Hydrogen as an additive to methane for spark ignition engine applications

Hydrogen addition to acetylene–air laminar diffusion flames: Studies on soot formation under different flow arrangements

“…In premixed combustion systems, such as those using natural gas or gasoline, the objective of hydrogen as supplementary fuel is to increase the flame speed and to widen the lean flammability limits [4,5]. The relatively low reaction rate of a typical hydrocarbon fuel can be accelerated by hydrogen addition, resulting in improved combustion.…”

Experimental study of the performance and emission characteristics of an adapted commercial four-cylinder spark ignition engine running on hydrogen–methane mixtures

“…Nevertheless, fuellean operation is required to limit NO x emissions. In this regard, methane shows some drawbacks associated to its relatively low flame propagation velocity that under lean-burn operation can lead to incomplete combustion, increased cycle-by-cycle variations and occasional flame failure [8]. Adding hydrogen to natural gas extends the lean limit of combustion; in this way, extremely low emissions can be achieved.…”

Combustion of CH4/H2/Air Mixtures in Catalytic Microreactors

“…[6,7] It was demonstrated that H 2 enrichment leads to a significant increase in the concentration of OH radicals, [8,9] with a consequent enhancement of the early heat release in the flame zone that causes an enhancement of the CH 4 ignition under conditions at which, otherwise, CH 4 combustion would be prone to undergo extinction. [10] Moreover, it was found that the addition of H 2 to CH 4 in ICEs can enhance their performance, particularly when operating at relatively low l ratios, [11] and reduces the CO 2 emissions. [12] Owing to the significantly higher flame speed, the wider flammability limits, and the potential effects on flame chemistry of H 2 blended with traditional HC fuels such as CH 4 (as compared to traditional CH 4 /air mixtures), the use of H 2 /HC blends shows considerable promise for improving the flame stability in lean combustion systems and limiting the amount of CO emissions-or at least extending low-CO emissions to leaner mixtures.…”