Turbomachinery
Online ISSN : 1880-2338
Print ISSN : 0385-8839
ISSN-L : 0385-8839
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Volume 38, Issue 8
Displaying 1-5 of 5 articles from this issue
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Technical papers
  • Optimization of Suction Channel for Improving Performance of Process Centrifugal Compressor
    Manabu YAGI, Takanori SHIBATA, Hiromi KOBAYASHI, Masanori TANAKA, Hide ...
    Article type: Original Article
    2010 Volume 38 Issue 8 Pages 456-463
    Published: 2010
    Released on J-STAGE: May 31, 2013
    DOIhttps://doi.org/10.11458/tsj.38.456
    JOURNAL FREE ACCESS
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    Design parameters for a suction channel of process centrifugal compressors were investigated, and an optimizing method to improve efficiency by using the new design parameters was proposed. Both pressure loss and circumferential flow distortion in the suction channel were evaluated by using computational fluid dynamics. The passage sectional area ratios Ac/Ae, Ae/As, and Ac/As were found to be the dominant parameters for the pressure loss and circumferential flow distortion, where Ac, Ae and As are passage sectional areas for the casing upstream side, casing entrance and impeller eye, respectively. The shape of the suction channel was optimized by using the new design parameters. In order to evaluate improvement effect of this optimizing method on stage efficiency, base and optimized types were manufactured and tested. Test results showed that the optimized suction channel achieved 3.8％ higher stage efficiency than the base one while maintaining the operating range.
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  • A Proposal for Improving Cavitation Model
    Motohiko NOHMI, Naoya OCHIAI, Yuka IGA, Toshiaki IKOHAGI
    Article type: Original Article
    2010 Volume 38 Issue 8 Pages 464-469
    Published: 2010
    Released on J-STAGE: May 31, 2013
    DOIhttps://doi.org/10.11458/tsj.38.464
    JOURNAL FREE ACCESS
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    Some issues about cavitation are discussed for improving cavitation model for CFD. Concerning the relatively large cavitation bubbles those are often observed in experiments, combination of grid scale bubbles：GSB and sub grid scale bubble model：SGSB are proposed. GSB shall be computed by using the computational scheme for free surface with phase change model. SGSB can be computed with conventional cavitation model. Breakup of GSB generates SGSB, and coalescence of SGSB makes GSB. Upper limit of void fraction of SGSB is estimated in the range of five or ten percent from the simple speculation of the structure of packed spheres. Two types of cavitation bubble inception model are also discussed. To verify the proposed concepts of cavitation model, a traveling bubble over a hydrofoil is computed by using free surface flow scheme of VOF approach. Computed results show qualitatively similar characteristics of bubble dynamics to those in experimental results.
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  • Numerical Analysis of Flow in Radial Turbine Rotors
    Influence of Nozzle Vane Angle
    Kenta OTSUKA, Tomoya KOMATSU, Hoshio TSUJITA, Satoshi YAMAGUCHI, Akihi ...
    Article type: Original Article
    2010 Volume 38 Issue 8 Pages 470-476
    Published: 2010
    Released on J-STAGE: May 31, 2013
    DOIhttps://doi.org/10.11458/tsj.38.470
    JOURNAL FREE ACCESS
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    Variable Geometry System（VGS）is widely applied to the nozzle vane for the radial inflow turbine constituting automotive turbochargers with the purpose of optimizing the power output at each operating condition. In order to improve the performance of radial turbines with VGS, it is necessary to clarify the influences of the setting angle of nozzle vane on the internal flow of the radial turbine. However, the experimental measurements are considered to be difficult for the flow in radial turbines because of the small size and the high rotational speed.
    In the present study, the numerical calculations were carried out for the flow in the radial turbine at three operating conditions by applying the nozzle vane exit angle set in the experimental study at the inlet boundary as the inlet boundary condition. The numerical results show the characteristic flow behavior at each operating condition.
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  • Blade Vibration Problems of the Turbine Rotor Model and Their Diagnosis
    Norihisa ANEGAWA, Hiroyuki FUJIWARA, Osami MATSUSHITA
    Article type: Original Article
    2010 Volume 38 Issue 8 Pages 477-487
    Published: 2010
    Released on J-STAGE: May 31, 2013
    DOIhttps://doi.org/10.11458/tsj.38.477
    JOURNAL FREE ACCESS
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    It is well known that zero and one nodal diamete（k=0 and k=1）modes of blade vibration interact with shafting system. The former is coupling with torsional and/or axial shaft vibrations, and the latter with bending shaft vibrations. Authors had already reported about coupled resonance vibration of in-plane blade system (Stagger angle θ0=0o) and out-of-plane blade system (θ0=90o) by using coupled 2DOF (Degree-of-freedom) model, and experimentally confirmed the results of simulations. This paper deals with abnormal vibrations encountered in experiments in the each case of in-plane blade system, out-of-plane blade system and θ0=45o blade system. Especially in the case of 45o blade system, we describe the analysis of experimental data and simulation result in detail.
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