Contd...
and from Equation 2.5 steady state concentration of N,
From the assumption of equilibration of O, OH, H and O2,
Eliminating [N] and [H] using equations 2.7 and 2.8, the equation 2.6 gives,
where K = (k1/k –1)(k2/k -2) is equilibrium constant for the reaction N2 + O2 ↔ 2NO.
The NO formation rates may be calculated by Eq. 2.10 using equilibrium concentrations of O, O2, OH and N2. Most of NO formation takes place in the burned gases behind the flame front after combustion is completed locally. The rate of NO formation being much slower than the combustion rates, the NO formation process may be decoupled from combustion process and rate of formation of NO can be calculated assuming equilibrium concentrations of O, O2, OH and N2 .
By introducing equilibrium assumption in the calculations, the Eq. 2.10 is further simplified by using the following notations;
R1= k1 [O]e [N2]e = k -1 [NO]e[N]e |
where R1 is the reaction rate using equilibrium concentrations for the reaction (2.1).
Similarly,
R2 = k2 [N]e [O2]e = k -2 [NO]e[O]e, and
R3 = k3 [N]e [OH]e = k -3 [NO]e[H]e |
Using the above notations the Eq. 2.10 is simplified to give rate of formation of NO as below,
where w = R1/( R2+ R3)
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