Numerical study of the physical and chemical effects of hydrogen addition on laminar premixed combustion characteristics of methane and ethane

Methane and ethane are taken as the research objects. Using H-2 as diluent, based on Chemkin II/Premix Code and modified detailed chemical reaction mechanism: GRI 3.0*-Mech (introducing three hypothetical substances of FH2 , PO2 and FN2), the physical and chemical effects of hydrogen on laminar burning velocities (LBVs), adiabatic flame temperatures (AFTs), net heat release rates (NHRRs) and elementary reactions responsible for temperature changes of two alkanes under different equivalence ratios were analyzed and determined. Results showed that the chemical effect of H-2 promotes the LBVs and ATFs of methane and ethane, while the physical effect decreases the two parameters. In addition, the physical effects of H-2 inhibit the chemical reactions of methane and ethane, resulting in the decrease of NHRRs. The chemical effect of H-2 accelerates the process of chemical reaction and obviously increases the NHRRs. The two most vital elementary reactions that promote the temperature rise of methane and ethane are H + O-2 <=> OH + O and CO + OH <=> H + CO2. The important reactions responsible for inhibiting the temperature rise are H + CH3 (+M) <=> CH4 (+M) and H + O-2 + H2O <=> HO2 + H2O.