Patent Description:
Fuel nozzles are used for injecting fuel and air mixtures into the combustors of gas turbine engines. Compressed fuel is typically fed under pressure into a central fuel swirler and a surrounding array of pressurized air flow channels is provided to form an atomized air/fuel mixture.

The fuel swirler may be assembled from a swirler housing with an interior chamber and a swirler core that is press fit into the interior chamber of the swirler housing. The combined configuration of control surfaces between the swirler housing and swirler core define fuel flow channels and shaped surfaces that control the direction, pressure and kinetic energy of the pressurized fuel flow to achieve a desired set of parameters for the fuel spray exiting the fuel outlet orifice.

<CIT> discloses a fuel spray nozzle. <CIT> discloses a return type spray nozzle. <CIT> discloses a helical channel fuel distributor.

In one aspect of the invention, there is provided a fuel swirler for a gas turbine engine fuel nozzle as set forth in claim <NUM>.

In an embodiment of the above, the exterior surface of the upstream shank portion has a uniform axial cross-section.

In a further embodiment of any of the above, the exterior surface is prismatic.

In a further embodiment of any of the above, the plurality of generally axially extending grooves comprise at least three grooves having identical cross-sectional area.

In a further embodiment of any of the above, the plurality of generally axially extending grooves comprise a first groove having a first cross-sectional area and a second groove having a second cross-sectional area that is unequal to the first cross-sectional area.

In a further embodiment of any of the above, the plurality of generally axially extending grooves comprise one of: axial grooves; and helical grooves and intermittent grooves
In accordance with a further aspect of the invention, there is provided a gas turbine engine fuel nozzle as set forth in claim <NUM>.

In accordance with a further aspect of the invention, there is provided a method as set forth in claim <NUM>.

<FIG> shows an axial cross-section through an example turbo-fan gas turbine engine. Air intake into the engine passes over fan blades <NUM> in a fan case <NUM> and is then split into an outer annular flow through the bypass duct <NUM> and an inner flow through the low-pressure axial compressor <NUM> and high-pressure centrifugal compressor <NUM>. Compressed air exits the compressor <NUM> through a diffuser <NUM> and is contained within a plenum <NUM> that surrounds the combustor <NUM>. Fuel is supplied to the combustor <NUM> through fuel tubes <NUM> and fuel is mixed with air from the plenum <NUM> when sprayed through nozzles into the combustor <NUM> as a fuel air mixture that is ignited. A portion of the compressed air within the plenum <NUM> is admitted into the combustor <NUM> through orifices in the side walls to create a cooling air curtain along the combustor walls or is used for cooling to eventually mix with the hot gases from the combustor and pass over the nozzle guide vane <NUM> and turbines <NUM> before exiting the tail of the engine as exhaust.

The present description is directed to fuel nozzles at the terminus of the fuel tubes <NUM> which direct an atomized fuel-air mixture into the combustor <NUM>. A fuel nozzle includes a concentric array of compressed air orifices to create a swirling air flow surrounding a central fuel injecting swirler. The resultant shear forces between air and fuel cause the fuel and air mix to together and form an atomized fuel-air mixture for combustion.

<FIG> shows an axial detail cross-section view through a fuel swirler <NUM>. The outer components of the fuel nozzle that serve to direct compressed air are not shown since the focus of the present description is on the central fuel swirler <NUM> of the fuel nozzle alone. <FIG> shows a swirler core <NUM> that is press fit with axial force sliding axially into an interior chamber <NUM> of a swirler housing <NUM>. The interior surfaces of the interior chamber <NUM> and the exterior surfaces of the swirler core <NUM> define fuel directing channels and other control surfaces that convey fuel between the swirler core <NUM> and housing <NUM>, as indicated with arrows in <FIG>, from a fuel inlet <NUM> to a fuel outlet orifice <NUM>.

The flow of fuel is best shown in <FIG> together with the isometric view of the swirler core <NUM> shown in <FIG>. Fuel under pressure enters via the fuel inlet <NUM> into the interior chamber <NUM> of the swirler housing <NUM>. The exterior surfaces of the swirler core <NUM> direct the fuel flow towards the outlet orifice <NUM> as follows.

As seen in <FIG>, the swirler core <NUM> has a generally cylindrical exterior surface with areas of reduced diameter to form an inlet waist zone <NUM> and a tip waist zone <NUM>. With reference to <FIG>, the inlet waist zone <NUM> creates an annular inlet gallery <NUM> and the tip waist zone <NUM> creates an annular tip gallery <NUM>. The galleries <NUM>, <NUM> serve to distribute fuel circumferentially about the swirler core <NUM>.

With reference to <FIG>, a flat portion <NUM> on the shank <NUM> of the swirler core <NUM> extends axially between the inlet waist zone <NUM> and the tip waist zone <NUM> to create an elongated axial fuel passage <NUM> (<FIG>) with a secant cross-section that conveys fuel from the annular inlet gallery <NUM> to the annular tip gallery <NUM>. With reference to <FIG>, the swirler core <NUM> has a conical downstream end <NUM> with three spaced apart recessed fuel channels <NUM>. As seen in <FIG>, the conical downstream end <NUM> abuts a conical transition portion <NUM> of the interior chamber <NUM>. Fuel flows through the fuel channels <NUM> from the tip waist zone <NUM> to the conical transition portion <NUM> and exits through the outlet orifice <NUM>.

With reference to <FIG>, to press fit the swirler core <NUM> into the interior chamber <NUM> an axial force is applied until the conical downstream end <NUM> of the swirler core <NUM> engages against the conical transition portion <NUM>. The fuel passage <NUM> constitutes a large gap between the flat portion <NUM> of the swirler core <NUM> and the interior chamber <NUM>. The axial force creates unbalanced compressive stress that can buckle or laterally distort the swirler core <NUM> due to the asymmetric cross-section in the area of the flat portion <NUM>. Since the swirler core <NUM> is not confined by the interior chamber <NUM> in the area of the flat portion <NUM>, the shank <NUM> can bend or buckle under axial force that tends to narrow the cross sectional area of the fuel passage <NUM>. Plastic deformation can reduce the fuel passage <NUM> or change its geometry. Unintended distortion can restrict fuel flow and lead to differences in the flow characteristics obtained from fuel swirlers <NUM> that are assembled from the swirler cores <NUM> and swirler housings <NUM>.

<FIG> and <FIG> show a swirler core <NUM> in accordance with at least one embodiment where the shank <NUM> has three axially extending grooves <NUM> disposed axisymmetrically about the exterior surface of the shank <NUM> (i.e. the grooves are disposed symmetrically around the axis of the shank <NUM>). Any number of axially extending grooves <NUM>, in excess of one groove <NUM>, can be arranged in a circumferentially spaced apart array that results in an axisymmetric cross-section. <FIG> shows three grooves <NUM> but two or more grooves <NUM> can be axisymmetrically distributed in other manners as well. Further the grooves <NUM> need not have identical cross-sectional areas provided that the resulting arrangement remains axisymmetrical.

An axisymmetrical shank <NUM> under axial force will have balanced compressive axial stresses radially across the uniform cross-sectional area of the shank <NUM>. There is no force imbalance to create non-elastic bending, buckling or lateral distortion since the axisymmetrical cross-section provides an axisymmetrical distribution of stress.

Accordingly referring to <FIG> the imbalanced stresses and resultant lateral distortion of the conventional asymmetric shank <NUM>, caused by the flat portion <NUM> on one side of the shank <NUM>, has been corrected by providing an axisymmetric shank <NUM> with a plurality of axially extending grooves <NUM> that produce a balanced stress distribution that is symmetrical about the central axis. The grooves <NUM> provide for fuel flow between the annular galleries <NUM>, <NUM> that is not restricted or otherwise distorted when axial press fitting forces are applied to the swirler core <NUM>.

The use of the swirler core <NUM> does not require any changes to the swirler housing <NUM> or interior chamber <NUM> of <FIG>. As such the swirler core <NUM> can easily replace the conventional swirler core <NUM> during manufacture or fuel nozzle maintenance.

To recap the description, the primary cone swirler housing <NUM> has a fuel outlet orifice <NUM> from the interior chamber <NUM>. The interior chamber <NUM> has a fuel inlet <NUM> in communication with a source of pressurized fuel. The interior chamber <NUM> has an arcuate or conical transition portion <NUM> with a conical interior surface <NUM> axially disposed upstream from a socket portion <NUM>. The socket portion <NUM> receives the shank <NUM> of the swirler core <NUM> with mating axisymmetric interior and exterior surfaces respectively.

The swirler core <NUM> is disposed within the interior chamber <NUM>. The swirler core <NUM> has a conical downstream end <NUM> with a conical exterior surface matching the conical transition portion <NUM>. The matching conical shapes are simple for machining or manufacturing processes however using additive manufacturing processes various arcuate shapes can be formed from axisymmetric surfaces of revolution (ex: S-shaped, parabola shaped, nested stepped surfaces etc). The upstream shank <NUM> of the swirler core <NUM> has an exterior surface matching the axisymmetric interior surface of the socket portion <NUM> of the interior chamber <NUM> of the swirler housing <NUM>.

The downstream end <NUM> includes a plurality of fuel channels <NUM> to convey fuel from the annular tip gallery <NUM> to the outlet orifice <NUM>. The shank <NUM> has a plurality of axially extending grooves <NUM> disposed axisymmetrically about the exterior surface of the shank <NUM>. As seen in <FIG>, the grooves <NUM> are spaced about the circumference of the shank <NUM> to provide an axisymmetric cross-section and balanced stress distribution under axial load. In the example illustrated the exterior surface of the shank <NUM> portion has a uniform axial cross-section and the exterior surface is prismatic. However the depth of the grooves <NUM> could vary axially, the width of grooves <NUM> could vary or the grooves <NUM> could be interrupted with intermediate galleries (not shown) machined into the shank <NUM>. The number of grooves <NUM> could also vary from the three grooves <NUM> illustrated. As mentioned above, use of additive manufacturing processes frees the designer from the limits of traditional machining or casting processes and the plurality of axially extending grooves <NUM> are axial grooves.

Since the swirler housing <NUM> does not change, use of the swirler core <NUM> shown in <FIG> continues to include a shank <NUM> with inlet and tip waist zones <NUM>, <NUM> (see <FIG>) of reduced cross-section that define the fuel accumulation annular inlet gallery <NUM> and annular tip gallery <NUM>. Also the plurality of axially extending grooves <NUM> serve to convey fuel from the fuel accumulation annular inlet gallery <NUM> to annular tip gallery <NUM>, in a manner similar to the fuel passage <NUM> created by the flat portion <NUM> of a conventional swirler core <NUM> (<FIG>).

Claim 1:
A fuel swirler (<NUM>) for a gas turbine engine fuel nozzle, the fuel swirler (<NUM>) comprising:
a primary cone swirler housing (<NUM>) defining an interior chamber (<NUM>) having a fuel outlet (<NUM>), the interior chamber (<NUM>) having a transition portion (<NUM>) with a conical interior surface (<NUM>) axially disposed downstream from a socket portion (<NUM>) relative to a fuel flow direction through the fuel swirler (<NUM>), the socket portion (<NUM>) having an axisymmetric interior surface; and
a swirler core (<NUM>) press fit with axial force into the interior chamber (<NUM>), the swirler core (<NUM>) having a downstream end (<NUM>) mating with the transition portion (<NUM>) and an upstream shank portion (<NUM>) having an exterior surface for mating with the axisymmetric interior surface of the socket portion (<NUM>), the upstream shank portion (<NUM>) having a plurality of axially extending grooves (<NUM>) being disposed axisymmetrically around an axis of the upstream shank portion (<NUM>), wherein the upstream shank portion (<NUM>) includes an inlet waist zone (<NUM>) of reduced cross-section defining a fuel accumulation gallery (<NUM>), and a tip waist zone (<NUM>) of reduced cross-section defining a tip gallery (<NUM>), the plurality of axially extending grooves (<NUM>) extending along the shank portion (<NUM>) from the inlet waist zone (<NUM>) to the tip waist zone (<NUM>) to convey fuel from the fuel accumulation gallery (<NUM>) to the tip gallery (<NUM>).