Aerating Fuel Nozzle

Abstract

An aerating fuel nozzle for a gas turbine engine combustion chamber. The nozzle has an annular fuel swirl chamber from which the fuel issues in a spray cone, blending with inner and outer layers of swirling air. Air from the engine compressor is mixed with the fuel to obtain a high degree of air-fuel blending close to the nozzle, thus promoting cleaner and more complete combustion.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to gas turbine engines, and more particularly to aerating nozzles which deliver fuel to the combustion chambers of such engines. The invention is particularly useful in the newer types of gas turbine engines which operate at higher temperatures, but the principles of the invention are also applicable to all types of gas turbine engines to achieve more even temperature distribution around the combustion chamber and improved performance, as well as smoke reduction because of clearer and more complete burning.

2. Description of the Prior Art

The prior art is exemplified by Grundman U.S. Pat. No. 3,310,240 and Gradon et al. U.S. Pat. No. 3,489,059. The Grundman nozzle is of the air atomizing type using relatively high air pressure, and furthermore does not teach swirl chamber configurations which achieves the very high degree of air-fuel blending of the present invention. The Gradon nozzle is not of the aerating or air atomizing type, and is therefore even less pertinent.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, the fuel nozzle uses a larger volume of burner inlet air to provide fuel atomization without any auxiliary air pressure increasing device. In one embodiment of the invention, a central primary fuel orifice is located at the exit of a swirl chamber while an annular secondary fuel swirl chamber and orifice are located outwardly of the primary orifice. An air swirl chamber surrounds the primary fuel chamber, and two air swirl chambers are disposed inwardly and outwardly of the secondary fuel chamber. The exit portions of all chambers are of frustoconical shape to increase the velocity of the air or fuel swirling therein, and the exits are so located as to create a very high degree of blending of the air and fuel. In another embodiment of the invention, the primary fuel delivery system is omitted, since the degree of air-fuel blending has been found so complete in some cases as to make unnecessary the provisions of a primary fuel system for starting or high altitude operation. The air swirl chambers are in communication with the space surrounding the nozzle, which receives air from the engine compressor. The ratio of inner to outer air surrounding the secondary fuel spray cone, as well as the relative axial positioning of the orifices are selected so as to obtain optimum mixing efficiency and fuel-air ratios, thus making possible a complete burning close to the nozzle, rather than downstream as in previous constructions.

The nozzle of this invention has been proven to give improved combustion performance because of the cleaner and more complete burning which imparts more even temperature distribution around the combustion chamber. The gas turbine engine can thus be operated at relatively higher temperatures without the use of more expensive or exotic materials. Even fuel distribution thus results in a higher engine efficiency. Another advantage of the invention is the significant reduction of smoke (unburned hydrocarbons) issuing from the engine, and contributing to air pollution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view in elevation of one embodiment of the invention having both primary and secondary fuel systems, the tangential passages being shown in full for purposes of clarity; and

FIG. 2 is a view similar to FIG. 1 of another embodiment of the invention having only one fuel system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to the embodiment of FIG. 1, the nozzle is generally indicated at 11 and is mounted in a gas turbine engine combustion chamber partially indicated at 12. The nozzle is secured to a nozzle support generally indicated at 14 and comprising two sections 15 and 16. Section 15 has a primary fuel passage 18 and a secondary fuel passage 19, and an adaptor insert 20 is brazed at spaced locations 21 and 22 to sections 15 and 16 respectively. Insert 20 has a central passage 23 connected to passage 18.

A primary body 24 is welded to the outer end of insert 20 and has a primary fuel swirl chamber 25 of frustoconical shape, ending in an orifice 26. A primary insert 27 having tangential slots 28 is mounted in chamber 25, being held in position by a spring 29. The primary fuel will flow from passage 23 through a screen filter assembly 31 to slots 28 and chamber 25, being sprayed from orifice 26.

A secondary body 32 is threadably mounted on support section 16 and welded thereto at 33. This body holds an insert 34 against the face 35 of section 16 to form a metal-to-metal seal. An annular passage 36 in insert 34 receives secondary fuel from a plurality of circumferentially spaced passages 37 in section 16 leading from passage 19. A series of circumferentially spaced tangential secondary fuel ports 38 lead from annular chamber 36 to a secondary swirl chamber 39 formed between body 32 and insert 34. Ports 38 are of a predetermined size whereby the fuel will flow at certain rates depending upon the pressure so as to follow a desired fuel flow curve. The first portion of annular chamber 39 is cylindrical in shape and the latter portion is frustoconical, a lip 41 being formed on body 32 over which the fuel will flow to form a spray cone.

A plurality of circumferentially spaced air passages 42 extend through support section 16 from the chamber 43 surrounding nozzle 11 to an annular passage 44 between inserts 20 and 34. Chamber 43 receives air from the gas turbine compressor which flows toward combustion chamber 12. The air in chamber 44 flows past a plurality of inner air swirl vanes 45 formed on and extending outwardly from primary body 24. A portion of this air flows into a frustoconical chamber 46 formed at the outer end of insert 34 and past a lip 47 on this insert. It will be observed that lip 47 is disposed axially inwardly of secondary fuel lip 41 so that the air flowing past lip 47 will intermix with the spray cone issuing from secondary swirl chamber 39. Another portion of the air flowing past swirl vanes 45 will be diverted by a deflector 48 into a series of apertures 49 from where it will pass into a primary air chamber 51, flowing past a lip 52 to intermix with the primary fuel spray cone. Deflector 48 is supported by a heat shield 53 which is mounted on primary body 24 and forms chamber 51.

A plurality of tangential outer air swirl slots 54 are formed in the outer portion of secondary body 32 and lead to a secondary air swirl chamber 55 formed by the frustoconical portion of a shroud 56. This shroud is mounted on secondary body 32. The lip 57 formed on shroud 56 at the exit of chamber 55 is spaced axially outwardly of secondary fuel lip 41 and is so located that the air issuing from chamber 55 will intermix with the secondary fuel. It will be observed that the frustoconical portions of all the swirl chambers will increase the velocity and therefore the centrifugal forces on the air or fuel flowing therethrough.

In operation, primary fuel will issue past lip 52 and secondary fuel past lip 41, the fuel forming hollow spray cones. The air issuing past lip 52 will intermix with the primary fuel spray cone while the secondary fuel will be intermixed with air issuing from chambers 46 and 55. The volume of air flowing, the ratio of inner and outer air to the secondary fuel, and the relative axial locations of the fuel and air lips will be so chosen as to achieve optimum fuel/air mixing, thus obtaining a proper fuel-air ratio and relatively complete combustion very close to the nozzle. The configuration of the nozzle chambers and lips is such as to obtain near perfect blending of air and fuel.

FIG. 2 shows a modification of the invention in which the primary fuel system is omitted. Normally the primary fuel system is needed during starting of the engine, when relatively low fuel flow is required, and also at high altitudes, in which case thinner air is being fed to the engine. However, because of the excellent action of this aerating nozzle it has been found that in some cases the engine can be started, and operated at high altitudes, using only the secondary fuel system.

Accordingly, FIG. 2 shows a nozzle generally indicated at 201 mounted in a combustion chamber indicated partially at 202. The nozzle has a support member 203 with a fuel passage 204 and a heat shield 205. A body is indicated at 206 and is threadably mounted on support 203 as well as being welded thereto at 207. The body holds an insert 208 in alignment with a heat shield 209 through which air will flow from the space 211 surrounding the combustion chamber. Insert 208 has a plurality of inner swirl vanes 212 and a frustoconical portion 213, the air flowing past the lip 214.

The fuel from passage 204 is fed through an annular chamber 215 to a plurality of tangential metering apertures 216 in body 206. A fuel swirl chamber 217 is formed between body 206 and insert 208, the outer portion of this chamber being frustoconical in shape and having a lip 218 formed on member 206 past which the fuel will flow to form a spray cone.

A plurality of circumferentially spaced outer air swirl slots 219 are formed in body 206 and lead to an outer air swirl chamber 221 formed by an air shroud 222. This shroud is mounted on body 206. Chamber 221 is frustoconical in shape and leads to a lip 223 on shroud 222 past which the air will flow to intermix with the fuel spray cone. It will be noted that, as in the previous embodiment, lip 223 of the outer air swirl chamber is located axially outwardly of secondary fuel lip 218 whereas lip 214 of the inner air chamber is axially inwardly of the fuel lip.

Claims

What is claimed is:

1. In a gas turbine engine having a burner and a chamber receiving compressor discharge air and feeding said air to the burner, an aerating nozzle using burner inlet air only to obtain optimum fuel atomization without any auxiliary air pressure increasing device, comprising an annular fuel swirl chamber having a first lip at its outer end past which the fuel will flow to form a spray cone entering the burner, an inner air chamber inwardly of said fuel chamber, means swirling the air entering the inner air chamber, an annular outer air chamber surrounding said fuel chamber, second and third lips at the outer ends of said air chambers separate from said first lip past which air will flow to intermix with said fuel spray cone, whereby fuel and air mixing will occur externally of said lips, and a plurality of circumferentially spaced passages having their entrances leading from said compressor discharge chamber and conducting engine compressor discharge air to each of said air chambers in sufficient volume to achieve the optimum fuel-air mixing.

2. The combination according to claim 1, the lip of said inner air chamber being axially inwardly of said fuel lip and the lip of said outer air chamber being axially outwardly of the fuel lip.

3. The combination according to claim 2, said nozzle being provided with tangential passages leading to said fuel chamber comprising swirl vanes.

4. The combination according to claim 1, portions of said chambers being frustoconical in shape to increase the velocity of the air or fuel therein.

5. The combination according to claim 4, the lip of said inner air chamber being axially inwardly of said fuel lip and the lip of said outer air chamber being axially outwardly of the fuel lip.

6. The combination according to claim 1, the diameters of said lips being substantially greater than their axial dimensions whereby the space within said lips is in non-confining relation with the fuel passing therethrough.

7. In a gas turbine engine, an aerating nozzle using burner inlet air only to obtain optimum fuel atomization without any auxiliary air pressure increasing device, comprising an annular fuel swirl chamber having a lip at its outer end past which the fuel will flow to form a spray cone, an inner air chamber inwardly of said fuel chamber, an annular outer air chamber surrounding said fuel chamber, lips at the outer ends of said air chambers past which air will flow to intermix with said fuel spray cone, passages conducting engine compressor discharge air to said air chambers in sufficient volume to achieve the optimum fuel-air mixing, said fuel chamber being part of a secondary fuel system, a primary fuel system comprising a frustoconical primary fuel chamber inwardly of said inner air swirl chamber, a primary air chamber between said primary fuel chamber and said inner air swirl chamber, and means for deflecting a portion of the air flowing through said inner air swirl chamber to said primary air chamber, the latter chamber having a lip surrounding the outlet orifice of said primary fuel chamber.

8. In a gas turbine engine, an aerating nozzle using burner inlet air only to obtain optimum fuel atomization without any auxiliary air pressure increasing device, comprising an annular fuel swirl chamber having a lip at its outer end past which the fuel will flow to form a spray cone, an inner air swirl chamber inwardly of said fuel chamber, an annular outer air swirl chamber surrounding said fuel chamber, portions of said chambers being frustoconical in shape to increase the velocity of the air or fuel swirling therein, lips at the outer ends of said air chambers past which air will flow to intermix with said fuel spray cone, passages conducting engine compressor discharge air to said air swirl chambers in sufficient volume to achieve the optimum fuel-air mixing, said fuel chamber being part of a secondary fuel system, a primary fuel system comprising a frustoconical primary fuel chamber inwardly of said inner air swirl chamber, a primary air chamber between said primary fuel chamber and said inner air swirl chamber, and means for deflecting a portion of the air flowing through said inner air swirl chamber to said primary air chamber, the latter chamber having a lip surrounding the outlet orifice of said primary fuel chamber.

9. In an aerating nozzle for gas turbine engines, an annular fuel swirl chamber having a lip at its outer end past which the fuel will flow to form a spray cone, an inner air swirl chamber inwardly of said fuel chamber, an annular outer swirl chamber surrounding said fuel chamber, portions of said chambers being frustoconical in shape to increase the velocity of the air or fuel swirling therein, lips at the outer ends of said air chambers past which air will flow to intermix with said fuel spray cone, passages conducting air to said air swirl chambers in sufficient volume to achieve the optimum fuel-air mixing, said fuel chamber being part of a secondary fuel system, a primary fuel system comprising a frustoconical primary fuel chamber inwardly of said inner air swirl chamber, a primary air chamber between said primary fuel chamber and said inner air swirl chamber, and means for deflecting a portion of the air flowing through said inner air swirl chamber to said primary air chamber, the latter chamber having a lip surrounding the outlet orifice of said primary fuel chamber.