Emission and heat transfer characteristics of methane-hydrogen hybrid fuel laminar diffusion flame

The effect of adding hydrogen to methane on the emission and heat transfer characteristics of a laminar diffusion flame was investigated. The total input thermal energy for each test was kept constant. The results showed that adding hydrogen increased the temperature, decreased the flame length, and significantly increased the soot-free length fraction. CO and CO2 emission decreased with the addition of hydrogen. The more efficient oxidation of CO to CO2 at higher hydrogen fractions was the main contributor to the reduction of CO, whereas decreased carbon input was the dominant factor for the reduction of CO2. The NOx emission increased owing to the increase of prompt, thermal NOx formation and NNH pathway. The ratio of radiative heat flux to total heat flux decreased, and the radiative heat flux did not exceed 5% of the total heat flux. The addition of hydrogen improved the total heat flux by approximately 20%. Copyright 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.