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Research Papers: Flows in Complex Systems

Loss Mechanisms in Shear-Force Pump With Multiple Corotating Disks

[+] Author and Article Information
Baotong Wang

Department of Advanced Energy,
Graduate School of Frontier Sciences,
The University of Tokyo,
Building of Transdisciplinary Sciences,
5-1-5 Kashiwanoha,
Kashiwa, Chiba 277-8561, Japan
e-mail: baotong@thermo.t.u-tokyo.ac.jp

Koji Okamoto

Department of Advanced Energy,
Graduate School of Frontier Sciences,
The University of Tokyo,
Building of Transdisciplinary Sciences,
5-1-5 Kashiwanoha,
Kashiwa, Chiba 277-8561, Japan
e-mail: k-okamoto@k.u-tokyo.ac.jp

Kazuo Yamaguchi

Department of Aeronautics and Astronautics,
School of Engineering,
The University of Tokyo,
Building of Engineering No.7,
7-3-1 Hongo,
Bunkyo, Tokyo 113-8656, Japan
e-mail: yamaguchi@thermo.t.u-tokyo.ac.jp

Susumu Teramoto

Department of Aeronautics and Astronautics,
School of Engineering,
The University of Tokyo,
Building of Engineering No.7,
7-3-1 Hongo,
Bunkyo, Tokyo 113-8656, Japan
e-mail: teramoto@thermo.t.u-tokyo.ac.jp

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received September 20, 2013; final manuscript received January 18, 2014; published online May 12, 2014. Assoc. Editor: Satoshi Watanabe.

J. Fluids Eng 136(8), 081101 (May 12, 2014) (10 pages) Paper No: FE-13-1568; doi: 10.1115/1.4026585 History: Received September 20, 2013; Revised January 18, 2014

In a shear-force pump with multiple corotating disks, the pressure gain is obtained by utilizing the shear force produced on the surfaces of the rotating disks. Thus, it is expected to have advantages as a microfluid device compared to a conventional bladed compressor or pump, which suffers greatly from viscous loss. However, in previous studies, a shear-force pump could not achieve high efficiency in experiments, even though very good efficiencies were predicted in numerical and analytical studies on the flow field between corotating disks. Therefore, the objective of the present work was to investigate the internal flow dynamics and clarify the loss mechanisms in a complete shear-force pump device consisting of both rotor and stationary components. In order to achieve this goal, a numerical simulation using an independent rotor analysis was first performed on the internal flow field between two corotating disks to evaluate the isentropic efficiency and pressure coefficient that could be achieved. Then, an experimental test rig for a shear-force pump was designed and built, and an experiment was carried out to determine the performance of a complete pump device with the same corotating disk design as the independent rotor analysis. In addition, a numerical simulation was executed for the flow field of a pump system consisting of both rotor and stationary components based on the present test rig to investigate the flow field and loss factors of this device. The results of this independent rotor analysis showed that the corotating disks can achieve a fairly high efficiency at a low flow coefficient with a high dynamic pressure, and the flow direction is extremely close to the tangential direction at the disk outlet, which caused difficulties in the design of the diffuser and scroll. In the experimental test, the high total pressure loss in the parallel diffuser and scroll parts was observed. This was found to be the result of the significant friction loss caused by the long flow path due to strong recirculation in the diffuser and scroll volute, which was found in the simulation results for the internal flow in the whole pump system. In addition, a reverse flow appeared in the rotor part at a low flow coefficient, which significantly deteriorated the rotor performance. These conclusions provided some clues for improving the performance of a shear-force pump device in future work.

FIGURES IN THIS ARTICLE
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References

Figures

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Fig. 1

Flow scheme in shear-force pump

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Fig. 2

Schematic view of radially outward flow between corotating disks

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Fig. 3

View of mesh and boundary conditions for the independent rotor analysis: (a) front view (r-θ section) and (b) cross-sectional view (r-z section)

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Fig. 4

Performance map of the independent rotor composed of a pair of corotating disks: (a) isentropic efficiency and (b) pressure coefficient

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Fig. 5

Outlet flow condition for the independent rotor analysis of case 1: (a) pressure, (b) normalized velocity components, and (c) outlet flow angle

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Fig. 6

Schematic view of the main part in the present experimental test rig: (a) front view (r-θ section), (b) cross-sectional view (r-z section, θ=90 deg,270 deg), and (c) enlarged view of Fig. 6(b)

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Fig. 7

Main part of experimental test rig in the present work: (a) side view, (b) Single-hole Pitot tube used at diffuser, and (c) picture of front view of A-B section

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Fig. 8

Schematic view of the experimental test rig and measurement system

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Fig. 9

Simulated zone and view of mesh for the CFD calculation of the flow field in the pump test rig

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Fig. 10

Performance map and average flow angle of the present test rig at a rotating speed of 25,000 rpm: (a) pressure coefficient, (b) isentropic efficiency, and (c) average flow angle

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Fig. 11

Entropy contours and flow vectors in the r-z section with a θ coordinate equal to 90 deg at a flow coefficient of 0.8

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Fig. 12

Entropy contours and flow vectors in the r-θ sections at a flow coefficient of 0.8: (a) middle section of gap 7 and (b) middle section of gap 1

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Fig. 13

Entropy contours and flow vectors in the r-z section with a θ coordinate equal to 90 deg at a flow coefficient of 0.1

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