Experimental study of natural gas flame enriched by hydrogen and oxygen in a coaxial burner

In air combustion, nitrogen brings about a low yield of combustion and a high energetic consumption because the nitrogen contained in the air acts as energy ballast. The substitution of air by oxygen or the oxygen addition to the air permits the improvement of the heat yield, the rise of the adiabatic flame temperature and the extension of the flammability limits. The hydrogen addition to the natural gas combustion shows an increase in adiabatic flame temperature, a reduction in flame thickness and further enhances the auto-ignition characteristics and the global rate of heat release. This work presents the effects of enrichment with oxygen and hydrogen on a non-premixed flame behavior. More specifically, the study focuses on the flame stability, the pollutants emissions such as NOx, CO2, and CO and the jet flow dynamic. Chemiluminescence of OH∗ radical and Particle Image Velocimetry (PIV) are conducted to describe the structure, the stability and the dynamic of the flame. The measurements are conducted at the stoichiometry for oxygen rate varying from 20 to 50% by volume and hydrogen varying from 0 to 15%. The results show that the addition of oxygen and hydrogen improves the flame stability, increases the CO2emission, decreases the CO formation but favors the NOx formation.