A Fundamental Investigation of Premixed Hydrogen Oxy-combustion in Carbon Dioxide
Keywords:hydrogen, carbon dioxide, CO2, H2, Constant Volume Combustion Chamber, combustion, laminar burning velocity, flammability, lean flammability limit, oxycombustion
Hydrogen (H2) is increasingly viewed as an attractive carbon-free fuel due to its potential compatibility with the existing transportation and conversion infrastructure. However, one of the major challenges facing large-scale deployment is the fundamentally different combustion properties it has in comparison to commonplace hydrocarbon fuels such as natural gas. For example, the laminar burning velocity (LBV) of a combustible mixture has a direct impact on how it can be used in internal combustion engine or gas turbines; the LBV of hydrogen is over 7 times greater than that of natural gas when combusted in air. Carbon dioxide (CO2) can be used as a working fluid, as opposed to nitrogen (in air), to reduce the flame speed of hydrogen combustion. A mixture of hydrogen, oxygen, and carbon dioxide as a working fluid can provide LBVs comparable to natural gas in air, which potentially enables existing conversion architectures. Furthermore, by replacing nitrogen (N2) with CO2 in the mixture, NOx emissions are avoided and opportunities for carbon sequestration or closed-cycle processes are possible. This study experimentally explores fundamental premixed oxy-combustion properties of H2/CO2 mixtures in a constant volume combustion chamber (CVCC) across a range of initial pressures (1, 1.5 and 2 bar) and equivalence ratios (0.4, 0.6, 0.8, 1). The spherically expanding flames are examined to determine the flame speed, LBV, and lower flammability limits (LFL) with respect to different CO2 concentrations (40%, 60%, 65%). Furthermore, it was identified that the flame speed of the 65% CO2 case at an equivalence ratio of 1 and initial pressure of 1 bar matches the closest with methane-air stoichiometric combustion.
Copyright (c) 2022 Md Nayer Nasim, Behlol Nawaz, Shubhra Kanti Das, Amina SubLaban, John Mack
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