Theoretical study on the inherent relationship between laminar burning velocity, ignition delay time, and NO emission of ammonia-syngas-air mixtures under gas turbine conditions

This study utilizes numerical methods with Chemkin 19.2 and Matlab R2020a to investigate the relationship between laminar burning velocity and free radical concentration, the relationship between laminar burning velocity and ignition delay time, and the relationship between NO emissions and free radical concentration for ammonia-syngas-air combustion. Additionally, it explores the mechanisms by which these three relationships change with variations in the initiate temperature and chamber pressure of the combustion chamber. Furthermore, to understand the theoretical foundation of these relationships, the study examines four global flame parameters: adiabatic flame temperature (Tad), activation energy (Ea), Zeldovich number (Ze), and Lewis number (Le). The results indicate that changes in initial temperature and pressure influence the laminar burning velocity by modifying the concentration of H + NH2 radicals. Simultaneously, alterations in initial temperature and pressure also adjust the quantitative relationship between laminar burning velocity and the concentration of H + NH2 radicals. Additionally, the results reveal that variations in initial temperature and pressure impact NO emissions by altering the concentration of H + NH2 radicals. Following a comprehensive examination of both the theoretical relationship between laminar burning velocity and ignition delay time and the empirical relationship between laminar burning velocity and ignition delay time, a relationship between the density-weighted collision rate BC in the laminar burning velocity expression and the pre-exponential factor A in the theoretical expression for ignition delay time was observed, where B2 A = C0 center dot Tu delta center dot P epsilon (where C0, delta and epsilon are constants). This offers a potential methodology for investigating thermal effects, chemical effects, and transport effects in complex mixed fuel combustion processes. Further investigation demonstrates that an increase in the initial temperature within a gas turbine combustion chamber will, by promoting thermal effects, inhibiting transport effects, and altering chemical effects, affect the quantitative relationship between laminar burning velocity and ignition delay time. Further research reveals that an increase in the initiate temperature of the gas turbine combustion chamber affects the quantitative relationships between laminar burning velocity and ignition delay time by promoting thermal effects, suppressing transport effects, and chemical effects. An increase in chamber pressure influences these relationships by enhancing chemical and transport effects while inhibiting thermal effects. Moreover, the functions characterizing chemical effects, transport effects, and thermal effects can be reasonably approximated in this study as functions of initial temperature and pressure, especially under the specific F-class gas turbine conditions presented herein. This finding holds significance for the design of combustion chambers under actual gas turbine operating conditions.