Zhou Yinggui, Zhang Pengxiang, Wang Shengfu, Cai Jie, Xi Jianfei
School of Environmental Science and Engineering, Yancheng Institute of Technology Yancheng 224051 China.
School of Energy and Mechanical Engineering, Nanjing Normal University Nanjing 210023 China
RSC Adv. 2024 Sep 23;14(41):30260-30271. doi: 10.1039/d4ra05249h. eCollection 2024 Sep 18.
An experimental and numerical investigation was conducted to examine the formation of soot in methane/air laminar diffusion flames under varying CO dilution ratios, ranging from 0% to 40%, and pressures between 5 and 10 atm. The experimental methodology incorporated diffuse-light two-dimensional line-of-sight attenuation (diffuse 2D-LOSA) to ascertain the volume fraction and peak temperature distribution of soot within the flames. For the numerical methodology, CoFlame-an open-source computational code-was utilized to calculate the detailed flame temperature, soot volume fraction, and the mole fractions of key intermediate species pivotal to soot generation. The study reveals that an increased dilution ratio of CO can reduce flame temperature and the molar fraction of hydrogen (H), while simultaneously increasing the molar fraction of hydroxyl (OH). This shift in chemical composition results in a reduced rate of soot nucleation and an intensified oxidation process during the later stages of soot development, thereby diminishing the overall soot volume fraction. An increase in pressure significantly boosts the processes of soot nucleation, HACA surface growth, and PAH condensation, thereby promoting the formation of soot. Elevated pressure corresponds to an increase in flame temperature and a narrower soot formation region. Additionally, the inhibitory effect of CO dilution on soot formation is mitigated under increased pressure. The findings from this research are expected to provide valuable insights and strategic guidance for the management and control of pollutants in the context of hydrocarbon fuel combustion, particularly when CO dilution is employed.
开展了一项实验和数值研究，以考察在0%至40%的不同CO稀释比以及5至10个大气压的压力条件下，甲烷/空气层流扩散火焰中炭黑的形成情况。实验方法采用漫射光二维视线衰减法（漫射二维LOSA）来确定火焰中炭黑的体积分数和峰值温度分布。对于数值方法，利用开源计算代码CoFlame来计算详细的火焰温度、炭黑体积分数以及对炭黑生成至关重要的关键中间物种的摩尔分数。研究表明，增加CO稀释比可降低火焰温度和氢（H）的摩尔分数，同时增加羟基（OH）的摩尔分数。这种化学成分的变化导致炭黑成核速率降低，且在炭黑生成后期氧化过程加剧，从而使整体炭黑体积分数减小。压力增加会显著促进炭黑成核、HACA表面生长和多环芳烃缩合过程，从而促进炭黑的形成。压力升高对应着火焰温度升高和炭黑形成区域变窄。此外，在压力增加的情况下，CO稀释对炭黑形成的抑制作用会减弱。预计本研究结果将为烃类燃料燃烧过程中污染物的管理和控制提供有价值的见解和战略指导，特别是在采用CO稀释时。
