Laser Absorption Measurements of Hydroperoxy-Related Reactions in Shock Tubes at Intermediate Temperatures

中温激波管中与过氧化氢有关的反应的激光吸收测量。K. Hanson，斯坦福大学公共摘要氢/氧氧化是当今燃烧中最重要的系统之一。 这导致了在高温（1200 K以上）下H2/O2化学的极其准确的描述的发展。 然而，在中间温度（约800至1200 K）下，许多重要化学反应的速率系数是不确定的，特别是那些涉及过氧化氢自由基HO 2和过氧化氢H2 O2的反应。 H2 O2动力学可以主导氢动力发动机（例如均质充量压缩点火发动机（HCCI））中的化学，并且对于描述发动机爆震和柴油点火是关键的。 了解过氧化氢化学也需要作为攻击的基础上更大的问题，过氧自由基（RO 2）的化学重要的氧化在中间温度的烃。 为了改进H_2O_2体系的化学模型和计算机模拟，迫切需要新的具有较小不确定度的H_2O_2体系中温速率系数的测量方法。烷烃是汽油、煤油和柴油等碳氢燃料的重要组成部分。 在燃烧过程中，这些烷烃（如正庚烷和异辛烷）分解成烷基自由基。 随后，这些烷基被氧化或进一步分解。这两种氧化和分解的烷基途径，以及它们的相对速率，决定了燃烧系统的后续行为。 这些反应的性质导致中温区氧化机理的改变，这导致烃氧化中的“负温度系数”（NTC）行为。 对烷基氧化反应机理的全面理解将对燃烧化学、自燃、发动机爆震、大气化学和自由基反应化学等领域产生重要影响，我们将利用激波管中的紫外激光吸收技术对这些体系中的瞬态自由基（包括OH、HO 2和烷基过氧自由基）进行定量测量。从这些测量的时间历程的物种浓度，反应速率将被确定为几个关键的碳氢化合物燃烧反应。 感兴趣的具体反应包括：H2 O2 OH + OH; H + H2 O2 HO 2 + H2; C2 H5 +O2 HO 2 + C2 H4; C3 H7 +O2 HO 2 + C3 H6。 这些反应已被确定为中温（800-1200 K）燃烧建模的不确定性的主要贡献者。关键的贡献将是测量本身，在一个关键的温度区域下降，并在1至100大气压的压力下测量，以及一个新的215纳米深紫外激光吸收诊断方法。这项研究将提供一个机会，培养一代工程科学家在现代燃烧动力学和国家的最先进的激光诊断和激波管技术。 利用现有数据库通过网络公开传播这些数据，将为公众、学生、教师和政府工作人员提供批判性地理解燃烧过程所需的信息。 随着当今美国人面临的重要问题之一是燃烧过程产生的温室气体以及随后的全球变暖效应，迫切需要对燃烧基本原理进行研究。

Laser Absorption Measurements of Hydroperoxyl-Related Reactions in Shock Tubes at Intermediate TemperaturesR. K. Hanson, Stanford UniversityPublic AbstractHydrogen/oxygen oxidation is one of the most important systems in combustion today. This has led to the development of an extremely accurate description of H2/O2 chemistry at high temperatures (above 1200 K). However, at intermediate temperatures (from about 800 to 1200 K) the rate coefficients of many important chemical reactions are uncertain, particularly those involving HO2, the hydroperoxyl radical, and H2O2, hydrogen peroxide. H2O2 kinetics can dominate the chemistry in hydrogen-powered engines, such as homogenous charge compression ignition engines (HCCI), and are critical to describing engine knock and diesel ignition. An understanding of H2O2 chemistry is also needed as a basis for attacking the larger problem of peroxy-radical (RO2) chemistry important in oxidation at intermediate temperatures of hydrocarbons. New measurements with smaller uncertainties of the rate coefficients in the H2O2 system at intermediate temperatures are urgently needed to improve chemical models and computer simulations of these processes.Alkanes are important components of all hydrocarbon fuels such as gasoline, kerosene and diesel. During combustion, these alkanes (such as n-heptane and iso-octane) decompose into alkyl radicals. Subsequently these alkyl radicals are either oxidized or further decompose. These two alkyl pathways of oxidation and decomposition, and their relative rates, dictate the subsequent behavior of the combustion system. The properties of these reactions cause a change in the oxidation mechanism in the intermediate temperature regime which results in the "negative temperature coefficient" (NTC) behavior in hydrocarbon oxidation. Complete understanding of the alkyl oxidation mechanism has implications in combustion chemistry, auto-ignition, engine knock, atmospheric chemistry and radical reaction chemistry.Quantitative measurements of transient radicals, including OH, HO2 and alkyl-peroxy-radicals, will be made in these systems using UV laser absorption in shock tubes. From these measurements of time histories for species concentrations, reaction rates will be determined for several critical hydrocarbon combustion reactions. Specific reactions of interest include: H2O2 OH + OH; H + H2O2 HO2 + H2; C2H5 +O2 HO2 + C2H4; C3H7 +O2 HO2 + C3H6. These reactions have been identified as major contributors to the uncertainty in the modeling of intermediate temperature (800-1200 K) combustion. Key contributions will be the measurements themselves, falling in a key temperature region and measured at pressures from 1 to 100 atm, and a new 215nm deep-UV laser-absorption diagnostic method.This research will provide an opportunity to train a generation of engineering scientists in modern combustion kinetics and state-of-the-art laser diagnostic and shock tube techniques. Public dissemination of this data through the web using current databases will provide the public, students, teachers and government workers with the information needed to critically understand combustion processes. With one of the important problems facing Americans today being generation of greenhouse gases from combustion processes and the subsequent effect of global warming, research on combustion fundamentals is critically needed.