Lift-off and blow-off of methane and propane subsonic vertical jet flames, with and without diluent air
Lift-off and blow-off of methane and propane subsonic vertical jet flames, with and without diluent air
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DOI：
10.1016/j.fuel.2016.06.073
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发表时间：
2016-11
期刊：
影响因子：
7.4
通讯作者：
A. Palacios;D. Bradley;L. Hu
中科院分区：
文献类型：
--
作者：
A. Palacios;D. Bradley;L. Hu
本文旨在通过实验研究，包括控制空气进入燃料射流，以增加对亚音速射流火焰吹散现象的理解。随着射流火焰气体中空气的摩尔浓度Aj的增加，反应区变细，火焰上升距离增大。最终，火焰振荡发展，随后火焰吹灭。射流混合分析可以估计混合物的倾斜程度。由此，得到了在纯燃料射流火焰位置的减小的平均燃烧速度ua。在有和没有添加空气的情况下，吹灭条件与甲烷和丙烷喷射火焰的无因次流动数Ub * *的最后测量稳定值相关。fub *值随着添加空气比例的增加而下降，甲烷的下降更为明显。这是由于火焰的倾斜，以及相关的火焰熄灭伸展率的降低。随着空气稀释度的增加，asb *的值下降，未燃烧的碳氢化合物在吹出之前的排放量增加。当在表达式中引入uis时，揭示了这些发现的潜在普遍性，并且用燃烧一摩尔燃料所需的空气的摩尔来标准化。
The paper seeks to increase understanding of subsonic jet flame blow-off phenomena, through experimental studies that include the controlled introduction of air into the fuel jet. As the molar concentration of air in the jet flame gas,Aj, is increased the reaction zone becomes leaner, and the flame lift-off distance increases. Eventually, flame oscillations develop and are followed by flame blow-off. A jet mixing analysis enables the extent of the leaning-off of the mixture to be estimated. From this, the reduced mean flamelet burning velocity,ua, is found at the location of the pure fuel jet flame. The conditions for blow-off are correlated with the last measured stable values of the dimensionless flow number,Ub∗, for methane and propane jet flames, with and without added air. Values ofUb∗decline as the proportion of added air increases, more markedly so with methane. This is attributed to the leaning-off of the flame, and the associated decrease in the flame extinction stretch rate. AsUb∗declines in value, with increasing air dilution, the emissions of unburned hydrocarbons just prior to blow-off increase. An underlying generality of the findings is revealed whenuais introduced into the expression forUb∗, andAjis normalised by the moles of air required to burn a mole of fuel.