PAH formation characteristics in hydrogen-enriched non-premixed hydrocarbon flames
PAH formation characteristics in hydrogen-enriched non-premixed hydrocarbon flames
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DOI：
10.1016/j.fuel.2022.124407
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发表时间：
2022-09
期刊：
影响因子：
7.4
通讯作者：
Chinonso Ezenwajiaku;M. Talibi;R. Balachandran
中科院分区：
文献类型：
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作者：
Chinonso Ezenwajiaku;M. Talibi;R. Balachandran
氢与传统碳氢化合物的结合使用为当前的能源系统脱碳提供了一个绝佳的机会，而无需进行重大的硬件升级。然而，这提出了新的科学挑战，其中之一是由于富氢火焰的复杂反应动力学而难以有效控制污染物烟尘排放。本文重点介绍了多环芳烃（PAHs），这是煤烟的组成部分，并负责其致癌性。详细了解氢对多环芳烃的形成和增长的基本过程的影响是重要的发展有效的战略，以削减多环芳烃的形成，从而减少碳烟排放量从燃烧系统。采用平面激光诱导荧光（PLIF）技术，对不同碳氢燃料（烷烃和烯烃）的层流反扩散火焰中多环芳烃（PAH）和羟基自由基（OH）的形成和增长特性进行了研究。OH PLIF用于指示火焰中的峰值温度位置（火焰前缘），而PAH PLIF用于确定PAH形成特性。甲烷（CH 4）也分别添加到相同的烃类燃料，以研究碳结合氢添加的效果，相比于H2添加。据观察，只有除了H2到CH4表现出显着的变化，PAH的减少水平的幅度作为长度沿着火焰前锋，Lf增加。结果还表明，虽然添加的H 2是更有效地降低PAH荧光信号的增加率（指示浓度增长）相比，CH 4的添加，两种燃料显示两个不同的区域在PAH的增长曲线，一个陡峭的增长区域，然后是一个较慢的增长区域。这可能表明PAH形成和生长的自限性。该研究得出结论，多环芳烃的增长率位于一个狭窄的范围内，无论燃料键合，分子结构和燃料混合物的H：C比测试。
The utilisation of hydrogen with conventional hydrocarbons offers an excellent opportunity to decarbonise current energy systems without significant hardware upgrades. However, this presents fresh scientific challenges, one of which is the difficulty in effective control of pollutant soot emissions due to complex reaction kinetics of hydrogen enriched flames. This paper focuses on polycyclic aromatic hydrocarbons (PAHs), which are the building blocks of soot and responsible for its carcinogenicity. Detailed understanding of the effect of H 2 on the underlying processes of PAH formation and growth is important for the development of effective strategies to curtail PAH formation and hence, reduce soot emissions from combustion systems. In this study, an experimental methodology was employed to analyse PAH formation and growth characteristics of laminar inverse diffusion flames of various hydrocarbon fuels (alkanes and alkenes) enriched with H 2 using simultaneous planar laser induced fluorescence (PLIF) imaging of PAHs and hydroxyl radicals (OH). OH PLIF was used to indicate peak temperature locations in the flame (flame front), while PAH PLIF was used to determine PAH formation characteristics. Methane (CH 4) was also separately added to the same hydrocarbon fuels to study effects of carbon-bound hydrogen addition, in comparison to H 2 addition. It was observed that only the addition of H 2 to CH 4 showed significant variation in the magnitude of PAH reduction levels as the length along the flame front, L f increased. The results also showed that while the addition of H 2 was more effective in reducing the rate of PAH fluorescence signal increase (indicative of concentration growth) when compared to CH 4 addition, both fuels showed two distinct regions in the PAH growth curve; a steep growth region followed by a slower growth region. This is potentially indicative of the self-limiting nature of PAH formation and growth. The study concluded that the growth rate of PAHs lies within a narrow band irrespective of the fuel bonding, molecular structure and the H: C ratio of the fuel mixtures tested.