ejector, the variation of flow parameters, such as temperature, velocity, Mach number and pressure in the ejector, were analyzed, and optimization strategies regarding the length–diameter ratio of the mixing chamber and semi-cone angle of the diffuser were proposed
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
