Methane (CH4)/air lean combustion can be enhanced
by
increasing the concentration of the oxidizer, like oxygen (O2) enrichment, or adding a strong oxidant to the reactant. Hydrogen
peroxide (H2O2) is a strong oxidizer that yields
O2, steam, and appreciable heat after decomposition. This
study numerically investigated and compared the effects of H2O2 and O2-enriched conditions on the adiabatic
flame temperature, laminar burning velocity, flame thickness, and
heat release rates of CH4/air combustion using the San
Diego mechanism. The result showed that in fuel-lean conditions, the
adiabatic flame temperature changed from H2O2 addition > O2-enriched scenario to O2-enriched
scenario > H2O2 addition with increasing
α.
This transition temperature was not affected by the equivalence ratio.
Adding H2O2 enhanced the laminar burning velocity
of the CH4/air lean combustion more than the O2-enriched scenario. The thermal and chemical effects are quantified
in various H2O2 additions, and it is found that
the chemical effect has a noticeable contribution to the laminar burning
velocity compared with the thermal effect, especially in higher H2O2 addition. Further, the laminar burning velocity
had a quasi-linear correlation with (OH)max in the flame.
The maximum heat release rate was observed at lower temperatures for
H2O2 addition and higher temperatures for the
O2-enriched scenario. The flame thickness was significantly
reduced upon adding H2O2. Finally, the dominant
reaction to the heat release rate changed from the reaction of CH3 + O ↔ CH2O + H in the CH4/air
or O2-enriched scenario to the reaction of H2O2 + OH ↔ H2O + HO2 in the
H2O2 addition scenario.