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Ryo SUZUKI, Kenta OKAJIMA, Kiyoshi KAWAGUCHI, Daisuke WATANABE
Article type: Article
Session ID: G0500-4-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In order to minute the micro-bubble diameter under low supplied pressure of 0.1MPa, the characteristics of the swirl-type micro-bubble generation device were investigated by changing swirl chamber length. The performance of the micro bubble generation device was evaluated by the bubble diameter measured by the image measurement method. Moreover the behavior of micro-bubbles was visualized by high speed camera, the flow velocity distribution around exit of micro-bubble generator was measured, and numerical analysis of the flow in the micro-bubble generator was conducted by using LES. It was clarified that the micro-bubble diameter became minuter in the shorter length of swirl chamber, and that the increase of shear stress in the surface of micro-bubble generator caused the decrease of micro-bubble diameter in radial flow out type.
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Gaku HIJIKATA, Sumio SAITO
Article type: Article
Session ID: G0500-4-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The pump was investigated about the behaviors under cavitating conditions. Change in the pump head and the shaft power curves are closely related to the cavitation growth on the suction side of the blades. By experiments on cavitation aspects of an axial-flow pump, the growth of cavitation due to the change of the net positive suction head (NPSH) and the pump performance were clarified. Moreover, the frequencies of cavitaion were disclosed by conducting the wavelet analysis on pressure fluctuation at the casing wall. It was made clear in this paper that the tip clearance cavitation is proven to have a specific frequency.
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Hiroaki TSUBONE, Kouhei TAKADA
Article type: Article
Session ID: G0500-4-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In recently years, extraordinary propagation of water-weed such as Water Lettus and so on in waterway, river and reservoir has been serious problem. However, some removal activities by heavy machine and human-wave sweep has not given desired effect due to the limited activity area and low efficiency. In this study, a water-weed collecting ship with Archimedean screw, which is amphibious ship and can move and remove them regardless of bottom condition of river and reservoir and propagation condition, has been developed in order to solve the problem. In this paper, for the purpose of a development of a design guideline of Archimedean screw, an effect of pitch of Archimedean screw on thrust was experimentally investigated and compared with the simulation. Furthermore, the motion of the water-weed collecting ship with two Archimedean screws was investigated and die mechanism was clarified
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Takayuki HARA, Daisuke MORITA, Yutaka OHTA, Eisuke OUTA
Article type: Article
Session ID: G0500-5-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of unsteady P-Q performance, casing wall pressure fluctuations and their wavelet analyses. The feature of the test compressor is a capacity tank facility connected in series to the compressor outlet in order to supply a compression wave from the compressor downstream. Research attention is focused on the post-stall characteristics of surge and rotating stall which occurs simultaneously. The behavior of the test compressor on the unsteady P-Q characteristic map shows that the surge cycle changes irregularly and the results of wavelet analyses of wall pressure fluctuations suggest increasing and decreasing of cascade flow blockage by variation of the rotating stall cell structure. The surge cycle may selectively determined by the rotating stall cell structure within the rotor cascade. The peculiar unsteady behaviors of the cascade flow by injecting the compression wave are also discussed.
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Takashi GOTO, yasumasa HIRATO, Yutaka OHTA, Eisuke OUTA
Article type: Article
Session ID: G0500-5-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The purpose of this research is to investigate the effects of tapered diffuser vane, which is installed into a centrifugal compressor with shortened impeller-diffuser distance, on compressor performance and radiated noise by experiments. In addition to shortening the length, a half of the original impeller-diffuser distance, diffuser vanes were placed on three variant inlet angle positions. The noise measurements show shortening impeller-diffuser distance enlarged radiated noise but changing inlet angles little influenced to noise. However in compressor performance, in the case of setting tapered diffuser vanes on the small inlet angle position, compressor performance improved 2.24% at designed flow-rate operation and stable operation range enlarged 30% compared with original diffuser setting The oil-film method at diffuser leading edge revealed that these remarkable improvements in compressor performance are caused by tapered diffuser vane. Tapered region suppresses the leading edge vortex growth that blocks the main stream into diffuser passages and causes a loss of a centrifugal compressor.
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Yuki SATIO, Toshimasa SHIRATORI
Article type: Article
Session ID: G0500-5-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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An experiment has been conducted to investigate static pressure fluctuation behind shock wave in self-excited shock wave oscillation phenomenon on 2D symmetrical circular-arc airfoil in internal transonic flow. Static pressure fluctuation was measured by high-response static pressure probe, and flow was visualized by Schlieren method. Experimental results show that static pressure fluctuation become smaller, as shock wave movement become smaller. In addition, concerning the phase delay of static pressure fluctuation behind shock wave, the overall trend is that the phase delay becomes larger, as the measured point leave for shock wave. When the shock wave form is saw tooth wave, phase delay trended to different from when the shock wave form is sine wave.
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Yuta YOSHIMOTO, Katsuhito MIHASHI, Nobuya MIYOSHI, Ikuya KINEFUCHI, Ka ...
Article type: Article
Session ID: G0500-5-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In order to generate high-energy molecular beam in a range of 1 - 5 eV without any undesirable impurities, we have developed a beam source with a non-diaphragm type shock tube which can operate at a repetition rate high enough for efficient data acquisition. The volume of our shock tube is much smaller than that of conventional ones so that the evacuation time between each shot can be made as short as possible. Our preliminary experiment showed that small inner diameter of the tube leads to the strong effect of boundary layer on the propagation of shock waves. In the present study, we measured shock Mach numbers in convergent tubes whose diameters linearly decrease from 4 mm to 2 mm and estimated the translational energy of shock-heated beam. The results suggested that a convergent shock tube with the optimized configuration could generate higher energy beam than straight one.
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Daisuke MAnABE, Hiroshi KATANODA, Minoru FUKUHARA
Article type: Article
Session ID: G0500-5-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Thermal spraying is one of the most effective surface coating technologies. The authors developed a cutting-edge thermal spray gun; the water-cooled two-stage HVOF thermal spray gun. The gun has a long water-cooled passage of supersonic hot gas. Therefore, the gun could be operated at the frictional choking condition, which is expected to decrease the velocity of the spray particles. It is experimentally well known, in general, that the larger impact velocity of the particle at the substrate results in better coating quality. In this study, therefore, the gas flow as well as the particle velocity of the water-cooled two-stage HVOF thermal spray gun is investigated by using one-dimensional analysis, which takes into account of the pipe friction and heat transfer. The operating conditions which occur the frictional choking are clarified in this research.
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Yuki HORI, Hiroki SASADA, Masahiro KAMEYAMA, Katsuhiro YAmAMOTO
Article type: Article
Session ID: G0500-5-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The purpose of this paper is analyzing the effect of valve closure time on water hammer phenomenon with column separation in viscoelastic pipes by experiment and numerical solution based on the Discrete Free Gas Model. The results are following: (1) Duration of column separation, pressure spike, water hammer pressure and superposition pressure increase linearly with a decrease of valve closure time. (2) The velocity of the tip of the cavity at collapse is bigger than the one at occurrence. (3) There are little differences between the results of numerical solution with linear interpolation and with curved interpolation in characteristic method, if Courant number is near 0.7 and dividing number of pipe length is bigger than 100. And both agree with the experimental results except pressure spike.
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Mitsufumi OKADA, Hiroshi KATANODA, Minoru FUKUHARA
Article type: Article
Session ID: G0500-6-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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There are some ceramic coating methods to spray ceramic particles at room temperature by low-density supersonic jet. In order to increase the deposition efficiency of the sprayed particle, the impact velocity of the particle need to exceeds the threshold fracture velocity. The authors have clarified the gas dynamic condition to crush the ceramic particle at substrate by numerical simulation. However, the physical details of the tracking performance of the particle to the low-density gas flow remain unclarified. In this study, the tracking performance of the ceramic particle to the low-density supersonic jet flow is investigated by numerical simulation. It is concluded in this study that the worse tracking performance of the ceramic particle for the low-density jet flow, compared to that of the high-density jet flow, is mainly due to the low density of the jet flow.
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Yusuke KARINO, Hiroshi KATANODA, Minoru FUKUHARA
Article type: Article
Session ID: G0500-6-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Thermal spraying is one of successful surface processing method that gives restoration of a new function on various mechanical components. The thermal spraying process accelerates the solid particle by a high temperature and a high velocity gas stream. After impacting on the surface of the substrates, the particles are formed into a coating. The present study is a gas-dynamic research on a cold spray, which is a cutting edge coating method. The cold spray process makes the solid particle impact on the substrate at a high velocity by the supersonic gas flow in the state of the solid phase to form a coating. It is experimentally clarified that the particle starts deposition on the substrate when particle velocity is exceeds a critical velocity. Therefore, it is important to clarify the tracking performance of solid particle to the gas velocity. In the present study, the tracking performance of solid particle to the gas velocity in the cold spray is clarified by the one-dimensional analysis.
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Ryota SHIMOJI, Hiroshi KATANODA, Minoru FUKUHARA
Article type: Article
Session ID: G0500-6-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Cold spray is one of the thermal spray technologies to make a coating on a solid surface. In the cold spray, the solid particles are accelerated by a supersonic flow of an inert gas with the temperature of less than 1000 degrees Celsius. It is experimentally well known that when a particle impact velocity exceeds a critical value, the particle is formed into a coating. From the practical point of view, the deposition efficiency, which is the ratio of the deposited mass on of the particle against the sprayed mass of the particles, is an important parameter. The parameters which affect the deposition efficiency are, for example, the particle diameter, the type of powder material, the gas pressure and temperature. The deposition efficiency can be obtained experimentally. However, a computational approach could efficiently reduce the cost of estimation evaluate the effects of parameters on the deposition efficiency. In the present study, the effect of particle size distribution of the powder on the deposition efficiency is clarified by numerical simulation.
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Yoichi TSUCHIDA, Yuji SUKENARI
Article type: Article
Session ID: G0500-6-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In a triple-product classifier using an almost rigidly rotating flow in which small feed-powder particles suspended in a liquid medium with a low mass-concentration are accurately classified into fine, medium and coarse products by the difference in centrifugal force and fluid drag acting on each particle due to the particle-size difference with the aim of considering the scaling law on a medium product, we have numerically simulated the liquid-medium flow with the Navier-Stokes and continuity equations and the particle motion with the Basset-Bousinesq-Oseen equation. First, partial fractional efficiencies Δη_F, Δη_C of fine and coarse products are represented by govering parameters as the scaling law. Second, the partial fractional efficiency Δη_M of a medium product is determined by Δη_F and Δη_C. Third, the yield and variation coefficient of the mean product are derived by Δη_M, in order to consider the medium-product throughput and uniformity of particle.
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Yoichi Tsuchida, Masato Mukae, Shintaro Yoshida
Article type: Article
Session ID: G0500-6-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In a single-stage classification system using an almost rigidly rotating flow in which very small feed-powder particles suspended in water are accurately classified into fine and coarse products by the difference in centrifugal force and fluid drag acting on each particle due to the particle-size difference, we conducted classification experiments, with the aim of raising throughput by increasing flow rate and feed-concentration for a constant centrifugal-effect parameter. Consequently, we have reached the following conclusions. (1) The cut size scarcely change for a high flow-rate and feed concentration. (2) Increasing flow-rate for a dilute feed-concentration improves classification accuracy while that for a dense feed-concentration decreases accuracy. (3) Increasing feed-concentration for a low flow-rate improves classification accuracy while that for a high flow-rate decreases accuracy.
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Yoichi TSUCHIDA, Shintaro YOSHIDA, Masato MUKAE
Article type: Article
Session ID: G0500-6-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In a single-stage classification system using an almost rigidly flow in which small feed-powder particles suspended in a liquid medium with a low mass-concentration are accurately classified into fine and coarse products by the difference in centrifugal force and fluid drag acting on each particle due to the particle-size difference, with the aim of considering the change in accuracy with increasing flow-rate, we have conducted classification experiments, keeping the centrifugal-effect parameter constant to hold the cut size constant. With increasing Rossby number (flow rate) by decreasing Ekman number (by increasing rotation rate), the cut size scarcely changes and the classification accuracy is more improved. This is due to decreasing Ekman number. With increasing Rossby number further, however, the accuracy decreases drastically. Corresponding to this fact, the flow state of the classification field changes definitely.
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Article type: Appendix
Pages
App4-
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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