Kinetics and chemiluminescence of some combustion reactions

This thesis discusses rate coefficients and chemiluminescence spectra some elementary reactions that are of interest in combustion.; The rate coefficients of N atoms with O₂, CO₂, and N₂O, which are of interest in the modeling of propellant combustion, are measured using a pseudo-static high-temperature photochemistry (HTP) reactor. A study of the O₂ reaction extends the temperature range of previous measurements and agrees with transition-state theory (TST) predictions, k(400–1220 K) = 2.0 × 10−18 (T/K) 2.15 exp(−2557 K/T) cm3 molecule −1 s−1. The CO₂ reaction yields upper limits of 5 × 10−16 cm3 molecule −1 s−1 which implies that the reverse reaction, NO+CO, is negligibly slow. Similarly, the N₂O reaction is also found to be too slow to contribute to combustion systems. Rate coefficient measurements of O+CHF₃, which are of interest in the search of suitable halon-replacement fire retardants, agree with those of an extrapolation from an earlier study and with TST predictions; here k(630–1330K) = 5.1 × 10−10 exp(−9536 K/T) cm3 molecules−1 s−1.; An aspect of the rate coefficient measurements considered here is the validation of the raw data. Under pseudo-first-order conditions these data are assumed to be exponential; however, noisy data are subject to uncertainty. Since the two existing quantitative validation methods, the runs and RCS tests, do not distinguish between random and non-random deviations, a new technique is developed: the bootstrap-validation technique, exponential model (BVTEM). A systematic comparison of these shows that: (a) the RCS test is biased (and is thus discarded) and (b) the BVTEM has a greater power than the runs test at a significance level of 0.5%. It is concluded that the BVTEM is a better method.; For the spectral studies, a flow tube was used to study the reactions O+C₂H₂ and C₂ with O₂ and NO. The vuv emission from C₂+O₂ is shown to be due to the CO Fourth Positive Band System, which exhibits an underlying continuum, suggesting the presence of a chemical intermediate. The visible spectrum of this reaction shows the presence of CO Triplet (d-a), Asundi (a′-a), Herman (e-a) and C₂ Swan (A-X) systems. The visible spectrum of C₂+NO is in good agreement with that of an earlier study. It was found that electron-ion recombination of CHO+, contributes negligibly to emission of CO (a-X) Cameron bands in the O+C₂H ₂ system.