Investigation of No Formation Kinetics in Combustion Processes: the Methane-Oxygen-Nitrogen Reaction

Abstract

An experimental and analytical investigation of the kinetics of formation of NO in shock-induced combustion of methane-oxygen-nitrogen mixtures diluted by argon has been carried out. Concentration histories of NO, OH and CO2 were measured during reaction behind reflected shock waves 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 2600–3200°K and for an initial post-shock pressure of 3.5 ± 0.5 atm. 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 fuel-rich mixture were consistent with a three-reaction mechanism for nitrogen chemistry, $$ O + {N_2} \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} NO + N $$ (1) $$ N + {O_2} \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} NO + O $$ (2) $$ N + OH \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} NO + H $$ (3)