Abstract: Lean direct injection is used in a gas turbine combustor to reduce NO.sub.x emissions. The combustor has a plurality of fuel jets for tangentially injecting fuel and a plurality of air jets for tangentially injecting air therein. The fuel jets and the air jets are preferably disposed in a common cross-sectional plane, although additional groups of fuel and air jets in other planes can be provided. The jets are all evenly spaced and alternate between fuel and air jets. All of the jets preferably point in the same circumferential direction. Alternatively, the jets can be arranged so that all fuel jets are located in a first cross-sectional plane, and all air jets are located in a second cross-sectional plane. Preferably, the fuel jets point in one circumferential direction while the air jets point in the opposite circumferential direction.

Abstract: Lean direct injection is used in a gas turbine combustor to reduce NO.sub.x emissions. The combustor has a multi-hole perforated plate disposed at the head end of the combustion chamber. The plate has a plurality of independent fuel jets and air jets for separately injecting fuel and air, respectively, into the combustion chamber in amounts which produce a lean fuel-air equivalence ratio. The perforated plate permits the fuel and air to be injected separately without any mixing outside of the combustion chamber. Fuel is delivered to the fuel jets by a fuel manifold having a branch connected to each one of the fuel jets. Air can be delivered to the air jets by an air plenum chamber located upstream of the perforated plate and in fluid communication with the air jets.

Abstract: Reducing NO.sub.x emission levels from a gas turbine combustor having a premixer section by mixing a small portion of air into the fuel prior to injection into the premixer section. The portion of diverted air is approximately five percent of the total amount of air injected into the premixer section or such that the resulting fuel-air mixture in the fuel line is approximately half fuel and half air. The injection of air into the fuel line, referred to as "head start partial premixing," is effective to reduce the fluctuations and nonuniformities in the fuel concentration levels which increase NO.sub.x output.