氫氣-甲烷同軸噴流擴散火焰之燃燒特性分析

Study on Combustion Characteristics of Hydrogen- Methane Coaxial Jet Diffusion Flames

王舜賢(Shun-Shian Wang)

指導教授 ： 侯順雄

崑山科技大學/工程學院/機械工程研究所/碩士(2012年)

摘要

本研究利用自由噴流和同心噴流擴散火焰探討氫氣濃度和外環空
氣速度對氫氣-甲烷混合燃料擴散火焰燃燒特性的影響。本文主要分成兩部分，首先探討自由噴流擴散火焰之富氫燃燒現象，結果顯示，火焰高度隨著內管流速增加而變高，且火焰高度隨著氫氣摻混比例增加而降低。當固定徑向距離為50cm時，輻射熱通量隨內管流速增加而變大，但隨氫氣摻混比例增加而降低。實驗量測得到的火焰高度與Roper(1977)及Altenkirch(1976)的經驗公式均相當吻合。
其次，探討不同氫氣濃度與外環空氣作用下的氫氣-甲烷混合燃料
噴流擴散火焰之火焰長度、火焰型態、火焰穩定性、火焰輻射和廢氣
排放。結果發現，噴流火焰長度會隨著外環空氣流速增加而變短；且
外環流速越大，火焰上飄(Liftoff)高度越高。此外亦發現氫濃度越高，火焰出現上飄與吹熄(blowoff)現象時的臨界速度也越大；亦即，摻混氫氣比例越高，火焰穩定性越佳。當固定徑向距離為50cm時，隨著外環空氣流速增加，輻射熱通量及輻射放熱率也隨之降低。另外，在固定內環燃料流速為12 m/s下，實驗量測氫氣摻混比例為20%、30%、40%、50%時之CO、CO2、NOX濃度，結果得到：隨著外環空氣流速增加，CO2和NOX濃度會隨之增加，但CO濃度卻會隨之降低。

關鍵字

氫氣 ； 擴散火焰 ； 火焰穩定性 ； 上飄 ； 飄離 ； 吹熄 ； 輻射 ； 廢氣排放

並列摘要

This study aimed at investigating the combustion characteristics of hydrogen/methane hybrid fuel jet diffusion flames. The influence of hydrogen addition and co-flow air on flame stability, flame appearance,
flame height, liftoff height, flame radiation and emissions was conducted. First, for the free jet diffusion flames, it was found that hydrogen addition sustained a progressive improvement in flame stability (including liftoff,
blowout and blowoff) and reductions in flame height and lifoff height. With increasing fuel velocity or decreasing hydrogen concentration, radiative heat transfer rate (radiative heat flux) increased for a fixed radial direction
distance 50 cm. The results of flame height measurements agree well with those of empirical correlation formula proposed by Roper (1977) and Altenkirch (1976).
Second, for the hydrogen-methane coaxial jet diffusion flames, with an increase in hydrogen content, flame height and lifoff height were shortened. However, with increasing co-flow air velocity, flame height decreased but lifoff height increased. The critical velocities corresponding
to liftoff, blowout or blowoff increased as the hydrogen content was higher in the hydrogen-methane blend. That is, the flame stability was widened as the hydrogen content was raised. With increasing co-flow air velocity or hydrogen concentration, radiative heat transfer rate (radiative heat flux) decreased for a fixed radial direction distance 50 cm at a constant fuel velocity of 12m/s. Additionally, with an increase in co-flow air velocity, the CO2 and NOx emissions increased, but the CO emission decreased

並列關鍵字

Hydrogen ； Diffusion Flame ； Flame Stability ； Liftoff ； Blowout ； Blowoff ； Radition ； Pollutant Emissions

參考文獻

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