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論文 |
論文
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石井, 哲人 ; 佐藤, 博之 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />The effects of gravity on the fluctuation characteristics of turbulent diffusion flames were experimentally investigated. Super gravity fields were formed using a spin tester. The gravity
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level G was changed from 1 to 20, where G was defined as the value of super gravity per normal gravity. Flame states such as laminar, flickering and turbulent flames were observed under the various conditions of gravity level, G and Reynolds number, Re. The transition from laminar to turbulent and blow out limit were summarized on a G-Re map. Characteristics of turbulent fluctuation were measured by a laser light reflection method. Power spectra and auto-correlations were derived from the signal of laser intensity. As the result, it was found that the turbulent flame was begun to periodic oscillation with increasing the gravity level. Time scale of turbulent fluctuation in the super gravity became long than that in the normal gravity. Spectrum component in power spectrum shifted to the low frequency side when the gravity level became high. And the full width at half-maximum of autocorrelation peak became wider in the super gravity conditions.
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| 2.
地図 |
地図
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山口昇一、佐藤博之、松井愈[編]
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論文 |
論文
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佐藤, 博之 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Effect of gravity level on the flickering motion was experimentally investigat
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ed for the propane and propane-hydrogen jet diffusion flames. A centrifuge was used for quantitative measurement of gravity effect, and frequency analysis was performed for the flickering flames. From the result of measurements under various gravity levels, it was clarified that the flickering frequency increased with an increase in the gravity level and it was correlated with two relationships expressed by the Strouhal number and the Froude number. One relationship was St∝Fr^<-0.41> for high Froude numbers (Fr≥100), and the other was St∝Fr^<-0.50> for low Froude numbers (Fr≤100). It meant that the Froude number gave the criterion of the flickering behavior and that flickering frequencies expressed by these two equations were affected by buoyancy in different ways. From the frequency analysis, it was found that oscillations of a flickering flame and a thermal convection around the flame were linked, but the characteristic of each flickering motion was different in the stability of periodicity.
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| 4.
論文 |
論文
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佐藤, 博之 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Quantitative investigation of the gravity effect was performed for acetone and kerosene pool fires. A centrifuge was used to examine the gravity effect. Small-scale pool fires were observed
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under various high gravity fields. Regions of stable flame, puffing flame and irregular oscillatory flame were mapped with the gravity level and pool diameter. Flame height decreased and oscillatory frequency increased with an increase in the gravity level. Behavior of the flame height was agreed quantitatively with the scaling prediction presented by Orloff and Heskestad. Puffing phenomena observed under various gravity fields were summarized with the Strouhal number and Froude number. As the result, we could obtain an empirical equation of St=0.517Fr^<-0.502>. From this equation, puffing frequency could be estimated for a flame of various pool diameter varying from 0.01 to 50 meters.
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| 5.
論文 |
論文
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佐藤, 博之 ; 天谷, 賢児 ; 新井, 雅隆
概要:
application/pdf<br />Journal Article<br />Flame lengths of gas jet diffusion flames were measured under various gravity
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evels. A spin tester was used to obtain a high gravity field which level was changed from normal gravity (G=1) to G-20. In order to investigate the fuel density effect on flame structure at high gravity level, two kinds of fuels (methane and propanw) and further methane-propane mixture fuel whose density was equivalent to the surrounding air were used. As the results, flame length decreased with an increase of gravity level regardless of the positive and negative buoyancy effect between the fuel and surroundings. To investigate the gravity effect on flame structure, length of blue flame which appeared at anchor portion of the flame was measured under various gravity levels. It was confirmed that the blue flame was expanded with an increase of the gravity level. This result was explained by the enhancement of the air entrainment at the anchor portion of the flame. Evaluation of flame length which was obtained by Altenkirch considering the relationship of fuel and required oxygen were used to evaluate the experimental data of flame length under the various gravity level. From this method the following empirical correlation was proposed : L_f/γ_o=1.72Re^<0.667>Fγ^<0.0846>, where L_f is a flame length, γ_o is a nozzle radius, Re is the Reynolds number based on nozzle radius and Fγ is the Froude number.
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| 6.
図書 |
図書
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山口昇一, 佐藤博之[編]
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地図 |
地図
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山口昇一ほか編
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地図 |
地図
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佐藤博之, 山口昇一編
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| 9.
図書 |
図書
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高井保明, 佐藤博之[著]
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