Structure of Incipiently Sooting Counterflow Diffusion Flames at High Pressure

对实际系统中烟尘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环境。研究的现实目标是检查层流逆流火焰的结构，在压力范围1-40大气压的条件下，初期炭黑。它需要表征的温度，稳定的气体物种，包括碳烟前体和生长物种，和火焰中的碳烟作为压力的函数。所选择的压力范围与燃气涡轮机和发动机应用相关。该项目是一项雄心勃勃、全面和前所未有的努力，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是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？流动反应器具有良好定义的温度时间历程。此外，由于系统是一维的，因此这种火焰配置对于建模目的非常方便，这对于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，其将以适度的浓度预蒸发并单独或组合地作为基线气体火焰的扰动引入这种环境中。该方法是实验和计算的性质。该计划的成果包括：1）一个试验台实验系统，用于研究不同炭黑倾向的气体和液体燃料的高压层流扩散火焰的结构及其在定义明确和控制良好的条件下的炭黑行为; 2）一个经过验证的代码，具有全面的炭黑形成/氧化模型，允许详细的传输和半详细的化学动力学机制; 3）一个全面的数据库，将提供给其他模拟。燃烧产生的煤烟颗粒从陆地来源，现在被认为是一个重大的健康风险，并已成为严格的新的环保署法规的主题。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极大关注，并面临加强监管的可能性。所有这些问题都因新燃烧器运行时的高压而加剧，因为烟灰的产生对压力非常敏感。 如果要控制烟尘和与之相关的问题，以计算模型支持的实验测量的形式定量了解烟尘生长和氧化机制是必不可少的，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.