Fundamental flame studies of soot formation and morphology at elevated pressures

为了实现更高的热效率和更小的发动机体积，内燃机被设计为在远高于大气的压力下运行。燃气轮机和柴油机排放的主要污染物之一是烟尘，也称为颗粒物或黑碳，它是在燃烧过程中形成的，当运行模式为非预混或部分预混时，其生成率随着燃烧压力的增加而显著增加。烟尘气溶胶通过改变大气的辐射特性，在区域和全球范围内影响地球的温度和气候。对全球变暖的贡献可能是巨大的，或许仅次于二氧化碳。此外，煤烟在冰雪上的沉积降低了表面反射率，从而捕获了辐射；这可能是全球变暖的四分之一原因。因此，政府间气候变化专门委员会指出，烟尘气溶胶是导致气候变化的正辐射强迫的第三大贡献者。此外，暴露在烟尘气溶胶中每年导致全球数十万人死亡。很大一部分烟尘是从陆上、空中和海上运输中使用的发动机排放的。对烟尘气溶胶的控制可以迅速产生区域和全球气候效益，并减少对人类健康的不良影响。控制燃烧烟尘的途径之一是防止或减少燃烧过程中的碳烟生成。对燃烧中碳烟形成过程的基本了解是这一控制方法的一个组成部分。然而，由于碳氢化合物火焰的高度复杂性质，燃烧中碳烟形成过程的化学和物理机制的细节仍然不确定，并且只有几个原则被牢固地确立，主要是针对大气条件。尽管大多数用于运输的燃烧设备都是在很高的压力下运行的，但我们对高压下的碳烟形成的了解并不是很理想，而且基本上缺乏实验数据和补充的预测模型。液体生物燃料的烟尘特性还不是很清楚，特别是在大多数发动机运行的高压环境下，这种缺乏了解的情况影响了在燃气轮机和其他陆上运输发动机中采用生物燃料和混合燃料。目前的提案旨在通过促进对烟尘形成及其在发动机相关压力下的特性的认识并帮助控制烟尘排放的努力来解决这些问题。这将通过使用独特的高压燃烧设施以及多伦多大学航空航天研究所的光学和侵入性燃烧诊断来精心规划的实验来实现。

To achieve higher thermal efficiencies and smaller engine volumes, combustion engines are designed to operate at pressures much higher than the atmospheric. One of the major pollutants emitted from the gas turbines and diesel engines is soot, also known as particulate matter or black carbon, which forms during the combustion process when the mode of operation is non-premixed or partially-premixed, and its formation rate is significantly increased by increasing the combustion pressure. Soot aerosols affect the Earth's temperature and climate, both regionally and globally by altering the radiative properties of the atmosphere. The contribution to global warming may be substantial, perhaps second only to that of CO2. In addition, the deposition of soot on snow and ice reduces the surface reflectivity thus trapping the radiation; this could be responsible for a quarter of the global warming. As a result, the Intergovernmental Panel on Climate Change states that the soot aerosol is the third largest contributor to the positive radiative forcing that causes climate change. Furthermore, exposure to soot aerosol is responsible for hundreds of thousands of global deaths each year. A significant portion of soot is emitted from engines used in land, air and sea transportation. Controls on soot aerosol can produce rapid regional and global climate benefits as well as reductions of ill effects on human health. One of the approaches in control is prevention or reduction of soot generation in combustion. A fundamental understanding of the soot formation processes in combustion is an integral part of this control approach. However, the details of the chemical and physical mechanisms of the soot formation process in combustion remain uncertain due to the highly complex nature of hydrocarbon flames, and only a few principles are firmly established mostly for atmospheric conditions. In spite of the fact that most combustion devices used for transportation operate at very high pressures, our understanding of soot formation at high pressures is not at a desirable level, and there is a fundamental lack of experimental data and complementary predictive models. Sooting characteristics of liquid bio-fuels are not known well, especially at high pressures where most engines operate, and this lack of understanding has implications in adopting bio-fuels and blends in gas turbines and other land transportation engines. The current proposal aims to address these issues by contributing to the advancement of knowledge in soot formation and its characteristics at engine-relevant pressures and helping with the soot emissions control efforts. This will be accomplished by carefully planned experiments using the unique high-pressure combustion facility, and optical and intrusive combustion diagnostics at the University of Toronto Institute for Aerospace Studies.