The escalating energy demand in today’s world has amplified exhaust emissions,
contributing significantly to climate change. One viable solution to mitigate
carbon dioxide emissions is the utilization of hydrogen alongside gasoline in
internal combustion engines. In pursuit of this objective, combustion
characteristics of iso-octane/hydrogen/air mixtures are numerically investigated
to determine the impact of hydrogen enrichment. Simulations are conducted at 400
K over a wide range of equivalence ratio 0.7 ≤ Ф ≤ 1.4 and pressure 1–10 atm.
Adiabatic flame temperature, thermal diffusivity, laminar burning velocity, and
chemical participation are assessed by varying hydrogen concentration from 0 to
90% of fuel molar fraction. As a result of changes in thermal properties and
chemical participation, it is noticed that the laminar burning velocity (LBV)
increases with higher hydrogen concentration and decreases as pressure
increases. Chemical participation and mass diffusion were found to be the main
contributors to the LBV increase in binary fuel blends. To circumvent
NOX formation, a binary fuel blend at Ф = 0.7 and 80%
H2 is selected to increase combustion intensity while maintaining
a relatively low flame temperature and retaining 85% of energy density by
volume. It is noted that the concentration of H, O, and OH radicals increase
with hydrogen enrichment. Furthermore, the analysis revealed that the LBV
increases linearly with the peak mole fraction of radicals. Key reactions are
identified through sensitivity analysis and net reaction rates. A significant
increase in net reaction rate is observed for H2 + O <=> H + OH
and H2 + OH <=> H + H2O, which in turn increases the
pool of radicals. This is evident by the increase in the net production rate of
H, O, and OH radicals.
