Effects of addition of electrolysis products in methane–air diffusion flames

Evaluation of steam-added methane–hydrogen blends through the comparison of flame structures and pollutant emissions is numerically conducted with detailed chemistry. The composition of fuel is systematically changed from pure methane and pure hydrogen to the blending fuel of methane–hydrogen-steam through the molar addition of H 2 O . Flame structure is changed considerably for CH 4 – H 2 flames and CH 4 – H 2 – H 2 O flames in comparison to pure methane flame. The discernible differences in major flame structure are compared among a pure methane flame, CH 4 – H 2 flames and CH 4 – H 2 – H 2 O flames. Especially, emission indices of CO increase and then decrease after showing a maximum in the increase of methane mole fraction for CH 4 – H 2 flames and in the increase of H 2 O mole fraction for CH 4 – H 2 – H 2 O flames, while those of CO 2 increase monotonously. These behaviors are mainly caused by the competition of the production through the reaction step HCO + H 2 O → H + CO + H 2 O with the destruction of CO by the reaction step CO + OH → CO 2 + H . The changes of thermal NO and Fenimore NO are also analyzed for various combinations of the fuel composition. Importantly, contributing reaction steps to thermal NO and Fenimore NO are addressed in pure methane, CH 4 – H 2 flames and CH 4 – H 2 – H 2 O flames.