Shape and stability characteristics of hydrogen-enriched natural-gas oxy-flames in a micromixer burner

ABSTRACT

This study investigated experimentally the effects of H₂-enrichment on premixed oxy-methane flames stabilized on a micromixer-like burner for clean energy production in gas turbines. The stable combustion zone was established over ranges of fuel hydrogen fraction (HF: 25–70% by vol.) and equivalence ratio (ϕ: 0.1–1) at fixed oxidizer oxygen fraction (OF = 30% by vol.) and fixed jet velocity (5.2 m/s). The blowout limit was plotted within the HF-ϕ space, superimposed on the contours of some operating parameters, namely adiabatic flame temperature (AFT), combustor power density (PD), jet Reynolds number (Re), and unburnt-mixture density (ρ_mix). Furthermore, images of visible flame shape were acquired at distinct points within the stable zone to study the effects of ϕ, HF, AFT, PD, Re, and ρ_mix on flame macrostructure. Results show that H₂-enrichment extends the blowout limit from ϕ = 0.35 down to ϕ = 0.1, thereby widening the stable combustion zone. The blowout limit has little correlation with AFT and PD but correlates strongly with ρ_mix, i.e., occurs consistently at the same ρ_mix. The analyses of blowout limit and flame images were used to infer that the flames blow out possibly at constant ignition delay.

KEYWORDS:

• Micromixer burner
• gas-turbine combustor
• oxy-fuel combustion
• hydrogen enrichment
• premixed flame
• blowout limit

Acknowledgments

This research work was supported by King Fahd University of Petroleum & Minerals (KFUPM) through the Deanship of Scientific Research (DSR) project number DF181020. The support provided by the King Abdullah City for Atomic and Renewable Energy (K.A. CARE) to one of the authors is also acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).