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首页> 外文学位 >Low temperature oxidation of biodiesel surrogates in a motored engine and the oxidation behavior of soot generated from the combustion of a biodiesel surrogate in a diffusion flame.
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Low temperature oxidation of biodiesel surrogates in a motored engine and the oxidation behavior of soot generated from the combustion of a biodiesel surrogate in a diffusion flame.

机译：机动发动机中生物柴油替代物的低温氧化，以及在扩散火焰中由生物柴油替代物燃烧产生的烟灰的氧化行为。

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摘要

As biodiesel becomes a viable alternative to petroleum-derived diesel fuels, there is a necessity to fundamentally understand the combustion and emissions characteristics of biodiesel. This study concerns the low temperature oxidation chemistry of biodiesel-relevant compounds and the impact of fuel-bound oxygen in fatty acid esters on soot oxidation behavior.;Low temperature oxidation of biodiesel surrogates (i.e., C7, C8, C10 and C11 esters with both saturated and unsaturated aliphatic chains) was studied in a motored cooperative fuels research (CFR) engine under fuel-lean conditions. Heat release results indicated that not only the presence of unsaturation in the aliphatic chain of fatty acid esters suppresses cool flame behavior, but also the suppression effect becomes more pronounced as the position of the double bond gets closer to the center of the aliphatic chain. Also, it was observed that cool flame behavior of fatty acid esters becomes stronger with the increase of the alkyl chain length.;Analyses of the intermediate species produced from low temperature oxidation of both saturated and unsaturated esters provided valuable insight into the major oxidation pathways of fatty acid esters at low to intermediate temperatures. It is observed that the abstraction of H-atoms on the α-carbon of the ester carbonyl group plays an important role in low temperature oxidation of saturated fatty acid esters. For unsaturated esters, under the current test conditions, the prominent feature of oxidation is the attack of radical species on the olefinic double bond. In addition, it was observed that a unique six-centered unimolecular elimination reaction channel may exist during the low temperature oxidation of fatty acid ethyl esters, yielding ethylene and alkyl acids.;In this study, soots generated from the combustion of methyl crotonate (MC) and n-pentane (PEN) in laminar co-flow diffusion flames were analyzed via various analytical techniques to determine the impact of fuel-bound oxygen in fatty acid esters on soot oxidation behavior.;Thermogravimetric analysis of the soot samples collected from the diffusion flames showed that MC soot exhibits only slightly higher oxidative reactivity than PEN soot, which indicates that the fuel-bound oxygen in MC may not be able to help to enhance soot oxidative reactivity to any significant extent under the well-defined diffusion flame test conditions with the test fuels having the same number of carbon atoms. Therefore, the remarkable difference in reactivity observed between biodiesel-derived soot and Fischer Tropsch (FT) diesel-derived soot in diesel engines is likely due to the difference in combustion characteristics and soot formation process between biodiesel and FT diesel under diesel combustion conditions.;Furthermore, structural analysis was performed on both MC soot and PEN soot. Based on the analysis of the XRD patterns of the two soots at different stages of oxidation, there is no notable difference in crystallite structural parameters between MC soot and PEN soot. Also, the analysis of the first-order Raman spectra of the two soots revealed that there is no statistically significant difference in the Id/Ig (i.e., the ratio of the integrated intensity of the D band relative to that of the G band) ratios between MC soot and PEN soot, indicating that MC soot is no more disordered than PEN soot. In addition, HRTEM images of the primary particles in unreacted MC and PEN soots showed that both PEN soot particles and MC soot particles exhibit a certain extent of graphitic structural arrangement. Moreover, there is no distinct difference in initial nanostructure observed between the two soots. Overall, structural analysis of the two soots via different analytical techniques consistently showed that there is no significant difference in structural arrangement between MC soot and PEN soot, which agrees with the lack of a notable difference in reactivity between the MC soot and PEN soot observed from the temperature-programmed oxidation experiments. (Abstract shortened by UMI.).
机译：随着生物柴油成为石油衍生柴油的可行替代品，有必要从根本上了解生物柴油的燃烧和排放特性。这项研究涉及与生物柴油有关的化合物的低温氧化化学以及脂肪酸酯中燃料结合的氧对烟灰氧化行为的影响。生物柴油替代物（即C7，C8，C10和C11酯同时具有两种在贫燃料条件下的机动合作燃料研究（CFR）发动机中对饱和和不饱和脂肪族链进行了研究。放热结果表明，不仅脂肪酸酯的脂肪族链中存在不饱和键抑制了冷焰行为，而且随着双键的位置更接近脂肪族链的中心，其抑制作用也更加明显。此外，还观察到，随着烷基链长度的增加，脂肪酸酯的冷火焰行为变得更强。；对饱和和不饱和酯的低温氧化产生的中间物种的分析提供了有价值的洞察力，其主要途径是中低温度下的脂肪酸酯。观察到在酯羰基的α-碳上H原子的抽象在饱和脂肪酸酯的低温氧化中起重要作用。对于不饱和酯，在当前测试条件下，氧化的主要特征是自由基对烯烃双键的攻击。此外，据观察，在脂肪酸乙酯的低温氧化过程中，可能会存在一个独特的六中心单分子消除反应通道，从而产生乙烯和烷基酸。;在这项研究中，巴豆酸甲酯（MC）燃烧产生的烟s ）和层流共流扩散火焰中的正戊烷（PEN）通过各种分析技术进行了分析，以确定脂肪酸酯中与燃料结合的氧对烟灰氧化行为的影响;热重分析了从扩散中收集的烟灰样品火焰表明，MC烟灰的氧化反应性仅比PEN烟灰略高，这表明在明确定义的扩散火焰测试条件下，MC中与燃料结合的氧可能无法在任何程度上显着增强烟灰的氧化反应性。具有相同碳原子数的测试燃料。因此，由于柴油燃烧条件下生物柴油和FT柴油之间的燃烧特性和烟灰形成过程的差异，在柴油发动机中观察到的生物柴油衍生的烟灰与Fischer Tropsch（FT）柴油衍生的烟灰之间的反应性显着差异。此外，对MC烟灰和PEN烟灰都进行了结构分析。根据两种烟灰在不同氧化阶段的XRD图谱分析，MC烟灰和PEN烟灰的微晶结构参数没有显着差异。同样，对两个烟ot的一阶拉曼光谱的分析表明，Id / Ig比（即D波段的积分强度与G波段的积分强度之比）没有统计学上的显着差异。在MC烟灰和PEN烟灰之间，表明MC烟灰没有比PEN烟灰更无序。另外，未反应的MC和PEN烟灰中的初级颗粒的HRTEM图像显示，PEN烟灰颗粒和MC烟灰颗粒均表现出一定程度的石墨结构排列。而且，在两个烟灰之间观察到的初始纳米结构没有明显的差异。总体而言，通过不同的分析技术对两种烟灰的结构分析一致表明，MC烟灰和PEN烟灰之间的结构排列没有显着差异，这与从观察到的MC烟灰和PEN烟灰之间的反应性缺乏显着差异相一致。程序升温氧化实验。 （摘要由UMI缩短。）。

著录项

  • 作者

    Zhang, Yu.;

  • 作者单位

    The Pennsylvania State University.;

  • 授予单位 The Pennsylvania State University.;
  • 学科 Engineering Chemical.;Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 187 p.
  • 总页数 187
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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