Jet-stirred reactor measurements and chemical kinetic study of ammonia with dimethyl ether

Abstract

To investigate the chemical kinetic effect of dimethyl ether (DME) on ammonia combustion and NO formation, experiment of ammonia mixed with DME was conducted in a jet-stirred reactor. Mole fractions of reactants and intermediates were measured at the equivalence ratio of 0.5–2.0, at the temperature range of 800–1250 K and the DME ratio of 0.0–0.8. Meng model was selected as the base model of ammonia and DME. Zhang model was chosen to update the NH3 sub-mechanism through validated against large set of experimental data. Pathway and sensitivity analysis were conducted to figure out the key reactions on ammonia combustion and NO formation. The result showed that NH2 can react with carbon-containing species, such as DME and CH3, producing NH3 and methylamine, respectively. NH2 reacting with DME, HO2 generating NH3 + CH3OCH2 and NH3 + O2, plays dominant chain-termination role in ammonia oxidation. In addition, HO2 can react with NH2, CH3 and NO generating OH radicals, promoting ammonia oxidation. Sensitivity analysis indicated that reactions like CH3 + NO2 = CH3O + NO, HNO + O2 = NO + HO2, essential to NO formation have promoting effect on ammonia consumption. In contrast, NH2 + CH3 = CH3NH2 have high sensitivity coefficients, regarded as chain terminal reactions inhibiting the reactivity.