Oxy-ethane combustion : Measurements of the laminar burning velocities and kinetic insights into CO2 effects

Abstract

Oxy-fuel combustion is regarded as an underpinning technology for carbon capture and utilization. Ethane (C2H6) is the primary non-methane component in natural gas and a fundamental C2 fuel. In this work, laminar burning velocities (LBV) of C2H6/O2/CO2 mixtures were measured using the heat flux method at atmospheric pressure, spanning initial temperatures of 308–348 K, equivalence ratios of 0.6–1.5, and CO2 fractions of 0.16–0.75. The temperature dependence of the LBV of C2H6/O2/CO2 mixtures was first determined, and the consistency of the new measurements was validated. Evaluations of three kinetic models (Oxymech 2.0, Konnov 2023, Alzueta 2015) demonstrated that Oxymech 2.0 accurately predicts LBVs and ignition delay times (IDTs) across all conditions. Nonlinear variation of LBV with CO2 amount in the mixture was observed from both experiments and simulations. Decoupling thermal, transport, and chemical effects revealed that the thermal and transport inhibiting effects of CO2 linearly increase with CO2 concentration, while CO2′s chemical inhibition initially strengthens (CO2 range: 0.16–0.39), then plateaus (CO2: 0.39–0.65). This nonlinearity stems from the reaction CO + OH=H + CO2 depleting H radicals, suppressing chain-branching, while the reduced ratio of 2CH3=H + C2H5 versus C2H4 + H(+M)=C2H5(+M) (promoting flame propagation) offsets inhibition at higher CO2 fractions