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. The reaction mechanisms read as

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

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

where and are the reaction rate constants in Arrhenius law. The overall global reaction is given by

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

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),

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

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

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.

NO formation

The rate of NO concentration increase is given by

N formation

Similarly, the rate of N concentration increase is

See also

• Zeldovich–Liñán model

References