Multi-stage fuel nozzle for reducing combustion instabilities in low NOX gas turbines

Abstract

A fuel nozzle for gas turbine combustors reduces combustion instabilities by injecting purge air into the combustor angularly instead of axially. The fuel nozzle has a substantially cylindrical body with a number of internal passages. One of the passages provides premix gas fuel to a plurality of fuel injectors attached to the fuel nozzle. The remaining passages can be for diffusion gas, atomizing air and liquid fuel. One or more of the remaining passages is connected to a respective group of discharge orifices formed in the cylindrical side surface of the nozzle body. During low NO.sub.x operation, premix gas is introduced through the fuel injectors, and the remaining passages are all purged with air to prevent the ingress of flame gases from the combustion chamber. The resulting jets of air emitted from discharge orifices formed in the side surface will disrupt or break-up spanwise vortices shed from the bluff end of the fuel nozzle, thereby reducing combustion instabilities. These air jets are preferably discharged at an angle of about 45 degrees to the longitudinal axis of the fuel nozzle. The orifices can be rectangular, circular or triangular in shape.

Dependencies are inferred from the claim text.