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Volume 38, Issue 2
Displaying 1-6 of 6 articles from this issue
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Technical Papers
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Akira KOTANI, Daisuke TAKAGI, Hiroshi MIKAMI2010 Volume 38 Issue 2 Pages 85-92
Published: 2010
Released on J-STAGE: January 21, 2011
JOURNAL FREE ACCESSThe present paper describes experimental and numerical studies to investigate effects of shock waves on the surface of a metallic material. Using shock tube which has a converging section, experiments of the collision between a shock wave and a test piece of metal which installed in the end wall of the section are conducted. The shock wave phenomenon in the shock tube is investigated by using numerical calculation. The hardness and the surface roughness of the test piece exposed to high-pressure and high-temperature regions behind the reflected shock waves generated by reflections on the end wall are measured. Furthermore, the surface and the cross section of the test piece are observed by a scanning electron microscope. The results show that the roughness of the surface of a metallic material decreases and its hardness increases by the collision between shock wave and material.View full abstractDownload PDF (150K) -
Toru SHIGEMITSU, Junichiro FUKUTOMI, Yuki OKABE2010 Volume 38 Issue 2 Pages 93-99
Published: 2010
Released on J-STAGE: January 21, 2011
JOURNAL FREE ACCESSSmall-sized axial fans are used as air cooler for electric equipments. But there is a strong demand for higher power of fan according to the increase of quantity of heat from electric devices. Therefore, higher rotational speed design is conducted although, it causes the deterioration of the efficiency and the increase of noise. Then, the adoption of contra-rotating rotors for the small-sized axial fan is proposed for the improvement of performance. In the present paper, the experimental results of a conventional small-sized axial fan with 100 mm diameter are shown and the important points to adopt the contra-rotating rotors are considered with these results. Furthermore, the performance and the flow field of the contra-rotating smallsized axial fan are clarified by the numerical analysis results and the advantages of the adoption of the contra-rotating rotors for the small-sized axial fan are discussed.View full abstractDownload PDF (124K) -
Shinji SATO, Akinori FURUKAWA2010 Volume 38 Issue 2 Pages 100-105
Published: 2010
Released on J-STAGE: January 21, 2011
JOURNAL FREE ACCESSIt's known that pump head of centrifugal impeller with higher blade outlet angle in air-water two-phase flow condition is kept higher, though the efficiency in water single-phase flow condition is inferior. This fact implies that high efficiency operation becomes possible in both water single-phase flow and air-water two-phase flow conditions by the use of centrifugal pump impeller with variable blade outlet angles. On the other hand, it is found that the installation of diffuser vanes is effective for the improvement of air-water two-phase flow performance of a centrifugal pump. In the present paper, pump performances of the centrifugal impeller with variable blade outlet angles in both water single-phase flow and air-water two-phase flow conditions are described. In addition, effects of installing diffuser vanes on the performances of centrifugal pump with movable bladed impeller are discussed.View full abstractDownload PDF (109K) -
Masahiro MIYABE, Akinori FURUKAWA, Hideaki MAEDA, Isamu UMEKI, Yoshino ...2010 Volume 38 Issue 2 Pages 106-113
Published: 2010
Released on J-STAGE: January 21, 2011
JOURNAL FREE ACCESSIn the present paper, the design guide line of mixed-flow pump with a low specific speed is discussed. Tested pump has a positive slope of head-flow characteristics at low flow rate due to a rotating stall in the vaned diffuser. In the authors' previous studies, it is confirmed that the flow instability is firstly formed in the vaned diffuser hub-side and it causes to diffuser rotating stall, based on the results obtained by both dynamic Particle Image Velocimetry (PIV) measurement and numerical simulation of Computational Fluid Dynamics (CFD). Considering those results, different vaned diffusers were designed to suppress the backflow at further low flow rates. Those pumps are simulated and tested. As a result, it is clarified that the leading edge of the vaned diffuser had better been approached toward the impeller outlet and the vane loading should be after-loaded in order to improve characteristic instability.View full abstractDownload PDF (187K) -
Masami SUZUKI2010 Volume 38 Issue 2 Pages 114-120
Published: 2010
Released on J-STAGE: January 21, 2011
JOURNAL FREE ACCESSComputational fluid dynamics (CFD) modeling and experiments have both advantages and disadvantages. Doing both can be complementary, and we can expect more effective understanding of the phenomenon. Although CFD has more advantages than experiments for the prediction where experiments are difficult to carry out, generally it is difficult to obtain the reliable results when compared with experimental results. However, it is possible to obtain useful results with CFD simulation based on verification by the experimental results. Moreover, experiments cannot deliver correct results for any arbitrary condition due to limitations to experimental equipment, measurement errors and problems with measurement systems. In this paper, the efficiency of a wind turbine is proposed, and the performance can be compared with the other turbomachineries, which is different from the traditional wind turbine factors, that is, the power coefficient, the torque coefficient, the thrust coefficient and so on. The characteristics of wind turbine are evaluated by combining simple approximate analysis based on wing section, CFD simulations and experimental results.View full abstractDownload PDF (112K) -
Mitsuo UNO, Ryunosuke KAWASHIMA2010 Volume 38 Issue 2 Pages 121-125
Published: 2010
Released on J-STAGE: January 21, 2011
JOURNAL FREE ACCESSThis paper proposes the oscillating type micro water power generation, which utilizes the oscillation of the cantilever bluff bodies in the flow field by flow induced vibration for induce the electromagnetic induction, and discusses the effects of each body locations and flow velocity on the oscillating pattern of the bodies and power generation experimentally based on the scale model and simulant model facilities. The oscillating pattern of the bodies varies with changing the distance between the bodies because the vortex, which separates from other body, acts as the excitation or suppression force to the oscillation of the body. When the bodies oscillate in antiphase condition the maximum electromotive force obtained.View full abstractDownload PDF (103K)
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