Stability and emissions characteristics of a lean premixed gas turbine combustor

Abstract

The effect of incomplete fuel-air mixing on NOx emission and combustion stability has been studied in an atmospheric pressure, optically accessible, laboratory-scale, premixed dump combustor. The degree of fuel-dimensional acetone fluorescence. Combustion stability was characterized both in terms of the level of combustion-generated noise during combustion oscillations and the lean blowouts limit. The structure of the flame zone was characterized using two-dimensional OH fluorescence measurements that were phase locked with the combustion-generated pressure oscillations. As has been observed previously, it was shown that incompletes fuel-air mixing results in increased NOx emissions at overall fuel-lean conditions. The results, however, indicate that “reaction zone” NO mechanisms, enhanced by superequilibrinm O-atom concentrations, are in part responsible for more than 50% of the increased NO production. It was also shown that incomplete fuel-air mixing in a premixed combustor can significantly reduce the stable operating range of the combustor both in terms of increasing the tendency for combustion oscillation and raising the lean blowont limit. Lastly, it was observed that during unstable combustion, the flame moves in a well-defined periodic manner: however, the details of the flame behavior and instability mechanism can vary significantly depending on the overall equivalence ratio and the degree of fuel-air mixing.