Super adiabatic combustion of H2/Air and H2/N2O mixtures

• While the impact of H2 chemistry on super adiabatic flame temperature (SAFT) for hydrocarbons is well understood, super adiabaticity for premixed H2 combustion has not been previously reported. In the present work, for the first time, premixed H2/air and H2/N2O combustion in 0D and 1D context have been analysed to show that the instantaneous (0D) or local (1D) temperature exceeds the equilibrium temperature at certain conditions. The open-source software Cantera with recently published mechanisms from the literature have been used for the simulations. The simulations consider varying unburnt mixture conditions, including pressure (1 atm ≤ Pu ≤ 20 atm), temperature (500 K ≤ Tu ≤ 4000 K), equivalence ratio (0.1 ≤ ϕ ≤ 4.0), and dilution by inert gases (10 vol%) to investigate their influence on super adiabatic combustion. The present study demonstrates the following: (a) H2/N2O cases show an order of magnitude higher super adiabaticity than H2/air mixtures, (b) the NOx chemistry is primarily responsible for super adiabaticity in H2/oxidizer combustion, and (c) for H2/air flames, super adiabaticity is caused by the endothermic reactions in the post flame region, while for H2/N2O flames, super adiabaticity is caused by the conversion of NO into N2. These findings contribute towards a better understanding of the premixed combustion of hydrogen and the role of nitrogen oxidation chemistry therein. Novelty and Significance Statement The super adiabaticity of H2/Air and H2/N2O mixtures is investigated for the first time. A novel 0D two-regime super adiabaticity for H2/Air mixture was found. However, such a double regime super adiabaticity has not been observed in 1D H2/Air flames. N2O produces super adiabaticity that is an order of magnitude stronger than that of air. Our results show that H2/Air and H2/N2O mixtures have different chemical reasons for manifesting the super adiabatic phenomenon.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik -- Annan kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering -- Other Chemical Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

Nyckelord

Flame

Hydrogen

Ignition

Modelling

Super adiabatic flame temperature

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