含氧燃料燃烧中燃料氧迁移路径及含氧中间体生成特性

Migration Pathways of Oxygen and the Formation of Oxygenated Intermediates in Oxygenated Fuel Combustion

与碳氢燃料相比,含氧燃料在燃烧过程中容易生成醛类等非常规污染物,这些含氧中间体的生成与燃料中氧的释放密切相关.本文从燃料氧迁移路径的角度来研究含氧中间体的生成特性及规律.并采用分子束质谱结合真空紫外同步辐射光电离技术(SVUV-PIMS)探测了丙烷、二甲醚、乙醇三种低压预混火焰中的主要含氧中间体,并获得了其摩尔分数分布.结果表明:与外部氧相比,燃料氧更易形成含氧中间体.生成的最主要的含氧中间体取决于燃料氧在分子中的结构.二甲醚火焰中甲醛为最主要的含氧中间体;乙醇火焰中乙醛为最主要的含氧中间体;丙烷火焰中,甲醛和乙醛的含量均很小,但碳氢中间体乙烯、乙炔和丙烯的含量较高.

The combustion of oxygenated fuel produces more non-regulated pollutants which usually contain oxygen such as aldehydes than the combustion of hydrocarbon fuel. The formation of these oxygenated intermediates may be associated with the release of oxygen from the oxygenated fuel. In this paper, migration pathways of oxygen from several oxygenated fuels were investigated to obtain the formation characteristics of oxygenated intermediates. Major oxygenated intermediates and other intermediates were identified using synchrotron vacuum ultraviolet photoionization mass spectrometry in a dimethyl ether flame, an ethanol flame, and a propane flame. Their mole fractions were also evaluated. The results indicate that the oxygen from oxygenated fuel leads to an easier production of oxygenated intermediates, compared with oxygen from the oxidizer. The major oxygenated intermediate depends on the structure of the oxygenated fuel and was found to be formaldehyde in the dimethyl ether flame, and acetaldehyde in the ethanol flame. However, formaldehyde and acetaldehyde are present in low concentrations while hydrocarbon intermediates, such as ethene, ethyne, and propene, are present in high concentrations in the propane flame.