湍流射流火焰抬举高度的实验研究

Studying of Lifted Height of Jet Flame in Turbulent Combustion by Experiment

湍流射流燃烧作为工业燃烧室中普遍存在的燃烧方式,研究湍流射流火焰不仅能促进实际燃烧室的设计改造,更能增强对湍流燃烧理论的理解。在轴对称伴流射流燃烧器实验平台上,研究了湍流自由射流火焰抬举高度随射流速度的变化及氮气稀释和伴流速度对火焰抬举高度的影响。实验结果表明湍流自由射流燃烧火焰抬举高度随射流速度呈线性增长;随氮气稀释摩尔分数的增加其抬举高度的线性斜率增大,射流火焰吹出喷嘴的雷诺数降低,火焰更易发生抬举;同时,氮气稀释摩尔分数的增加也导致射流火焰发生吹熄时雷诺数减小,射流火焰在射流速度完全进入湍流之前发生吹熄;伴流速度小于0.3 m/s时对火焰抬举高度的影响不大,当伴流速度大于0.3 m/s时抬举高度随伴流速度的增加呈线性增长,当射流速度大于20 m/s时,伴流速度的影响降低;对比伴流与稀释对抬举高度的影响可知射流速度大于30 m/s时对伴流的敏感性大于稀释,而在射流速度小于30 m/s时对稀释更敏感。

Turbulent Jet flame is wide spread in combustion chamber of industry. The study of jet flame in turbulent combustion is not only help to promote the design of the actual combustion chamber, but also be more conducive to the understanding of combustion theory. On the experiment platform with the axisymmetric burner of jet with co-flow, lifted height of free jet flame in turbulent combustion was studied along with the change of jet velocity and the influence of jet flame in blowout and blowoff by the jet fuel diluted with nitrogen , effect of co-flow. The results indicate that the lifted height of free jet flame in turbulent combustion grows linearly with the velocity of jet , and with increasing the mole fraction of nitrogen dilution linear slope turn into sharp and the Reynolds number of blowout will be ease for lifting off;simultaneously, it also causes blowoff with the value of Reynolds decreases, and blowoff comes up completely before entering the turbulent range;effect of co-flow speed on the lifted height of flame will be little when ti is less than 0.3 m/s , otherwise the lifted height will increase linearly with the wake velocity; and the influence of the wake velocity will be small when the jet velocity is greater than 20 m/s;compared the affection of co-flow and dilution on lifted height of flame, when the jet velocity is greater than 30 m/s, the height of jet flame is a greater sensitivity to co-flow than dilution, otherwise it is more sensitive to dilute.