Evolution in size and structural order for incipient soot formed at flame temperatures greater than 2100 K
Evolution in size and structural order for incipient soot formed at flame temperatures greater than 2100 K
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DOI：
10.1016/j.fuel.2021.120196
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发表时间：
2021-02-05
期刊：
影响因子：
7.4
通讯作者：
Camacho, Joaquin
中科院分区：
文献类型：
--
作者：
Dasappa, Shruthi;Camacho, Joaquin
在比常规燃烧应用更热的火焰中形成的烟灰预计经历独特的形成过程并形成不同于典型烟灰的碳结构。一个补充的实验和建模方法在这里报告，以评估火焰温度和当量比的影响，在较高的温度制度（1950 K < Tf < 2250 K）形成的碳烟。使用三个独立的燃烧化学模型的计算表明，预测的多环芳烃（PAH）浓度分布的高温火焰更敏感的选择机制，而不是特定的火焰条件。至于材料性质，拉曼签名从一个典型的烟灰光谱中观察到的无序sp2碳材料的功能过渡。当火焰温度超过2200 K时，从拉曼谱带提取的缺陷距离几乎是通常报道的烟灰值的两倍。较高浓度的气相前体可以促进有序碳结构的形成，正如在最高当量比系列中观察到的相对较高的缺陷距离所表明的那样。流动性测量的粒度分布表明，随着火焰温度的升高，烟灰的尺寸和产率降低，双峰分布福尔斯落在超细范围内的所有火焰条件。如果从拉曼光谱的演变推断出的碳结构的显著转变能够开发功能性高表面积sp2碳材料，则这是特别有希望的。也就是说，目前的观察表明，火焰形成的碳结构向高缺陷sp2碳演变，其尺寸和碳结构可以在一定程度上进行调整。
Soot formed in flames hotter than conventional combustion applications is expected to undergo unique formation processes and develop a carbon structure distinct from typical soot. A complementary experimental and modeling approach is reported here to assess flame temperature and equivalence ratio effects for soot formed in the higher-temperature regime (1950 K < Tf < 2250 K). Computations using three separate combustion chemistry models show that predictions of polycyclic aromatic hydrocarbon (PAH) concentration profiles for the higher-temperature flames are more sensitive to the choice in mechanism rather than specific flame conditions. As for material properties, the Raman signatures transition from a typical soot spectrum to features observed in disordered sp2 carbon materials. The defect distance extracted from the Raman bands nearly doubles from values typically reported for soot as the flame temperature exceeds 2200 K. Higher concentrations of gas-phase precursors may facilitate development of an ordered carbon structure as indicated by the relatively high defect distance observed for the highest equivalence ratio series. Particle size distributions measured by mobility sizing show size and yield of soot decreases with increasing flame temperature and the bimodal distribution falls within the ultra-fine range for all flame conditions. This is especially promising if the significant transformation in carbon structure inferred from the evolution in Raman spectra enables development of functional high-surface area sp2 carbon materials. Namely, the current observations indicate that the flame-formed carbon structure evolves towards high-defect sp2 carbon with size and carbon structure that can be tuned to some extent.