In
a real hydrogen engine intake stoke, air is used as the main oxidation rather
than pure oxygen. Therefore, when the temperature in combustion chambers is
over 2500°F (1371.1°C), the following reaction could take place [3].
H2 + O2 +
N2 = H2O + N2 + Nox
Figure
10 [16] illustrates the Nox emission curve related to equivalence ratio (Φ) and
the amount of Nox per kilowatt-hour (g/Kwh).
It
can be clearly seen that at lean mixture range (Φ<0.55), the emission of Nox
is quite low. Hence, it is better to make hydrogen engines running at lean
range which Φ<0.55 in order to decrease the Nox emission. Moreover, a good
cooling system is vital for hydrogen engines which can keep the combustion in a
relative low temperature.
Emissions Control