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    Please use this identifier to cite or link to this item: http://ir.lib.ksu.edu.tw/handle/987654321/6644


    Title: 多環及多管層流擴散火焰之理論分析和實驗研究
    Theoretical and Experimental Investigation of Confined Laminar Diffusion Flames in a Multi-Port Burner
    Authors: 侯順雄
    Keywords: Diffusion flame
    Multiple-Port burner
    Flame transition
    Flame configuration
    Burke-Schumann擴散火焰
    反置擴散火焰
    多環及多管燃燒器
    Date: 2004-07-31
    Issue Date: 2009-12-31 10:30:45 (UTC+8)
    Abstract: The influence of stream concentrations and velocities on the flame structure in a multiple-port burner is theoretically and experimentally studied in this work. A general solution of normal and inverse diffusion flame configurations in a multiple-port burner is obtained with the inclusion of the effects of axial diffusion and unequal stream velocities. The theoretical results show that not only the flame height but also the flame structure is affected by the Peclet number. In the theoretical analysis, the temperature and velocity of stream are two important parameters. Flame configurations can be predicted well by including temperature effect in calculating the Peclet number. For relatively weak (or strong) flame intensity, the prediction of flame configurations agrees well with the experimental results if a lower (or higher) temperature is used. In the experiment, different flame configurations are observed and discussed for various stream velocities and concentrations. The transition of inverse diffusion flame from a single-cone-shaped flame to a double-cone-shaped flame to an envelop flame occurs when the inner stream velocity is adjusted for fixed middle and outer stream velocities. It is of interest to note that under the same operating conditions the flame has history-dependent configuration decided by increasing or decreasing inner stream velocity.
    擴散火焰因不需考慮回火的問題,因此在實際工業應用系統是比較安全的。但因擴散火焰之燃料與氧化物是以化學計量比燃燒(stoichiometric burning),且燃燒氣體在高溫區的遲滯時間較長因而通常會導致較嚴重的污染排放,特別是氮氧化物(NOx)和碳顆粒(soot)。兩環同軸噴流燃燒器中的標準擴散火焰為燃料由中心管噴出,空氣由外環供給。而反置擴散火焰則為空氣由中心管噴出,燃料由外環供給。雖然反置擴散火焰的概念已廣泛應用於諸多重要的氣體燃燒器,但有關反置擴散火焰的文獻卻仍十分匱乏,且大多侷限於兩環同軸反置擴散火焰。有別於以往的文獻,本計畫所提出之中心管噴空氣、第二環噴燃料、第三環噴空氣的三環同軸反置擴散火焰不但能有效降低NOx 排放和抑制碳顆粒形成,更可用來模擬分段燃燒技術。此外,雖然火焰形狀為層流擴散火焰非常重要的特性,且相當多的理論分析及實驗量測均多所著墨。但理論分析的文獻大多僅侷限於噴流型態擴散火焰1(jet-like diffusion flame)或者典型Burke-Schumann 擴散火焰,對於多環同軸標準及反置擴散火焰或多管矩形標準及反置擴散火焰的火焰面預測則尚付之闕如。為了更進一步深入了解多環同軸反置擴散火焰的燃燒特性,並釐清分段燃燒技術的主宰機制,本計畫將以理論分析預測多環同軸和多管矩形具侷限邊界擴散火焰之火焰形狀及高度,探討噴流出口速度、噴流出口幾何尺寸、噴流出口燃料與氧化物濃度、優先擴散(preferential diffusion)及Pe 數(Peclet number)對火焰形態及其結構之影響。同時將以三環同軸擴散火焰燃燒器之實驗設備探討各噴流管之管徑尺寸大小、噴流出口速度、燃料與氧化物出口濃度、侷限邊界等參數變化對標準和反置擴散火焰的火焰型態和穩定性的影響。理論解並將與實驗結果進行驗證。本計畫之研究成果,在學術探討方面可促進吾人對多環同軸或多管矩形擴散火焰的了解與認識,在實際應用方面可作為工業用爐之燃燒室與燃燒器噴嘴設計之重要參考依據,藉以尋求高效率、省能源、低污染、以及易製造與操作之終極目標。
    Appears in Collections:[Graduate School and Department of Mechhanical Engineering] Research Projects

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