Zeldovich mechanism

Zel'dovich mechanism is a chemical mechanism that describes the oxidation of nitrogen and NO_x formation, first proposed by the Russian physicist Yakov Borisovich Zel'dovich in 1946.Y.B. Zel'dovich (1946). "The Oxidation of Nitrogen in Combustion Explosions". Acta Physicochimica U.S.S.R. 21: 577–628Zeldovich, Y. A., D. Frank-Kamenetskii, and P. Sadovnikov. Oxidation of nitrogen in combustion. Publishing House of the Acad of Sciences of USSR, 1947.Williams, Forman A. "Combustion theory". (1985).Zeldovich, I. A., Barenblatt, G. I., Librovich, V. B., Makhviladze, G. M. (1985). Mathematical theory of combustion and explosions. The reaction mechanisms read as

:{N2} + O <->[k_1] {NO} + {N}

:{N} + O2 <->[k_2] {NO} + {O}

where $k\_1$ and $k\_2$ are the reaction rate constants in Arrhenius law. The overall global reaction is given by

: {N2} + {O2} <->[k] 2NO

The overall reaction rate is mostly governed by the first reaction (i.e., rate-determining reaction), since the second reaction is much faster than the first reaction and occurs immediately following the first reaction. At fuel-rich conditions, due to lack of oxygen, reaction 2 becomes weak, hence, a third reaction is included in the mechanism, also known as extended Zel'dovich mechanism (with all three reactions),Lavoie, G. A., Heywood, J. B., Keck, J. C. (1970). Experimental and theoretical study of nitric oxide formation in internal combustion engines. Combustion science and technology, 1(4), 313–326.Hanson, R. K., Salimian, S. (1984). Survey of rate constants in the N/H/O system. In Combustion chemistry (pp. 361–421). Springer, New York, NY.

:{N} + {OH} <->[k_3] {NO} + {H}

Assuming the initial concentration of NO is low and the reverse reactions can therefore be ignored, the forward rate constants of the reactions are given by{{cite web |url=http://web.eng.ucsd.edu/mae/groups/combustion/mechanism.html |title=San Diego Mechanism}}

:$\backslash begin\{align\}$

k_{1f} &= 1.47\times 10^{13} \, T^{0.3} \mathrm e^{-75286.81/RT}\\

k_{2f} &= 6.40\times 10^9 \, T \mathrm e^{-6285.5/RT} \\

k_{3f} &= 3.80\times 10^{13}

\end{align}

where the pre-exponential factor is measured in units of cm, mol, s and K (these units are incorrect), temperature in kelvins, and the activation energy in cal/mol; R is the universal gas constant.