Ignition and formaldehyde formation in dimethyl ether (DME) reacting spray under various EGR levels
Ignition and formaldehyde formation in dimethyl ether (DME) reacting spray under various EGR levels
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DOI：
10.1016/j.proci.2016.07.054
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Khanh Cung;A. Moiz;Xiucheng Zhu;Seong-Young Lee
中科院分区：
文献类型：
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作者：
Khanh Cung;A. Moiz;Xiucheng Zhu;Seong-Young Lee
二甲醚(DME)作为压燃式发动机柴油的替代燃料，因其具有高十六烷值、快速着火和超低颗粒物排放等优点，在燃烧研究中备受关注。在这项研究中，着火和包括甲醛(CH2O)在内的重要中间物种在定容燃烧容器装置中进行了实验研究，该装置包括用于液体二甲醚喷雾行为的燃料喷射系统。通过模拟不同水平废气再循环的不同氧气浓度实验，研究了废气再循环对二甲醚燃烧过程中火焰结构和排放的影响。然后，实验结果被用来验证使用详细的化学解算器进行的3D CFD模拟。提供了以温度分布为特征的不同点火阶段，以及开始喷射后的某些物种(例如，用于冷火焰的CH2O)，以概念化在氧气环境气体浓度从低到高的影响下的二甲醚燃烧过程。模拟和实验都表明，在扩散控制火焰之前，CH2O的生成和低温燃烧之间存在支持联系，这对于DME来说是唯一的。通过对不同O2水平、不同着火阶段和CH2O形成的反应喷雾的温度和当量比关系的研究表明，CH2O开始耗尽可以作为点火指示器。
As an alternative fuel to diesel in compression-ignition (CI) engines, dimethyl ether (DME) has gained interest in combustion research due to its high cetane number for fast ignition and ultra-low emission of particulate matter. In this study, ignition and important intermediate species including formaldehyde (CH2O) are experimentally investigated in a constant-volume combustion vessel facility that includes a fuel injection system for spray-like behavior of liquid DME. Experiments of different oxygen concentrations simulating various levels of exhaust-gas recirculation (EGR) were performed to study its corresponding effect on the flame structure and emissions from DME combustion. Results from the experiment were then used to validate a 3-D CFD simulation using a detailed chemistry solver. Different stages of ignition characterized by temperature profile, and certain species (e.g., CH2O for cool flame) after start of injection, are provided to conceptualize the DME combustion process under the effect of low-to-high oxygen ambient gas concentrations. Both simulations and experiments showed that there is a supporting link between CH2O formation and low-temperature combustion prior to diffusion-controlled flame uniquely for DME. By studying the temperature and equivalence ratio dependence of the reacting spray at different O2levels, different stages of ignition along with the formation of CH2O suggested that the start of the depletion of CH2O can be used as an ignition indicator.