Synergetic Effects in Flames of Mixtures of Methane and Carbon Monoxide with Air
V. M. Shvartsberg, V. A. Bunev
Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: dual-fuel flames, synergistic effects during combustion, superadiabatic temperatures, flame structure, carbon monoxide
Abstract
Numerical simulation has shown that replacing a part of methane by carbon monoxide in a rich mixture while maintaining the equivalence ratio leads to a decrease in the superadiabatic temperature effect due to the competition of chemical reactions. This has been explained by a decrease in the H content in the combustible mixture and a decrease in the superequilibrium concentration of water in combustion products. Using the tracer numerical simulation method and a comparative analysis of the rates of consumption of CH4 and CO, it has been established that the consumption of both fuels in the CH4/CO/air flame is a competitive reaction path and CO monoxide does not act as an inert component in the low-temperature region of the front (contrary to the statements of a number of authors). Furthermore, the rate of consumption of CH4 is much higher than that of CO due to the larger number of paths of consumption of CH4 and their higher rates. The main contribution to the increase in the concentration of H atoms in the flame when replacing a methane-air mixture with a CH4/CO/air mixture is due to the same reactions that increase the heat release rate: O + CH3 = H + CH2O and CO + OH = CO2 + H. The results obtained and their comparison with literature data lead to the conclusion that the increase in the heat release rate and, hence, flame propagation rate should be greater in rich mixtures, since there the thermophysical effect is higher.
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