Minimum tube diameters for detonation propagation in CH4/H2-air mixtures: Implications for natural gas cooktop burners

The minimum detonation diameter for methane (CH4)/hydrogen (H2)-air mixtures is numerically evaluated to assess detonation risks in cooktops designed to work with natural gas. A one-dimensional mathematical model that considers heat and friction losses for detonations propagating in pipes is used for that purpose. The initial conditions are selected to emulate the operation of a commercial cooktop working with different CH4/H2 blends. Results show that for H2 content in the blend higher than 45%, a conventional cooktop air-fuel mixer may pose a detonation hazard since the minimum detonation diameters predicted by the model are smaller than the diameter of the mixing tube (i.e. dmin < dmixer). Additionally, the individual effect of equivalence ratio, (phi), and hydrogen content, % H2, in the fuel blend are evaluated separately. An increased risk of detonation is present for (i) CH4/H2-air mixtures with 𝛷 → 1 1, and (ii) higher % H2 content. Finally, the effect of the natural gas composition was evaluated, showing that 100% CH4 is not a good surrogate for this fuel since there is a considerable decrease in dmin and in the admissible H2 content in the blend when the real composition is considered.

Minimum tube diameters for detonation propagation in CH4/H2-air mixtures: Implications for natural gas cooktop burners Articles