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Predicting chemical flame lengths and lift-off heights in enclosed, oxy-methane diffusion flames at varying O2/CO2 oxidizer dilution ratios

Krishnamoorthy G., Ditaranto M.

Journal of Power Technologies

2017

Vol. 97, nr 4

370--377

Experiments have shown reactor confinement, wall temperatures and radiative transfer to influence the flame length and lift-off characteristics of oxy-methane flames. In this study, the performances of the Shear Stress Transport (SST) k-ω turbulence model, a skeletal methane combustion mechanism (16 species and 41 reactions) and two weighted sum of gray gas models (WSGGM) towards capturing these flame characteristics are evaluated against measurements obtained from oxy-methane flames across a wide range of oxidizer O2/CO2 ratios and fuel Reynolds numbers. Gas composition, gas and wall temperatures, flame length measurements and inferences of lift-off heights from OH* chemiluminescence imaging are employed in the assessment. The corresponding numerical estimate of flame length and lift-off heights were made by determining the flame shape by the locus of points at which the CO concentrations reduce to 1% of their peak values within the flame. The predicted gas temperatures and compositions compared reasonably well against measurements. The criterion for defining the flame shape based on CO concentrations appears promising since the trends in chemical flame length and lift-off height predictions agreed reasonably well with the measurements across the range of oxidizer concentrations and fuel Reynolds numbers. Flame length prediction sensitivities to the wall temperatures and the WSGGM model were also assessed.

Emission characteristics of a novel low NOx burner fueled by hydrogen-rich mixtures with methane

Dutka M., Ditaranto M., Løvås T.

Journal of Power Technologies

2015

Vol. 95, nr 2

105--111

The use of hydrogen-rich fuels may be challenging for burner designers due to unique properties of hydrogen compared to conventional fuels such as natural gas. Burner retrofit may be required to use hydrogen-enriched fuels in combustion systems that are designed for natural gas combustion. This study aimed to experimentally investigate NOx emissions from a novel low NOx burner fueled by methane-hydrogen mixtures. The burner was tested in a cylindrical combustion chamber at atmospheric pressure. Burner thermal load of 25 kW (LHV) and air-fuel equivalence ratio of 1.15 were maintained throughout the experimental campaign. The influence of burner design parameters on NOx emissions was tested for various fuel compositions using a statistically cognizant experimental design. The study revealed that shifting the burner head upstream can deliver NOx emission reduction. In contrast, supplying fuel to the burner through secondary fuel ports increases NOx emissions, particularly when the burner head is shifted upstream. The lowest predicted NOx emissions from the burner are below 9 ppmvd at 3% of O2 and 14 ppmvd at 3% of O2 for 5% and 30% mass fraction of hydrogen in the fuel, respectively.