Partial premix dual circuit fuel injector

Abstract

A low emission fuel injection system and combustion chamber for use in gas turbine engines comprises one fuel injection body having a dual circuit to supply both pilot and main fuel systems. Both pilot fuel circuit and a main fuel circuit inject fuel at essentially the same axial and radial location. The recessed pilot fuel injection site is along the combustor centerline into a swirling air passage produced by axial air swirlers. The main fuel is injected radially through a plurality of injection sites, at a compound angle, into the inner diameter of a swirling air passage produced by radial air swirlers. The fuel/air residence time prior to entering the combustion chamber is relatively short, minimizing the likelihood of auto ignition. During pilot circuit only operation, the flame is stabilized by a swirler produced recirculation zone, producing high temperatures to completely burn the fuel producing low CO and UHC emissions. During intermediate and high engine power conditions, both the main fuel and pilot circuits discharge fuel into a swirler produced, high air flow, recirculation zone producing a fuel lean, low temperature flame to reduce NOx emissions.

We claim:  
     
         1 . A gas turbine engine fuel injection and combustor system, comprising: 
 an outer casing extending from an upstream end to a downstream end, an internal space of the downstream end defining a combustion chamber;    an annular dome connected to an internal, upstream end of the outer casing;    a radial flow air swirler mounted to an internal surface of the annular dome and to an external surface of a fuel injector body, said swirler providing swirled air to the combustion chamber;    a fuel injector body mounted to an internal surface of the radial flow air swirler, said fuel injector body comprising a plurality of axially oriented air swirlers, an axially located pilot circuit fuel nozzle, and a plurality of radially oriented main circuit fuel nozzles;    whereby during low power gas turbine engine operation, pilot circuit fuel is mixed with axial swirler produced air flow, and is thereby caused to rotate in a vortex around a longitudinal axis of the combustion chamber and upon ignition produces a stable high temperature emission free flame;    whereby during intermediate and high power gas turbine engine operation, pilot circuit and main circuit fuel is mixed with radial and axial swirler produced air flow, and is thereby caused to rotate in a double vortex around the longitudinal axis of said combustion chamber, and upon ignition produces a stable, fuel lean, low temperature, low pollutant emission flame.    
     
     
         2 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby a single fuel injector body incorporates both the pilot circuit and the main circuit fuel injection systems.  
     
     
         3 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby the fuel injector body for the pilot and main circuit fuel injection systems is cylindrical.  
     
     
         4 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby pilot circuit fuel and main circuit fuel are injected in the combustion chamber at essentially the same axial and radial locations.  
     
     
         5 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby a pilot circuit fuel nozzle encircled by a plurality of axial air swirlers discharges fuel into a combustor creating a rotating vortex of vaporized fuel and air.  
     
     
         6 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby main circuit fuel nozzles discharge fuel at a compound angle into a radial swirler passage creating a rotating vortex of vaporized fuel and air within the combustion chamber.  
     
     
         7 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby the combined geometry of the pilot circuit and main circuit fuel injection systems provides short fuel-air residence times prior to entering the combustion chamber.  
     
     
         8 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby at least four radially oriented main circuit fuel nozzles are employed.  
     
     
         9 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby said fuel injection system is usable for both can type and annular type combustors.  
     
     
         10 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby aerospace type fuels can be utilized can be utilized as the combustion medium.  
     
     
         11 . The gas turbine engine fuel injection and combustor system of  claim 1 , whereby a variety of non-aerospace type fuels can be utilized as the combustion medium.  
     
     
         12 . A method of producing a low emission gas at low and high power in a gas turbine engine combustor, comprising the steps of: 
 injecting pilot circuit fuel spray through a axially disposed nozzle into a combustor chamber;    swirling a first portion of air axially and flowing said swirled air into said combustor chamber to form a swirling mixture of pilot circuit fuel and air for low, intermediate, and high power operations;    swirling a second portion of air radially and flowing said swirled air into an air swirler passageway;    injecting main circuit fuel spray through radially disposed nozzles into said air swirler passageway and thereafter into said combustion chamber to form a swirling mixture of main circuit fuel and air for intermediate and high power operations;    expanding and igniting said swirling mixture of pilot circuit fuel and air to form said low emission gas for low and high power operations; and    expanding and igniting said swirling mixture of main circuit fuel and air to form said low emission gas for intermediate and high power operations.    
     
     
         13 . The method of  claim 12 , wherein the step of expanding pilot circuit fuel and air forms a fuel rich, high flame temperature, zone in the combustion chamber.  
     
     
         14 . The method of  claim 12 , wherein the step of expanding main circuit fuel and air forms a fuel lean, low flame temperature, zone in the combustion chamber.