초록 ▼

A method for providing cooling air to the venturi and the combustion chamber in a low NOx emission combustor as used in a gas turbine engine that includes the steps of providing an annular air passage surrounding said combustion chamber and venturi where said cooling air under pressure enters the co

A method for providing cooling air to the venturi and the combustion chamber in a low NOx emission combustor as used in a gas turbine engine that includes the steps of providing an annular air passage surrounding said combustion chamber and venturi where said cooling air under pressure enters the combustion chamber/venturi near the aft portion of the combustion chamber, passing the air along the combustion chamber, past the venturi where the air exits near the front portion of the convergent area of the venturi. The method prevents any channel/passage cooling air from being received into the combustion chamber, and at the same time, introduces the outlet of the cooling air, after the air has passed over the combustion chamber of the venturi and has been heated, back into the premix chamber thereby improving the efficiency of the combustor while reducing and lowering NOx emission in the combustion process. In an alternate embodiment, a venturi is disclosed that incorporates a cooling passageway have a region of reduced area proximate a venturi throat region. The reduced area in conjunction with a plurality of raised ridges, located along the cooling passageway, for disturbing the cooling flow, enhance overall cooling effectiveness and improve venturi throat heat transfer.

대표청구항 ▼

1. An improved low emission (NOx) combustor for use with gas turbine engine comprising:a liner having a first generally annular wall and including a premix chamber for mixing fuel and air and a combustion chamber for combusting said fuel and air, said premix chamber in communication with said combus

1. An improved low emission (NOx) combustor for use with gas turbine engine comprising:a liner having a first generally annular wall and including a premix chamber for mixing fuel and air and a combustion chamber for combusting said fuel and air, said premix chamber in communication with said combustion chamber, said first generally annular wall having at least one first aperture and at least one second aperture, said second aperture being radially outward of said premix chamber;a venturi having a second generally annular wall that includes a first converging wall and a first diverging wall, said first converging wall abutting said first diverging wall at a first plane, said first plane generally perpendicular to said first generally annular wall, said venturi further containing a throat portion at said first plane, said throat portion being positioned between said premix chamber and said combustion chamber, said second generally annular wall being radially inward from said first generally annular wall and having an aft end adjacent said at least one first aperture, said venturi having a third generally annular wall being radially outward of said second generally annular wall and radially inward of said first generally annular wall, said third generally annular wall including a second converging wall and a second diverging wall, said second converging wall connected to said second diverging wall at a first region of curvature proximate said first plane and having a first radius R 1 , said second convergent wall having a first convergent member and a second convergent member, said second diverging wall having a first divergent member and a second divergent member, wherein said second convergent member and said second divergent member are located adjacent said first region of curvature, said first divergent member oriented at an angle α 1 relative to said first plane, said second divergent member oriented at an angle α 2 relative to said first plane, said first convergent member oriented at an angle α 3 relative to said first plane, and said second convergent member oriented at an angle α 4 relative to said first plane, wherein α 2 <α 1 and α 4 <α 3 , thereby forming a first region of reduced cross sectional area A 1 between said first diverging wall and said second divergent member and a second region of reduced cross sectional area A 2 between said first converging wall and said second convergent member;a passageway for flowing cooling air through said venturi, said passageway extending from said at least one first aperture to said at least one second aperture, said passageway including a first portion radially inward from said third generally annular wall and radially outward from said second generally annular wail, and said passageway including a second portion radially outward from said first portion of said passageway, said second portion extending from said passageway first portion to said at least one second aperture, and said first aperture being radially outward from said first portion, and said first portion of said passageway having a second region of curvature with radius R 2 proximate said throat;a plurality of raised ridges fixed to said second generally annular wall extending into said first portion of said passageway; and,a blocking ring extending from said aft end of said second generally annular wall to said first generally annular wall in sealing contact therewith, said blocking ring preventing cooling air that is in said first portion of said passageway from flowing directly into said combustion chamber without flowing through said second portion of said passageway;wherein said passageway is in fluid communication with said at least one first aperture and said at least one second aperture, said passageway communicates with said premix chamber through said at least one second aperture, and cooling air, after being heated by cooling said ven turi, exits from said passageway into the premix chamber thereby increasing the efficiency of the combustion process and reducing NOx emissions. 2. The low emission combustor of claim 1 wherein said plurality of raised ridges are round in cross section and have a diameter D 1 . 3. The low emission combustor of claim 2 wherein said raised ridges have a diameter D 1 of at least 0.031 inches. 4. The low emission combustor of claim 3 wherein said plurality of raised ridges are spaced along said second generally annular wall by a distance L 1 . 5. The low emission combustor of claim 4 wherein said distance L 1 is between 4 and 15 times diameter D 1 . 6. The low emission combustor of claim 1 wherein said raised ridges immediately adjacent said throat are spaced a distance L 2 from said throat. 7. The low emission combustor of claim 6 wherein said distance L 2 is between 5 and 25 times diameter D 1 . 8. The low emission combustor of claim 1 wherein said angles α 1 and α 3 are at least 40 degrees. 9. The low emission combustor of claim 1 wherein said angle α 2 equals said angle α 4 . 10. The low emission combustor of claim 1 wherein said first radius R 1 < said second radius R 2 . 11. The low emission combustor of claim 10 wherein said second radius is at least 0.150 inches. 12. The low emission combustor of claim 1 wherein said first reduced cross sectional area A 1 is substantially the same as said second reduced cross sectional A 2 . 13. The low emission (NOx) combustor of claim 1 further including a substantially annular bellyband wall radially outward from the first annular wall, and at least one third aperture in said first annular wall, said first portion of said passageway communicating with said second portion of said passageway through said third aperture, wherein said bellyband wall defines a radially outer boundary of the second portion of the passageway. 14. The low emission (NOx) combustor as in claim 13 wherein said at least one first aperture comprises a plurality of first apertures spaced circumferentially about the first annular wall, and each of said first apertures is radially outward of the first portion of the passageway. 15. The low NOx emission combustor of claim 14 wherein said at least one second aperture comprises a plurality of second apertures spaced circumferentially about the first generally annular wall, and each of said second apertures is radially outward of the premix chamber. 16. The low NOx emission combustor as in claim 15 wherein said at least one third aperture comprises a plurality of third apertures spaced circumferentially about the first annular wall, and each of said third apertures is radially outward of the venturi.