Fuel injector and a combustion chamber

Abstract

A fuel injector includes pilot and main fuel injectors. The pilot fuel injector includes at least one pilot air swirler and the main fuel injector includes a main air blast fuel injector located between inner main and outer main air swirlers. A first air splitter is located between the pilot and inner main air swirlers and a second air splitter is located between the pilot and inner main air swirlers. The first air splitter has a downstream portion converging to a downstream end. The second air splitter has a downstream portion diverging to a downstream end. The second air splitter downstream end is downstream of the first air splitter downstream end and the ratio of the distance from the first air splitter downstream end to the second air splitter downstream end to the diameter of the second air splitter downstream end is in the range of 0.22 to 0.30.

1 . A fuel injector comprising a pilot fuel injector and a main fuel injector, the pilot fuel injector comprising at least one pilot air swirler, the main fuel injector comprising a main air blast fuel injector located between an inner main air swirler and an outer main air swirler, a first air splitter located between the at least one pilot air swirler and the inner main air swirler and a second air splitter located between the at least one pilot air swirler and the inner main air swirler, the first air splitter comprising a downstream portion converging to a downstream end, the second air splitter comprising a downstream portion diverging to a downstream end, the downstream end of the second air splitter is downstream of the downstream end of the first air splitter, the downstream end of the second air splitter is downstream of the downstream end of a member defining the outer surface of the outer main air swirler and the ratio of the distance from the downstream end of the first air splitter to the downstream end of the second air splitter to the diameter of the downstream end of the second air splitter is in the range of 0.22 to 0.30. 
     
     
         2 . A fuel injector as claimed in  claim 1  wherein the ratio of the distance from the downstream end of the first air splitter to the downstream end of the second air splitter to the diameter of the downstream end of the second air splitter is in the range of 0.24 to 0.28. 
     
     
         3 . A fuel injector as claimed in  claim 1  wherein the ratio of the distance from the downstream end of the first air splitter to the downstream end of the second air splitter to the diameter of the downstream end of the second air splitter is in the range of 0.25 to 0.27. 
     
     
         4 . A fuel injector as claimed in  claim 1  wherein the pilot fuel injector comprising a pilot air blast fuel injector located between an inner pilot air swirler and an outer pilot air swirler. 
     
     
         5 . A fuel injector as claimed in  claim 1  wherein the second air splitter is located between the first air splitter and the inner main air swirler, an additional air swirler is provided between the first air splitter and the second air splitter to direct air over the second air splitter. 
     
     
         6 . A fuel injector as claimed in  claim 1  wherein the outer main air swirler comprises a plurality of swirl vanes arranged in an annular duct, the annular duct is defined by a radially inner surface of an outer wall and a radially outer surface of an inner wall. 
     
     
         7 . A fuel injector as claimed in  claim 6  wherein the radially inner surface of the outer wall of the annular duct converges to a minimum diameter downstream of the swirl vanes, the radial width of the annular duct at the trailing edges of the swirl vanes is in the range of 1.1 to 1.3 times the radial width of the annular duct at the minimum diameter of the radially inner surface of the outer wall of the annular duct. 
     
     
         8 . A fuel injector as claimed in  claim 7  wherein the radially outer surface of the inner wall of the annular duct converges to a minimum diameter downstream of the swirl vanes, the radial distance of convergence of the radially outer surface of the inner wall is in the range of 0.5 to 1.0 times the radial width of the annular duct at the minimum diameter of the radially inner surface of the outer wall of the annular duct. 
     
     
         9 . A fuel injector as claimed in  claim 7  wherein the axial length of the annular duct from the trailing edges of the swirl vanes to the minimum diameter of the radially inner surface of the outer wall of the annular duct is in the range of 1.7 to 2.5 times the radial width of the annular duct at the minimum diameter of the radially inner surface of the outer wall of the annular duct. 
     
     
         10 . A fuel injector as claimed in  claim 6  wherein the downstream end of the second air splitter is downstream of the downstream end of the inner wall of the annular duct. 
     
     
         11 . A combustion chamber comprising at least one fuel injector as claimed in  claim 1 . 
     
     
         12 . A combustion chamber as claimed in  claim 11  wherein the combustion chamber comprises an igniter and the igniter is positioned downstream of the at least one fuel injector. 
     
     
         13 . A gas turbine engine comprising at least one fuel injector as claimed in  claim 1 . 
     
     
         14 . A gas turbine engine as claimed in  claim 13  is a turbofan gas turbine engine, a turbo-jet gas turbine engine, a turbo-shaft gas turbine engine or a turbo-prop gas turbine engine. 
     
     
         15 . A gas turbine engine as claimed in  claim 14  wherein the gas turbine engine is an aero gas turbine engine, a marine gas turbine engine, an industrial gas turbine engine or an automotive gas turbine engine. 
     
     
         16 . A fuel injector comprising a pilot fuel injector and a main fuel injector, the pilot fuel injector comprising at least one pilot air swirler, the main fuel injector comprising a main air blast fuel injector located between an inner main air swirler and an outer main air swirler, a first air splitter located between the at least one pilot air swirler and the inner main air swirler and a second air splitter located between the at least one pilot air swirler and the inner main air swirler, the first air splitter comprising a downstream portion converging to a downstream end, the second air splitter comprising a downstream portion diverging to a downstream end, the downstream end of the second air splitter is downstream of the downstream end of the first air splitter and the ratio of the distance from the downstream end of the first air splitter to the downstream end of the second air splitter to the diameter of the downstream end of the second air splitter is in the range of 0.22 to 0.30. 
     
     
         17 . A method of operating a combustion chamber, the combustion chamber comprising an igniter and at least one fuel injector, the igniter being positioned downstream of the at least one fuel injector, the fuel injector comprising a pilot fuel injector and a main fuel injector, the pilot fuel injector comprising at least one pilot air swirler, the main fuel injector comprising a main air blast fuel injector located between an inner main air swirler and an outer main air swirler, a first air splitter located between the at least one pilot air swirler and the inner main air swirler and a second air splitter located between the at least one pilot air swirler and the inner main air swirler, the first air splitter comprising a downstream portion converging to a downstream end, the second air splitter comprising a downstream portion diverging to a downstream end, the downstream end of the second air splitter is downstream of the downstream end of the first air splitter, the downstream end of the second air splitter is downstream of the downstream end of a member defining the outer surface of the outer main air swirler and the ratio of the distance from the downstream end of the first air splitter to the downstream end of the second air splitter to the diameter of the downstream end of the second air splitter is in the range of 0.22 to 0.30, the method comprising supplying pilot fuel to the pilot fuel injector and supplying main fuel to the main fuel injector, atomising the pilot fuel using a swirling flow of air from the at least one pilot air swirler, atomising the main fuel using swirling flows of air from the inner main air swirler and the outer main air swirler, producing an S shaped flow path for the pilot fuel supplied from the pilot fuel injector to the main fuel supplied by the main fuel injector, and mixing the pilot fuel with the main fuel and air flow upstream of the igniter. 
     
     
         18 . A method as claimed in  claim 17  wherein the combustion chamber comprises a plurality of fuel injectors. 
     
     
         19 . A method as claimed in  claim 18  wherein the combustion chamber is an annular combustion chamber. 
     
     
         20 . A method as claimed in  claim 17  wherein the pilot fuel injector comprising a pilot air blast fuel injector located between an inner pilot air swirler and an outer pilot air swirler.