WO2000019146A2

WO2000019146A2 - Fuel spray nozzle

Info

Publication number: WO2000019146A2
Application number: PCT/CA1999/000862
Authority: WO
Inventors: Lev A. Prociw; Dany Gaudet
Original assignee: Pratt and Whitney Canada Corp
Current assignee: Pratt and Whitney Canada Corp
Priority date: 1998-09-24
Filing date: 1999-09-21
Publication date: 2000-04-06
Anticipated expiration: 2001-03-24
Also published as: WO2000019146A3

Abstract

A swirler for a fuel spray nozzle comprises a body (30) having a longitudinal axis and an annular array of V-shaped slots (58) defined on a frusto-conical portion (56) thereof. The frusto-conical portion is adapted to be engaged with an annular mating inner surface (60) of the fuel spray nozzle to define therewith a plurality of fluid swirl passages. By having V-shaped slots rather than the conventional square or rectangular slots, a range of swirlers having different flow characteristics may be produced with a unique cutting tool.

Description

FUEL SPRAY NOZZLE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel spray nozzles and, more particularly, pertains to a new swirl member for such nozzles. 2. Description of the Prior Art Liquid spray nozzles are used in a wide variety of applications. For instance, in a conventional gas turbine engine, fuel nozzles are provided for supplying atomised fuel and air mixture in the combustion area of the gas turbine engine. Generally, the fuel nozzles are mounted at circumferentially spaced-apart locations on a combustor wall of a combustion chamber. In such an arrangement, all fuel nozzles must supply exactly the same quantity of fuel in order to promote efficient burning of the fuel in the combustion chamber. Furthermore, it is also important that the fuel and the air supplied to the combustion chamber be appropriately mixed. It is known that by imparting a swirl to the fuel and to the air, a relatively high degree of air-fuel blending can be achieved. The swirl can be provided by passing the fluid through a plurality of swirl vanes disposed in a fluid conduit or, alternatively, through a plurality of skewed or converging swirl passages.

United States Patent No. 3,302,399, issued February 7, 1967 to Tini et al . , discloses a fuel spray nozzle having a swirl member disposed within a cylindrical cavity defined in an external body. The swirl member is provided with a FRUSTO-CONICAL outer surface which is engaged with a mating inner surface of the external body. A circular array of square or rectangular cross-sectional slots are defined in the frusto-conical outer surface. The slots and the inner wall of the external body define a plurality of fluid swirl conduits arranged to provide a swirl to the fuel passing therethrough. These fluid conduits also cooperate with a spray orifice defined at an outlet end of the external body to meter the flow of fuel through the nozzle. As such, the machining operation used to produce the slots must be controlled carefully.

Although the above described swirler construction is efficient, it requires that a specifically sized slotting cutter be used to form square or rectangular slots of a specific flow area, and since it is frequently necessary to produce fuel spray nozzles having different fuel swirl and pressure drop characteristics, it would be highly beneficial to be able to use the same machining tool for producing a wide range of fuel spray nozzle sizes.

SUMMARY OF THE INVENTION It is therefore an aim of the present invention to provide a new swirler which is adapted to impart a swirl to a fluid flowing therethrough.

It is also an aim of the present invention to provide such a swirler which is relatively simple and economical to manufacture.

It is still an aim of the present invention to provide a method of forming such a swirler.

Therefore, in accordance with the present invention, there is provided a fuel nozzle for spraying pressurised liquid fuel. The fuel nozzle comprises a body having an inlet end and an outlet spray orifice. Swirl means are disposed within the body for providing a swirl to the fuel entering the body. The swirl means comprise an insert having an outer surface in which a plurality of circumferentially spaced-apart swirl slots are defined to form with an inner surface of the body a plurality of swirl conduits leading to the outlet spray orifice. The swirl conduits are configured to impart a swirl component to the fuel emanating therefrom. Each swirl slot has a substantially V-shaped cross-section.

According to a more specific aspect of the present invention, the swirl slots are defined in a portion of the insert which is frusto-conical in shape. In accordance with general aspect of the present invention, there is provided a swirler for a fuel spray nozzle. The swirler comprises a body having a longitudinal axis and an annular array of V-shaped slots defined on at least an axial portion thereof. The axial portion is adapted to be engaged with an annular mating inner surface of the fuel spray nozzle to define therewith a plurality of fluid swirl passages which are configured to impart a swirl component to the fuel emanating therefrom. In accordance with a further general aspect of the present invention, there is provided a fuel spray nozzle for a combustor in a gas turbine engine, wherein the combustor includes a combustor wall defining a combustion chamber surrounded by pressurised air, and wherein the fuel spray nozzle is adapted to protrude, in use, through the combustor wall into the combustion chamber. The fuel spray nozzle comprises an annular array of fuel swirl conduits arranged around an axis of the fuel spray nozzle to impart a swirl to the fuel emanating therefrom. The fuel swirl conduits are formed by an inner surface of the fuel spray nozzle and a plurality of circumferentially spaced-apart V-shaped slots defined on the mating outer surface of an insert engaged with the inner surface of the fuel spray nozzle. In accordance with a still general aspect of the present invention, there is provided a method of forming a swirl member for a spray nozzle, comprising the steps of: a) providing a solid piece of material having a frusto- conical portion; and b) defining a plurality of circumferentially spaced- apart V-shaped slots on the frusto-conical portion.

In accordance with a more specific aspect of the present invention, each V-shaped slot is obtained by translating a revolving end mill along a prescribed cutting path to form a V-shaped slot of a desired cross- sectional area on the frusto-conical portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: Fig. 1 is a simplified axial cross-section of a combustor of a gas turbine engine which includes the present invention;

Fig. 2 is an enlarged side elevational view, partly in cross-section, of a fuel spray nozzle in accordance with the present invention;

Fig. 3 is an enlarged perspective view of a swirl member of the fuel spray nozzle of Fig. 2; and

Fig. 4 is a front plan view of the swirl member of Fig. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, Fig. 1 shows a combustor section 10 which includes an annular casing 12 and an annular combustor tube 14 concentric with a turbine section 16 of a gas turbine engine. The turbine section 16 is shown with a typical rotor 18 having blades 19 and a stator vane 20 upstream from the blades. A fuel injector 22 or nozzle is shown in Fig. 1 as being located at the end of the annular combustor tube 14 and directed axially thereof. The injector 22 includes a fuel manifold adapter 24 to be connected to a fuel source. There may be several fuel injectors 22 located on the wall 26 of the combustor tube 14, and they may be annularly spaced-apart. For the purpose of the present description, only one fuel injector 22 will be described. The fuel injector 22 includes a stem member 28 and a spray nozzle tip 30 which is mounted to the combustor wall 26. The stem member 28 defines a primary fuel passage 32 and a secondary fuel passage 34 which are respectively connected in fluid flow relationship with primary and secondary fuel outlets (not shown) of the fuel manifold adapter 24 for directing a primary fuel flow and a secondary fuel flow. The stem member 28 may be of the type described in applicant's U.S. Patent Application 08/960,331, filed October 29, 1997, entitled "Fuel Nozzle for Gas Turbine Engine", and which is herein incorporated by reference. As seen in Fig. 2, the spray nozzle tip 30 includes a tubular head 36 which is mounted to the outlet end of the stem portion 28. Disposed inside a cavity defined by the tubular head 36 and the stem member 28 is an insert 38. The insert 38 is provided with a first ring portion 40 which is sealingly engaged with an inner cylindrical wall 42 of the stem member 28 to define therewith a primary fuel chamber 44 which is in flow relationship with the primary fuel passage 32 of the stem member 28. The primary fuel will flow from the primary fuel chamber 44 through the insert 38 where a conventional swirling structure (not shown) will cause the primary fuel to swirl within the insert 38. The primary fuel will then exit through a primary discharge orifice 46 defined at a downstream end of the insert 38. The metering of the primary fuel flow through the insert 38 is ensured by the discharge orifice 46.

The secondary fuel emanating from the secondary fuel passage 34 of the stem member 28 is received in a secondary fuel chamber 48 which is in fluid communication with an annular array of fuel swirl conduits 50 by means of a plurality of spaced-apart feed conduits 51 define in a second ring portion 41 of the insert 38. The fuel swirl conduits 50 lead to an annular swirl chamber 52, ending in a secondary frusto-conical discharge orifice 54. The secondary fluid flow is metered by the fuel swirl conduits 50 and the frusto-conical discharge orifice 54. The second ring portion 41 is provided with a plurality of circumferentially space-apart slots 53 which form with a mating inner wall of the tubular head 36 the feed conduits 51.

Similarly, the fuel swirl conduits 50 are formed by engaging a frusto-conical portion 56 of the insert 38 having a plurality of converging circumferentially spaced-apart slots 58 defined thereon with a mating inner frusto-conical wall 60 of the tubular head 36.

In accordance with the present invention and as illustrated in Fig. 3, the slots 58 are of a V-shaped cross-section. By having V-shaped slots instead of conventional rectangular or square cross-section slots, a unique cutting tool may be used to form slots of a wide variety of flow profiles on the frusto-conical portion 56 of different inserts 38. Accordingly, an entire range of fuel injectors 22 having different fuel swirl and pressure drop characteristics may be produced with a unique cutting tool .

According to one embodiment of the present invention, each slot 58 is machined with an end mill 62 having a revolving axis 64 and a plane cutting surface 66. By engaging the cutting surface 66 of the revolving end mill 62 and subsequently translating the end mill 62 along a prescribed cutting path a V-shaped slot of a desired cross-sectional area may be formed on the frusto-conical portion 56 of the insert 38. A similar process is conducted at circumferentially spaced-apart locations on the frusto-conical portion 56 of the insert 38 so as to form the desired number of V-slots 58. By varying the orientation of the end mill 62 relative to the frusto-conical portion 56 and/or the depth at which the cutting surface 66 is translated into the frusto- conical portion 56, slots of various cross-sectional area may be provided. As seen in Fig. 2, each slot 58 have a longitudinal axis which forms an angle of about 10 to 35 degrees with the longitudinal axis of the insert 38.

Fig. 4 shows the disposition of the slots 58 on the frusto-conical portion 56. It can be seen that the inner side walls of the slots 58 are offset with respect to the centre of the insert by a distance C extending in a range of about 0. Id to 0.25d, wherein d is the diameter of the front section of the frusto-conical portion 56. The feed slots 53 may be defined in a manner similar to that just described with respect to the swirl slots 58.

Although the slots 53 and 58 have been described as being linear, it is understood that they could be helical . As seen in Fig. 2, the tubular head 36 is provided with a plurality of circumferentially spaced- apart skewered air passages 68 which are adapted to direct pressurised air to mix and atomise the secondary flow. The air may be coming from the cooling air between the casing 12 and the combustor wall 26 into the combustor 14. The air passages 68 are designed to provide a swirl to the pressurised air emanating therefrom and to form a spray cone. A second series of skewered air passages 70 are provided to help contain the spray cone of the atomised air and fuel.

Claims

CLAIMS :

1. A fuel nozzle for spraying pressurised liquid fuel, comprising a body having an inlet end and an outlet spray orifice, swirl means disposed within said body for providing a swirl to the fuel entering said body, said swirl means comprising an insert having an outer surface in which a plurality of circumferentially spaced-apart swirl slots are defined to form with an inner surface of said body a plurality of swirl conduits leading to said outlet spray orifice, said swirl conduits being configured to impart a swirl component to the fuel emanating therefrom, wherein each said swirl slot has a substantially V-shaped cross-section.

2. A fuel nozzle as defined in claim 1, wherein said swirl slots are defined in a portion of said insert which is frusto-conical in shape.

3. A fuel nozzle as defined in claim 1, wherein said body includes a stem portion and a head portion mounted at an outlet end of said stem portion, said insert being disposed in a cavity defined by said stem portion and said head portion.

4. A fuel nozzle as defined in claim 3, wherein said head portion include an annular array of swirl air passages .

5. A swirler for a fuel spray nozzle, comprising a body having a longitudinal axis and an annular array of V-shaped slots defined on at least an axial portion thereof, said axial portion being adapted to be engaged with an annular mating inner surface of the fuel spray nozzle to define therewith a plurality of fluid swirl passages which are configured to impart a swirl component to the fuel emanating therefrom.

6. A swirler as defined in claim 5, wherein said axial portion and said mating inner surface are frusto- conical in shape.

7. A fuel spray nozzle for a combustor in a gas turbine engine, wherein the combustor includes a combustor wall defining a combustion chamber surrounded by pressurised air, and wherein said fuel spray nozzle is adapted to protrude, in use, through the combustor wall into the combustion chamber, said fuel spray nozzle comprising an annular array of fuel swirl conduits arranged around an axis of said fuel spray nozzle to impart a swirl to the fuel emanating therefrom, said fuel swirl conduits being formed by an inner surface of said fuel spray nozzle and a plurality of circumferentially spaced-apart V-shaped slots defined on the mating outer surface of an insert engaged with said inner surface of said fuel spray nozzle.

8. A fuel spray nozzle as defined in claim 7, wherein said inner surface and said mating outer surface are frusto-conical in shape.

9. A method of forming a swirl member for a spray nozzle, comprising the steps of: a) providing a solid piece of material having a frusto- conical portion; and b) defining a plurality of circumferentially spaced- apart V-shaped slots on said frusto-conical portion.

10. A method as defined in claim 9, wherein each said V-shaped slot is obtained by translating a revolving end mill along a prescribed cutting path to form a V- shaped slot of a desired cross-sectional area on said frusto-conical portion.

11. A method as defined in claim 9, wherein each said V-shaped slot is formed by only engaging a portion of a cutting surface of a machining tool with said frusto-conical portion.