Accurate Determination of Branching Fractions in Ammonia Combustion

氨是碳中性燃烧的潜在过渡燃料。然而，氨的燃烧会导致各种氮氧化物（NOx），这是主要的污染物，可以加剧气候变化。为了减轻氮氧化物对人类健康和环境的影响，政府法规越来越多地要求减少燃烧源的氮氧化物排放。准确预测氮氧化物形成水平的能力将有利于工程师和科学家，他们需要量化新燃料或新发动机设计对氮氧化物排放的影响。这些氮氧化物子机制也将使更广泛的大气科学界受益，无论是在地方层面（例如烟雾）还是在全球层面（例如气候变化）。该项目的目标是测量在氨燃烧动力学中重要的几个反应的分支分数，特别是那些与各种氮氧化物有关的反应。研究人员假设，通过同时测量两种或多种物质的瞬态浓度，分支分数的不确定性可以相对于NOx文献中目前的技术状态而降低。为了验证这一假设，研究人员将使用可调谐二极管激光吸收光谱（TDLAS）来测量激波管中反射激波后的NO， NO2, N2O， H2O的瞬态浓度和/或温度。这些剖面将作为动力学模型的验证目标。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Ammonia is a potential bridge fuel for carbon-neutral combustion. However, the combustion of ammonia can lead to various nitrogen oxides (NOx), which are major pollutants, and which can exacerbate climate change. To mitigate the impact of NOx on human health and the environment, government regulations increasingly require reduced emissions of nitrogen oxides from combustion sources. The ability to make accurate predictions of NOx formation levels will benefit engineers and scientists who need to quantify the impact of a new fuel or a new engine design on NOx emissions. These NOx submechanisms also will benefit the broader atmospheric science community, both at the local level (e.g. smog) and at the global level (e.g. climate change). The goal of this project is to measure the branching fractions for several reactions that are important in the kinetics of ammonia combustion, particularly those related to various nitrogen oxides. The investigators hypothesize that by measuring the transient concentration of two or more species simultaneously, the uncertainty in the branching fractions can be reduced relative to the current state of the art in NOx literature. To test this hypothesis, the investigators will use tunable diode laser absorption spectroscopy (TDLAS) to measure the transient concentration of NO, NO2, N2O, H2O, and/or temperature behind the reflected shock in a shock tube. These profiles will serve as validation targets for a kinetic model.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.