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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Fluid Machinery and Systems
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Korean Fluid Machinery Association
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Volume & Issues
Volume 3, Issue 4 - Dec 2010
Volume 3, Issue 3 - Sep 2010
Volume 3, Issue 2 - Jun 2010
Volume 3, Issue 1 - Mar 2010
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Computational Study of Magnetically Suspended Centrifugal Blood Pump (The First Report: Main Flow and Gap Flow)
Ogami, Yoshifumi ; Matsuoka, Daisuke ; Horie, Masaaki ;
International Journal of Fluid Machinery and Systems, volume 3, issue 2, 2010, Pages 102~112
DOI : 10.5293/IJFMS.2010.3.2.102
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.
Computational Fluid Dynamics of Cavitating Flow in Mixed Flow Pump with Closed Type Impeller
Kobayashi, Katsutoshi ; Chiba, Yoshimasa ;
International Journal of Fluid Machinery and Systems, volume 3, issue 2, 2010, Pages 113~121
DOI : 10.5293/IJFMS.2010.3.2.113
LES(Large Eddy Simulation) with a cavitation model was performed to calculate an unsteady flow for a mixed flow pump with a closed type impeller. First, the comparison between the numerical and experimental results was done to evaluate a computational accuracy. Second, the torque acting on the blade was calculated by simulation to investigate how the cavitation caused the fluctuation of torque. The absolute pressure around the leading edge on the suction side of blade surface had positive impulsive peaks in both the numerical and experimental results. The simulation showed that those peaks were caused by the cavitaion which contracted and vanished around the leading edge. The absolute pressure was predicted by simulation with -10% error. The absolute pressure around the trailing edge on the suction side of blade surface had no impulsive peaks in both the numerical and experimental results, because the absolute pressure was 100 times higher than the saturated vapor pressure. The simulation results showed that the cavitation was generated around the throat, then contracted and finally vanished. The simulated pump had five throats and cavitation behaviors such as contraction and vanishing around five throats were different from each other. For instance, the cavitations around those five throats were not vanished at the same time. When the cavitation was contracted and finally vanished, the absolute pressure on the blade surface was increased. When the cavitation was contracted around the throat located on the pressure side of blade surface, the pressure became high on the pressure side of blade surface. It caused the 1.4 times higher impulsive peak in the torque than the averaged value. On the other hand, when the cavitation was contracted around the throat located on the suction side of blade surface, the pressure became high on the suction side of blade surface. It caused the 0.4 times lower impulsive peak in the torque than the averaged value. The cavitation around the throat caused the large fluctuation in torque acting on the blade.
Cavitation in Pump Inducer with Axi-asymmetrical Inlet Plate Observed by Multi-cameras
Kim, Jun-Ho ; Atono, Takashi ; Ishizaka, Koichi ; Watanabe, Satoshi ; Furukawa, Akinori ;
International Journal of Fluid Machinery and Systems, volume 3, issue 2, 2010, Pages 122~128
DOI : 10.5293/IJFMS.2010.3.2.122
The attachment of inducer in front of main impeller is a powerful method to improve cavitation performance; however, cavitation surge oscillation with low frequency occurs with blade cavity growing to each throat section of blade passage simultaneously. Then, one conceptual method of installing suction axi-asymmetrical plate has been proposed so as to keep every throat passage away from being unstable at once, and the effect on suppression of the oscillation were investigated. In the present study, cavitation behaviors in the inducer is observed with distributing multi-cameras circumferentially, recording simultaneously and reconstructing multi-photos on one plane field as moving a linear cascade. Observed results are utilized for discussion with other measuring results as casing wall pressure distribution. Then the suppression mechanism of oscillation by installing axi-asymmetrical inlet plate will be clarified in more details.
Internal Flow of a Two-Bladed Helical Inducer at an Extremely Low Flow Rate
Watanabe, Satoshi ; Inoue, Naoki ; Ishizaka, Koichi ; Furukawa, Akinori ; Kim, Jun-Ho ;
International Journal of Fluid Machinery and Systems, volume 3, issue 2, 2010, Pages 129~136
DOI : 10.5293/IJFMS.2010.3.2.129
The attachment of inducer upstream of main impeller is an effective method to improve the suction performance of turbopump. However, various types of cavitation instabilities are known to occur even at the designed flow rate as well as in the partial flow rate region. The cavitation surge occurring at partial flow rates is known to be strongly associated with the inlet back flow. In the present study, in order to understand the detailed structure of internal flow of inducer, we firstly carried out the experimental and numerical studies of non-cavitating flow, focusing on the flow field near the inlet throat section and inside the blade passage of a two bladed inducer at a partial flow rate. The steady flow simulation with cavitation model was also made to investigate the difference of flow field between in the cavitating and no-cavitating conditions.
Suppression of Cavitation Instabilities in an Inducer by Circumferential Groove and Explanation of Higher Frequency Components
Kang, Dong-Hyuk ; Arimoto, Yusuke ; Yonezawa, Koichi ; Horiguchi, Hironori ; Kawata, Yutaka ; Hah, Chunill ; Tsujimoto, Yoshinobu ;
International Journal of Fluid Machinery and Systems, volume 3, issue 2, 2010, Pages 137~149
DOI : 10.5293/IJFMS.2010.3.2.137
The purpose of the present research is to suppress cavitation instabilities by using a circumferential groove. The circumferential groove was designed based on CFD so that the tip leakage vortex is trapped by the groove and does not interact with the next blade. Experimental results show that the groove can suppress rotating cavitation, asymmetric cavitation and cavitation surge. However, weak instabilities with higher frequency could not be suppressed by the groove. From the analysis of pressure pattern similar to that for rotor-stator interaction, it was found that the higher frequency components are caused by the interaction of backflow vortices with the inducer blades.
Multi-objective Optimization of a Laidback Fan Shaped Film-Cooling Hole Using Evolutionary Algorithm
Lee, Ki-Don ; Husain, Afzal ; Kim, Kwang-Yong ;
International Journal of Fluid Machinery and Systems, volume 3, issue 2, 2010, Pages 150~159
DOI : 10.5293/IJFMS.2010.3.2.150
Laidback fan shaped film-cooling hole is formulated numerically and optimized with the help of three-dimensional numerical analysis, surrogate methods, and the multi-objective evolutionary algorithm. As Pareto optimal front produces a set of optimal solutions, the trends of objective functions with design variables are predicted by hybrid multi-objective evolutionary algorithm. The problem is defined by four geometric design variables, the injection angle of the hole, the lateral expansion angle of the diffuser, the forward expansion angle of the hole, and the ratio of the length to the diameter of the hole, to maximize the film-cooling effectiveness compromising with the aerodynamic loss. The objective function values are numerically evaluated through Reynolds- averaged Navier-Stokes analysis at the designs that are selected through the Latin hypercube sampling method. Using these numerical simulation results, the Response Surface Approximation model are constructed for each objective function and a hybrid multi-objective evolutionary algorithm is applied to obtain the Pareto optimal front. The clustered points from Pareto optimal front were evaluated by flow analysis. These designs give enhanced objective function values in comparison with the experimental designs.