International Journal of Fluid Machinery and Systems
Online ISSN : 1882-9554
Volume 7 , Issue 4
Showing 1-5 articles out of 5 articles from the selected issue
Review Papers
Original Papers
  • Linlin Cao, Satoshi Watanabe, Hironori Honda, Hiroaki Yoshimura, Akino ...
    Type: Original Paper
    2014 Volume 7 Issue 4 Pages 130-141
    Published: 2014
    Released: November 08, 2014
    As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.
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  • Hironori Horiguchi, Tomonori Tsukiya, Takeshi Nomoto, Toratarou Takemi ...
    Type: Original papers
    2014 Volume 7 Issue 4 Pages 142-150
    Published: 2014
    Released: November 08, 2014
    In the cardiopulmonary support system with an ECMO (extracorporeal membrane oxygenation), ahigher pump head is demanded for a blood pump. In order to realize a blood pump with higher pump head, higher anti-hemolysis and thrombosis performances, astudy on the development of unprecedented multistage blood pump was conducted. In consideration of the applicationof the blood pump for pediatric patients, a miniature two-stage centrifugal blood pump with the impeller’s diameter of40mm was designed and the performance was examined in experiments and computations. Some useful knowledge for a design of the blood pump with higher anti-hemolysis and thrombosis performances was obtained.
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  • Daisuke Matsushita, Kei Tanaka, Satoshi Watanabe, Kusuo Okuma, Akinori ...
    Type: Original paper
    2014 Volume 7 Issue 4 Pages 151-159
    Published: 2014
    Released: December 25, 2014
    Low head hydropower is one of realistic renewable energies. The Darrieus-type hydro turbine with an inlet nozzle is available for such low head conditions because of its simple structure with easy maintenance. Experimental and numerical studies are carried out in order to examine the effects of gap distances between the runner pitch circle and two edges of inlet nozzle on turbine performances. By selecting narrower gaps of left and right edges, the performance could be improved. From the results of two dimensional numerical simulations, the relation between the performance and flow behaviors around the Darrieus blade are discussed to obtain the guideline of appropriate inlet nozzle design.
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  • Nobuyuki Yamaguchi
    Type: Original Papers
    2014 Volume 7 Issue 4 Pages 160-173
    Published: 2014
    Released: December 03, 2014
    Surge phenomena in multi-stage axial flow compressors were studied with attention to the frequency behaviors. A new parameter “volume-modified reduced surge frequency” was introduced, which took into consideration the essential surge process, i.e., emptying and filling of the working gas in the delivery plenum. The behaviors of the relative surge frequencies at the stall stagnation boundaries, compared with the corresponding duct resonance frequencies, have demonstrated the existence of two types of surges; i.e., a near-resonant surge and a subharmonic surge. The former, which has fundamentally a near-resonance frequency, occurs predominantly at the stall stagnation boundary for the short-and-fat plenum delivery flow-path and the long-and-narrow delivery duct flow-path, and possibly in the intermediate conditions. The latter, which has a subharmonic frequency of the fundamental near-resonant one and occurs mainly in the inter-mediate zone, is considered to be caused by the reduced frequency restricted to a limited range. In relation with those dimensionless frequencies at the stall stagnation boundary, the surge frequency behaviors in more general situations away from the boundaries could be estimated, though very roughly.
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  • Yasuyuki Nishi, Terumi Inagaki, Yanrong Li, Ryota Omiya, Kentaro Hatan ...
    Type: Original paper
    2014 Volume 7 Issue 4 Pages 174-182
    Published: 2014
    Released: December 23, 2014
    The ultimate objective of this study is to develop a water turbine appropriate for low-head open channels to effectively utilize the unused hydropower energy of rivers and agricultural waterways. The application of a cross-flow runner to open channels as an undershot water turbine has been considered and, to this end, a significant simplification was attained by removing the turbine casing. However, the flow field of an undershot cross-flow water turbine possesses free surfaces, and, as a result, the water depth around the runner changes with variation in the rotational speed such that the flow field itself is significantly altered. Thus, clear understanding of the flow fields observed with free surfaces to improve the performance of this turbine is necessary. In this study, the performance of this turbine and the flow field were evaluated through experiments and numerical analysis. The particle image velocimetry technique was used for flow measurements. The experimental results reflecting the performance of this turbine and the flow field were consistent with numerical analysis. In addition, the flow fields at the inlet and outlet regions at the first and second stages of this water turbine were clarified.
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