Flame propagation in the mixtures of O₂/N₂ oxidizer with fluorinated propene refrigerants (CH₂CFCF₃, CHFCHCF₃, CH₂CHCF₃)

ABSTRACT

A kinetic model is presented for high-temperature oxidation and combustion of the refrigerants: 2,3,3,3-tetrafluoropropene (R-1234yf), 1,3,3,3-tetrafluoropropene (R-1234ze(E)), and 3,3,3-trifluoropropene (R-1243zf) at atmospheric pressure. The kinetic model is based on: GRI-Mech-3.0 and previously developed models for the inhibition of hydrocarbon flames by 2-bromo-3,3,3-trifluoropropene (2-BTP) and C₁-C₂ hydrofluorocarbons. The model includes 1001 reactions and 105 species. Thermodynamic equilibrium calculations indicate a maximum combustion temperature of 2047 K, 2037 K, and 2312 K for R-1234yf, R-1234ze(E), and R-1243zf, respectively, in air for standard conditions. Calculations of the 1D, steady, adiabatic, laminar burning velocity for these refrigerants with air or oxygen-enriched air indicate reasonable agreement with experimental data from the literature when the burning velocity is above 10 cm/s. The simulations are used to understand the relevant reactions. Despite the relatively high F/H ratio in the reactants (2), the combustion is dominated by reactions with radical pool radicals typical of hydrocarbons (O, OH, and H). The combustion of R-1234yf or R-1234ze(E) is characterized by a two-zone flame, the second of which is a slow reaction zone accounting for CO and CF₂O consumption and additional temperature rise of a few hundred K. Simulations of the effects of water vapor on the burning velocity of R-1234yf and R-1234ze(E) capture qualitatively the trends in the experimental results. For certain values of the equivalence ratio and oxygen content of air, the premixed flame structure shows temperature peak in the main reaction zone higher than the equilibrium value.

KEYWORDS:

• Refrigerant flammability
• burning velocity
• low-GWP refrigerants
• kinetic model
• hydrofluorocarbons
• R-1234yf
• R-1234ze(E)
• R-1243zf

Acknowledgements

This work was supported by the Buildings Technologies Office of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under contract no. DE-EE0007615 with Antonio Bouza serving as Project Manager.

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