Airblast fuel nozzle assembly
View Patent ↗An airblast fuel nozzle assembly ( 10 ) comprising a sleeve structure having a series of coaxial sleeves forming an inner-air circuit, an outer-air circuit, a main-fuel-feed circuit, and a pilot-fuel-feed circuit. The pilot-fuel-feed circuit includes a channel ( 44 ), and a discharge region ( 45 ) with exits ( 46 ). The exits ( 46 ) have a combined cross-sectional area that is substantially less than the cross-sectional area of the channel ( 44 ) upstream of the discharge region ( 45 ). In this manner, the pilot-fuel-feed circuit itself can provide a relatively large pressure drop across the channel region ( 44 ), and thereby assist in self atomization during ignition stages of engine operation.
1. An airblast fuel nozzle assembly comprising a sleeve structure forming an inner-air circuit, an outer-air circuit, a main-fuel-feed circuit, and a pilot-fuel-feed circuit;
the inner-air circuit including a central passageway through the sleeve structure extending to a nozzle outlet;
the outer-air circuit including an annular passageway radially surrounding the central passageway and extending to the nozzle outlet;
the pilot-fuel-feed circuit comprising a channel surrounding the inner-air-circuit central passageway, a prefilming surface surrounding the inner-air-circuit central passageway, and a discharge region with exits configured to convey pilot-feed fuel from the channel against the prefilming surface;
the main-fuel-feed circuit, the pilot-fuel-feed circuit, the inner-air circuit and the outer-air circuit being arranged such that flows through the main-fuel-feed circuit and the pilot-fuel-feed circuit merge with flows through the inner-air circuit and the outer-air circuit downstream of the prefilming surface;
the pilot-fuel-feed-circuit exits having a combined cross-sectional area that is substantially less than the cross-sectional area of the channel upstream of the discharge region; and
the pilot-fuel-feed-circuit and the main-fuel-feed-circuit downstream of the discharge region are separated by and immediately adjacent a sleeve.
2. An airblast fuel nozzle assembly as set forth in claim 1 , wherein the channel and/or the exits of the pilot-fuel-feed circuit are sized to cause the pilot fuel to experience a pressure drop of at least 3 psi across the discharge region.
3. An airblast fuel nozzle assembly as set forth in claim 1 , wherein the channel and/or the exits of the pilot-fuel-feed circuit are sized to cause the pilot fuel to experience a pressure drop of at least 5 psi across the discharge region.
4. An airblast fuel nozzle assembly as set forth in claim 1 , wherein the channel and/or the exits of the pilot-fuel-feed circuit are sized to cause the pilot fuel to experience a pressure drop of at least 10 psi across the discharge region.
5. An airblast fuel nozzle assembly comprising a sleeve structure forming an inner-air circuit, an outer-air circuit, a main-fuel-feed circuit, and a pilot-fuel-feed circuit;
the inner-air circuit including a central passageway through the sleeve structure extending to a nozzle outlet;
the outer-air circuit including an annular passageway radially surrounding the central passageway and extending to the nozzle outlet;
the pilot-fuel-feed circuit comprising a channel surrounding the inner-air-circuit central passageway, a prefilming surface surrounding the inner-air-circuit central passageway, and a discharge region with exits configured to convey pilot-feed fuel from the channel against the prefilming surface;
the main-fuel-feed circuit, the pilot-fuel-feed circuit, the inner-air circuit and the outer-air circuit being arranged such that flows through the main-fuel-feed circuit and the pilot-fuel-feed circuit merge with flows through the inner-air circuit and the outer-air circuit downstream of the prefilming surface;
the pilot-fuel-feed-circuit exits having a combined cross-sectional area that is substantial less than the cross-sectional area of the channel upstream of the discharge region;
wherein the main-fuel-feed circuit comprises a channel surrounding the inner-air circuit, and a discharge region having exits configured to convey the main-feed fuel to the same prefilming surface as the pilot-fuel-feed-circuit exits.
6. An airblast fuel nozzle assembly as set forth in claim 5 , wherein the main-fuel-feed-circuit channel is situated radially outward from the pilot-fuel-feed-circuit channel.
7. An airblast fuel nozzle assembly as set forth in claim 5 , wherein the main-fuel-feed-circuit channel is situated radially inward from the pilot-fuel-feed-circuit channel.
8. An airblast fuel nozzle assembly as set forth in claim 5 , wherein the main-fuel-feed-circuit channel is situated radially in the same annular space as the pilot-fuel-feed-circuit channel.
9. An airblast fuel nozzle assembly as set forth in claim 5 , wherein the main-fuel-feed circuit, the pilot-fuel-feed circuit, the inner-air circuit and the outer-air circuit are arranged such that flows through the main-fuel-feed circuit and the pilot-fuel-feed circuit merge with flows through the inner-air circuit and the outer-air circuit upstream of the nozzle outlet.
10. An airblast fuel nozzle assembly as set forth in claim 1 , wherein the main-fuel-feed circuit comprises a channel surrounding the inner-air circuit, and a discharge region having exits configured to convey the main-feed fuel to another prefilming surface.
11. An airblast fuel nozzle assembly as set forth in claim 10 , wherein the main-fuel-feed-circuit channel is situated radially outward from the pilot-fuel-feed-circuit channel.
12. An airblast fuel nozzle assembly as set forth in claim 10 , wherein the main-fuel-feed-circuit channel is situated radially inward from the pilot-fuel-feed-circuit channel.
13. An airblast fuel nozzle assembly as set forth in claim 5 , wherein the main-fuel-feed circuit, the pilot-fuel-feed circuit, the inner-air circuit and the outer-air circuit are arranged such that flows through the main-fuel-feed circuit and the pilot-fuel-feed circuit merge with flows through the inner-air circuit and the outer-air circuit upstream of the nozzle outlet.
14. An airblast fuel nozzle assembly as set forth in claim 1 , wherein the sleeve structure comprises a series of coaxial sleeves, including a sleeve forming the central passageway of the inner-air circuit, and wherein the pilot-fuel-feed-circuit channel is formed between two of the sleeves.
15. An airblast fuel nozzle assembly as set in claim 14 , wherein the main-fuel-feed circuit comprises a channel surrounding the inner-air circuit and wherein this channel is formed between two of the sleeves.
16. A gas turbine engine comprising a combustion chamber and the nozzle assembly set forth in claim 1 positioned to inject a fuel-air mixture into the combustion chamber, wherein fuel can be selectively supplied to one or both of the fuel-feed circuits.
17. A method of using the airblast fuel nozzle assembly as set forth in claim 1 , said method comprising the steps of:
supplying fuel substantially only to the pilot-fuel-feed circuit during ignition stages of engine operation; and
supplying fuel to only the main-fuel-feed circuit, or both the pilot-fuel-feed circuit and the main-fuel-feed circuit, during post-ignition stages of engine operation.
18. An airblast fuel nozzle assembly comprising a sleeve structure forming an inner-air circuit, an outer-air circuit, and a fuel-feed circuit;
the inner-air circuit including a central passageway through the sleeve structure extending to a nozzle outlet;
the outer-air circuit including an annular passageway radially surrounding the central passageway and extending to the nozzle outlet;
the fuel-feed circuit comprising a channel surrounding the inner-air-circuit central passageway, a prefilming surface surrounding the channel passageway upstream of the outer-air circuit, and a discharge region between the channel and the prefilming surface;
the discharge region comprising passages extending radially outward in the downstream direction and each passage having a downstream end configured to direct fuel from the channel against the prefilming surface.
19. An airblast fuel nozzle assembly as set forth in claim 18 , wherein the fuel-feed circuit is a pilot-fuel-feed circuit, and wherein the sleeve structure forms another fuel-feed-circuit which is a main-fuel-feed circuit.
20. A gas turbine engine comprising a combustion chamber and the nozzle assembly set forth in claim 18 positioned to inject a fuel-air mixture into the combustion chamber.