Pilot impact on turbulent premixed methane/air and hydrogen-enriched methane/air flames in a laboratory-scale gas turbine model combustor

The impact of pilot flame operation on the combustion of pure methane and hydrogenenriched methane (H2/CH4: 50/50 in vol%) fuels was investigated in a gas turbine model combustor under atmospheric conditions. The burner assembly was designed to mimic the geometry of an industrial burner, the Siemens DLE Burner, in which a concentric annular ring equipped with pilot flame burners is implemented in the dome of the combustor. Two pilot burner configurations have been investigated: a non-premixed and a partially premixed pilot arrangement. The performance of the pilot burners was evaluated for varying Reynolds number (Re) and H2 enrichment. High-speed OH* chemiluminescence imaging, as well as simultaneous planar laser-induced fluorescence measurements of the OH radicals and formaldehyde (CH2O) were used for evaluating the dynamics and structures of the flames for different conditions. Furthermore, emission measurements were carried out to determine the influence of hydrogen dilution on the NO,, and CO emission levels. The main findings are (a) the effect of the pilot flame is sensitive to the Reynolds number of the main flame and the type of the pilot flame, (b) the stability range becomes narrower with increasing hydrogen ratio, due to the tendency to flashback, (c) non-premixed pilot flames lower the NO,, and increase the CO emissions, albeit rather small differences in the emissions have been detected, and (d) the NO,, and CO emissions become significantly lower with increasing hydrogen ratio.(c) 2022 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications