Investigation of Nitric Oxide Formation Kinetics in Combustion Processes: The Hydrogen-Oxygen-Nitrogen Reaction

Abstract

An experimental and analytical investigation of the kinetics of formation of NO in shock-induced combustion of hydrogen-oxygen-nitrogen mixtures has been carried out. In the experimental study, concentration lime-histories of NO, OH and H₂0 were measured during reaction using spectroscopic techniques. Experimental concentration profiles were obtained for an oxidizer-rich and a fuel-rich mixture for initial post-shock temperatures in the range 2150−2800 °K and for an initial post-shock pressure of 2.2 ± 0.3 atm. In the analytical study, time rates of change of species concentrations and thermodynamic properties during reaction were calculated by numerically integrating the coupled reaction kinetic, state and energy equations. Calculated concentration profiles were compared with experimental profiles to obtain information on the reaction mechanism for formation of NO. Observed NO formation rates in both the oxidizer-rich and the fuel-rich mixture were consistent with a two-reaction mechanism for nitrogen chemistry,

There was no evidence to suggest that reactions other than (1) and (2) were of importance in the NO formation mechanism. NO concentration profiles obtained from two simplified models for NO formation were compared with experimental profiles. It was found that under certain conditions these simplified models predicted NO formation rates substantially lower than observed experimentally.