Ultrafine Particulate Matter in Methane-Air Premixed Flames With Oxygen Enrichment
Ultrafine Particulate Matter in Methane-Air Premixed Flames With Oxygen Enrichment
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DOI：
10.3389/fmech.2021.739914
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发表时间：
2021-08
期刊：
影响因子：
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通讯作者：
S. Dasappa;J. Camacho
中科院分区：
文献类型：
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作者：
S. Dasappa;J. Camacho
对甲烷层流空气预混火焰中超细颗粒物的形成进行了补充计算和实验研究。具体地说，在预混拉伸稳定火焰中检查碳烟的形成，以观察在富氧应用中常见的相对较高的火焰温度下碳烟的形成和生长。当当量比从Φ=2.2时增加到Φ=2.4时，由迁移率测量得到的颗粒大小分布函数显示出明显的趋势。对于给定的当量比，随着最高火焰温度从大约1,950-2,050K的增加，测量的中位迁移率颗粒尺寸分布减小。在所有研究的火焰条件下，中位迁移率颗粒尺寸为20 nm或更小。在所有当量比条件下，体积分数均随火焰温度的升高而降低。Φ=2.2时接近碳烟起始极限，数密度和体积分数均随火焰温度的升高而单调减小。在较高的当量比条件下，在2000K处出现数密度的峰值，这可能表明竞争的碳烟起始过程在这个温度下是优化的。火焰结构计算采用阿佩尔、伯克霍恩、弗伦克拉赫(ABF)模型的详细气相燃烧化学，以检验观测到的PSDF与碳烟前体化学之间的联系。火焰滞留距离的实测值与计算值的一致性表明，ABF模型可以为当前研究的火焰提供合理的火焰温度和碳烟前体形成的预测。对于第一级，在测量的PSDF中观察到的趋势可以通过计算的苯、萘和其他碳烟前体的形成趋势来理解。目前的研究结果为甲烷和天然气燃烧应用在高温和富氧条件下的颗粒物行为提供了信息。
A complementary computational and experimental study is carried out on the formation of ultrafine particulate matter in premixed laminar methane air flames. Specifically, soot formation is examined in premixed stretch-stabilized flames to observe soot inception and growth at relatively high flame temperatures common to oxygen enriched applications. Particle size distribution functions (PSDF) measured by mobility sizing show clear trends as the equivalence ratio increases from Φ = 2.2 to Φ = 2.4. For a given equivalence ratio, the measured distribution decreases in median mobility particle size as the maximum flame temperature increases from approximately 1,950–2,050 K. The median mobility particle size is 20 nm or less for all flame conditions studied. The volume fraction decreases with increasing flame temperature for all equivalence ratio conditions. The Φ = 2.2 condition is close to the soot inception limit and both number density and volume fraction decrease monotonically with increasing flame temperature. The higher equivalence ratio conditions show a peak in number density at 2,000 K which may indicate competing soot inception processes are optimized at this temperature. Flame structure computations are carried out using detailed gas-phase combustion chemistry of the Appel, Bockhorn, Frenklach (ABF) model to examine the connection of the observed PSDF to soot precursor chemistry. Agreement between measured and computed flame standoff distances indicates that the ABF model could provide a reasonable prediction of the flame temperature and soot precursor formation for the flames currently studied. To the first order, the trends observed in the measured PSDF could be understood in terms of computed trends for the formation of benzene, naphthalene and other soot precursors. Results of the current study inform particulate matter behavior for methane and natural gas combustion applications at elevated temperature and oxygen enriched conditions.