Numerical Study on H₂ Enriched NG Lean Premixed Combustion

Hydrogen enriched LNG flame is tested to understand hydrogen effect on the flame such as temperature, flame speed, emissions (NO_x, CO), and extinction at lean premixed (ф=0.4~0.6) various pressure (p=1~25 bar) conditions using CHEMKIN-Pro with GRI 3.0 detailed chemistry. Hydrogen flame temperature is much higher than that of LNG, which may affect high NO_x emission production. The flame speed increases with the addition of H₂, so a design speed change should be considered to prevent flashback at the nozzle. The addition of H₂ reduces CO emissions and increases NO_x emissions, but can be overcome with a lower equivalent ratio due to the increased flame stabilization due to the addition of H₂. Extinction stretch rate gradually increases with hydrogen addition which shows that enriched hydrogen LNG premixed flame could be sustainable in high turbulent condition which means more stable than LNG itself flame. Even though in 100% H₂ operating condition, gas turbine operating condition shows similar combustion air and exit flue gas flow rate with LNG which means the compressor and turbine may not need major modification.