Study on the influence of hydrogen addition on ethane/air laminar burning velocity, key species production, and implied physicochemical effects

Abstract

In the context of carbon emission reduction, this study investigates the mixed combustion characteristics of zero-carbon hydrogen and ethane—the second major component of natural gas—under gas turbine operating conditions. Ethane not only has fuel properties but also serves as a chemical feedstock (for ethylene production). The quantitative relationship between laminar flame speed and key free radicals (O, H, and OH) was analyzed, and the underlying mechanism of the influence of free radicals on combustion speed was decoupled, considering the effects of heat, mass transfer, and chemical interactions. The study shows that under heated and pressurized conditions in the gas turbine, the hydrogen addition can significantly increase the laminar burning velocity (LBV) of ethane, as hydrogen enhances the concentrations of H, O, and OH free radicals. More importantly, a clear linear positive correlation exists between the LBV and the peak mole fractions of H, O, and OH species. The addition of hydrogen alters the linear correlation coefficient of the above linear relationship, but the linear relationship between LBV and the peak molar fractions of H, O and OH is not affected by pressure and equivalent ratio. The change in the linear correlation coefficient caused by hydrogenation is mainly influenced by chemical effects, followed by thermal effects, with the least impact from transport effects. These numerical results can provide a valuable reference for the design and operational condition selection of gas turbine combustors.