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Chemiluminescence experiments have been performed to assess the state of current CO * 2 kinetics modeling. The difficulty with modeling CO * 2 lies in its broad emission spectrum, making it a challenge to isolate it from background emission of species such as CH * and CH 2 O * . Experiments were performed in a mixture of 0.0005H 2 + 0.01N 2 O + 0.03CO + 0.9595Ar in an attempt to isolate CO * 2 emission. Temperatures ranged from 1654 K to 2221 K at two average pressures, 1.4 and 10.4 atm. The unique time histories of the various chemiluminescence species in the unconventional mixture employed at these conditions allow for easy identification of the CO * 2 concentration. Two different wavelengths to capture CO * 2 were used; one optical filter was centered at 415 nm and the other at 458 nm. The use of these two different wavelengths was done to verify that broadband CO * 2 was in fact being captured, and not emission from other species such as CH * and CH 2 O * . As a baseline for time history and peak magnitude comparison, OH * emission was captured at 307 nm simultaneously with the two CO * 2 filters. The results from the two CO * 2 filters were consistent with each other, implying that indeed the same species (i.e., CO * 2 ) was being measured at both wavelengths. A first-generation kinetics model for CO * 2 and CH 2 O * was developed, since no comprehensively validated one exists to date. CH 2 O * and CH * were ruled out as being present in the experiments at any measurable level, based on calculations and comparisons with the data. Agreement with

Autoignition delay time measurements were recorded for blends of CH4/n-C4H10 in “air” at pressures of approximately 10, 16, 20, 25, and 30 atm from fuel-lean to fuel-rich conditions at two different fuel compositions, 90% CH4/10% n-C4H10 and 70% CH4/30% n-C4H10, and temperatures from 660 to 1330 K in both a rapid compression machine and a shock-tube facility. A detailed chemical kinetic model consisting of 1328 reactions involving 230 species was validated using the ignition delay data from this study. This mechanism has already been used to simulate previously published ignition delay times over a wide range of conditions. It was found that the model quantitatively reproduces the ignition delays from both rapid compression and reflected shock waves, accurately capturing reactivity as a function of the temperature, pressure, equivalence ratio, and fuel composition.

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Electronically excited carbon dioxide (CO 2 *) is known for its broadband emission, and its detection can lead to valuable information; however, owing to its broadband characteristics, CO 2 * is difficult to isolate experimentally, and its chemical kinetics are not well known. Although numerous works have monitored CO 2 * chemiluminescence, a full kinetic scheme for the excited species has yet to be developed. To this end, a series of shock-tube experiments was performed in H 2 -N 2 O-CO mixtures highly diluted in argon at conditions where emission from CO 2 * could be isolated and monitored. These results were used to evaluate the kinetics of CO 2 *, in particular the main CO 2 * formation reaction CO + O + M CO 2 * + M (R1). Based on collision theory, the quenching chemistry of CO 2 * was estimated for 11 collision partners. The final mechanism developed for CO 2 * consists of 14 reactions and 13 species. The rate for (R1) was determined to within about ±60% using low-pressure experiments performed in five different (H 2 -)N 2 O-CO-Ar mixtures, as follows:where R is the universal gas constant in cal/mol-K and T is the temperature in K. Final mechanism predictions were compared with experiments at low and high pressures, with good agreement at both conditions for the temperature dependence of the peak CO 2 * and the CO 2 * species time histories. Comparisons were also made with previous experiments in methane-oxygen mixtures, where there was slight overprediction of CO 2 * experimental trends, but with the results otherwise showing a dramatic improvement over an earlier mechanism. Experimental results and model predictions were also compared with past literature rates for CO 2 *, with good agreement for peak CO 2 * trends and slight discrepancies in CO 2 * species time histories. Overall, the ability of the CO 2 * mechanism developed in this work to reproduce a range of experimental trends represents an important improvement over the existing knowledge base on chemiluminescence chemistry. C

Chemiluminescence continues to be of interest as a cost-effective optical diagnostic for gas turbine combustor health monitoring. However, most chemical kinetics mechanisms of the chemiluminescence of target species such as OH*, CH*, and CO2* were developed from atmospheric-pressure data. The present paper presents a study wherein the ability of current kinetics models to predict the chemiluminescence trends at engine pressures was assessed. Shock-tube experiments were performed in highly diluted mixtures of H2/O2/Ar at a wide range of pressures to evaluate the ability of a current kinetics model to predict the measured trends. At elevated pressures up to 15 atm, the currently used reaction rate of H + O + M = OH* + M (i.e., without any pressure dependence) significantly over predicts the amount of OH* formed. Other important chemiluminescence species include CH* and CO2*, and separate experiments were performed to assess the validity of existing chemical kinetics mechanisms for both of these species at elevated pressures. A pressure excursion using methane-oxygen mixtures highly diluted in argon was performed up to about 15 atm, and the time histories of CH* and CO2* were measured over a range of temperatures from about 1700 to 2300 K. It was found that the existing CH* mechanism captured the T and P trends rather well, but the CO2* mechanism did a poor job of capturing both the temperature and pressure behavior. With respect to the modeling of collider species, it was found that the current OH* model performs well for N2, but some improvements can be made for CO2.

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