[논문]Computational Study of Magnetically Suspended Centrifugal Blood Pump (The First Report: Main Flow and Gap Flow)

Ogami, Yoshifumi; Matsuoka, Daisuke; Horie, Masaaki

doi:10.5293/ijfms.2010.3.2.102

[국내논문] Computational Study of Magnetically Suspended Centrifugal Blood Pump (The First Report: Main Flow and Gap Flow) 원문보기

International journal of fluid machinery and systems, v.3 no.2, 2010년, pp.102 - 112

Ogami, Yoshifumi (Department of Mechanical Engineering, Ritsumeikan University) , Matsuoka, Daisuke (Department of Mechanical Engineering, Ritsumeikan University) , Horie, Masaaki (Department of Mechanical Engineering, Setsunan University)

Abstract ▼ AI-Helper

Artificial heart pumps have attracted the attention of researchers around the world as an alternative to the organ used in cardiac transplantation. Conventional centrifugal pumps are no longer considered suitable for long-term application because of the possibility of occurrence of blood leakage and thrombus formation around the shaft seal. To overcome this problem posed by the shaft seal in conventional centrifugal pumps, the magnetically suspended centrifugal pump has been developed; this is a sealless rotor pump, which can provide contact-free rotation of the impeller without leading to material wear. In Europe, clinical trials of this pump have been successfully performed, and these pumps are commercially available. One of the aims of our study is to numerically examine the internal flow and the effect of leakage flow through the gap between the impeller and the pump casing on the performance of the pump. The results show that the pressure head increases compared with the pump without a gap for all flow rates because of the leakage of the fluid through the gap. It was observed that the leakage flow rate in the pump is sufficiently large; further, no stagnant fluid or dead flow regions were observed in the pump. Therefore, the present pump can efficiently enhance the washout effect.

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가설 설정

1. If there is a gap, the amount of the impeller flow increases as the fluid which comes back through the gap re-enters the impeller; hence, the backward current is reduced inside the impeller compared to that in the model without the gap, and as a consequence, the generated pressure increases.
2. If there is a gap, the impeller flow is rectified since vortexes, which are symmetrical between the upper and lower sides, develop inside the volute. Moreover, when the amount of flow increases, these vortexes grow in size and control the backward current inside the gap.
3. Within this computational range, the backward current (leakage flow) from the volute to the inlet always develops in the gap. Therefore, it can be thought that the wash-out effect, which is one of the most crucial elements in the blood pump, has been adequately achieved.

제안 방법

In this study, we created a calculation model which reproduced the gap between the impeller and the casing, and another model assuming that there is no gap. Then, we performed a numerical simulation to clarify the effect of the gap flow on the entire pump, including the main flow and the characteristics of the pump.
In this study, we created a calculation model which reproduced the gap between the impeller and the casing, and another model assuming that there is no gap. Then, we performed a numerical simulation to clarify the effect of the gap flow on the entire pump, including the main flow and the characteristics of the pump. As a result, it was confirmed that the gap could give the following advantages with such a special pump system, although it is usually considered undesirable as the leakage flow results in decreased efficiency.
was used in this study. The numerical analysis was performed with the finite volume method; conservation equations for mass and momentum were integrated at each control volume, and then the discretized equations were resolved. As the mechanical Reynolds number R_e is about 5.
The actual pump has a slight taper at the inlet to change the axial flow to radial, and the rectangular section at the volute is changed to circular at the outlet. However, instead of using such a complex-shaped system, we have designed a pump which has a flat wall at the inlet and a rectangular section at the pump outlet with the area size similar to that of the actual pump as the purpose of this study is to clarify qualitative nature of the pump. The rest of the shape is the same, and even the gap between the impeller and casing (Gap in Fig.
In this study, comparisons were made between a model with which the gap between the impeller and casing of the magnetically suspended centrifugal blood pump was reproduced and another model without the gap. Using the thermal fluid analysis software numerical simulations were performed inside the pump to clarify the effect of the gap flow to the entire pump system.
In this study, comparisons were made between a model with which the gap between the impeller and casing of the magnetically suspended centrifugal blood pump was reproduced and another model without the gap. Using the thermal fluid analysis software numerical simulations were performed inside the pump to clarify the effect of the gap flow to the entire pump system. As a result, the followings have been revealed.

이론/모형

As the mechanical Reynolds number Re is about 5.0×104 in this study, the k-ω model, which is appropriate for the complex flow with separation, was used for the turbulence model (Ansys Inc. [14]).
The “QUICK” method was used for the difference schemes of the equations of motion, turbulent energy, and the dissipation rate, and “SIMPLE” method was for the analyses of pressure / velocity (Ferziger [15]).

참고문헌 (15)

Kyo, S., et al., 2005, The Leading Edge Technology of Artificial Organ and Regeneration Medicine (in Japanese), Research Institute of advanced medical technology, Tokyo.
Matsumiya, G., 2007，“Current state and the future of supplementary artificial heart treatment in our country (in Japanese),” Artificial Organs, Vol. 36, No. 3, pp. 244-247.
Ono, M., 2007, “Artificial heart (clinical practice),” Artificial Organs, Vol. 36, No. 3, pp. 172-174.
Akamatsu, T., 1994, “Centrifugal Blood Pump (in Japanese),” Turbomachinery, Vol. 22, No. 1, pp. 40-46.
Akamatsu, T., 2001, “Study of the magnetically suspended centrifugal blood pump (in Japanese),” Turbomachinery, Vol. 29, No. 1, pp. 7-16.
Akamatsu, T., et al., 1992, “Centrifugal Blood Pump with a Magnetically Suspended Impeller,” Artificial Organs，Vol. 16, No. 3, pp. 305-308

상세보기
Tsukiya, T. and Akamatsu, T., 1995, “Development of the Centrifugal Blood Pump with Magnetically Suspended Impeller (in Japanese),” Transactions of JSME, 61-591，B，pp. 3913-3920.

상세보기
Terumo Heart Inc. Press Releases, http://www.terumo.co.jp/English/press/2007/005.html.
Kurokawa, J., et al., 1990, “Characteristics of Spiral Pump at Low Specific Speed (in Japanese),” Turbomachinery, Vol. 18, No. 5, pp. 300-307.
Kurokawa, J., et al., 1997, “Characteristics of Impeller at Very Low Specific Speed (in Japanese),” Turbomachinery, Vol. 25, No. 7, pp. 337-345.
Matsui, J. et al., 2006，“Application of Circular Casing to the Centrifugal Pump of Low Specific Speed and the Internal Flow (in Japanese),” Turbo machine, Vol. 34, No. 8, pp. 463-470.
Chua, L.P., et al.，2006, “Numerical Analysis of the Inner Flow Field of a Biocentrifugal Blood Pump,” Artificial Organs，Vol. 30, No. 6，pp. 467-477.

상세보기
Chua, L.P., et al.，2005，“Computational Fluid Dynamics of Gap Flow in a Biocentirifugal Blood Pump,” Artificial Organs, Vol. 29, No. 8, pp. 620-628.

상세보기
Ansys Inc.，2002，FLUENT 6.0 User’s Guide.
Ferziger, J. H., 2001, Computational Methods for Fluid Dynamics, Springer, New York.

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