利用火焰发射光谱来研究汽油机的燃烧过程

本文用一套精密的光电转换系统，采集了一台汽油机燃烧过程中火焰辐射在可见光到近紫外波段内的光谱，探测到了燃烧中间产物ＣＨ、ＣＮ、Ｃ２、Ｈ２Ｏ等的特征光谱，并分析了这些产物在燃烧过程中的变化规律，以及随过量空气系数，缸内压力的变化．实验结果表明，汽油机三个不同的燃烧阶段具有不同的燃烧光谱特征：着火过程中，存在着大量的处于激发态的分子、原子、离子、自由基等活化中心的束缚态光谱，随着燃烧发展，ＣＨ、Ｃ２自由基的光谱强度明显加强；当减小过量空气系数时，光谱强度变弱并且着火延迟期增长；自由基特征光谱的光强变化曲线可以反映它们在燃烧过程中的浓度变化．所以火焰发射光谱是实时检测燃烧中间产物，特别是ＣＨ、Ｃ２等有害排放物变化规律的有效手段，可以为分析、模拟燃烧过程，控制排放提供有用的实验数据．

Study of Combustion Process in Gasoline Engine Via Flame Emission Spectra

A precise opto-electronic system is used to collect the flame radiation spectra from visible to ultraviolet range during a gasoline engine combustion process. The characteristic spectra of intermediate combustion products such as CH. CN. C2. H2O are detected and their variation during the combustion are analyzed. The effects of excess air coefficient and cylinder pressure on these spectra are also studied. The experimental resultS show that the three different combustion phases in a gasoline engine have different combustion characteristic spectra: a large number of atoms, molecules, ions and radicals which are in their excited saltes are existing during the ignition process, with the development of the combustion, the spectra intensities of CH, C2 radicals increase rapidly. When the excess air coefficient is diminished, the spectra intensities decrease and the ignition delay which can be seen from the change of the spectra P8ttern becomes longer; The variation of the radical light intensity indicates the change of its concentration during the combustion. As the result, the flame emission spectroscopy is a POwerful method to analyze and monitor the formation of poisonous exhaustS, especially as.CH, C2 and it can provide useful data for theoretical analysis, computor simulation of the combustion process and the controlling of the poisonous exhausts.