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Volume 41, Issue 2
Displaying 1-7 of 7 articles from this issue
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Technical papers
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Masaaki MIYA, Toshiyuki HIRANO, Hoshio TSUJITAArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 72-77
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSIn the operation of a centrifugal compressor of turbocharger, instability phenomena such as rotating stall and surge are observed at lower flow rate than that at the designed point. Therefore, it is important to control the onset of instability phenomena to extend the stable operation range of centrifugal compressor to the low flow rate region. In the present study, the control of rotating stall and surge for a centrifugal compressor was tried by using a nozzle injection system in which a part of the flow from the delivery duct was re-circulated to the impeller inlet. The three types of air injection nozzle were used to investigate the effect of nozzle inner diameter on the performance characteristics. In addition, the circumferential position of the injection nozzle was changed in order to examine the relationship between the optimum position and the nozzle inner diameter.View full abstractDownload PDF (113K) -
（2nd Report：Optimization of a Rocket Turbopump Turbine for Reduction of Thomas Force）Junya TAKIDA, Kenichi FUNAZAKI, Masaharu UCHIUMI, Mitsuru SHIMAGAKIArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 78-88
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSAn application of optimization design process for reduction of Thomas force of rocket turbopump turbines is presented in this paper. Because of its special specification, rocket turbopump turbine blades have higher loading. In such a situation, there is a possibility of rotor vibration problem generated by turbine instability force, that is, “Thomas Force”. Actually in the past engine development in Japan, there was the shaft vibration problem due to “Thomas Force”. In order to reduce shaft vibrations, it is important to keep “Thomas Force” small. In this paper, the results of optimization for the existing rocket turbopump turbine by using Robust Design Process and Multi-Objective Genetic Algorithm(MOGA)are discussed.View full abstractDownload PDF (308K) -
Nobuyuki YAMAGUCHIArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 89-97
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSCompressor-duct systems could be configured by several layouts of compressors, suction and delivery ducts, and valves. Dynamic flow behaviors in surge have been surveyed in three duct-layouts consisted of a nine-stage axial-flow compressor and ducts by use of a computer-code SRGTRAN(Surge Transients Simulation and Analysis)of own coding. The cases for study are ; (1) a suction duct with an open inlet, a compressor, and a delivery duct terminating with an exit valve, (2) a suction duct starting with an inlet-valve, a compressor, and a delivery duct having an open exit, and (3) a close-loop duct system having a compressor, a suction duct, a delivery duct, an intercooler and a valve interconnecting both ducts inbetween. The results have shown that the surge frequencies, and the local distributions of the amplitudes of pressure, mass flows, densities, etc. in surge, change very much, depending on the layouts.View full abstractDownload PDF (239K) -
Yasuyuki ENOMOTO, Hideyuki KAWAJIRIArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 98-103
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSRecently the case which pressure fluctuation enlarges with high partial load of the Francis turbine is reported. In this study, model test was conducted to investigate this instability vibration. When the instability vibration occurred, large pressure fluctuation those frequency is about 40 Hz occurred at casing and between runner and guide vane. On this condition, cross-section of the whirl is oval and the whirl rotates in the whirl core circumference at about 20 Hz. So the oval cross section whirl knocks the wall surface twice in 1 round and the frequency is about 40 Hz. This frequency is near the dominant frequency at casing inlet and between runner and guide vane. It is thought to be the instability vibration is caused by this oval cross section whirl.View full abstractDownload PDF (180K) -
Naoko INOUE, Sayaka NISHIMURA, Yutaka HARA, Takahiro SUMIArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 104-109
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSMany vertical axis wind turbines(VAWTs)have been recently studied and developed by virtue of the non-directionality of wind. For the design and performance prediction of wind turbines, the blade element momentum(BEM)theory is useful because of its much less computational time than CFD approach. However, when using BEM theory, accurate aerodynamic characteristics of the blade airfoils are needed in order to predict wind turbine performance with high accuracy. In this study, two-dimensional RANS was carried out for NACA 0018 airfoil, which aerodynamic data has been published over broad ranges of angle of attack and Reynolds number, in order to validate the present CFD. Moreover, by using the present CFD results, performance predictions of VAWTs by the BEM theory were carried out, and were confirmed to be improved with respect to small VAWT compared with the aerodynamic data given by other researchers.View full abstractDownload PDF (133K) -
Toru SHIGEMITSU, Junichiro FUKUTOMI, Ryosuke SONOHATAArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 110-115
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSRenewable energy attracts a great deal of attention from the point of view of energy problem and global warming by CO2 emission. Small hydropower is recognized as a new energy in Japan. There are many places to install pico hydropower in irrigation water channels and small rivers, so there is a strong demand for small hydro turbine to minimize environmental impacts. In this research, contra-rotating rotor and low solidity rotor were applied for high performance and stable operation of small hydro turbine. In this paper, performance and internal flow of contra-rotating small hydro turbine were clarified by numerical analysis and the possibility of the contra-rotating rotor for small hydro turbine used as electrical appliance and a control method to improve the performance were considered.View full abstractDownload PDF (151K) -
Masami SUZUKI, Kazumasa AMEKU, Masahiro FUTAMIArticle type: Technical papers
2013 Volume 41 Issue 2 Pages 116-121
Published: 2013
Released on J-STAGE: May 10, 2015
JOURNAL FREE ACCESSBased on the Navier-Stokes equation, a numerical method is presented to simulate flows around a Savonius rotor. The computational code is composed of the finite volume method using curve-linear boundary fitted coordinates and the overset grids, and the solution is solved by SIMPLE algorithm. It is attempted to make clear the complex flow around the turbine blades using computer graphics and computational fluid dynamics. The flow is shown using both absolute coordinate system and rotating coordinate system. The flow is drawn by the velocity vectors, the grey-scale contour of pressure, and the vorticity using OpenGL(Open Graphic Library). It is shown that to understand the effect of the lift and the vortex around the turbine in addition to the drag is important for improvement the turbine performance.View full abstractDownload PDF (117K)
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