Structure of Incipiently Sooting Counterflow Diffusion Flames at High Pressure

对实际系统中烟灰形成的基本理解仍然是一个艰巨的挑战，实验室火焰仍然是在该领域取得进展的更好的环境。本研究的现实目的是研究1 ~ 40atm压力范围内初烟条件下层流逆流火焰的结构。它需要表征温度，稳定的气体种类，包括烟尘前体和生长种类，以及火焰中的烟尘作为压力的函数。所选压力范围与燃气轮机和发动机应用有关。该项目代表了一项雄心勃勃的、全面的、前所未有的努力，在燃烧的环境足迹方面具有潜在的变革性影响。选择逆流扩散火焰作为最佳环境，因为它对烟灰形成过程提供了无与伦比的控制水平。火焰基本上被视为？流核反应堆?有明确的温度时程。此外，这种火焰结构非常便于建模，因为系统是一维的，这对具有非常大的化学机理的燃料是有利的。要考虑的燃料包括液体燃料，例如庚烷和甲苯，它们将以中等浓度预汽化，并作为对基线气体火焰的扰动单独或组合引入这种环境。这种方法在本质上是实验性的和计算性的。项目成果包括：1)研究不同燃灰倾向的气体和液体燃料高压层流扩散火焰的结构及其在良好控制条件下的燃灰行为的试验台实验系统；2)经过验证的代码，具有烟尘形成/氧化的综合模型，允许详细的运输和半详细的化学动力学机制；3)一个全面的数据库，将提供给其他建模者。来自陆地的燃烧产生的烟尘颗粒现已被认为对健康构成重大威胁，并已成为美国环保署严格的新法规的主题。此外，飞机飞行通过高空烟尘排放对大气气溶胶水平的贡献及其对长期全球气候变化和臭氧消耗机制的影响也受到高度关注，并可能面临更严格的监管。由于烟灰的产生对压力非常敏感，新燃烧器运行时的高压加剧了所有这些问题。如果要控制烟灰及其相关问题，以计算模型支持的实验测量形式对烟灰生长和氧化机制的定量理解是必不可少的，也是该项目的主要目标。

A fundamental understanding of soot formation in practical systems is still a daunting challenge and laboratory flames remain a better setting to make progress in the field. The research has the realistic objective of examining the structure of laminar counterflow flames in the pressure range 1-40 atm under conditions of incipient sooting. It entails the characterization of temperature, stable gas species, including soot precursors and growth species, and soot in flames as a function of pressure. The selected pressure range is of relevance to gas turbines and engine applications. The project represents an ambitious, comprehensive and unprecedented effort with potentially transformative impact in the context of the environmental footprint of combustion. The counterflow diffusion flame is selected as an optimal environment because of the unparalleled level of control that it provides on the soot formation process. The flames are treated essentially as ?flow reactors? with well defined temperature time-histories. Furthermore, this flame configuration is very convenient for modeling purposes since the system is one-dimensional, which is advantageous for fuels with a very large chemical mechanism. Fuels to be considered include liquid fuels, such as heptane and toluene, that would be prevaporized at modest concentrations and introduced in such environments either individually or in combination as a perturbation of baseline gaseous flames. The approach is both experimental and computational in nature. Deliverables of the program include: 1) a test-bed experimental system to study the structure of high-pressure laminar diffusion flames of gaseous and liquid fuels of different sooting propensity and their sooting behavior under well-defined and well-controlled conditions; 2) a validated code with a comprehensive model of soot formation/oxidation, allowing for detailed transport and a semi-detailed chemical kinetic mechanism; and 3) a comprehensive database that will be made available to other modelers.Combustion-generated soot particulates from land-based sources are now acknowledged to pose a significant health risk and have been the subject of stringent new EPA regulations. Moreover, the contributions of aircraft flights to atmospheric aerosol levels via high altitude soot emissions and their impact on the mechanisms of long term global climate change and ozone depletion are also receiving great attention and face the likelihood of tightened regulation. All these issues are exacerbated by the high pressures at which new combustors are operated, because soot production is very sensitive to the pressure. If soot and the problems associated with it are to be controlled, quantitative understanding of the soot growth and oxidation mechanisms in the form of experimental measurements supported by computational models is essential and is the primary goal of the project.