Reduced Mechanisms for Prediction of NO2 Formation and Ignition Delay in Methane-Air Combustion

Abstract

Two new 14-step and 16-step reduced mechanisms for methane-air combustion were systematically developed by assuming the quasisteady state for 26–28 species in the starting mechanism. A series of comparison between the reduced mechanisms and the starting mechanism was carried out with the emphasis on their capabilities in predicting NO2 formation and ignition delay. The two reduced mechanisms successfully capture the complex behaviors of NO2 formation, which depends on the characteristic mixing time, pressure, and the contamination of hydrocarbon in air. The flame structure and NOx formation in diffusion flame were well predicted by the 16-step mechanism, while the 14-step showed less satisfactory performance on predicting prompt NO formation. The 16-step mechanism was shown accurate in predicting ignition delay over a wide range of equivalence ratio, temperature and pressure. The necessity of including CH2O,C2H6,C2H4, and HO2 in the reduced mechanisms was discussed.