Fuel injector

Abstract

A lean burn fuel injector comprises a fuel feed arm and a fuel injector head. The fuel feed arm has a single pilot fuel supply passage and a single main fuel supply passage extending there-through. The fuel injector head has a coaxial arrangement of an inner pilot air-blast fuel injector and a coaxially arranged outer main air-blast fuel injector. The inner pilot air-blast fuel injector comprises a coaxial arrangement of a pilot inner air swirler passage and a pilot outer air swirler passage. The outer main air-blast fuel injector comprises a coaxial arrangement of a main inner air swirler passage and a main outer air swirler passage. The single main fuel supply passage is arranged to supply main fuel to the main inner air swirler passage. The single pilot fuel supply passage is arranged to supply pilot fuel onto the pre-filming surfaces in the pilot inner and outer air swirler passages.

1 . A fuel injector comprising a fuel feed arm and a fuel injector head,
 the fuel feed arm having a fuel supply passage extending there-through,   the fuel injector head having an air-blast fuel injector, the air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of an inner air swirler passage and an outer air swirler passage, the inner air swirler passage and the outer air swirler passage being arranged immediately adjacent each other,   an annular member defining the radially outer extremity of the outer air swirler passage, a downstream end of the annular member defining the radially outer extremity of the outer air swirler passage being frustoconical, the downstream end of the annular member defining the radially outer extremity of the outer air swirler passage being convergent in a downstream direction,   the fuel supply passage being arranged to supply a first portion of the fuel into the inner air swirler passage and to supply a second portion of the fuel into the outer air swirler passage, the inner air swirler passage having a pre-filming surface, the outer air swirler passage having a pre-filming surface, the fuel supply passage being arranged to supply fuel onto the pre-filming surface in the inner air swirler passage, the fuel supply passage being arranged to supply fuel onto the pre-filming surface in the outer air swirler passage.   
     
     
         2 . A fuel injector as claimed in  claim 1 , wherein the fuel injector is a rich burn fuel injector, the fuel injector having an additional air swirler passage arranged coaxially around the outer air swirler passage. 
     
     
         3 . A fuel injector as claimed in  claim 1 , wherein the fuel injector is a lean burn fuel injector,
 the fuel feed arm having a single pilot fuel supply passage extending there-through and a single main fuel supply passage extending there-through,   the fuel injector head having a coaxial arrangement of an inner pilot air-blast fuel injector and an outer main air-blast fuel injector, the outer main air-blast fuel injector being arranged coaxially radially outwardly of the inner pilot air-blast fuel injector, the inner pilot air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a pilot inner air swirler passage and a pilot outer air swirler passage, the outer main air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a main inner air swirler passage and a main outer air swirler passage.   
     
     
         4 . A fuel injector as claimed in  claim 3 , wherein the single main fuel supply passage being arranged to supply main fuel to the main inner air swirler passage or the main outer air swirler passage, the single pilot fuel supply passage being arranged to supply a first portion of pilot fuel into the pilot inner air swirler passage and to supply a second portion of pilot fuel into the pilot outer air swirler passage, the single main fuel supply passage being arranged to supply main fuel onto a pre-filming surface in the main inner air swirler passage or the single main fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the main outer air swirler passage, the single pilot fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the pilot inner air swirler passage, the single pilot fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the pilot outer air swirler passage. 
     
     
         5 . A fuel injector as claimed in  claim 3 , wherein the single pilot fuel supply passage being arranged to supply pilot fuel into the pilot inner air swirler passage or the pilot outer air swirler passage, the single main fuel supply passage being arranged to supply a first portion of the main fuel into the main inner air swirler passage and to supply a second portion of the main fuel into the main outer air swirler passage, the single main fuel supply passage being arranged to supply main fuel onto a pre-filming surface in the main inner air swirler passage, the single main fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the main outer air swirler passage, the single pilot fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the pilot inner air swirler passage or the single pilot fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the pilot outer air swirler passage. 
     
     
         6 . A fuel injector as claimed in  claim 3 , wherein the single pilot fuel supply passage being arranged to supply a first portion of pilot fuel into the pilot inner air swirler passage and to supply a second portion of pilot fuel into the pilot outer air swirler passage and the single main fuel supply passage being arranged to supply a first portion of the main fuel into the main inner air swirler passage and to supply a second portion of the main fuel into the main outer air swirler passage, the single main fuel supply passage being arranged to supply main fuel onto a pre-filming surface in the main inner air swirler passage, the single main fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the main outer air swirler passage, the single pilot fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the pilot inner air swirler passage and the single pilot fuel supply passage being arranged to supply pilot fuel onto a pre-filming surface in the pilot outer air swirler passage. 
     
     
         7 . A fuel injector as claimed in  claim 3 , wherein a pilot fuel passage is arranged coaxially between the pilot inner air swirler passage and the pilot outer air swirler passage, the single pilot fuel supply passage is arranged to supply pilot fuel to the pilot fuel passage. 
     
     
         8 . A fuel injector as claimed in  claim 7 , wherein the pilot fuel passage is arranged to supply the pilot fuel into the pilot inner air swirler passage and into the pilot outer air swirler passage. 
     
     
         9 . A fuel injector as claimed in  claim 7 , wherein the pilot fuel passage has a fuel swirler to swirl the pilot fuel supplied onto the pre-filming surface in the pilot inner air swirler passage. 
     
     
         10 . A fuel injector as claimed in  claim 7 , wherein the pilot fuel passage has a fuel swirler to swirl the pilot fuel supplied onto the pre-filming surface in the pilot outer air swirler passage. 
     
     
         11 . A fuel injector as claimed in  claim 7 , wherein a second pilot fuel passage is arranged coaxially between the pilot outer air swirler passage and the main inner air swirler passage, the single pilot fuel supply passage is arranged to supply pilot fuel to the second pilot fuel passage, the pilot fuel passage is arranged to supply the pilot fuel into the pilot inner air swirler passage and the second pilot fuel passage is arranged to supply pilot fuel into the pilot outer air swirler passage. 
     
     
         12 . A fuel injector as claimed in  claim 11 , wherein the pilot fuel passage has a fuel swirler to swirl the pilot fuel supplied onto the pre-filming surface in the pilot inner air swirler passage. 
     
     
         13 . A fuel injector as claimed in  claim 11 , wherein the second pilot fuel passage has a fuel swirler to swirl the pilot fuel supplied onto the pre-filming surface in the pilot outer air swirler passage. 
     
     
         14 . A fuel injector as claimed in  claim 3 , wherein the pilot inner air swirler passage and the pilot outer air swirler passage are arranged to swirl the air in opposite directions. 
     
     
         15 . A fuel injector as claimed in  claim 1 , wherein the number of points at which the fuel is supplied into the outer air swirler passage is the same as the number of swirl vanes in the outer air swirler passage. 
     
     
         16 . A fuel injector as claimed in  claim 15 , wherein the points at which the pilot fuel is supplied into the outer air swirler passage are located adjacent the leading edge of the swirl vanes, adjacent the trailing edge of the swirl vanes or between the leading edge of the swirl vanes and the trailing edge of the swirl vanes. 
     
     
         17 . A fuel injector as claimed in  claim 15 , wherein the points at which the fuel is supplied into the outer air swirler passage are aligned circumferentially with the leading edge of the swirl vanes, aligned circumferentially with the trailing edge of the swirl vanes or arranged circumferentially between the leading edge of the swirl vanes and the trailing edge of the swirl vanes. 
     
     
         18 . A fuel injector as claimed in  claim 3 , wherein a main fuel passage is arranged coaxially between the main inner air swirler passage and the main outer air swirler passage. 
     
     
         19 . A fuel injector as claimed in  claim 3 , wherein an intermediate air swirler passage is sandwiched between the pilot outer air swirler passage of the inner pilot air-blast fuel injector and the main inner air swirler passage of the outer main air-blast fuel injector. 
     
     
         20 . A method of operating a fuel injector, the fuel injector comprising a fuel feed arm and a fuel injector head,
 the fuel feed arm having a fuel supply passage extending there-through,   the fuel injector head having an air-blast fuel injector, the air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of an inner air swirler passage and an outer air swirler passage, the inner air swirler passage and the outer air swirler passage being arranged immediately adjacent each other,   an annular member defining he radially outer extremity of the outer air swirler passage, a downstream end of the annular member defining the radially outer extremity of the outer air swirler passage being frustoconical, the downstream end of the annular member defining the radially outer extremity of the outer air swirler passage being convergent in a downstream direction,   the fuel supply passage being arranged to supply a first portion of the fuel into the inner air swirler passage and to supply a second portion of the fuel into the outer air swirler passage, the inner air swirler passage having a pre-filming surface, the outer air swirler passage having a pre-filming surface,   the method comprising supplying a first portion of the fuel to the pre-filming surface in the inner air swirler passage and supplying a second portion of the fuel to the pre-filming surface in the outer air swirler passage.   
     
     
         21 . A method as claimed in  claim 20  wherein the fuel injector is a lean burn fuel injector, the fuel feed arm having a single pilot fuel supply passage extending there-through and a single main fuel supply passage extending there-through, the fuel injector head having a coaxial arrangement of an inner pilot air-blast fuel injector and an outer main air-blast fuel injector, the outer main air-blast fuel injector being arranged coaxially radially outwardly of the inner pilot air-blast fuel injector, the inner pilot air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a pilot inner air swirler passage and a pilot outer air swirler passage, the outer main air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a main inner air swirler passage and a main outer air swirler passage, the method comprising supplying a first portion of the pilot fuel to a pre-filming surface in the pilot inner air swirler passage and supplying a second portion of the pilot fuel to a pre-filming surface in the pilot outer air swirler passage in a first mode of operation and supplying a first portion of the pilot fuel to the pre-filming surface in the pilot inner air swirler passage, supplying a second portion of the pilot fuel to the pre-filming surface in the pilot outer air swirler passage and supplying main fuel to a pre-filming surface in the main inner air swirler passage or to a pre-filming surface in the main outer air swirler passage in a second mode of operation. 
     
     
         22 . A method as claimed in  claim 20  wherein the fuel injector is a lean burn fuel injector the fuel feed arm having a single pilot fuel supply passage extending there-through and a single main fuel supply passage extending there-through, the fuel injector head having a coaxial arrangement of an inner pilot air-blast fuel injector and an outer main air-blast fuel injector, the outer main air-blast fuel injector being arranged coaxially radially outwardly of the inner pilot air-blast fuel injector, the inner pilot air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a pilot inner air swirler passage and a pilot outer air swirler passage, the outer main air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a main inner air swirler passage and a main outer air swirler passage, the method comprising supplying the pilot fuel to a pre-filming surface in the pilot inner air swirler passage or to a pre-filming surface in the pilot outer air swirler passage in a first mode of operation and supplying the pilot fuel to the pre-filming surface in the pilot inner air swirler passage or to the pre-filming surface in the pilot outer air swirler passage, supplying a first portion of the main fuel to a pre-filming surface in the main inner air swirler passage and supplying a second portion of the main fuel to a pre-filming surface in the outer air swirler passage in a second mode of operation. 
     
     
         23 . A method as claimed in  claim 20  wherein the fuel injector is a lean burn fuel injector the fuel feed arm having a single pilot fuel supply passage extending there-through and a single main fuel supply passage extending there-through, the fuel injector head having a coaxial arrangement of an inner pilot air-blast fuel injector and an outer main air-blast fuel injector, the outer main air-blast fuel injector being arranged coaxially radially outwardly of the inner pilot air-blast fuel injector, the inner pilot air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a pilot inner air swirler passage and a pilot outer air swirler passage, the outer main air-blast fuel injector comprising, in order radially outwardly, a coaxial arrangement of a main inner air swirler passage and a main outer air swirler passage, the method comprising supplying a first portion of the pilot fuel to a pre-filming surface in the pilot inner air swirler passage and supplying a second portion of the pilot fuel to a pre-filming surface in the pilot outer air swirler passage in a first mode of operation and supplying a first portion of the pilot fuel to the pre-filming surface in the pilot inner air swirler passage, supplying a second portion of the pilot fuel to the pre-filming surface in the pilot outer air swirler passage, supplying a first portion of the main fuel to a pre-filming surface in the main inner air swirler passage and supplying a second portion of the main fuel to a pre-filming surface in the outer air swirler passage in a second mode of operation. 
     
     
         24 . A method as claimed in  claim 20 , wherein the mass flow of the fuel to the inner air swirler passage to the mass flow of the fuel to the outer air swirler passage is between 10:1 and 1:10. 
     
     
         25 . A method as claimed in  claim 20 , wherein the mass flow of the fuel to the inner air swirler passage to the mass flow of the fuel to the pilot outer air swirler passage is 1:1.