Swirl-Bypass Nozzle for CO 2 Two-Phase Ejectors: Numerical Design Exploration

Knut Emil Ringstad (), Krzysztof Banasiak, Åsmund Ervik and Armin Hafner ()
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Knut Emil Ringstad: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1B, 7491 Trondheim, Norway
Krzysztof Banasiak: SINTEF Energy Research, Kolbjørn Hejes vei 1d, 7465 Trondheim, Norway
Åsmund Ervik: SINTEF Energy Research, Kolbjørn Hejes vei 1d, 7465 Trondheim, Norway
Armin Hafner: Department of Energy and Process Engineering, Norwegian University of Science and Technology, Kolbjørn Hejes vei 1B, 7491 Trondheim, Norway

Energies, 2022, vol. 15, issue 18, 1-30

Abstract: In this work, a novel ejector design concept of a swirl-bypass nozzle is proposed to improve off-design performance of CO 2 two-phase ejectors. The swirl-bypass nozzle allows part of the flow to bypass into the ejector mixing chamber to generate swirl. The design of such a device is investigated using a 3D multiphase CFD model. An extensive experimental test campaign is conducted to validate the baseline homogeneous equilibrium CFD model. The model’s prediction motive mass flow rate within 2–12% error and suction mass flow rate was predicted with 3–50% error. Based on the tested ejector geometry, simulations of different ejector swirl-bypass inlets are conducted. The results show that, for the current design, total entrainment of the ejector is reduced by 2–20% with the swirl-bypass inlet. The axial position of the bypass inlet plays a primary role in the bypass inlet flow rate, and, consequently, in suction flow reduction. This is found to be due to the bypass flow blocking off the suction mass flow rate, which has a net negative impact on performance. Finally, several design improvements to improve future designs are proposed.

Keywords: computational fluid dynamics; two-phase ejector; CO 2; bypass ejector; swirl bypass (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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