Amongst different effective means to control the NOx
emission in gas turbine combustors (e.g. water or steam
injection, selective catalytic reduction [9], rich-quench-lean
(RQL) [10,11], staged combustion [6,13]), lean premixed
combustion technique is effective because of its easy adaptability
in combustors. The temperature in the reaction zone,
which strongly affects the NOx emission, is reduced by
supplying a lean fuel/air premixed mixture. The fuel and air
are mixed via a premixer installed at upstream region of the
combustion zone in the gas turbine combustor. In particular,
the NOx formation is profoundly influenced by the hot spot
zones in gaseous fuel flames, which usually result from
insufficient mixing between the fuel and air at inlet of the
combustor. Even though lean premixed combustion is well
understood in theory, its practical application to gas turbine
combustor is still limited, because fuel/air mixing characteristics,
recirculation flow patterns, and flame stability in reaction
zone have not been understood fully. These parameters
play a significant role in characterizing the fuel-lean flame in