Turbomachinery
Online ISSN : 1880-2338
Print ISSN : 0385-8839
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Technical papers
  • Kosuke UEDA, Yuzo INOKUCHI, Nobuhiko YAMASAKI, WAKAKI Daichi, YAMAGATA ...
    Type: Technical papers
    Volume 43 (2015) Issue 12 Pages 714-720
    Released: February 11, 2018
    JOURNALS FREE ACCESS
    The rotational frequency noise emitted from the small centrifugal compressor of automobile turbocharger is called the pulsation noise. The cause of the pulsation noise is not fully understood, but is considered to be due to some manufacturing errors, which is called the mistuning. The effects of the mistuning of the impeller blade on the noise field inside the flow passage of the compressor are numerically investigated. Here, the flow passage includes the volute and duct located downstream of the compressor impeller. The present numerical approach is found to successfully capture the wavelength of the pulsation noise at given rotational speeds by the comparison with the experiments. One of the significant findings is that the noise field of the pulsation noise in the duct is highly one-dimensional although the flow fields are highly three-dimensional.
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  • Daisuke MATSUSHITA, Akinori FURUKAWA, Satoshi WATANABE
    Type: Technical papers
    Volume 43 (2015) Issue 12 Pages 721-729
    Released: February 11, 2018
    JOURNALS FREE ACCESS
    A two dimensional Darrieus-type turbine with a vertical shaft, in dammed extra-low head waterway, has been proposed. As a flow rate in the waterway is varied temporally and seasonally in the practical use, it should be considered at the design stage to avoid the flooding from the waterway and to squeeze the hydropower effectively even at low flow rates. In the present paper, while useful data for a high performance design, based on the present stage of authors' experimental investigation are shown, how to select key parameters of the turbine geometry such as a Darrieus turbine diameter, a blade spanlength and a weir-height in the turbine section is at first demonstrated against the waterway with a rectangular section. Secondly the effective operations will be discussed for various flow rate conditions by an adjustment of an inlet nozzle height.
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  • Masashi YASUDA, Yoshiichirou HAYASHI
    Type: Technical papers
    Volume 43 (2015) Issue 12 Pages 730-737
    Released: February 11, 2018
    JOURNALS FREE ACCESS
    We found large fatigue cracks on the runner surfaces of pump-turbines at Kalayaan pumped storage power plant and measured the dynamic stress generated on the runner to find the root cause of the cracks. In this paper, the crack propagation is simulated based on the fracture mechanics using the measured dynamic stresses and the validity of inspection procedure is evaluated whether it is effective to avoid any severe fatigue crack in future.
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  • Nobuhiro MURAKAMI, Hiroaki HASEGAWA, Toshihiro HANIU, Masahide NAKAMUR ...
    Type: Technical papers
    Volume 43 (2015) Issue 12 Pages 738-746
    Released: February 11, 2018
    JOURNALS FREE ACCESS
    In order to clarify the mechanism of lift enhancement for a spiral Magnus windmill, wind tunnel experiments were carried out by using a rotating cylinder with fins. Spiral Magnus is a unique wind turbine system that rotates with cylinders which have spiral-shaped fins coiled around them instead of the usual propeller-like blades, and the spiral Magnus windmill shows high power generation performance. However, its mechanism has not been fully elucidated. In the present study, three models (cylinder with no fins, straight fins and spiral fins) were installed, and fluid force measurements were performed by a strain gauge force balance. The PIV system was also used to better understand the flow fields around the cylinder.
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  • Yoshiichirou HAYASHI, Mitsuru HANDA, Masashi YASUDA
    Type: Technical papers
    Volume 43 (2015) Issue 12 Pages 747-752
    Released: February 11, 2018
    JOURNALS FREE ACCESS
    In pump-turbine runner, fatigue cracks after welding works are occasionally found. To avoid the generation of cracks, we developed ultrasonic shot peening system to improve fatigue life by introducing to the runner surface with beneficial compressive residual stress. This developed system consists of supporting frames, movable frames, peening machine and its chamber, and the ultrasonic transmitter. This system has been applied to a pump-turbine runner which had been damaged with fatigue cracks and repaired by welding. We confirmed high compression residual stress by portable X-ray analyzer.
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  • Takashi ARINO, Kozo KAWAMOTO, Satoshi KUWANO, Takayuki KITAMURA
    Type: Technical papers
    Volume 43 (2015) Issue 12 Pages 753-759
    Released: February 11, 2018
    JOURNALS FREE ACCESS
    High and intermediate pressure turbine rotors of the thermal power plants embrittle because impurities in the material segregate to grain boundaries in service. Users ensure safety by non-destructive evaluations during outages and warming up at the cold startup. Meanwhile, the amount of impurities in the material have reduced due to advances in steelmaking technology especially since the 1980s. Therefore, we evaluated embrittlement of the turbine rotors non-destructively from the impurity amount. Consequently, the rotors' FATT will not exceed the service temperature even if we use them continuously for 30 years, and the possibility of brittle fracture was found to be low.
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