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Research Papers

Investigation of the Flow Phenomenon Inside Gas Ejectors With Moist Gas Entrainment

[+] Author and Article Information
Yuping Wang

Department of Mechanical Engineering,
University of Michigan–Dearborn,
Dearborn, MI 48128
e-mail: yupingw@umich.edu

Mark Pellerin

Ford Motor Company,
Dearborn, MI 48124
e-mail: mpelleri@ford.com

Pravansu Mohanty

Department of Mechanical Engineering,
University of Michigan–Dearborn,
Dearborn, MI 48128
e-mail: pmohanty@umich.edu

Subrata Sengupta

Department of Mechanical Engineering,
University of Michigan–Dearborn,
Dearborn, MI 48128
e-mail: razal@umich.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received January 26, 2016; final manuscript received June 29, 2016; published online October 4, 2016. Assoc. Editor: Pedro Mago.

J. Thermal Sci. Eng. Appl 9(1), 011005 (Oct 04, 2016) (9 pages) Paper No: TSEA-16-1021; doi: 10.1115/1.4034510 History: Received January 26, 2016; Revised June 29, 2016

This paper focuses on the gas flow study of an ejector used in applications where moist gases are being entrained. Two parts of work are presented. In the first part, characteristics of gas flow inside an ejector, as well as the ejector's performance under various operating and geometric configurations, were studied with a three-dimensional computational model. Measurements were also performed for validation of the model. In the second part, focus was given to the potential condensation or desublimation phenomena that may occur inside an ejector when water vapor is included in the entrained stream. Experiments using light-attenuation method were performed to verify the presence of a second phase; then, the onset of phase change and the phase distribution were obtained numerically. A two-dimensional axis-symmetric model was developed based on the model used in the first part. User-defined functions were used to implement the phase-change criteria and particle prediction. A series of simulations were performed with various amounts of water vapor added into the entrained flow. It was found that both frost particles and water condensate could form inside the mixing tube depending on the operating conditions and water vapor concentrations. When the concentration exceeds 3% by mass, water vapor could condense throughout the mixing tube. Some preliminary results of the second phase particles formed, e.g., critical sizes and distributions, were also obtained to assist with the design and optimization of gas ejectors used in similar applications.

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References

Figures

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Fig. 1

Computational domain for the ejector flow model: (a) computation domain and (b) key dimensions

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Fig. 2

Solution fields of the gas flow: (a) pressure field, (b) velocity field, (c) velocity vector, and (d) pathline plot

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Fig. 3

Ejector testing setup

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Fig. 4

Comparison of model prediction and measurement data: (a) mass flow rate of the primary flow, (b) mass flow rate of the entrained flow, and (c) entrainment ratio

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Fig. 5

Effects of two geometric parameters on the entrainment ratio: (a) variation of primary nozzle exit location and (b) variation of diameter ratio of mixing tube and nozzle throat

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Fig. 6

Experimental setup using light-attenuation method

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Fig. 7

Flow visualization setup: (a) schematic of flow visualization setup and (b) flow visualization setup

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Fig. 8

Mass fraction distribution of water vapor for the case with moist air

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Fig. 9

Computational domain for phase analysis and bulk condensation

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Fig. 10

Typical temperature and velocity field

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Fig. 11

Phase map and characterizing pressures for different water vapor concentrations: (a) 1% water vapor, (b) 2% water vapor, and (c) 3% water vapor

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Fig. 12

Preliminary results for particle formation (2% water vapor concentration): (a) t = 100 μs after nucleation and (b) t = 500 ms after nucleation

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