Effects of oxygen concentrations on the ignition and quasi-steady processes of n-heptane spray flames using large eddy simulation
Effects of oxygen concentrations on the ignition and quasi-steady processes of n-heptane spray flames using large eddy simulation
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大涡模拟氧浓度对正庚烷喷射火焰点火和准稳态过程的影响
DOI：
10.1016/j.fuel.2018.12.097
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发表时间：
2019-04
期刊：
影响因子：
7.4
通讯作者：
L. Zhou
中科院分区：
文献类型：
--
作者：
H. Wei;W.H Zhao;Z. Lu;L. Zhou
废气再循环（EGR）是一种常用的减少NOx产生的技术。采用大涡模拟方法，研究了EGR对正庚烷喷雾火焰早期发展、两阶段着火过程和喷雾火焰结构的影响。根据关键组分的形成和早期放热过程，确定了两阶段着火过程。结果表明，在低氧浓度条件下，较长的点火延迟（ID）和火焰离地长度（LOL）可以增加燃料和空气的混合时间。然而，第一阶段点火仍然开始在燃料更丰富的区域的情况下，由于缺乏氧气，具有较高的EGR率。相反，与具有相同初始氧含量但在1000 K的较高气体温度下的情况相比，第一阶段点火在900 K下移动到化学计量混合物分数区域。基于羟基和甲醛的燃烧模式分析进行区分低温和高温燃烧区。最重要的是，为了研究稳定化机理，在分析局部流动时间尺度和化学时间尺度的基础上，进行了化学爆炸模式分析（CEMA）。在点火的早期阶段，反应和混合之间的平衡意味着冷火焰从点火点传播到整个流场。在准稳态阶段，自燃起主导作用。
Exhaust Gas Recirculation (EGR) is a frequently used technique to reduce the production of NOx. The effect of EGR on the early flame evolution, two-stage ignition process and spray flame structures for n-heptane spray flames are investigated using large eddy simulation. The two-stage ignition process is identified based on the formation of key species and early heat release process. Results demonstrate that a longer ignition delay (ID) and flame lift-off length (LOL) under lower oxygen concentration conditions could increase the mixing time for fuel and air. However, the first-stage ignition still initiates in fuel-richer regions for the cases with higher EGR rates due to the lack of oxygen. In contrast, compared to the case with the same initial oxygen content but at a higher gas temperature of 1000 K, the first-stage ignition moves to stoichiometric mixture fraction regions at 900 K. The combustion mode analysis based on hydroxyl and formaldehyde is conducted to distinguish between the low- and high-temperature combustion regions. Most importantly, to study the stabilization mechanism, the chemical explosive mode analysis (CEMA) is conducted based on analysis on the local flow time scale and the chemical time scale. During the early stage of ignition, a balance between reaction and mixing implies that cool flame propagates from the ignition spots through the entire flow field. And during the quasi-steady state, autoignition plays a dominant role.
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影响因子：
4.4
作者：
Zhaoyu Luo;C. Yoo;E. Richardson;Jacqueline H. Chen;C. Law;T. Lu
通讯作者：
Zhaoyu Luo;C. Yoo;E. Richardson;Jacqueline H. Chen;C. Law;T. Lu
不同温度和密度正十二烷分流喷射火焰结构的大涡模拟
影响因子：
1.9
作者：
Zhou Lei;Zhao Wanhui;Wei Haiqiao
通讯作者：
Wei Haiqiao
DOI：
10.1016/j.proci.2010.06.147
发表时间：
2011
期刊：
--
影响因子：
--
作者：
C. Yoo;E. Richardson;R. Sankaran;Jacqueline H. Chen
通讯作者：
C. Yoo;E. Richardson;R. Sankaran;Jacqueline H. Chen
影响因子：
7.4
作者：
M. Bolla;Daniele Farrace;Y. Wright;K. Boulouchos
通讯作者：
M. Bolla;Daniele Farrace;Y. Wright;K. Boulouchos
影响因子：
3.4
作者：
Ji, Weiqi;Zhao, Peng;Law, Chung K.
通讯作者：
Law, Chung K.