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論文
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藤沢, 延行 ; 松浦, 勉 ; 船谷, 俊平 ; 弦巻, 明
概要:
application/pdf<br />Journal Article<br />Field temperature measurement technique with encapsulated liquid crystal particles suspended in a liquid has been investigated considering the viewing angle effect on the color to
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temperature transformation. Two calibration techniques are studied, one is a neural network and the other is a spline fitting technique, where the calibration points are distributed over the image plane in order to consider the viewing angle effect. The calibration study is carried out with uniform temperature field image captured at various temperatures. It is found that the calibration error due to the viewing angle variation is reduced with an increase in the number of calibration points and by the introduction of smoothing technique. It is found that the spline fitting technique is superior to the neural network technique considering the evaluated temperature error and computing time. The spline fitting technique is applied to the temperature measurement of thermal convection over a heated surface and the thermal structures generated near the top and bottom boundaries are discussed.
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| 2.
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長谷川, 和之 ; 茂木, 俊夫 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Behavior of a spray combustion in a hot air was studied experimentally. A kerosene spray was injected from swirl atomizer into a hot air stream. The air temperature was controlled from room
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temperature to 1 100 K which was higher than the self-ignition temperature of a kerosene spray. Flame shape and temperature distribution were measured to characterize the spray combustion appeared in the hot air stream. Flow state around the spray was visualized by a Schlieren method to analyze the behavior of the air entrainment into the flame. Furthermore, Mie scattering from the spray droplets by irradiation of the laser beam was observed to visualize the spray concentration in a flame. As the result, ignition point was shifted to the upstream side with an increase of air temperature. When the air temperature became higher than 800 K, the blue flame appeared at the bottom portion of the flame. Penetration of the spray became shorter with an increase of air temperature. Spatial distribution of the spray which were not vaporized in a flame was strongly affected by the air temperature.
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| 3.
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論文
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藤沢, 延行 ; 井上, 智 ; 横田, 正二 ; 田名網, 弘 ; 渡部, 功 ; 高野, 祐二
概要:
application/pdf<br />Journal Article<br />Air flows in a heater unit for automobiles are studied by flow visualization w
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ith tracer injection technique and the visualized images are analyzed by cross correlation method to obtain the velocity distributions in the unit at various mixdoor angles. The results indicate the variations of flow pattern in the heater unit with the mixdoor angles and the appearance of strong interaction between separated main flow and circulating heater flow at relatively large mixdoor angles, which promotes the flow mixing and simultaneously increases the pressure loss inside the unit. The flow fields in the heater unit are calculated numerically based on three dimensional momentum equations combined with κ-ε model of turbulence and with an experimental flow model of heater core. The numerical results reproduce well the experimental flow patterns in the heater unit, but there exits some deviations in the mean velocity and surface pressure distributions at large mixdoor angles.
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| 4.
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藤沢, 延行 ; Ronald, J.Adrian
概要:
application/pdf<br />Journal Article<br />A new calibration technique of liquid crystal thermometry has been introduced
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to the quantitative measurement of temperature in a thermal fluid and applied to the study of turbulent thermal convection. The present calibration technique improves the accuracy of temperature measurement in comparison with the classical calibration technique with hue. Three-dimensional temperature measurement of turbulent thermal convection over a horizontal smooth surface is carried out at a flux Rayleigh number of 3×10^9 by scanning a light sheet normal to the image plane and capturing a number of sequential visualized images. The spatial temperature distributions of thermal plumes over a horizontal surface are demonstrated by the reconstruction of isothermal contour surfaces and various cross-sectional views of the plumes. These results indicate the presence of a polygonal cell structure close to the surface and the generation of plumes at the intersections of high-temperature lines.
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| 5.
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藤沢, 延行 ; 堀, 陽一
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application/pdf<br />Journal Article<br />Flow around a Darrieus wind turbine operating at low tip-speed ratios is studied by flow visualization using the dye injection technique and also by measuring the velocity field using a particle
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imaging and conditional sampling technique. The instantaneous flow patterns observed upon the visualization pictures correspond well to the measured velocity distributions, vorticity contours and velocity magnitude maps. It is found that two pairs of mushroom-type vortices are shed from the blade during a rotation of the rotor, which is due to the dynamic stall phenomenon. These stall vortices are produced by the flow separation over the suction side of the blade and the formation of roll-up vortices from the pressure side. The stall vortices at small incidence angles advance to the returning blade side, while those at large incidence angles grow along the moving blade and interact with flow near the blade. The effect of tip-speed ratios on the growth of stall vortices is also examined.
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FUJISAWA, Nobuyuki ; KURIBARA, Toshiaki ; YOKOTA, Masaji ; TANA-AMI, Hiroshi ; WATANABE, Isao
概要:
application/pdf<br />Journal Article<br />Flow mixing in an air conditioning unit for automobiles is studied experimentally in a water tunnel to investigate the mixing mechanisms of flow inside the unit at various mix-door angles. Flow
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visualization is carried out using tracer particles and the fluorescent dyes illuminated by Ar laser sheet, which allows the simultaneous measurement of velocity and diffusion distributions of the flow mixing in the unit by analyzing the captured color images. The measurement of velocity and diffusion distributions indicates enhanced flow mixing at certain mix-door angles, which is caused by the intense mixing of the main flow and the recirculating heater flow downstream of the mix-door. The temperature distribution measured in a prototype unit supports the mixing characteristics observed in the model unit, suggesting the usefulness of the present image analysis.
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| 7.
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藤沢, 延行 ; 栗原, 俊昭 ; 横田, 正二 ; 田名網, 弘 ; 渡部, 功
概要:
application/pdf<br />Journal Article<br />Flow mixing in an air conditioning unit for automobiles is studied experimentally in a water tunnel to investigate the mixing mechanisms of flow inside the unit at various mixdoor angles. Flow
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visualization is carried out using tracer particles and fluorescent dyes illuminated by an Ar laser sheet, which allows the simultaneous measurement of velocity and diffusion distributions of flow mixing in the unit by analyzing the captured color images. The measurement of velocity and diffusion distributions indicates enhanced flow mixing at certain mixdoor angles, which is caused by the intense mixing of the main flow and the recirculating heater flow downstream of the mixdoor. The temperature distribution measured in a full-scale unit supports the mixing characteristics observed in the model unit, suggesting the usefulness of the present image analysis.
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| 8.
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藤沢, 延行 ; 田口, 祥和 ; 佐藤, 毅 ; 植村, 知正 ; 長屋, 幸助 ; 井開, 重男
概要:
application/pdf<br />Journal Article<br />Conditional sampling and the point-averaging technique have been introduced to particle-tracking velocimetry using a binary cross-correlation algorithm. This system is applied to the
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measurement of unsteady flow inside a rotating Savonius rotor, and the quantitative nature of the power mechanisms of the rotor at various rotor angles and tip-speed ratios are newly discussed and the usefulness of this techique is demonstrated. It is found that all velocity fields in and around the rotor vary markedly with the tip-speed ratio, and that the separation of Coanda-like flow on the convex side of the advancing blade is delayed by the velocity fields induced by the rotor rotation and also by the production of vortices downstream of the advancing blade.
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