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Research Papers: Flows in Complex Systems

Modeling and Computer Simulation of Centrifugal CO2 Compressors at Supercritical Pressures

[+] Author and Article Information
Farhad Behafarid

Mem. ASME
Department of Aerospace Engineering Sciences,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: farhad.behafarid@colorado.edu

Michael Z. Podowski

Professor
Mem. ASME
Center for Multiphase Research,
Rensselaer Polytechnic Institute,
Troy, NY 12180
e-mail: podowm@rpi.edu

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received January 26, 2015; final manuscript received January 7, 2016; published online March 24, 2016. Assoc. Editor: Kwang-Yong Kim.

J. Fluids Eng 138(6), 061106 (Mar 24, 2016) (9 pages) Paper No: FE-15-1059; doi: 10.1115/1.4032570 History: Received January 26, 2015; Revised January 07, 2016

The use of supercritical carbon dioxide (SC-CO2) as a working fluid in energy conversion systems has many benefits, including high efficiency, compact turbomachinery, and the abundance of CO2. A very important issue for design optimization and performance analysis of future SC Brayton cycles is concerned with the SC-CO2 flow inside high-speed compressors and turbines. The objective of this paper is to present a novel modeling approach to, and its use in numerical simulations of, SC-CO2 flow inside a high-speed compact compressor. The proposed approach capitalizes on using three different physical and mathematical formulations of one-dimensional (1D) models, i.e., compressible and incompressible flow models using actual properties of SC-CO2 and a compressible ideal gas model, as a reference to verify the predictive capabilities of a three-dimensional (3D) incompressible flow model. The incompressible model has been used to perform simulations for a complete detailed multidimensional model of an SC-CO2 high-speed compact compressor. The advantages of the new model include numerical stability, computational efficiency, and physical accuracy. In particular, it has been shown that the model's predictions are consistent with selected published technical data.

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References

Figures

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Fig. 2

SANDIA SC-CO2 centrifugal compressor rotating at 75,000 rpm [5]

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Fig. 1

SANDIA SC-CO2 compression loop, including a centrifugal compressor rotating at 75,000 rpm [5]

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Fig. 3

Pressure, temperature, density, and velocity distributions based on 1D analysis using incompressible and compressible flow models of SC-CO2, as well as a simplified ideal gas model, under accelerations corresponding to a rotational speed of 75,000 rpm

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Fig. 4

Errors in the predicted outlet conditions, using the compressible SC-CO2 model as a reference

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Fig. 12

Velocity vectors inside the compressor wheel rotating at 75,000 rpm (bottom view)

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Fig. 13

Streamlines inside the compressor wheel rotating at 75,000 rpm (top view)

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Fig. 5

Top and isometric views of the computer-aided design (CAD) model of the compressor used as computational domain for numerical simulation

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Fig. 6

Unstructured/boundary-layer mesh with 32.7 × 106 elements and 7.9 × 106 nodes

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Fig. 7

Velocity, pressure, and temperature distribution at cross sections of the compressor wheel (off-design, rotating at 50,000 rpm)

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Fig. 8

Pressure distribution on the blade surfaces inside the compressor wheel rotating at 75,000 rpm

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Fig. 9

Temperature distribution on the blade surfaces inside the compressor wheel rotating at 75,000 rpm

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Fig. 10

Velocity, pressure, and temperature distribution for a compressor wheel rotating at 75,000 rpm using incompressible SC-CO2 model

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Fig. 11

Velocity, pressure, and temperature distribution at cross sections of the compressor wheel (rotating at 75,000 rpm)

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