There is a critical need for the measurement of elementary reaction rates for species and reactions relevant to combustion. Our ability to model combustion processes with high fidelity relies on the existence of accurate measurements of fundamental reaction rates of a smaller set of key reactions that control the reaction progress. This project proposes to measure the high-temperature rate coefficients for reactions of HO2 with CH3, C2H5, HO2, and OH. These reactions have been difficult to measure because of both the highly reactive nature of the reactants and the challenges in developing quantitative and sensitive diagnostics for the reactant and product concentrations. These reactions have been identified as major contributors to the uncertainty in the modeling of hydroperoxyl radical concentration in combustion systems. Measurements of these reaction rates will be performed in high-purity shock tubes using UV laser absorption of OH, HO2, H2O2, and CH3 radicals and mid-IR laser absorption of H2O. The overall range of temperature and pressure to be studied is from 800 to 2200 K and from 0.5 atm to 10 atm. This work will take advantage of a recently acquired tunable ultra-fast (76 MHz) quasi-CW laser system for ready access to broad deep-UV absorption transitions and recent advances in distributed feedback diode lasers in the mid-IR.
Intellectual Merit
Reactions involving the hydroperoxyl radical (HO2) play an important role in oxidation pathways of hydrogen and hydrocarbons. Much of what we already know about the role of these hydroperoxyl radical reactions has been derived from lower temperature (below 800 K) experiments, or from estimates. Direct experimental results for these reactions at high temperatures are rare (or non-existent) or contradictory, and are critically needed to enable development and validation of combustion kinetic models. The development of new and sensitive species diagnostics methods are also needed to advance these studies.
Broader Impact
This research will provide an opportunity to train a new generation of engineering scientists in modern combustion kinetics and state-of-the-art laser diagnostic and shock tube techniques. These techniques have provided, in the past, the highest quality high temperature kinetic data available and continue to be a source of reliable information. Public dissemination of this data through the web using current databases (the Kinetic Database Utilizing Shock Tube Measurements at Stanford and the PrIMe data warehouse currently located at Berkeley) will provide the public, government workers, and other researchers with the information needed to critically understand combustion processes. With one of the important problems facing Americans today being the generation of greenhouse gases from combustion processes and the subsequent effect of global warming, the proposed research is both appropriate and needed.
