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As the most efficient way to transport large quantities of hydrogen over long distances, Hydrogendoped NG pipeline has been actively promoted and developed. Hydrogen into the pipeline will have a variety of effects, as the smallest gas molecules, hydrogen on the pipeline valve, and other key equipment nonmetallic materials have a stronger penetration than natural gas, which is bound to increase the leakage of equipment, there are huge security risks. In this paper, the permeability of non-metallic materials in hydrogendoped NG pipelines is studied by permeability experiments. Seven common non-metallic materials for natural gas pipeline valves and key equipment are compared and selected. The numerical simulation model of hydrogen permeation in non-metallic materials was established to explore the permeability of non-metallic materials under different pressures, temperatures, and mixing ratios of hydrogen. The non-metallic sealing materials suitable for the hydrogen-doped environment are optimized, which can furnish reference for the engineering promotion and technology development of hydrogen-doped natural gas pipeline transportation.

Burning hydrogen-rich syngas fuels derived from various sources in combustion equipment is an effective pathway to enhance energy security and of significant practical implications. Emissions from the combustion of hydrogen-rich fuels have been a main concern in both academia and industry. In this study, the NO and CO emission characteristics of both laminar and turbulent counterflow premixed hydrogen-rich syngas/air flames were experimentally and numerically studied. The results showed that for both laminar and turbulent counterflow premixed flames, the peak NO mole fraction increased as the equivalence ratio increased from 0.6 to 1.0 and decreased as the strain rate increased. Compared with the laminar flames at the same bulk flow velocity, turbulent flames demonstrated a lower peak NO mole fraction but broader NO formation region. Using the analogy theorem, a one-dimensional turbulent counterflow flame model was established, and the numerical results indicated that the small-scale turbulence-induced heat and mass transport enhancements significantly affected NO emission. Considering NO formation at the same level of fuel consumption, the NO formation of the turbulent flame was significantly lower than that of the laminar flame at the same level of fuel consumption, implying that the turbulence-induced heat and mass transfer enhancement favored NOx suppression. [ABSTRACT FROM AUTHOR]

When blending hydrogen into existing natural gas pipelines, the non-uniform concentration distribution caused by the density difference between hydrogen and natural gas will result in the fluctuations of local hydrogen partial pressure, which may exceed the set one, leading to pipeline failure, leakage, measurement error, and terminal appliance. To solve the problem, the H 2 –CH 4 stratification in the horizontal and undulated pipe was investigated experimentally and with numerical simulations. The results show that in the gas stagnant situation, hydrogen-methane blending process will cause an obvious stratification phenomenon. The relations between the elevation, pressure, hydrogen fraction, etc., and the gas stratification are figured out. Moreover, even when the blended gas flows at a low rate, the hydrogen-caused stratification should also be considered. Thereafter, the blended gas should be controlled into a situation with low pressure and high speed, which could help to set the pressure, speed, the fraction of H 2. • Stratification models of H 2 –CH 4 blended gas in different pipes are established. • Simulation shows stratification of H 2 –CH 4 blended gas due to density difference. • The model and stratification of blended gas are verified by experiments. • Standing and flowing stratification of H 2 –CH 4 blended gas are revealed. [ABSTRACT FROM AUTHOR]