Contd...
NO concentrations were computed by numerically integrating the Eq. 2.11. NO concentration in the above two elements as a function of crank angle are shown in Fig 2.7. The equilibrium concentrations of NO for the two elements are also shown in this figure. In the early burned element as the peak temperature reaches significantly high values due to compression to peak cylinder pressure ( the first burned element attains the highest temperature of all), the kinetically controlled NO reaches to near equilibrium levels. Later, as the temperature starts falling as a result of expansion, NO starts decomposing. The rate of decomposition is controlled by the backward reactions of NO kinetics (Reactions 2.1 to 2.3) until the NO chemistry freezes due to falling temperatures.
Figure 2.7 |
Kinetically formed NO in an early burned and a late burned charge element. Equilibrium NO concentration in each of these elements is also shown. |
The net mass fraction of NO emissions in the exhaust is computed as the weighted average of the frozen mass NO fraction over all the burned gas elements.
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