OH* Chemiluminescence Characteristics and Structures of the Impinging Reaction Region in Opposed Impinging Diffusion Flames

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• 作者：Xudong Song ; Qinghua Guo ; Chonghe Hu ; Yan Gong ; Guangsuo Yu
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：February 18, 2016
• 年：2016
• 卷：30
• 期：2
• 页码：1428-1436
• 全文大小：622K
• ISSN：1520-5029

文摘

OH* is an important indicator of the generation of the flame reaction region. According to the OH* characteristic emissions obtained by high-spatial-resolution UV imaging and fiber optics, the effects of the velocity, the distance between the two nozzles (L), and the O/C equivalence ratio ([O/C]_e) on the flame chemiluminescence characteristics and structures in opposed impinging regions are discussed herein. The flame impinging region includes an upward stream, a downward stream, and the impinging core region. The experimental results show that the reaction area in the impinging region increases until becoming steady as the velocity increases. [O/C]_e can influence the OH* distributions in the upward and downward streams of the impinging region. Under fuel-rich conditions, the reaction area in the downward stream varies greatly, whereas the reaction areas in the upward and downward streams are the same under fuel-lean conditions. The ratio of L to the equivalent diameter D has the most complicated influence on the formation of the reaction area in the impinging region. Under fuel-rich conditions, the size of the reaction area in the impinging region increases as L/D increases, but the opposite relationship exists under fuel-lean conditions. From the OH* radical distribution, the reaction area in the impinging region can be divided into four types: (I) no reaction area, where no reactions in the impinging region; (II) upward-stream reaction area, where reactions occur only in the upward stream region; (III) two-stream reaction area, where reactions occur in both the upward and downward stream regions; and (IV) impinging reaction area, where reactions occur in the whole impinging region and a clear center appears in the impinging core region. The OH* radical distribution reflects the heights of the upward and downward streams, and the height of the upward stream indicates whether reactions exist in the impinging region. Moreover, the height of the upward stream in flames was predicted according to the values of [O/C]_e, the flame Froude number (Fr), and L/D.