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Influence of spindle tip geometry on the performance of a controllable CO2 ejector.

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Bibliographic Details
Title: Influence of spindle tip geometry on the performance of a controllable CO2 ejector.
Authors: Chandran R., Jishnu1 (AUTHOR), Sadasivan, Sreeja2 (AUTHOR) sreeja.sadasivan@vit.ac.in, Arumugam, Senthil Kumar3 (AUTHOR) asenthilkumar@vit.ac.in
Source: International Journal of Modern Physics C: Computational Physics & Physical Computation. Oct2026, Vol. 37 Issue 10, p1-22. 22p.
Subjects: Fluid dynamics, Injectors, Mathematical models, Refrigeration & refrigerating machinery
Abstract: Variable geometry ejectors are crucial in CO2 refrigeration systems for the recovery of expansion work and in the regulation of refrigerating capacity. The performance of a variable geometry ejector is sensitive to the spindle geometry and its positioning. This study employs numerical analysis to explore how the spindle tip angle affects the performance and flow behavior of a variable geometry CO2 ejector. The study analyzes the flow characteristics of the ejector for various angles of the spindle tip, considering both critical and sub-critical operating modes. An increase in the spindle tip angle lowers the motive flow rate, for a fixed spindle position. A sharper tip for the spindle reduces secondary flow entrainment in the critical operating mode and improves the secondary flow rate in the subcritical operating mode. Vapor quality from the ejector improves for a larger tip angle in the critical mode, and the opposite trend is observed for the subcritical mode. For spindle tip angles larger than the convergent angle of the motive nozzle, the pre-expanding motive flow before the nozzle throat plane in critical mode lowers the pressure in the mixing region and amplifies secondary flow entrainment. As the spindle tip angle increases in the subcritical mode, the rise in flow obstruction from recirculating flows leads to a significant decrease in secondary flow entrainment. The critical and the maximum functional discharge pressures decrease with an increase in the spindle tip angle. However, even when the ejector operates in subcritical mode, larger spindle tip angles can achieve higher entrainment ratios compared to narrower spindle tips for a given pressure lift. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Variable geometry ejectors are crucial in CO2 refrigeration systems for the recovery of expansion work and in the regulation of refrigerating capacity. The performance of a variable geometry ejector is sensitive to the spindle geometry and its positioning. This study employs numerical analysis to explore how the spindle tip angle affects the performance and flow behavior of a variable geometry CO2 ejector. The study analyzes the flow characteristics of the ejector for various angles of the spindle tip, considering both critical and sub-critical operating modes. An increase in the spindle tip angle lowers the motive flow rate, for a fixed spindle position. A sharper tip for the spindle reduces secondary flow entrainment in the critical operating mode and improves the secondary flow rate in the subcritical operating mode. Vapor quality from the ejector improves for a larger tip angle in the critical mode, and the opposite trend is observed for the subcritical mode. For spindle tip angles larger than the convergent angle of the motive nozzle, the pre-expanding motive flow before the nozzle throat plane in critical mode lowers the pressure in the mixing region and amplifies secondary flow entrainment. As the spindle tip angle increases in the subcritical mode, the rise in flow obstruction from recirculating flows leads to a significant decrease in secondary flow entrainment. The critical and the maximum functional discharge pressures decrease with an increase in the spindle tip angle. However, even when the ejector operates in subcritical mode, larger spindle tip angles can achieve higher entrainment ratios compared to narrower spindle tips for a given pressure lift. [ABSTRACT FROM AUTHOR]
ISSN:01291831
DOI:10.1142/S0129183126500099