The Development of Sensitive Diagnostics and Their Use in Shock Tube Studies of Formaldehyde and Formyl Reaction Rate Coefficients

项目总结这是一个由两部分组成的研究计划，包括开发一种新的可调谐紫外激光吸收诊断仪，并将该诊断仪应用于甲醛氧化和氮氧化物动力学的研究。利用230 nm附近的强紫外(UV)甲酰(HCO)吸收特性，开发了一种灵敏的甲酰基(HCO)吸收诊断方法，该方法使用带有外部倍频的环形染料激光器。这种方法应该会使HCO的灵敏度比目前在614 nm处进行的激光吸收测量增加三倍。还使用了先前开发的在306 nm处敏感的(ppm级别)羟基(OH)激光吸收诊断和在174 nm处的甲醛(CH2O)灯吸收诊断。羟基是燃烧体系中自由基池形成的重要标志，这一过程可以更好地分离复杂的CH2O/HCO/O2动力学体系中的某些反应。这些诊断方法允许在大约1000至1600K的温度范围内测量以下反应：HCO+O2？CO+HO2(A)HCO+NO？CO+HNO(B)CH2O+O2？HCO+HO2(C)CH2O+OH？涉及甲醛(CH2O)和甲酰基(HCO)的HCO+H2O(D)反应位于甲烷和其他碳氢燃料的初级氧化途径上。即使有了这一主要作用，这一次机制中许多关键反应的高温速率系数仍然存在很大的不确定性。这些反应速率的实验测量的不确定性在很大程度上是因为无法以足够的灵敏度测量重要的反应物种，如HCO，并无法从动力学上将单个反应与干扰反应分离。更高灵敏度的HCO测量和对OH的补充诊断相结合，允许设计更简单、更直接的实验，干扰反应更少，从而能够更可靠地确定几个重要元素反应的速率系数。广泛影响这项工作对研究生教育和科学数据库有重要贡献，并影响政府实验室和工业的燃烧化学建模活动。该项目为研究生提供了学习最先进的激光和激波管方法并在世界级实验室获得实践经验的机会。在这个项目中开发的实验技术包括在研究生院的实验室课程和教科书中。在该计划中获得的数据、结果和专业知识积极与政府和行业共享，特别是通过开发和分发基于网络的动力学数据库、审查与燃烧相关的反应速率和个人联系。

PROJECT SUMMARYThis is a two-part research program consisting of the development of a new tunable ultraviolet-laser absorption diagnostic and the application of this diagnostic to the investigation of formaldehyde oxidation and nitrogen-oxide kinetics. A sensitive formyl (HCO) absorption diagnostic using a ring-dye laser with an external frequency doubler is developed that takes advantage of the strong ultraviolet (UV) HCO absorption feature near 230 nm. This method should yield a threefold increase in HCO sensitivity over the current laser absorption measurements made at 614 nm. Also used are a sensitive (ppm level) hydroxyl (OH) laser absorption diagnostic at 306 nm and a formaldehyde (CH2O) lamp absorption diagnostic at 174 nm that have been developed previously. Hydroxyl is an important marker of radical pool development in combustion systems and this procedure will enable better isolation of certain reactions in the complex CH2O/HCO/O2 kinetic system. These diagnostics permit measurement of the following reactions over the approximate temperature range 1000 to 1600 K:HCO + O2 ? CO + HO2 (a)HCO + NO ? CO + HNO (b)CH2O + O2 ? HCO + HO2 (c)CH2O + OH ? HCO + H2O (d)Reactions involving formaldehyde (CH2O) and formyl radical (HCO) lie on the primary oxidation pathway for methane and other hydrocarbon fuels. Even with this primary role, there are still large uncertainties in the high-temperature rate coefficients of many of the key reactions in this sub-mechanism. The uncertainty in the experimental measurements of these reaction rates stems largely from an inability to measure important reaction species, such as HCO, with sufficient sensitivity and to kinetically isolate the individual reactions from interfering reactions. Higher-sensitivity measurements of HCO combined with the use of complementary diagnostics for OH permit the design of simpler, more direct experiments with fewer interfering reactions, and hence enable more reliable determinations of rate coefficients for several important elementary reactions.Broader impactThis work contributes significantly to graduate education and scientific databases and impacts combustion-chemistry modeling activities in government laboratories and industry. The program provides an opportunity for graduate students to learn state-of-the-art laser and shock-tube methods and gain practical experience in a world-class laboratory. Experimental techniques developed in this program are included in graduate laboratory classes and textbooks. Data, results and expertise acquired in this program are actively shared with government and industry, particularly through the development and distribution of web-based kinetics databases, reviews of combustion-related reaction rates, and personal contacts.