Low emission combustion system for a gas turbine engine

Abstract

The control systems for reducing NOx in the combustion systems of past gas turbine engines has incorporated a variety of expensive and complicated techniques to reduce the NOx level. For example, such systems use schemes for introducing more air into the primary combustion zone, recirculating cooled exhaust products into the combustion zone and injecting water spray into the combustion zone. The present system reduces the formation of NOx within the combustion zone by controlling the air/fuel ratio and more explicitly by controlling the air portion of the air/fuel ratio. The present system includes a device for directing a portion of the flow of compressed air exiting a compressor section into an injection nozzle and into a combustor, a device for reducing the flow of compressed air into the combustor. The system monitors an engine parameter, such as a power turbine inlet gas temperature, sends a signal to a computer which interpreters the signal and directs a second signal to a power cylinder which causes a throttling mechanism to move between an open position and a closed position depending on the temperature of the gases. The system provides an economical, reliable and effective method for reducing and controlling the amount of nitrogen oxide, carbon monoxide and unburned hydrocarbon emitted from the gas turbine engine.