Computational and Experimental Study of Oxygenated Hydrocarbon Fuel Chemistry in Non-premixed Flames

1133211PfefferleIntellectual Merit：按重量计算，植物含有约50%的氧气。因此，随着社会不可避免地从化石燃料转向可再生燃料，燃烧燃料的含氧量将会增加。燃料中含氧碳氢化合物的存在引入了重要的燃烧科学和公共卫生问题，这些问题由拟议的研究解决。首先，含氧化合物可以减少烟尘颗粒的排放。其次，它们还会增加其他有毒燃烧副产品的排放，比如醛类物质。为了在合理优化烟尘减排的同时最大限度地减少空气中有毒物质的排放，我们需要了解燃料分解和含氧化合物生成芳烃的化学机制。植被可生成的含氧物数量较多，且随着含氧物结构的不同，其排烟倾向和燃料分解产物差异较大；因此，用严格的经验方法在它们之间进行选择是不可靠的。需要一种分析大量含氧燃料并从燃料结构中预测机理和反应性的方法。虽然碳氢化合物和一些小的含氧化合物的燃烧化学已经被广泛研究，但对大多数含氧化合物知之甚少。我们提出了一种新的方法，该方法基于快速，在线物种测量和共流火焰中的计算模拟，其中少量含氧燃料添加到甲烷的基础燃料中。碱式甲烷火焰具有很好的特征，计算结果与实验测量结果吻合较好。我们的策略包括对一个特征良好的系统进行扰动，从而实现高质量的测量，也便于模拟，因为先前计算的碱甲烷火焰的解可以用作所有掺杂火焰的起始估计。重要的是，我们的方法比较了在相同火焰条件下含氧燃料种类的命运，强调了化学机制的差异而不是其他因素。在早期的工作中，我们验证了这种方法的常规碳氢化合物，包括庚烷、己烯、己二烯、环烷烃和芳烃。这里我们将扩展到100+含氧碳氢化合物，最多有20个碳原子。我们的研究结果将为其他含氧化合物燃烧化学研究提供重要的比较，这些研究大多使用预混火焰和有限数量的含氧燃料结构。为了发展结构/反应性关系，需要对广泛的结构进行分析，从而允许进行稳健的机制测试，并为选择含氧燃料以优化排放效益提供合理的基础。更广泛的影响：我们的工作通过将数据库扩展到含氧碳氢化合物，并通过为燃料结构对烟尘产生和可能的有毒含氧排放的影响提供合理的相关性和外推数据，为更清洁的发动机设计和可再生燃料的利用奠定了基础。我们会与本地业界合作，推动这方面的工作。我们已经向世界各地的许多团体提供了我们以前研究的详细结果，他们用它们来测试计算模型。这里生成的数据库将被存档，供世界各地的研究人员直接使用。本科生已经参与了我们之前的研究，并将进行与本项目相关的实验模块。我们也会让本地不授予博士学位的大学和高中的学生参与我们的工作，帮助他们在自己的学校开展研究项目，并让他们对继续学习科学感兴趣。

1133211PfefferleIntellectual Merit: Plants are about 50 % oxygen by weight. Thus as society inevitably moves from fossil fuels towards renewable fuels, the oxygen content of combustion fuels will increase. The presence of oxygenated hydrocarbons in the fuel introduces important combustion science and public health issues that are addressed by the proposed research. First, oxygenates may reduce emissions of soot particles. Second, they can also increase emissions of other toxic combustion byproducts such as aldehydes. In order to rationally optimize soot reductions while minimizing air toxics emissions, we need to understand the chemical mechanisms of fuel decomposition and aromatic hydrocarbon formation for oxygenates. The number of oxygenates that can be made from vegetation is large, and the sooting tendencies and fuel decomposition products vary greatly as a function of oxygenate structure; thus strictly empirical approaches for choosing among them are not reliable. A strategy that analyzes a large number of oxygenated fuels and leads to methods that can predict mechanisms and reactivity from fuel structure is needed. Although the combustion chemistry of hydrocarbons and some small oxygenates has been widely studied, little is known for most oxygenated hydrocarbons. We propose a novel approach that is based on rapid, on-line species measurements and computational simulations in co-flow flames where a small amount of the oxygenated fuel is added to a base fuel of methane. The base methane flame is has been well characterized and computations provide good agreement with experimental species measurements. Our strategy involving perturbation of a well-characterized system enables high-quality measurements and also facilitates simulations because the solutions from previously computed base methane flames can be used as a starting estimate for all of the doped flames. Importantly, our methods compare the fate of oxygenated fuel species under identical flame conditions emphasizing differences in chemical mechanisms over other factors.In earlier work we validated this methodology for regular hydrocarbons including heptanes, hexenes, hexadienes, cycloalkanes and aromatics. Here we will extend it to 100+ oxygenated hydrocarbons with up to 20 carbon atoms. Our results will provide an important comparison to other studies of oxygenates combustion chemistry, most of which use premixed flames and a limited number of oxygenated fuel structures. The analysis of a wide range of structures is required for development of structure/reactivity relationships allowing robust mechanism testing and a rational basis for oxygenated fuel selection to optimize emissions benefits.Broader Impacts: Our work sets the stage for cleaner engine design and renewable fuels utilization by expanding the database to oxygenated hydrocarbons, and by providing rational correlation and extrapolation data for the effect of fuel structure on soot production and possible toxic oxygenated emissions. We will collaborate with local industry to facilitate this. We have provided detailed results from our previous studies to numerous groups around the world who have used them to test computational models. The databases generated here will be archived for direct access to researchers around the world. Undergraduate students have participated in our previous research and will perform laboratory modules related to this project. We will also involve students from local non-PhD granting colleges and high schools in our work and helping them develop research projects at their home institutions and to interest them in continuing study in the sciences.