CO2* chemiluminescence study at low and elevated pressures
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abstract
Chemiluminescence experiments have been performed to assess the state of current CO2* kinetics modeling. The difficulty with modeling CO2* lies in its broad emission spectrum, making it a challenge to isolate it from background emission of species such as CH* and CH 2O*. Experiments were performed in a mixture of 0.0005H 2+0.01N2O+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 CO2* concentration. Two different wavelengths to capture CO2* 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 CH2O*. As a baseline for time history and peak magnitude comparison, OH* emission was captured at 307 nm simultaneously with the two CO2* filters. The results from the two CO2* filters were consistent with each other, implying that indeed the same species (i.e., CO2* ) was being measured at both wavelengths. A first-generation kinetics model for CO2* and CH2O* was developed, since no comprehensively validated one exists to date. CH2O* 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 the CO2* model was only fair, which necessitates future improvements for a better understanding of CO2* chemiluminescence as well as the kinetics of the ground state species. 2012 Springer-Verlag.
