Influence of reactive species on the lean blowout limit of an industrial DLE gas turbine burner

In order to achieve ultra-low emissions of both NOX and CO it is imperative to move the blow out limit towards leaner equivalence ratios and by supplying heat and reactive species to the flame zone the
lean stability limit can be lowered. Heat and reactive species can be supplied to the flame zone by use of a pre-chamber combustor. In this study a central body burner, called the RPL (Rich-Pilot-Lean), is
used as a pre-chamber combustor to supply heat and radicals to a downscaled industrial burner. Emission probe measurements have been used for detection of the lean blow out limit for Methane and
a generic Syngas (10 % CH4, 67.5 % H2, and 22.5 % CO).The syngas was also investigated after being diluted with nitrogen to Wobbe index 15 MJ/m3 .In addition, OH-LIF measurements show the exhaust gases from the central body continue to react with the surrounding air. The lean blow out limit is modeled using two perfectly stirred reactors (PSR) in series. By using PSR reactors the chemical influence on lean blow out limit can be isolated. The resulting trends for modeled lean blow out limit are in agreement with both measured data and the visualized OH distribution of the OH-LIF images. Increasing the equivalence ratio in the RPL, thus increasing the supplied fuel energy, is a major
contributor for the combustion stability up to a limit where the temperature drop is too large. For leaner RPL combustion the reactive species O, H, and OH in combination enhance the stability beyond
the thermal influence. At richer equivalence ratios in the RPL the conversion of methane to hydrogen and carbon monoxide, in the RPL, is an important factor influencing the lean blow out limit besides the
temperature.