著者

高橋 陽一 末永 陽介 北野 三千雄 工藤 めぐみ

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.71, no.712, pp.3046-3052, 2005

被引用文献数

2

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Response of a cylindrical premixed flame to periodic concentration fluctuation was investigated. The flame was formed in a porous cylinder by percolating the mixture uniformly through the cylinder wall. The burner used here was devised so as to fluctuate the mixture concentration (equivalence ratio) only in the radial direction of the flow (vertically to the cylindrical flame surface) without varying the flow field. With this burner the time variations of burning velocity, burnt gas temperature and flame luminosity were measured for the lean methane-air mixture in the range of fluctuation frequency from 3 Hz to 50 Hz, and the results were examined from the viewpoint of flame curvature effects. The results show that the variation width of the burning velocity of the dynamic flame is larger than that of the static flame corresponding to the concentration fluctuation. Burnt gas temperature and flame luminosity also exhibit similar tendencies. The magnification ratio of the variation width depends on the flame curvature and the large flame curvature makes the flame sustainable even for the mixture leaner than the flammability limit of the static flame.

著者

末永 陽介 柳岡 英樹 菊池 護 佐々木 駿

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.852, pp.17-00160-17-00160, 2017 (Released:2017-08-25)

参考文献数

19

被引用文献数

1

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Experimental study was performed to reveal the response characteristics of a stretched cylindrical diffusion flame to sinusoidal oscillation of air flow velocity. The cylindrical flame used in this study has a convex curvature with respect to air stream and is formed in air stream. The fuel is methane, diluted with nitrogen, and the oxidizer is air. Oscillation frequency f is varied from 5 Hz to 250 Hz. Velocity at the outlet of air supplying nozzle was changed sinusoidally with four speakers. Velocity at the fuel nozzle outlet was kept constant. The air velocity at the nozzle outlet is measured using particle image velocimetry. Flame radius rf, flame thickness δ, and flame luminosity Lf are obtained by using high speed video camera. Results are summarized as follows: Though fluctuation amplitude of the velocity gradient of air stream Δga is constant with increasing f, that of the fuel stream Δgf increases. The fluctuation amplitude of rf varies to quasi-steady at low frequency, while the fluctuation amplitude is reduced with increasing f. Lf does not respond to quasi-steady at low frequency. The fluctuation amplitude of Lf has maximum value at 50 Hz and is larger than that for the steady flame corresponding to the velocity fluctuation. It is considered that this complex change of the flame luminosity with respect to f is related to δ/rf which is associated with the flame curvature effect, ga which affects the flame stretch effect, and gf which impacts fuel transport.