田松杰,任豪,徐顺塔,席礼阳,涂垚杰,刘豪
TIAN Songjie,REN Hao,XU Shunta,XI Liyang,TU Yaojie,LIU Hao

• 1:华中科技大学煤燃烧与低碳利用全国重点实验室

摘要(Abstract)：

中强度低氧稀释(Moderate or Intense Low-oxygen Dilution,MILD)燃烧是一种新型低氧稀释燃烧技术，能够同时实现低NO_x和碳烟排放。基于化学动力学分析软件CHEMKIN-PRO中的对冲火焰模型，通过数值模拟研究了丙烷MILD燃烧方式下碳烟的生成路径及其与常规燃烧之间的差异，并深入探讨了拉伸率（50～80 s~(-1)）和CO_2稀释（体积分数0～60%）对丙烷MILD方式下碳烟生成路径的影响。结果表明：MILD燃烧方式下碳烟生成的主要路径是2C_3H_3→A1、A1~-+H(+M)?A1(+M)、A1~-+CH_4?A1+CH_3、A1~-+C_2H_4?A1+C_2H_3、C_6H_5CH_3+H=A1+CH_3和C_4H_5~(-2)+C_2H_2=A1+H；与常规燃烧相比，MILD燃烧方式下2C_3H_3→A1和A1~-+H(+M)?A1(+M)反应速率降低，减少了A1生成进而抑制了碳烟成核，最终导致碳烟表面质量生长速率降低78.6%，最终碳烟峰值体积分数降低了83.7%；相比之下，MILD燃烧方式下2C_3H_3→A1路径对碳烟生成的贡献率降低了7.7%，而C_6H_5CH_3+H=A1+CH_3和C_4H_5~(-2)+C_2H_2=A1+H路径的贡献率重要性明显上升，分别提升5.36%和7.59%；此外，MILD燃烧方式下碳烟峰值体积分数随拉伸率的变化呈非线性特征，碳烟峰值体积分数随拉伸率的增加呈现先升高后降低的趋势，其机理源于成核速率的非单调变化与表面生长速率的持续上升之间的竞争效应。CO_2的物理和化学效应随着稀释比例的上升呈增加趋势，在稀释范围为0～40%时，CO_2的物理效应对碳烟峰值影响不大，CO_2通过CO+OH?CO_2+H反应促进H消耗从而削弱PAH生长所需的HACA机制，导致A1和A4物质的量分数显著降低，在CO_2稀释.比例为60%时碳烟峰值体积分数进一步降低至6.4×10~(-9)，从而进一步减少MILD燃烧方式下碳烟的生成。
Moderate or intense low-oxygen dilution(MILD) combustion is an advanced low-oxygen diluted combustion technology capable of achieving simultaneous reductions in NOx and soot emissions. This study employs numerical simulations based on the counterflow flame model in the chemical kinetics analysis software CHEMKIN-PRO to investigate the soot formation pathways in propane MILD combustion and their distinctions from conventional combustion. Furthermore,the effects of strain rate(50–80 s~(-1)) and CO_2 dilution(volume fraction:0–60%) on soot formation pathways under MILD conditions are systematically analyzed. The results reveal that the dominant soot formation pathways in MILD combustion are: 2C_3H_3→A1, A_1~-+H(+M)?A1(+M), A_1~-+CH_4?A1+CH_3,A_1~-+C_2H_4?A1+C_2H_3, C_6H_5CH_3+H=A1+CH_3 and 2C_3H_3→A1 and A_1~-+ H(+M)? A1(+M) under MILD conditions are significantly reduced,leading to suppressed A1 formation and thus inhibiting soot nucleation. Consequently,the surface mass growth rate of soot decreases by 78.6%,and the peak soot volume fraction diminishes by 83.7%. Notably,the contribution of the 2C_3H_3→A1 pathway to soot formation decreases by 7.7% under MILD combustion,while the importance of the C_6H_5CH_3+H?A1+CH_3 and Additionally,the peak soot volume fraction under MILD conditions exhibits a nonlinear dependence on strain rate,initially increasing and subsequently decreasing with rising strain rates. This behavior stems from the competitive interplay between the non-monotonic variation in nucleation rates and the continuous increase in surface growth rates. Both the physical and chemical effects of CO_2 dilution intensify with higher dilution ratios. At CO_2 dilution levels of 0-40%,the physical effect of CO_2 exerts minimal influence on peak soot volume fraction. However,CO_2 chemically promotes H consumption via the CO+OH?CO_2+H reaction,thereby weakening the H-abstraction C_2H_2-addition(HACA) mechanism critical for polycyclic aromatic hydrocarbon(PAH) growth. This results in significant reductions in A1 and A4 concentrations. At 60% CO_2 dilution,the peak soot volume fraction further declines to 6.4×10~(-9),demonstrating enhanced suppression of soot formation in MILD combustion.

关键词(KeyWords)： MILD燃烧;常规燃烧;丙烷;碳烟;拉伸率;CO_2稀释
MILD combustion;conventional combustion;propane;soot;strain rates;CO_2 dilution

Abstract:

Keywords:

基金项目(Foundation): 国家自然科学基金面上资助项目（52376112）

作者(Author): 田松杰,任豪,徐顺塔,席礼阳,涂垚杰,刘豪
TIAN Songjie,REN Hao,XU Shunta,XI Liyang,TU Yaojie,LIU Hao

DOI: 10.13226/j.issn.1006-6772.23122801

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