On the role of C$_2$O radicals in the prompt-NO mechanism

The measurements of NO concentrations in the post-flame zone of different hydrocarbon + O$_2$ + N$_2$ flames at standard temperature and atmospheric pressure available in the literature are compared with predictions of the original Konnov reaction mechanism and with the same mechanism extended by the reaction of C$_2$O with N$_2$. The goal was to investigate the possible role of this reaction proposed by Williams and Fleming [Proc. Combust. Inst., Vol. 31 (2007), pp. 1109–1117]. This new reaction of C$_2$O with N$_2$ seems to be a reasonable explanation of the deficiencies in the prompt-NO route. Direct comparisons of the experimental measurements performed in different flames with the modeling strongly suggests that the upper limit of this reaction rate constant is $k$ = 7 $\cdot$ 10$^{11}\exp$(-17,000/$RT$) [cm$^3$/(mole $\cdot$ sec)].