Zeldovitch mechanism

While the results from the present work do show scatter, they clearly support the higher rate of Monat et. al (1). The data of Monat et. al are the most direct measurements of the 0 + N2 reaction and appear to be the most carefully obtained. Accordingly, these data should be used by those calculating NO formation from the Zeldovitch mechanism. 

Pure Methane Flames. In a pure methane flames the NO fraction undergoes a small jump passing through the flame front, then increases linearly with time-distance. This linear increase is due to low NO concentration after the flame front (approximately 30 ppm in a stoichiometric flame) which is far less than the equilibrium concentration of NO (3100 ppm). The reaction(R3) driving the formation of NO is part of the Zeldovitch mechanism ... 

The reverse reactions are negligible. The Zeldovitch mechanism is rate limiting in these near stoichiometric flames having no added nitrogen species. There is no significant NH or N production. 

The very slow reduction of the NO through the flame is a result of the back reactions of the extended Zeldovitch mechanism. N atoms are slowly produced from NO by reactions R4 and R5 but then rapidly react again with NO via R3. R3 is the major reaction producing Nj with its fastest rate occuring at the radical maximum just past the inflection point in the temperature profile. 

NO alone doped into methane flames is only reduced by the slow three-reaction Zeldovitch mechanism. No appreciable reduction due to the ammonia reaction mechanism is found. 

NO is formed to some extent from N2 and O2 in flame products when N atoms are produced at a significant rate. Above 1700 K, the important step in the much studied Zeldovitch (thermal) mechanism is the production of N atoms by ... 

In the combustion of fuels that do not contain nitrogen compounds, NO.v compounds (primarily NO) are formed by two main mechanisms, the thermal mechanism proposed by Zeldovitch and the prompt mechanism [5]. In the thermal mechanism NO is formed by the oxidation of molecular nitrogen through the following reactions ... 

Thermal NO, which is formed by the combination of atmospheric nitrogen and oxygen at high temperatures according to Zeldovitch s mechanism. 

The reducing region is due to the NH2+NO reactions, while the oxidizing zone is dominated by the Zeldovitch reactions. The relative importance of the two mechanisms is dependent on the shape of the temperature profile of the flame. It is concluded that the reducing effect of fuel-nitrogen on hydrocarbon fuel mixtures containing NO is dependent on the flame structure. 

R = 0 would then extend from 0 to N along the line x = and then follow the parabola h = 0 from to 1. This would correspond to the von Neumann-Doring-Zeldovitch picture of a detonation being a shock wave followed by a flame or reaction zone. For small values of R, the shock and reaction zones are essentially uncoupled. However, for large values of R the von Neumann-Doring-Zeldovich mechanism is no longer followed. 

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