Turbomachinery
Online ISSN : 1880-2338
Print ISSN : 0385-8839
ISSN-L : 0385-8839
Volume 33, Issue 10
Displaying 1-6 of 6 articles from this issue
Technical Papers
  • Junichi KUROKAWA, Hiroshi IMAMURA, Young-Do CHOI, Masahiro ITO, Masafu ...
    2005 Volume 33 Issue 10 Pages 592-600
    Published: 2005
    Released on J-STAGE: January 10, 2007
    JOURNAL FREE ACCESS
    Cavitation is the most serious problem in developing high-speed turbopump, and inducer is often used to avoid cavitation in main impeller. Thus, inducer is always operating in the worst cavitation condition. If it is possible to control and suppress cavitation in inducer by some new device, it might be possible to suppress cavitation occurring in any type of pumps. The purpose of present study is to develop a new effective method of controlling and suppressing cavitation in inducer using shallow grooves, which is named "J-Groove". J-Groove is installed on the casing wall near the blade tip to use the pressure difference between high pressure region and low pressure region of the inducer blade. The results show that proper combination of backward-swept inducer with J-Groove improves suction performance of turbopump remarkably in the range of partial flow rate as well as designed flow rate. The rotating backflow cavitation occurring in the range of low flow rate and the cavitation surge occurring in the vicinity of the best efficiency point can be almost suppressed by installing J-Groove.
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  • Hideaki TAMAKI, Ji DAI
    2005 Volume 33 Issue 10 Pages 601-606
    Published: 2005
    Released on J-STAGE: January 10, 2007
    JOURNAL FREE ACCESS
    There is a possibility that the exchange of the piping system changes surge characteristic of a compressor. The piping system of a plant is not always the same as that of a test site. Then it is important to predict the effect of piping systems on surge in centrifugal compressors. Several turbochargers combined with the different piping systems were tested. The lumped parameter model was applied for the prediction of surge. Surge lines were calculated with the linearlized lumped parameter model. The difference between the test and calculated results was within 10%. Trajectory of surge cycle is also examined, solving the lumped parameter model. Mild surge and deep surge were successfully predicted. This study confirmed that the lumped parameter model is a very useful tool to predict the effect of piping systems on surge in centrifugal compressors, even though that is a simple model.
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  • Toshinori KASHIWABARA, Toshiaki KANEMOTO
    2005 Volume 33 Issue 10 Pages 607-613
    Published: 2005
    Released on J-STAGE: January 10, 2007
    JOURNAL FREE ACCESS
    The authors have proposed the counter-rotating type hydroelectric unit in which two stage runners successfully counter-rotate the inner and the outer armatures of the peculiar generator. This paper proposes the optimum profile of the floating type tidal current power station to have this hydroelectric unit on board. The runners are installed in the vertical passage where the flow runs downward. The downward flow is caused by the pressure difference between the flat upper-wall and the convex down-wall of the runner housing submerged. The hydrodynamic characteristics are fundamentally investigated and discussed to give effectively the tidal current energy to the runners. Resultantly, the optimum profile is (1) to make the front and the rear ends of the runner housing dress with the brim edges, (2) to set the semicircular fence at the outlet of the runner passage, and (3) to equip with the flow guide of the circular arc around the runner housing.
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  • Akira INAGAKI, Toshiaki KANEMOTO
    2005 Volume 33 Issue 10 Pages 614-621
    Published: 2005
    Released on J-STAGE: January 10, 2007
    JOURNAL FREE ACCESS
    To slow the global warming, greenhouse gas emissions should be reduced in the electric power generation. Though the hydroelectric source has the least unit requirement of CO2 gas emissions among various electric power resources, a large-scale dam-oriented hydro-power is not regarded as desirable due to its significant impact on natural ecosystem in rivers and/or forests. In such a situation, the authors have proposed the new type hydraulic turbine, named "Gyro-Type Hydraulic Turbine". The turbine rotor is composed of several blades with high aspect ratio and is submerged nearly parallel to the stream. Thus, it is suitable for shallow streams. From this study, the following features are found out: The maximum torque/output is at higher rotational speed, which is desirable as the turbine performance for the micro hydroelectric power generation, and the output can be improved with the twisted blades.
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  • (1st. Report Effects of Number of Blades on Fan Performance and Noise Characteristics)
    Kiyoshi KAWAGUCHI, Kenichi OKUI, Yuji SHINYA, Naofumi MIMURA
    2005 Volume 33 Issue 10 Pages 622-628
    Published: 2005
    Released on J-STAGE: January 10, 2007
    JOURNAL FREE ACCESS
    In recent years the fan heater used for industry and residence has become smaller, lighter, and more silent as the result of improvement. However there are problems that the fan heater size is very large, and the noise is very high due to air pressure loss of heat exchangers. Therefore we have been developing the centrifugal type fan with the function of heat exchanger. The features of this new type fan heater are that the fan heater size is very small and silent because the fan and the heat exchanger are in one body. This paper described the effects of number of fan blades on fan performance and noise characteristics of the centrifugal fan with the function of heat exchanger. The fan performance and noise characteristics of the fan having different number of blades (number of blades: 12,20,28) were clarified by measuring fan performance, fan noise spectrum and 3-dimensional flow velocity of fan outlet. In results, the fan static pressure decreased with the increase of number of fan blades at high flow rate region, and the noise of fan with blades number of 20 was the highest.
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  • Yuji KANEMORI, Ying Kang PAN
    2005 Volume 33 Issue 10 Pages 629-636
    Published: 2005
    Released on J-STAGE: January 10, 2007
    JOURNAL FREE ACCESS
    This paper reports on an experiment in a centrifugal pump with several different impeller exit blade shapes. A pump is usually designed to a specification associated with the maximum impeller diameter. Therefore, when higher head: H or capacity: Q is demanded, a larger impeller diameter will be required.
    On the other hand, in order to make a slight improvement in head-capacity curve, without changing the impeller diameter, underfiling could be used. Namely the metal removal of a section of the blade at suction side of impeller exits, is a method to achieve modest gain in head. Inversely to the underfiling of blade exits, another method to control pump performance is the formation of flaps at impeller blade exits.
    Moreover, an analytical method of predicting the pump performance related to the introduction of a flap at the trailing edge of impeller blade is presented.
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