CAREER: Energetic Radical Reactions and Impact on High and Low Pressure Combustion

高压燃烧是节能、低排放燃烧装置的新兴战略之一。在许多优点中，高压允许较低的温度，稀薄的燃烧，同时保持负荷要求。燃料/氧化剂和产物之间的许多反应速率和反应路径在燃烧温度和高压下是不确定的，特别是对于自由基中间体。这些反应速率和反应路径是用高灵敏度的工具测量的，通常是在非常低的压力下，然后外推到高压。最近的理论预测表明，在低压条件下，高能自由基反应可以迅速通过不同的途径。尽管大多数燃烧系统的压力较高，但在极低压力下的测量是这些系统模型的基础，这可能会导致预测模型中的极大不确定性。这项工作的一些目标是在低压下对这些影响进行实验测试，并估计它们在较高压力下对机制不确定性的贡献。另一个目标是将高灵敏度的测量技术扩展到高压。在五年的时间里，PI将使用先进的实验和建模工具来测量燃烧相关温度和压力范围内高能自由基反应的速率和产物。这项工作有助于通过更好地了解与煤烟形成和高压预燃化学相关的化学反应，来设计更清洁的燃烧装置。与高温下卤素的抽提有关的信息也有助于灭火模型，这是工作的一个方面。此外，这项提案中的努力包括为高中AP物理课程开发一个以燃烧为主题的模块，该模块还包括通过学生指导的、基于探究的调查来改进教学。为了测试能量通路在低压下的影响，将在较宽的压力范围内测量碳氢化合物的反应速率和自由基提取的产物。将使用各种自由基，包括卤素，以改变碰撞稳定化水平相近的反应热和产物的热容。本研究将使用微型高重复频率激波管(HRRST)。HRRST是一种工具，用于生成高度可重复、高度受控的燃烧条件，适合使用先进的分析技术进行测量。将使用选定时间分辨物种的可调谐半导体激光吸收和产品的质谱学相结合的方法来测量物种浓度，包括与Argonne国家实验室和劳伦斯伯克利国家实验室的高级光源研究人员合作的同步加速器源光电离质谱。通过详细的化学模拟，可以从这些实验中确定反应速率和产物通道。除了这项研究的重点是自由基反应外，这项工作还开发了一种新的诊断技术，HRRST，可以被各种学科采用。

High pressure combustion is one aspect of emerging strategies for fuel efficient, low emission combustion devices. Among many advantages, high pressure permits lower temperature, lean combustion while maintaining load requirements. Many of the reaction rates and reaction pathways between fuel/oxidizer and products are uncertain at combustion temperatures and high pressure, especially for radical intermediates. These reaction rates and reaction pathways are measured using highly sensitive tools, typically at very low pressure, and are then extrapolated to high pressure. Recent theoretical predictions suggest highly energetic radical reactions can quickly pass through different pathways in low pressure conditions. Even though most combustion systems are at higher pressures, the measurements at very low pressure underpin the models of these systems, which may lead to great uncertainty in predictive models. Some of the goals of this work are to experimentally test these effects at low pressure and estimate their contribution to mechanism uncertainty at higher pressure. Another goal is to extend highly sensitive measurement techniques to high pressure. Over the course of five years, the PI will use advanced experimental and modeling tools to measure the rates and products of energetic radical reactions spanning combustion relevant temperatures and pressures. The work contributes to cleaner combustion device designs, via improved understanding of chemical reactions relevant to soot formation and high pressure pre-ignition chemistry. Information relating to the abstractions by halogens at high temperature, one aspect of the work, also contributes to fire suppression models. Additionally, efforts in this proposal include development of a combustion themed module for high school AP Physics curricula, which also incorporates pedagogic improvements through student-directed, inquiry-based investigations. In order to test the effects of energetic pathways at low pressure, reaction rates and products of radical abstractions from hydrocarbons will be measured over wide pressure ranges. Various radicals will be employed, including halogens, in order to vary the enthalpy of reaction and the heat capacity of products at similar levels of collisional stabilization. The miniature high repetition rate shock tube (HRRST), will be used in this study. The HRRST is a tool for generating highly repeatable, highly controlled combustion conditions suitable for measurements using advanced analytical techniques. Species concentrations will be measured with a combination of tunable diode laser absorption for selected time-resolved species and mass spectrometry for products, including synchrotron sourced photoionization mass spectrometry in collaboration with researchers at Argonne National Laboratory and at the Advanced Light Source at Lawrence Berkeley National Laboratory. Reaction rates and product channels can be ascertained from these experiments with detailed chemical modeling. Besides the radical reactions which are the focus of this study, the work develops a nascent diagnostic technique, the HRRST, which can be adopted by a variety of disciplines.