| Abstract: | Avoiding global warming necessitates using alternative fuels on a large scale to decarbonize the power generation sector. Ammonia (NH²́³), the second-most produced chemical globally, is a carbon-free fuel that has the potential to be the primary driver of this sector. However, the combustion chemistry of NH²́³ is not well understood, limiting its large-scale application. In particular, the species-specific kinetics interactions during NH²́³ combustion have been seldom studied, and new measurements of this kind provide optimization targets for the enhanced understanding of NH²́³ combustion chemistry. In this study, a new NH²́³ laser absorption diagnostic, intended for chemical kinetics measurements, was developed to access twelve NH²́³ transitions in the v²́² fundamental band near 10.4 Îơm. Spectroscopic characterization of these transitions, located between 957.5 and 963.0 cm¹́»℗£, was conducted via scanning-wavelength absorption experiments to measure the line strength and broadening coefficients due to collisions of Ar, He, O²́², N²́², and NH²́³. Using this new and other diagnostics, laser absorption experiments were performed to study NH²́³ chemical kinetics at high temperatures and near-atmospheric pressures in a shock tube. First, experiments were performed to monitor NH²́³ time histories during the thermal decomposition of ~ 0.5% NH²́³/Ar and ~ 0.42% NH²́³/2% H²́²/Ar over a temperature range of 2096⁰́₃3007 K. Using these data, along with literature data, a detailed NH²́³ thermal decomposition kinetics mechanism was proposed and validated. Second, experiments were conducted to monitor N²́²O time histories during NH²́³/O²́²/Ar oxidation between 1829 and 2198 K for equivalence ratios of 0.54, 1.03, and 1.84. These equivalence ratios were determined accurately by measuring the NH3 concentration in the mixtures using the new diagnostic. Third, simultaneous measurements of NH²́³ and H²́²O time histories were obtained during the oxidation of several NH²́³/O²́²/Ar and NH²́³/H²́²/O²́²/Ar over a temperature range of 1474⁰́₃2307 K, equivalence ratios varying from 0.56 to 2.07, and NH²́³:H²́² ratios of 100:0, 80:20, and 50:50. These large time-history datasets were used to investigate the literature NH²́³ kinetics mechanisms and illustrate several improvements. The reported time-history data offer stringent constraints for the accurate assessment and validation of future NH²́³ kinetics mechanisms. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/197772 |
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