Dual fuel nozzles are known for use in gas turbine engines for such purposes as smoke reduction by injecting water along with the fuel, minimization of carbon formation and build-up on the fuel nozzle, suppression of nitrogen oxide formation during the combustion process and thrust augmentation.
The Coburn et al. U.S. Pat. No. 4,290,558 issued Sept. 27, 1981 discloses a gas turbine fuel nozzle and support assembly capable of operating in a fuel/water injection mode for smoke reduction purposes. Water is injected from a passage in the nozzle support into a space between the support and heat shield behind the nozzle and is carried through a plurality of nozzle passages extending from the nozzle exterior to an inner annular chamber. In the nozzle, the water is subjected to a centrifuging action in the annular chamber for eventual discharge around the outside of the fuel spray cone which is discharged from primary and secondary fuel orifices.
The Stratton U.S. Pat. No. 4,311,277 issued Jan. 19, 1982 discloses a fuel nozzle and support assembly for use with external air swirler blades in a flame tube. The assembly includes gaseous fuel supply passages and orifices located external of the liquid fuel passages and orifices and operable in one mode when the liquid fuel supply is discontinued. In another mode, the gaseous fuel supply is interrupted when the liquid fuel is supplied to the nozzle.
So-called piloted air blast or dual orifice fuel nozzles for gas turbine engines are shown in the Helmrich U.S. Pat. No. 3,684,186 issued Aug. 15, 1972 and the Simmons U.S. Pat. No. 4,139,157 issued Feb. 13, 1979. These types of fuel nozzles are not designed to use dual fuels but rather have a primary fuel supply system providing a low fuel flow rate for engine start-up and high altitude conditions and a secondary fuel supply system capable of high fuel flow rates for high engine power conditions. During high engine power conditions, the primary fuel flow may be maintained at the start-up rate, reduced to a lower rate, or possibly shut off. In fact, air-blast fuel nozzles having only a secondary fuel system but nevertheless operable over most engine power conditions have been used and are shown, for example, in FIG. 2 of the Helmrich U.S. Pat. No. 3,684,186 referred to above and the Simmons et al. U.S. Pat. No. 3,980,233 issued Sept. 14, 1976.
Other fuel nozzle and support assembly constructions for use in gas turbine engines are illustrated in U.S. Pat. No. 2,701,164 issued Feb. 1, 1955; U.S. Pat. No. 3,520,480 issued July 14, 1970; U.S. Pat. No. 3,638,865 issued Feb. 1, 1972; U.S. Pat. No. 3,662,959 issued May 16, 1972; U.S. Pat. No. 3,662,959 issued May 16, 1972; U.S. Pat. No. 3,662,960 issued May 16, 1972 and U.S. Pat. No. 3,675,853 issued July 11, 1972.