When hydrogen is slower than methane to ignite

Numerical and Experimental Investigations of CH4/H2 Mixtures: Ignition Delay Times, Laminar Burning Velocity and Extinction Limits

“…One reaction is CH 4 + H • − − − − CH 3 • + H 2 [93]. The parameters of this reaction are different in the Aramco Mech 3.0 [68] in comparison to the NUI Galway Mech studied in the work of Panigrahy et al [93]. However, the trend was still captured well for all mixtures.…”

“…At lower temperatures, the difference in IDT for CH 4 and H 2 decreased. When the temperature decreased further, the H 2 ignition became slower than for CH 4 as shown by Panigrahy et al [93]. This is explained by the higher reactivity of CH 3 • in comparison to H atoms at low temperatures [93].…”

“…Panigrahy et al [93] found several reactions that are important for CH 4 /H 2 mixtures but less important for pure CH 4 or pure H 2 . One reaction is CH 4 + H • − − − − CH 3 • + H 2 [93].…”

“…Panigrahy et al [93] found several reactions that are important for CH 4 /H 2 mixtures but less important for pure CH 4 or pure H 2 . One reaction is CH 4 + H • − − − − CH 3 • + H 2 [93]. The parameters of this reaction are different in the Aramco Mech 3.0 [68] in comparison to the NUI Galway Mech studied in the work of Panigrahy et al [93].…”

Hydrogen Combustion: Features and Barriers to Its Exploitation in the Energy Transition

“…Moreover, hydrogen has a considerably broader flammability range than natural gas, leading to heightened concerns regarding environmental, health, and safety aspects during both hydrogen transportation and combustion. Although it has recently been observed [7] that mixtures containing higher H 2 concentrations are slower to ignite compared to those with higher CH 4 concentrations at low temperatures (below 930 K, for hydrogen combustion, the self-recombination of HO 2 radicals leads to chain propagation which inhibits reactivity, whereas for methane combustion, the reaction between radicals and HO 2 leads to chain branching, increasing reactivity), for higher temperatures hydrogen largely enhances the reactivity of fuel blends: the ignition delay time decreases [8][9][10][11]; at room temperature and pressure, the flammability limits (0.1-7.1) are well wider than those of natural gas (0.5-1.67); the flame speed is higher [12] and the critical strain rate increases, thus reducing potential flame quenching [13,14]. At a fixed equivalence ratio (Φ), the hydrogen/air premixed flame burns with an adiabatic flame temperature higher than the corresponding natural gas one (see Figure 2, left).…”