WO2013115671A1

WO2013115671A1 - Liquid fuel nozzle for gas turbine and method for injecting fuel into a combustor of a gas turbine

Info

Publication number: WO2013115671A1
Application number: PCT/RU2012/000073
Authority: WO
Inventors: Borys Borysovych SHERSHNYOV; Andrey Pavlovich Subbota
Original assignee: General Electric Company
Priority date: 2012-02-01
Filing date: 2012-02-01
Publication date: 2013-08-08
Also published as: JP2015505596A; CN104094056A; EP2809992A1; RU2014130231A

Abstract

A liquid fuel nozzle assembly for a combustor of a gas turbine including: a pilot nozzle at an end of an inner tube and which discharges liquid fuel from the inner tube into a combustion chamber of the combustor; a deflector coaxial with the pilot nozzle and including a cylindrical section and a frustoconical section; a middle tube coaxial with the inner tube and having an end extending around the cylindrical section of the deflector, wherein a purge air passage is between the middle and inner tubes, wherein an outlet of the purge air passage faces the frustoconical section of the deflector, and a jet nozzle having an annular open end receiving liquid fuel from a fuel passage between the middle tube and an outer tube, wherein the jet nozzle includes an annular array of nozzle passages having an outlets directed to the frustoconical section of the deflector and the nozzle passages are radially inward of an outer rim of the frustoconical section.

Description

LIQUID FUEL NOZZLE FOR GAS TURBINE AND METHOD FOR INJECTING FUEL INTO A COMBUSTOR OF A GAS TURBINE

BACKGROUND OF THE INVENTION

[0001] The invention relates to fuel combustion in a gas turbine, and particularly to liquid fuel nozzles for a combustor in a gas turbine.

[0002] A gas turbine combustor mixes large quantities of fuel and compressed air, burns the resulting mixture and generates combustion gases to drive a turbine. Conventional combustors for industrial gas turbines typically include an annular array of cylindrical combustion "cans" in which air and fuel are mixed and combustion occurs. Compressed air from a compressor, e.g., an axial compressor, flows into the combustor.

[0003] Fuel is injected through fuel nozzle assemblies that extend into each can. The fuel nozzle assemblies may be configures to burn a liquid fuel. These fuel nozzle assemblies typically include liquid atomizing nozzles that spray a metered amount of fuel into the combustion chamber of a can. The fuel nozzle assembly may discharge fuel from a pair of coaxial atomizing nozzles. The fuel may mix as it is discharged from the nozzles to assist with the atomization of the fuel.

[0004] Fuel nozzle assemblies for liquid fuel tend to be complex mechanical devices. There is a long felt need for fuel nozzle assemblies having relative few passages and orifices for fuel and purge gasses, are mechanically simple, are durable and are relatively simple to control.

SUMMARY OF INVENTION [0005] A novel liquid fuel nozzle assembly has been conceived that creates a film of fuel on a conical deflector immediately downstream of nozzles discharging the liquid fuel. Purge air assists in moving the film over the surface of the deflector. As the film flows over the rim of the deflector, the film breaks up into droplets and is atomized. The breaking up and atomization of the fuel is enhanced by the shearing of airblast air directed at the rim of the deflector and the aerodynamic stalling just downstream of the deflector. The use of a fuel film and the interactions of the purge air and airblast air enhance the quality of liquid fuel atomization and the stability of combustion of the fuel. [0006] A liquid fuel nozzle assembly has been conceived and is disclosed herein for a combustor of a gas turbine including: a pilot nozzle at an end of an inner tube and which discharges liquid fuel from the inner tube into a combustion chamber of the combustor; a deflector coaxial with the pilot nozzle and including a cylindrical section and a frustoconical section; a middle tube coaxial with the inner tube and having an end extending around the cylindrical section of the deflector, wherein a purge air passage is between the middle and inner tubes, wherein an outlet of the purge air passage faces the frustoconical section of the deflector, and a jet nozzle having an annular open end receiving liquid fuel from a fuel passage between the middle tube and an outer tube, wherein the jet nozzle includes an annular array of nozzle passages having an outlets directed to the frustoconical section of the deflector and the nozzle passages are radially inward of an outer rim of the frustoconical section.

[0007] A fuel nozzle assembly has been conceived and is disclosed herein for a gas turbine, the assembly comprising: a pilot nozzle at an end of a liquid fuel center tube; a middle tube coaxial and extending around the center tube, wherein an annular passage for purge air is between the middle tube and center tube; a deflector including a cylindrical section and a frustoconical section extending outwardly from the cylindrical section, wherein the cylindrical section seats on an outer annular surface of the pilot nozzle, is coaxial to the pilot nozzle and includes openings to duct purge air from an outer surface of the cylindrical section to an inner annular duct formed between the cylindrical section and the pilot nozzle; the annular passage for purge air extends to between the middle tube and the outer surface of the cylindrical section of the deflector, wherein the outlet of the annular passage is proximate to a junction between the cylindrical section and the frustoconical section of the deflector; and a jet nozzle having an annular open end configured to receive liquid fuel from a fuel passage between the middle tube and an outer tube, wherein the jet nozzle includes an annular array of nozzle passages having an outlet aligned with the frustoconical section of the deflector and the nozzle passages are radially inward of an outer rim of the frustoconical section.

[0008] A method has been conceived and is disclosed herein to atomize liquid fuel being discharged by a fuel nozzle assembly in a combustor of a gas turbine comprising: discharging purge air along an outer surface of a deflector at an discharge end section of the fuel nozzle assembly, wherein the deflector has a cylindrical section and frustoconical section extending outwardly of the cylindrical section and the outer surface at least includes the surface of the frustoconical section facing the discharging purge air; discharging the liquid fuel onto the outer surface of the deflector, wherein the liquid fuel forms a film on the outer surface and the purge air flowing over the outer surface moves the liquid fuel over the outer surface; as the film of liquid fuel flows over a rim of the frustoconical section, the liquid fuel is atomized; directing airblast air towards a rim of the frustoconical section to enhance the atomization of the liquid fuel, and combusting the liquid fuel, airblast air and purge air in a combustion zone downstream of the fuel nozzle assembly. BRIEF DESCRIPTION OF THE INVENTION

[0009] The structure, operation and features of the invention are further described below and illustrated in the accompanying drawings which are:

[0010] FIGURE 1 is a cross-sectional diagram of a conventional combustor in an industrial gas turbine.

[001 1] FIGURE 2 is a cross-sectional diagram of a fuel nozzle assembly mounted to an end casing of combustion can in an industrial gas turbine.

[0012] FIGURE 3 is a cross-sectional diagram of an outlet region of the fuel nozzle assembly shown in Figure 2. [0013] FIGURE 4 is a side view showing in cross-section the pilot nozzle and deflector mounted on the fuel nozzle assembly.

[0014] FIGURE 5 is a side view of a cross-section of a jet nozzle which is a component of the fuel nozzle assembly.

[0015] FIGURE 6 is a perspective view of a cross-section of deflector which is a component of the fuel nozzle assembly.

[0016] FIGURE 7 is a cross-sectional view of the side of the fuel nozzle assembly, wherein the view is directed to the pilot nozzle and deflector.

DETAILED DESCRIPTION OF THE INVENTION

[0017] FIGURE 1 is side view, showing in partial cross section, a turbine engine 10 including an axial turbine 12, an annular array of combustors 14, and an axial compressor 16. A working fluid 18, e.g., atmospheric air, is pressurized by the compressor and ducted to each of the combustors 14. An end of each combustor is coupled to manifolds which deliver liquid fuel 20 and a purge gas 22, e.g., atmospheric air under pressure, to the combustors. The fuel and purge gas flow through fuel nozzle assemblies 24 in each combustion chamber, mix with the pressurized working fluid and combust in a combustion chamber 26 of each combustor. Combustion gases 28 flow from the combustion chamber through a duct 30 between the combustion chamber and the turbine to drive buckets (blades) 32 of the turbine and turn a shaft of the gas turbine. The rotation of the shaft drives the compressor 16 and transfers useful output power from the gas turbine. [0018] Each combustor 14 has an outer cylindrical casing 34. Compressed air from the compressor, e.g., the working fluid 18, flows through an annular duct 40 in the combustor formed between a cylindrical sleeve 36 and a cylindrical combustion liner 38. The combustion chamber 26 is within the hollow liner of the combustor. The compressed air flows in a counter-current direction to the flow of combustion gases through the combustion zone

[0019] An end cover 42 caps each combustor at an end opposite to the duct 30 for hot combustion gases. The end cover supports couplings 44 to manifolds that provide the liquid fuel 20 and passive purge air 22 to each combustor. The end cover 42 includes passages which direct the liquid fuel 20 and purge air 22 to the fuel nozzle assemblies 24.

[0020] FIGURE 2 is a cross-sectional diagram of a fuel nozzle assembly 24 mounted to the end cover 42 of a combustion can in a gas turbine. The fuel nozzle assembly is attached to a mounting flange 46 that seats on a front surface of the end cover 42. A conical base 49 supports a set of concentric tubes through which flow liquid fuel and purge air. An inner tube 50 forms a generally straight passage for the liquid fuel or liquid fuel emulsion (collectively referred to herein as liquid fuel). An example of a liquid fuel emulsion is a diesel emulsion, such as an emulsion of water in diesel fuel mixture. The liquid fuel 20 is supplied through a coupling to an inlet 52 of the inner tube, flows through the tube and is discharged through a pilot nozzle 54 at the front of the fuel nozzle assembly. [0021] Purge air 22 flows under pressure through a coupling to the fuel nozzle assembly and into an annular purge air passage 58 which is coaxial to the inner tube 50. The purge air passage 58 is defined between the inner tube 50 and a middle tube 60 concentric to the inner tube.

[0022] The liquid fuel flows through a second fuel passage 62 in addition to flowing through the inner tube. The second fuel passage 62 is an annular passage defined by the middle tube 60 and an outer tube 64. The second fuel passage and the first fuel passage feed liquid fuel to a dual fuel nozzle arrangement at the front (discharge) end of the fuel nozzle assembly. A first fuel nozzle is the pilot nozzle 54 at the center axis of the fuel nozzle assembly. A second fuel nozzle is a jet nozzle 84 at the discharge end of the second fuel passage 62. The pilot nozzle 54 and jet nozzle 84 discharge liquid fuel from the front end of the fuel nozzle assembly.

[0023] As the liquid fuel is discharged by the pilot and jet nozzles, purge air discharged from the purge air passage 58 mixes with and assists in atomizing the liquid fuel. The atomized liquid fuel and air combusts downstream of the end of the fuel nozzle assembly and as the mixture of fuel and purge air enters the combustion zone in the combustor.

[0024] Airblast air 68 assists in atomizing the fuel being discharged from the fuel nozzles and provides additional air for combustion and mixing with the combustion gases. The airblast air passage 66 is coaxial to the tubes 50, 60, 64 transporting fuel and purge air to the combustion zone. An airblast air passage 66 may be an annular passage that directs airblast air 68 to the discharge end of the fuel nozzle assembly. The airblast air passage may be divided into multiple annular passages. Air ports 69 (fig. 3) in tubes separating the airblast air passages allow the diffusion air to flow between and through these passages. [0025] An air tube 70 may surround the tubes 50, 60, 64, and extends slightly downstream of the discharge ends of these tubes. The air tube directs compressed air 76 flowing from the annular duct 40 (Fig. 1) to a discharge end 78 which is adjacent the combustion chamber 26. The air tube 70 may include annular turning guide vanes 72 which turn the air flowing from the duct 40 into the air tube and parallel to the axis of the fuel nozzle assembly. The air tube 70 may include swirlers 74 that impart a swirling rotation to the compressed air flowing through the tube.

[0026] FIGURE 3 is a cross-sectional diagram of an outlet region of the fuel nozzle assembly 24. The liquid fuel flowing through the center tube 50 passes through and is discharged by an exit orifice 80 in the pilot nozzle 54. The exit orifice 80 may be coaxial with the axis of the fuel nozzle assembly. The pilot nozzle is attached to the end of the inner tube 50. The pilot nozzle may be generally cylindrical with a conical nose with the center nozzle at its tip. The liquid fuel discharged from the pilot nozzle flows towards the combustion chamber 26 downstream of the end of the fuel nozzle assembly. The pilot nozzle may have channels or vanes 104 (Fig. 4) to impart a swirl to the fuel as it flows through the center nozzle. The swirl assists in causing the fuel sprayed from the exit orifice 80 to expand radially out from the centerline of the nozzle in a conical spray pattern. [0027] Liquid fuel flowing through the second fuel passage 62 discharges through the annular jet nozzle 84 attached to the end of the outer tube 64. The annular jet nozzle may include a circular array of nozzle passages 86 through which the liquid fuel flows from the second fuel passage 62 into a surface 88 of the deflector 48.

[0028] The nozzle passages 86 may be circular in cross-section. The nozzle passages may be oriented with a yaw of 5 to 25 degrees with respect to an axis of the center tube. The yaw angle of the nozzle passages impart a swirl to the fuel flowing from the jet nozzle. The direction of swirl from the jet nozzle may be the same rotational direction as the swirls in the fuel discharged from the center nozzle, and the swirl imparted by the fuel nozzle assembly to the air flows, e.g., purge air and main combustion air. [0029] The liquid fuel is discharged by the nozzle passages 86 such that the fuel forms a film on the outer surface 88 of the conical section 1 14 of the deflector 48. The film of fuel flows over the outer surface 88 of the deflector and flows off the outer circular edge rim of the deflector. From the rim 92, the fuel is atomized and enters the combustion chamber. [0030] The purge air flowing through the purge air passage 58 is split by a cylindrical section 93 of the deflector. The deflector directs a first stream of the purge air to the surface 88 of conical section 114 the deflector. The purge air flowing over the outer surface 88 to assist in moving the fuel film over the outer surface 88 and off the rim 92. [0031] The cylindrical section 93 of the deflector directs a second stream of purge air along the outer conical surface of the pilot nozzle to the discharge region of the exit orifice 80. The second stream flows from passage 58 through openings 96 arranged in the cylindrical section and into an annular passage 108 (Fig. 4) formed between the inside surface of the deflector and an outer surface of the pilot nozzle. The second stream mixes with the fuel spray discharged from the pilot nozzle to assist in atomizing the fuel and cools deflector 48. [0032] Airblast air flows through nozzles 82 that discharge the airblast air into a frustoconical cavity 90 formed in the outer cylindrical tube 94 at the end of the tube. The nozzles 82 for the airblast air may be canted with respect to the axis of the fuel nozzle assembly to impart a swirl to the airblast air as it enters the cavity. The pilot nozzle 54, deflector 48 and jet nozzle 84 may also be within the cavity 90. The outer rim 92 of the deflector may be aligned with end of the outer tube.

[0033] FIGURE 4 is a cross-sectional view of the pilot nozzle 54, deflector 48 and jet nozzle 84 mounted on the front of the fuel nozzle assembly 24. This figure illustrates the spatial relationship between the pilot nozzle, deflector and jet nozzle, as well as the flow of purge air over the deflector and the flow of liquid fuel through the exit orifice 80 and also through the jet nozzle and over the outer surface 88 of the deflector.

[0034] The pilot nozzle is attached to the end of the inner tube 50 and discharges a spray of liquid fuel along a centerline axis of the tube 50. The pilot nozzle 54 may fit over the end of the inner tube and held to the tube by a brazing 100. Liquid fuel 102 flows through the inner tube, through a s wirier 104 and out the exit orifice 80 of the pilot nozzle.

[0035] The outer cylindrical surface of the pilot nozzle 54 supports an annular inner surface 106 of an end of the cylindrical portion 93 of the deflector. A passage 108 for purge air is formed between the outer cylindrical surface of the pilot nozzle and the annular inner surface 106. Purge air from the purge air passage 58 reaches the passage 108 through an annular array of openings 96 in the cylindrical portion of the deflector. The annular passage 108 turns radially inward to conform to the conical nose portion of the pilot nozzle and a frustoconical section 1 10 of the deflector. The purge air 1 12 flows from the end of the passage 108 and towards the outlet of the exit orifice 80 from which liquid fuel flows. The purge air may flow from all directions (360 degrees) towards the liquid fuel exiting from the exit orifice 80. The impingement of the purge air 112 on the fuel assists in atomizing the liquid fuel being discharged from the exit orifice 80. [0036] The purge air flowing through passage 58 also flows through a passage 1 16 formed between the outer surface of the cylindrical portion 93 of the deflector and a cylindrical portion 1 18 of the jet nozzle. The cylindrical portion 118 extends axially from the end of the middle tube. The rear end of the cylindrical portion 1 18 may include an end 1 19 (Fig. 5) with annular steps that fits on a stepped end of the middle tube. At the front end of the cylindrical portion, the inside surface may include ribs 120 that extend radially inwardly and abut against the outer surface of the cylindrical section 93 of the deflector. The ribs 120 support the front of the cylindrical extension 1 18. The ribs may be parallel to the axis of the middle tube 60 or may be canted with respect to the axis. Canting of the ribs may be used to impart a swirl to the purge air 122 as the air exits the jet nozzle and flows along the outer surface 88 of the frustoconical section 1 14 of the deflector. The direction of swirl of the purge air may in the same direction, e.g., concurrent swirl, of a swirl applied to the liquid fuel being discharged through the canted holes 86 of the jet nozzle 84. [0037] As the purge air flows from the passage 1 16, the air 122 flows over the outer surface 88 of the outwardly extending frustoconical section 114 of the deflector. The air 122 flowing over the outer surface 88 assists in moving the film of liquid fuel 124 that is also flowing over surface 88. The air 122 may form a barrier air layer between the fuel and surface 88 of the deflector. The purge air 122 assists in transporting the film of fuel 124 radially outward along the surface 88 of the frustoconical section 1 14 of the deflector. The purge air 122 may accelerate the flow of the film of fuel 124 towards the outer circular rim 92 of the frustoconical section 114 of the deflector.

[0038] As the films of fuel and purge air flow over the rim 92, the fuel and air leave the surfaces of the fuel nozzle assembly and enters the combustion chamber 26, shown in Fig. 1. As the fuel flows over the rim 92, the fuel is atomized into droplets 126 by the purge air which may be swirling to assist in atomization. In addition, the airblast air 68 flowing from the airblast air passage 66 and through the cavity 90 at the end of fuel nozzle assembly impinges on the rim 92 of deflector. The impinging airblast air 68 assists in atomizing the liquid fuel by shearing the film of fuel off the rim 92 of the deflector.

[0039] Fuel droplets flowing over the rim 92 of the deflector may be entrained in a stalling or stagnant fluid flow immediately downstream of the frustoconical section 114 of the deflector. This zone of aerodynamic stalling and stagnant air assists in a quick and efficient combustion of the fuel. [0040] FIGURE 5 is a perspective view of a cross-section of the jet nozzle 84. The jet nozzle includes a cylindrical portion 1 18 having an open end with steps 1 19 to seat on the open end of the middle tube 60. At the front of the jet nozzle, the ribs 120 may be trapezoidal in cross-section and each have a flat surface that abuts against the outer surface of the cylindrical portion 93 of the deflector. Between the ribs are channels 127 that allow the purge air to flow past the end of the jet nozzle and over the conical surface 88 of the deflector. The ribs and channels may be canted to impart a swirl to the purge air flowing through the jet nozzle. The height of the ribs and width of the channels may be used to define the size of the air flow passages from the jet nozzle. [0041] A partially frustoconical nose 128 of the jet nozzle overlaps a front portion of the cylindrical portion 1 18. The open end of the nose attaches to the end of the outer tube 64. The open end of the nose may have a step that forms a lip 130 that engages an step on the end of the outer tube. The nose may be tapered radially inward to a front annular face 132. The fuel holes 86 open at the face to allow liquid fuel to flow from the jet nozzle and onto the outer surface 88 of the deflector. An annular cavity 132 formed between the cylindrical portion 1 18 of the jet nozzle and the overlapping frustoconical portion 128 provide a liquid fuel passage extending between the second fuel passage 62 and the holes 86.

[0042] The holes 86 may be canted with respect to the axis of the tubular passages 50, 60 and 64, wherein the angle may correspond to the angle of the channel 127 on the annular inward surface of the jet nozzle. The canted angles for the fuel holes 86 and channel 127 may be uniform and between 10 to? 45 degrees, for example.

[0043] FIGURE 6 is a perspective view of a cross-section of deflector 48, wherein the cross-section taken along the axis of the deflector. The deflector may be formed of a metallic material, such as stainless steel, or a ceramic. The deflector may be formed by machining or casting.

[0044] The cylindrical portion 93 of the deflector may include an annular interior surface 106 which includes a raised step 132 that seats on the outer surface of the pilot nozzle 54. The height of the step 132 may also be used to define the width of the purge air passage 108, which is shown in Figure 4.

[0045] The annular array of openings 96 in the cylindrical portion 93 of the deflector direct purge air into the purge air passage 108. The openings may be angled, e.g., between 15 to 45 degrees, with respect to a radial line from the axis. The angle of the openings may be set to impart a swirling flow to the purge air flowing through the nozzles and into the passage 108. [0046] The front of the deflector includes the outwardly extending frustoconical section 114 and the inwardly extending frustoconical section 1 10. The rim 92 on the outwardly extending frustoconical section 1 14 may be relatively thin and circular in cross section. [0047] The inward frustoconical section 1 10 may taper inward at an angle conforming to the taper on the nose of the pilot nozzle 54, in Figure 4. The annular opening 134 at the front of the inward frustoconical section 1 10 may be sufficiently large to allow the nose of the pilot nozzle to extend through the opening. The opening 134 may be aligned with the exit orifice 80 in the pilot nozzle or set back axially from the exit orifice, as shown in Figure 4.

[0048] FIGURE 7 is a cross-sectional view of the side of the fuel nozzle assembly, wherein the view is directed to the pilot nozzle 54, deflector 48 and jet nozzle 84. The surface 88 of the outer frustoconical section 1 14 may be coated with a fuel or carbon phobic coating. The phobic coating causes the fuel 124 flowing from the holes 86 to tend to not stick to the surface 88 of the deflector. The fuel forms a film over the surface 88 and the film flows freely over the surface and off the edge 92 of the deflector. The flow of purge air 122 forms an air film over the surface 88 of the deflector which also assists in preventing the fuel from sticking to the surface 88. [0049] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A liquid fuel nozzle assembly for a combustor of a gas turbine including: a pilot nozzle at an end of an inner tube and which discharges liquid fuel from the inner tube into a combustion chamber of the combustor; a deflector coaxial with the pilot nozzle and including a cylindrical section and a frustoconical section; a middle tube coaxial with the inner tube and having an end extending around the cylindrical section of the deflector, wherein a purge air passage is between the middle and inner tubes, wherein an outlet of the purge air passage faces the frustoconical section of the deflector, and a jet nozzle having an annular open end receiving liquid fuel from a fuel passage between the middle tube and an outer tube, wherein the jet nozzle includes an annular array of nozzle passages having an outlets directed to the frustoconical section of the deflector and the nozzle passages are radially inward of an outer rim of the frustoconical section.

2. The fuel nozzle assembly as in claim 1 wherein the deflector includes a second frustoconical section extending inwardly of the cylindrical section, wherein an annular air passage is formed between the second frustoconical section and a tapered nose of the pilot nozzle.

3. The fuel nozzle assembly as in claim 1 or 2 further comprising an annular passage for airblast air, wherein the outlet of the annular passage directs airblast air against the rim of the deflector.

4. The fuel nozzle assembly as in nay of claims 1 to 3 wherein the nozzle passages in the jet nozzles are oriented with a yaw of 5 to 25 degrees with respect to an axis of the center tube.

5. The fuel nozzle assembly as in any of claims 1 to 4 wherein a surface of the frustoconical portion of the deflector is coated with a fuel phobic composition.

6. The fuel nozzle assembly as in any of claims 1 to 5 further comprising a cavity formed within a hollow end region of the outer tube, wherein the cavity is open to a combustion zone at the end of the outer tube and the ends of the jet nozzle and deflector are within the cavity.

7. The fuel nozzle assembly as in claim 6 wherein an outer rim of the deflector is downstream of the cavity.

8. A fuel nozzle assembly for a gas turbine, the assembly comprising: a pilot nozzle at an end of a liquid fuel center tube; a middle tube coaxial and extending around the center tube, wherein an annular passage for purge air is between the middle tube and center tube; a deflector including a cylindrical section and a frustoconical section extending outwardly from the cylindrical section, wherein the cylindrical section seats on an outer annular surface of the pilot nozzle, is coaxial to the pilot nozzle and includes openings to duct purge air from an outer surface of the cylindrical section to an inner annular duct formed between the cylindrical section and the pilot nozzle; the annular passage for purge air extends to between the middle tube and the outer surface of the cylindrical section of the deflector, wherein the outlet of the annular passage is proximate to a junction between the cylindrical section and the frustoconical section of the deflector, and a jet nozzle having an annular open end configured to receive liquid fuel from a fuel passage between the middle tube and an outer tube, wherein the jet nozzle includes an annular array of nozzle passages having an outlet aligned with the frustoconical section of the deflector and the nozzle passages are radially inward of an outer rim of the frustoconical section.

9. The fuel nozzle assembly as in claim 8 wherein the deflector includes a second frustoconical section extending inwardly of the cylindrical section, wherein an annular air passage is formed between the second frustoconical section and a tapered nose of the pilot nozzle.

10. The fuel nozzle assembly as in claim 8 or 9 further comprising an annular passage for airblast air, wherein the outlet of the annular passage is aligned to direct airblast air against the rim of the deflector.

1 1. The fuel nozzle assembly as in any of claims 8 to 10 wherein the nozzle passages in the jet nozzles are oriented at a yaw angle of 5 to 25 degrees with respect to an axis of the center tube.

12. The fuel nozzle assembly as in any of claims 8 to 11 wherein a surface of the frustoconical portion of the deflector is coated with a fuel phobic composition.

13. The fuel nozzle assembly as in any of claims 8 to 12 further comprising a cavity formed within a hollow end region of the outer tube, wherein the cavity is open to a combustion zone at the end of the outer tube and the ends of the jet nozzle and deflector are within the cavity.

14. The fuel nozzle assembly of claim 13 wherein a rim of the frustoconical section of the deflection is downstream of the cavity.

15. A method to atomize liquid fuel being discharged by a fuel nozzle assembly in a combustor of a gas turbine comprising: discharging purge air along an outer surface of a deflector at an discharge end section of the fuel nozzle assembly, wherein the deflector has a cylindrical section and frustoconical section extending outwardly of the cylindrical section and the outer surface at least includes the surface of the frustoconical section facing the discharging purge air; discharging the liquid fuel onto the outer surface of the deflector, wherein the liquid fuel forms a film on the outer surface and the purge air flowing over the outer surface moves the liquid fuel over the outer surface; as the film of liquid fuel flows over a rim of the frustoconical section, the liquid fuel is atomized; directing airblast air towards a rim of the frustoconical section to enhance the atomization of the liquid fuel, and combusting the liquid fuel, airblast air and purge air in a combustion zone downstream of the fuel nozzle assembly.

16. The method of claim 15 wherein the discharge of the liquid fuel on the outer surface of the deflector occurs in a cavity a hollow end region of a tube included in the fuel nozzle assembly, wherein the cavity is open to the combustion zone.

17. The method of claim 16 or 15 further comprising discharging the film of the liquid fuel from the rim, wherein the rim is downstream of the cavity.

18. The method of any of claims 15 to 17 wherein the liquid fuel discharged on the outer surface is discharged with a swirling motion about an axis of the deflector, and the purge gas is discharged onto the deflection with a swirling motion in a same rotational direction as the swirl of the liquid fuel.

19. The method of any of claims 15 to 18 further comprising splitting the purge air into a first stream which flows over the outer surface of the deflector and into a second stream which is directed to the liquid fuel being discharged by a pilot nozzle aligned with an axis of the fuel nozzle assembly.

20. The method of any of claims 15 to 19 wherein the discharging of the liquid fuel imparts a swirling motion to the liquid fuel and the discharging of the purge air along the outer surface impart a swirling motion to the purge air which is in the same rotational direction as the swirling motion of the liquid fuel.