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舩津, 賢人 ; 伊藤, 一磨 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />In order to investigate the effectiveness as a heat shield of SiC-based and carbon-based materials, the ablation experiments were performed in micro-air plasma-jet at an atmospheric
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pressure. Test materials are SiC/SiC, SiC, C/C, and C. These materials were inserted into the plasma-jets and ablation properties were measured, that is weight loss rate and the heat of ablation. In order to investigate the physical behaviors of the materials in the plasma-jets, the ablating C/C and C were observed by a high-speed video camera. In addition, the surface of the ablated materials was observed with a scanning electron microscope and was analyzed quantitatively with an electron probe microanalyzer. It was found that SiC-based materials might be effective as an ablation material because of its small weight loss. The heats of ablation of C/C and C were almost the same. The surface observation and quantitative analyses showed that the ablated surfaces of SiC-based materials were covered with silicon oxides.
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| 2.
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舩津, 賢人 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Spectroscopic measurements of micro-air plasma-jets were performed at an atmospheric pressure in the wavelength region of 280 to 420nm where N^+_21- and N_22+ bands were
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predominant. The spectra were measured at many radial and axial points to obtain its radiative characteristics in detail. Abel inversion method was applied to all the experimental data measured laterally to obtain true spectral intensity distribution at all radial points. The comparison of the experimental and Abel-inverted spectra showed that the experimental data could not be used directly to deduce temperatures without the Abel inversion except around the flow axis. Temperatures of the plasma jets were estimated by applying the spectral matching method to N^+_21- bands. Rotational temperature for N^+_21- bands was about 8000K, and was almost independent of radial positions. Vibrational temperature was about 28000K in the core region with much higher in the outermost region.
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| 3.
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久保田, 聖 ; 舩津, 賢人 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Spectroscopic measurements of micro-air plasma-jets were performed at an atmospheric pressure in the wavelength region of 280 to 420nm where N^+_21- and N_22+ bands were
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predominant. The spectra were measured at many radial and axial points to obtain its radiative characteristics in detail. Abel inversion method was applied to all the experimental data measured laterally to obtain true spectral intensity distribution at all radial points. The comparison of the experimental and Abel-inverted spectra showed that the experimental data could not be used directly to deduce temperatures without the Abel inversion except around the flow axis. Temperatures of the plasma jets were estimated by applying the spectral matching method to N^+_21- bands. Rotational temperature for N^+_21- bands was about 8000K, and was almost independent of radial positions. Vibrational temperature was about 28000K in the core region with much higher in the outermost region.
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久保田, 聖 ; 舩津, 賢人 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Spectroscopic measurements of micro-air plasma-jets generated at low pressures were performed at several points on flow axis, using a spectrometer in the wavelength region of 200 to 900
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nm. The N_22+ bands and N_2^+1- bands were predominant in the region of 280 to 480nm, and atomic lines of N and O in the visible and infrared regions. Temperatures of the plasma-jets were estimated by applying a spectral matching method to N_2^+1- bands along a flow axis for low-pressure conditions. Rotational temperatures for N_2^+1- bands were 6000 to 7000K, and vibrational temperatures 25000 to 28000K, almost independent of pressures and axial positions. It was found that the rotational temperatures measured had great difference from the gas temperature based upon an empirical formula for supersonic free jets, and also the vibrational temperatures were much higher than those expected.
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久保田, 聖 ; 舩津, 賢人 ; 白井, 紘行 ; 田部井, 勝稲
概要:
application/pdf<br />Journal Article<br />A micro-air plasma-jet, whose size was 3.0mm in length and about 0.7mm in diameter, was measured spectroscopically in the wavelength region of 200 to 900nm using a spectrometer. The N_2 2+ and N^+_2
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1- bands were predominant in the region of 280 to 500nm and intense atomic lines of N and O in the infrared region. Temperatures of the plasma-jet were determined by applying a spectral matching method to those band spectra. There was a very good agreement between the theoretical and experimental spectra in the main part of the measured wavelength region. It was found that the rotational temperature was 7,000 to 9.000K depending on the band, vibrational temperature about 28,000K for both the bands, and the jet was remarkably in thermal non-equilib-rium state.
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田部井, 勝稲 ; 春山, 周夏 ; 山口, 修市 ; 白井, 紘行 ; 高草木, 文雄
概要:
application/pdf<br />Journal Article<br />Characteristics of a micro bubble generator using a strong swirl jet were studied experimentally and numerically. Experiments were conducted by changing the nozzle diameter, the inflow pressure
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and the gas flow rate, systematically. For measurements of the bubble distribution function of PDF, a simple method using a light transmission was proposed. Principle of the method was based on changes of the light transmission due to the bubble rising to the surface of water. The bubble distribution measured by the method agreed well with that by a usual backlight method. In this study four non-dimensional parameters governing the micro bubble generation were adopted, that is, Weber number for the average diameter of bubbles, Reynolds number, the ratio of flow rate and the velocity ratio for the swirl jet. It was found that the relationship between Weber number and Reynolds number could be arranged with each velocity ratio as a parameter. An approximate experimental expression for the average diameter showed that the micro bubble diameter strongly depended on the axial flow velocity and the rotational speed of the swirl jet.
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田部井, 勝稲 ; 白井, 紘行 ; 益子, 俊二 ; 木村, 忠夫 ; 高草木, 文雄 ; 蜂須賀, 賢
概要:
application/pdf<br />Journal Article<br />Cavitation bubbles emit very weak light (luminescence) due to the bubble collapses. It is expected that the light emission may be closely related to the cavitation erosion. In order to confirm
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the relationship between the erosion damage rate and the lumin
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斉藤, 正浩 ; 荻原, 五郎 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Behavior of spray-to spray impingement, where two spray jets were formed EFI (Electronic Fuel Injection) nozzles and impinged each other, was studied experimentally. This system was
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named MISS EFI. Spray penetration and the Sauter mean diameter of the spray were measured to investigate the effect of spray-to-spray impingement. When the impingement location was set at the vicinity of the nozzles, impingement phenomena became to be jet to jet impingement of the liquid column. In this condition, the penetration became shorter than that of the individual penetration. However, the penetration did not changed after spray-to-spray impingement. From the photographs of jet-to-jet impingement, it was confirmed that the liquid film was formed by the impingement, and then this liquid film disintegrated to small droplets. In the spray-to-spray impingement, on the other hand, the relatively large droplets still existed in the impinged spray, because the two sprays crossed each other without disintegration of the droplets. The photograph of the spray-to-spray impingement showed that the droplet-to-droplet impingement in the spray was rarely observed. Further, the chance of coagulation of the droplets was less observed than the disintegration of the dropled. These behavior of the spray-to-spray impingement agreed with the reduction of the Sauter mean diameter of the impinged spray.
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| 9.
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江原, 拓未 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />In the previous paper, the authors clarified that an impingement spray have the slip flow region near the impingement point on the wall. Then, behavior of a diesel spray impinging on an
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inclined wall was modeled to make an empirical formula of impingement spray tip penetration. To introduce a new model of spray growth behavior, uniform velocity penetration of the spray growth behavior in the slip region were framed and included into the traditional formula about the free spray. The momentum conservation theory was applied to the spray of after slipping. The growth behavior of an impingement spray was expressed as the function of wall distance and inclined wall angle. Spray path length calcurated from this formula showed qualititaively well agreement with an actual measurement.
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| 10.
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江原, 拓未 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />In this paper, behavior of a diesel spray impinging on an inclined wall was experimentally investigated in a pressurized vessel. In order to clarify the wall effect on a diesel spray
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structure, a relative angle of the inclined wall to the spray axis was varied. Spray penetration along the wall was observed optically and compared with that of a free spray. To observe an internal structure of the spray, it was visualized by a YAG laser sheet light and its tomographic image was captured on a film. The photo-image on a film was taken into an image analyzing computer using a high resolved image scanner. High density ridges in the tomographic image were extracted to clarify the internal structure of an impingement spray. Further, the growth characteristics of impingement spray was observed by a high speed photograph. To evaluate various spray motion quantitatively, a spray path penetration which described a development of a spray tip along the wall was used. As the result, the slip flow region of spray was found near the impingement point on the wall. It seemed that the injected fuel does not make a mixture and slipped on the wall surface in this slip region. The length of this region was measured in various impingement wall condition.
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