Conversion of natural gas jet flame burners to hydrogen

In a study of conversion from CH4 to H2, jet flame characteristics of these gases and their blends are compared on a burner diameter scale of mm. Low velocity H2 and CH4 jets, burned on pipes of different diameters, indicate higher blow-off limits for H2, but lower heat release rates, a consequence of its lower specific energy. Compensation for this might be obtained through increased H2 flow velocity, or a small increase in pipe diameter. Blended CH4/H2 flames have lower heat release rates than CH4 alone, yet small proportions of H2, with CH4 might still be burned, on a CH4 burner. Throughout, fundamental understanding is enhanced through two dimensionless groups: laminar flame thickness normalised by burner diameter, dk/D, and the dimensionless flow number, U*. These suggest an optimal role for H2 combustion, utilizing its high acoustic and blow-off velocities, in high intensity, subsonic, combustors, at low dk/D, and high U*. (c)& nbsp;2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study compared the jet flame characteristics of H2 and CH4 on burner diameter scale, finding that H2 has higher blow-off limits but lower heat release rates compared to CH4, suggesting that increasing H2 flow velocity or slightly increasing pipe diameter could compensate for this. Blended CH4/H2 flames have lower heat release rates than CH4 alone, yet small proportions of H2 with CH4 can still be burned on a CH4 burner.