Laminar flame speed correlations for pure-hydrogen and high-hydrogen content syngas blends with various diluents

Hydrogen is an attractive fuel for large-scale combustion systems due to its high flame speeds and clean burning characteristics. This paper presents a new set of correlations for the laminar flame speeds of hydrogen-oxygen mixtures with nitrogen (air) and helium as diluents, using a recently updated chemical kinetics mechanism. A wide excursion of equivalence ratios (φ = 0.5–5.0), pressures (1–30 atm) and temperatures (270–620 K) was performed. Flame speed correlations were developed at five pressures, namely 1, 5, 10, 20, and 30 atm for the pure-hydrogen case. The disparities between the kinetic model predictions and the correlation estimates, commonly associated with existing correlations, were significantly reduced, and the correlation estimates are within ±13 cm/s of the model predictions. Also, a correlation for lean and high-hydrogen content (HHC) syngas blends of H2 + CO + H2O was developed from the pure-hydrogen correlations. A wide range of pressures (1–30 atm), initial temperatures (323–550 K), steam contaminant levels (5–15%), and hydrogen content in the fuel blend (15–100%) were simulated. A design of experiments approach was adopted to determine the critical mixtures necessary to develop the correlation. The developed HHC correlation agrees within ±12% of the model predictions.

► Flame speed correlations are developed using an updated chemical kinetics mechanism.
► Wide range of pressures, temperatures and equivalence ratios are simulated.
► Two diluents, namely, nitrogen (air) and helium (O2/He) are studied.
► Close agreement (±13 cm/s) with the kinetics model is observed at all conditions.
► Correlation for moist syngas (H2/CO) is constructed from the pure-hydrogen cases.