Zel'dovich 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

: + O <-> _1 +
: + O2 <-> _2 +

where $k_1$ and $k_2$ are the reaction rate constants in Arrhenius law. The overall global reaction is given by

: + <-> 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),

: + <-> _3 +

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
:$\begin k_ &= 1.47\times 10^ \, T^ \mathrm e^\\ k_ &= 6.40\times 10^9 \, T \mathrm e^ \\ k_ &= 3.80\times 10^ \end$
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

:\frac= k_ mathrm_2 mathrm+ k_ mathrm mathrm_2+ k_ mathrm mathrm- k_ mathrm mathrm- k_ mathrm mathrm- k_ mathrm mathrm

N formation

Similarly, the rate of N concentration increase is

:\frac= k_ mathrm_2 mathrm- k_ mathrm mathrm_2- k_ mathrm mathrm- k_ mathrm mathrm+ k_ mathrm mathrm+ k_ mathrm mathrm

See also

* Zeldovich–Liñán model

References

{{Reflist, 30em

Combustion
Reaction mechanisms
Chemical reactions
Chemical kinetics
Pollutants