Kinetics of Free Radical Reactions of Combustion Importance at Elevated Pressures

该研究旨在为包括内燃机在内的实际重要燃烧过程建立重要的高压燃烧化学需求。燃烧效率和稳定性、发动机内部爆震、环境有害物质排放等问题都需要详细的化学动力学机制，以及在广泛的温度和压力范围内具有良好特征的基本反应。然而，在高压下推进燃烧模型所需的动力学数据仍然不足。实验室测量通常提供“方便”压力下的速率常数（0.001 - 1bar）。它们必须根据理论基础外推到更高的压力，但这种预测可能会在模型预测中引入显著的额外不确定性。具体的研究目标是对HCO、CH3、OH、HO2等具有燃烧重要性的自由基在延长的温度和高压范围内的单分子和双分子反应动力学和机理进行系统的基础研究。实验研究将采用脉冲激光光解结合高压流系统和瞬态吸收光谱技术。缓冲气体密度影响解离和异构化反应、通过中间络合物进行的双分子反应以及相应的逆反应的速率和分支比。将该反应的压降测量值与理论计算结果进行比较，将进一步推动单分子解离理论和具有孤立共振的RRKM理论的发展。总的来说，所提出的研究计划将有助于扩大对缓冲气体密度效应的认识和理解。通过在技术和科学界的出版物和演讲，通过对学生和新科学家的教育和培训，以及通过促进国内和国际学科和机构之间的协同合作，所提出的工作将产生更广泛的影响。这项研究将依靠研究生和本科生的培训和参与。

CBET-0827398KrasnoperovThe research seeks to establish the important high-pressure combustion chemistry need for practically important combustion processes, including internal combustion engines. Combustion efficiency and stability, internal engine knock, emission of environmentally noxious substances are the problems which require detailed chemical kinetics mechanisms with well-characterized elementary reactions over extended temperature and pressure ranges. However, the kinetic data necessary for advancement of combustion models at elevated pressures are still insufficient. Laboratory measurements usually provide rate constants at "convenient" pressures (0.001 - 1 bar). They are necessarily extrapolated to higher pressures based on theoretical foundations, but such predictions may introduce significant additional uncertainties into the model predictions. The specific research objective is a systematic fundamental study on the kinetics and mechanisms of unimolecular and bimolecular reactions of free radicals of combustion importance such as HCO, CH3, OH, and HO2 over extended temperature and elevated pressure ranges. Pulsed laser photolysis combined with high-pressure flow system and transient absorption-spectroscopy techniques will be used in the experimental studies. Buffer gas density affects the rates and branching ratios of dissociation and isomerization reaction, bimolecular reactions that proceed via an intermediate complex, as well as the corresponding reverse reactions. The comparison of the measurements of the pressure fall-off in this reaction with theoretical calculations will lead to the further advancement of the theory of unimolecular dissociation and the RRKM theory with isolated resonances. Overall, the proposed research program will contribute to extending the knowledge and understanding the buffer gas density effects. Broader impacts of the proposed work arise through publications and presentations in the technical and scientific community, by the education and training of students and new scientists, and through advancement of synergetic collaborations between disciplines and institutions, both domestic and international. The research will rely upon training and participation of graduate as well as undergraduate students.