A modeling approach for soot formation in non-premixed flames with elevated stoichiometric mixture fraction
A modeling approach for soot formation in non-premixed flames with elevated stoichiometric mixture fraction
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DOI：
10.1016/j.combustflame.2021.02.029
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发表时间：
2021-07
影响因子：
4.4
通讯作者：
Phillip R. Johnson;R. Chakrabarty;B. Kumfer
中科院分区：
文献类型：
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作者：
Phillip R. Johnson;R. Chakrabarty;B. Kumfer
大多数烟灰形成模型都是针对特定应用而开发的，因此仅对代表目标应用的燃料-空气燃烧条件范围有效。这限制了大多数模型的适用性和多功能性，特别是对于化学计量混合分数 Zst 可能变化很大的燃烧过程。随着 Zsteven 的增加，在保持恒定的火焰温度的同时，产生烟灰的火焰可能会变成非烟灰（蓝色）。本文提出了一种新颖的建模方法来解释高 Zst 环境下的独特火焰特性及其对烟灰形成的影响。这种建模方法旨在以稳健、简单且可用于多种应用的方式捕获扩散火焰燃料侧发生的形成过程和可逆过程。此外，还开发了一种新的半经验模型来扩展两种广泛使用的模型——Leung-Lindstedt 和 Moss-Brookes——这两种模型在不同的 Zst 条件下都会给出不准确的预测。当应用于逆流火焰系统时，通过结合我们的新模型和修改模型预测的烟灰体积分数分布与文献中报告的 lowZst 实验观察结果非常吻合。使用这种建模方法还首次预测了非预混逆流火焰中的蓝色（无烟灰）极限条件。我们表明，仅考虑形成过程无法获得这一结果，并且如果考虑高温下烟灰形成的可逆性质，则当应用于较高 Zst 火焰时，半经验烟灰形成模型的性能可以得到显着改善。
Most soot formation models have been developed with particular applications in mind and as such, are valid only for the range of fuel-air combustion conditions representative of the target application. This limits the applicability and versatility of most models, especially for combustion processes wherein the stoichiometric mixture fraction,Zst, could vary widely. A soot-producing flame could become non-sooting (blue) with an increase inZsteven while maintaining constant flame temperature. This paper presents a novel modeling approach to account for the unique flame characteristics at elevated-Zstenvironments and their effect on soot formation. This modeling approach is designed to capture both the formation and the reversible processes that occur on the fuel-side of a diffusion flame in a way which is robust, simple, and can be utilized in diverse applications. Additionally, a new semi-empirical model is developed for extending two widely-used models–Leung-Lindstedt and Moss-Brookes–both of which render inaccurate predictions under varyingZstconditions. When applied to the counterflow flame system, the soot volume fraction profiles predicted by incorporation of our new and modified models agree well with experimental observations reported in the literature for lowZst. Using this modeling approach also resulted in the prediction of blue (soot-free) limit condition in a non-premixed counterflow flame for the first time. We show that this result cannot be obtained by considering formation processes alone and that the performance of semi-empirical soot formation models can be dramatically improved when applied to higher-Zstflames if the reversible nature of soot formation at high temperature is considered.