COMBINED EFFECT OF HYDROGEN-ENRICHMENT AND STRATIFICATION ON THE STABILITY AND STRUCTURE OF PREMIXED SWIRL-STABILIZED CH4/AIR FLAMES

Hydrogen-enriched flames are a viable solution to reduce greenhouse gas emissions and improve combustion efficiency in gas turbines and industrial applications. Hydrogen has advantages over conventional fuels, such as higher flame speed and a broader flammability range. These benefits lead to more efficient and stable combustion, resulting in improved efficiency, reduced emissions, and increased power output. However, a drawback of hydrogen-enriched flames is the elevated temperature, leading to higher NOx emissions. To tackle this issue, lean swirl-stabilized combustion and stratification techniques are used. The first one enhances combustion efficiency, stability, and reduces emissions, while stratification introduces a non-uniform distribution of fuel, improving the static stability of flames. The DACRS burner is an example of stratified combustors used in gas turbines. By combining hydrogen-enrichment, stratification, swirl-stabilization, and lean operation, combustion systems in gas turbines and industrial combustors can be significantly improved. The present study examined the stability and combustion properties of a hydrogen-enriched, lean, stratified CH4/air flame in a gas-turbine burner. The study varied the hydrogen fraction and equivalence ratio and found that the combination of stratification and hydrogen enrichment had conflicting effects on flame stability. The flame blowout limit remained unchanged, even with up to 20% hydrogen enrichment. NOx emissions were not affected by hydrogen addition up to 20%, but increasing the equivalence ratio promotes NOx formation, as anticipated.