Experimental and Kinetic Study on Laminar Burning Velocities of High Ratio Hydrogen Addition to CH4+O-2+N-2 and NG+O-2+N-2 Flames

In 2020, energy-related CO2 emissions reached 31.5 Gt, leading to an unprecedented atmospheric CO2 level of 412.5 ppm. Hydrogen blending in natural gas (NG) is a solution for maximizing clean energy utilization and enabling long-distance H-2 transport through pipelines. However, insufficient comprehension concerning the combustion characteristics of NG, specifically when blended with a high proportion of hydrogen up to 80%, particularly with minority species, persists. Utilizing the heat flux method at room temperature and 1 atm, this experiment investigated the laminar burning velocities of CH4/NG/H-2/air/He flames incorporating minority species, specifically C2H6 and C3H8, within NG. The results point out the regularity of S-L enhancement, reaching its maximum at an equivalence ratio of 1.4. Furthermore, the propensity for the enhancement of laminar burning velocity aligned with the observed thermoacoustic oscillation instability during fuel-rich regimes. The experimental findings were contrasted with kinetic simulations, utilizing the GRI 3.0 and San Diego mechanisms to facilitate analysis. The inclusion of H-2 augments the chemical reactions within the preheating zone, while the thermal effect from temperature is negligible. Both experimental and simulated results revealed that CH4 and NG with a large proportion of H-2 had no difference, no matter whether from a laminar burning velocity or a kinetic analysis aspect.

Automated summary

In 2020, energy-related CO2 emissions reached a record high of 31.5 Gt, resulting in an unprecedented atmospheric CO2 level of 412.5 ppm. Hydrogen blending in natural gas is a solution for maximizing clean energy utilization and enabling long-distance H-2 transport. However, there is still insufficient understanding of the combustion characteristics of natural gas blended with a high proportion of hydrogen, especially with minority species. Experimental and simulated results indicate that there is no difference between CH4 and NG with a large proportion of H-2 in terms of laminar burning velocity and kinetic analysis.