Patent Description:
Fuel nozzles are used for injecting fuel and air mixtures into the combustors of aircraft 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 typically brazed or 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.

Typical fuel nozzles are designed to inject a single type of fuel, for instance kerosene, and must be replaced if a different fuel type is to be used. In cases where a gaseous fuel such as hydrogen or methane is selected as the fuel type, there is a risk that the gaseous fuel ignites as soon as it comes into contact with compressed air at or before a mixing site. This may lead to dangerous and/or damaging consequences if the flame were to propagate upstream through the fuel nozzle.

<CIT> discloses a fuel injector to facilitate reduced nox emissions in a combustor system.

<CIT> discloses a fuel supply system according to the preamble of claim <NUM>.

According to the invention, there is provided a fuel supply system for an aircraft engine as set forth in claim <NUM>.

According to the invention, the plurality of discrete apertures are positioned at the fuel inlet of the fuel swirler.

The plurality of discrete apertures are defined through a radially exterior surface of the fuel swirler relative to a longitudinal axis of the fuel swirler.

In an embodiment, the fuel supply system further comprises an insert with an annular body, the insert positionable between the housing and the fuel swirler at the fuel inlet of the fuel swirler, the insert including the plurality of discrete apertures.

In a further embodiment, the plurality of discrete apertures have circular cross-sectional shapes.

According to the invention, the plurality of discrete apertures have cross-sectional diameters of at most <NUM> inches (<NUM>).

In a further embodiment of any of the above, the fuel supply system further comprises a second fuel path in fluid communication with a second fuel source and terminating at a second fuel outlet.

In a further embodiment of any of the above, the fuel outlet is positioned on an outer surface of the fuel swirler bordering a mixing site downstream of the fuel swirler, the fuel outlet leading directly to the mixing site.

According to a further aspect there is provided an aircraft engine comprising a fuel supply system according to any of the above, the aircraft engine comprising a liquid fuel source and a gaseous fuel source, the first fuel path fluidly connected to the gaseous fuel source, the second fuel path fluid connected to the liquid fuel source.

In an embodiment of the above, the liquid fuel source is kerosene and the gaseous fuel source is hydrogen.

<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. Although <FIG> shows a turbofan-type engine, the present disclosure is also applicable to other types of aircraft engines, including hybrid engines among others.

As will be discussed in further detail below, the present description is directed to a fuel supply system comprising fuel nozzles at the terminus of the fuel tubes <NUM> which direct an atomized fuel-air mixture into the combustor <NUM>. A fuel nozzle may include one or more concentric arrays 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 to mix together and form an atomized fuel-air mixture for combustion. Although not visible in <FIG>, the present disclosure is directed to fuel nozzles to be used in aircraft engines having one or more fuel sources and thus one or more distinct fuel paths, passages or circuits. In various embodiments, two fuel sources or fuel manifolds may be utilized, one being a liquid fuel such as kerosene and the other being a gaseous fuel such as hydrogen. In other cases, a single, gaseous fuel source may be utilized. Other numbers and types of fuels may be contemplated as well. As will be discussed in further detail below, the fuel nozzles described herein may be operable to deliver the different types of fuel alternatingly and/or simultaneously, depending on the specific engine application.

Referring to <FIG> an exemplary embodiment of a fuel nozzle <NUM> for an aircraft engine, for instance the gas turbine engine of <FIG>, is shown. The fuel nozzle <NUM> includes a housing <NUM> and a fuel swirler, illustratively including an outer fuel swirler <NUM>, an inner fuel swirler <NUM> and a swirler core <NUM>. Other arrangements for the fuel swirler may be contemplated as well, for instance a unitary fuel swirler with an interior chamber for mounting a swirler core. The depicted fuel nozzle <NUM> is said to be a dual fuel nozzle as it is operable to deliver two different fuel types, either selectively or simultaneously, towards a mixing location or site <NUM> where the fuel(s) are to be mixed with compressed air before delivery to the combustor <NUM>. In various cases, certain fuels such as hydrogen might auto-ignite or combust as soon as they mix with compressed air. As such, the mixing site <NUM> may also be referred to as a combustion site or a precursor to the combustor <NUM> in these cases. The term 'fuel swirler' may be employed herein to refer to the various components that swirl, mix or otherwise disturb the flow of fuel(s) as it passes through the fuel nozzle <NUM>. The fuel nozzle <NUM> has a general upstream end U. and a general downstream end D. along a swirler core central longitudinal axis L relative to an overall direction of flow of fuel and compressed air through the fuel nozzle <NUM>, as will be discussed in further detail below.

The housing <NUM> provides structural support for the fuel swirler. In the shown case, the housing <NUM> is a fuel stem <NUM>. According to other embodiments, the fuel swirler could be directly mounted to an internal manifold ring, internal manifold segments or any other suitable fuel supply structures that may act as the housing <NUM>. In the shown case, the stem <NUM> provides fuel to the fuel nozzle <NUM> through first and second fuel supplies <NUM>, <NUM>, illustratively longitudinal bores through the stem <NUM>. In other cases, fuel may be supplied to the fuel nozzle <NUM> via other assemblies within the engine. A first fuel F1 is provided from a first fuel source S1 and a second fuel F2 is provided from a second fuel source S2. In the shown case, the first fuel supply <NUM> is operable to transport a gaseous fuel from the first fuel source S1 that may be susceptible to auto-ignite upon mixing with air, such as hydrogen, to the fuel swirler, while the second fuel supply <NUM> is operable to transport a liquid jet fuel from the second fuel source S2 to the fuel swirler, although other fuel type arrangements may be contemplated as well.

In the shown case, the gaseous fuel is hydrogen and the liquid jet fuel is kerosene. Various kerosene-based fuels may be contemplated, such as Jet A, Jet A-<NUM>, JP-S and JP-<NUM>. Other fuel types may be contemplated as well. For instance, in an industrial application, the fuel nozzle <NUM> may be operable to receive natural gas, diesel and/or biofuels via the first and second fuel supplies <NUM>, <NUM>.

The distal end of the stem <NUM> defines an interior chamber <NUM> having an upstream opening <NUM> and a downstream opening <NUM> spaced apart along axis that is in a direction normal to the longitudinal axis of the stem <NUM>. The stem interior chamber <NUM> is operable to house the various fuel swirler components, as will be discussed in further detail below, and may include one or more stops or protrusions <NUM> for aligning and retaining the various inserted components.

As discussed above, in the shown embodiment, although not necessarily the case in all embodiments, the fuel swirler includes an outer fuel swirler <NUM>, an inner fuel swirler <NUM>, and a swirler core <NUM>. The shown outer fuel swirler <NUM> is disposed inside the interior chamber <NUM> and is illustratively axially held in place by stops <NUM>. The shown outer fuel swirler <NUM> has an outer fuel swirler interior chamber <NUM> with an outer fuel swirler upstream end <NUM> and a frustoconically-shaped outer fuel swirler downstream end <NUM>. Other shapes for the outer fuel swirler <NUM> may be contemplated as well. The shown outer fuel swirler <NUM> protrudes outwardly from the interior chamber <NUM> in a direction towards the downstream end D. and includes an end face <NUM> at the outer fuel swirler downstream end <NUM>. In the shown case, the end face <NUM> is annular, although other forms for the end face <NUM> may be contemplated as well. As shown, the annular end face <NUM> incudes a plurality of circumferentially-arranged end face compressed air outlets, illustratively two concentric circumferentially extending rows of end face compressed air outlets, i.e. an outer row of end face compressed air outlets 45a for delivering a first stream of compressed air A1 and an inner row of end face compressed air outlets 45b for delivering a second stream of compressed air A2. Various sources for the compressed air within the engine may be contemplated. In other cases, the annular end face <NUM> may have other arrangements of compressed air outlets, such as a single row of compressed air outlets or one or more annular ring-type compressed air outlets.

The compressed air may be sourced from various compressed air sources within the engine. In the shown case, the outer end face compressed air outlets 45a are smaller and spaced further apart than the inner end face compressed air outlets 45b, although other arrangements may be contemplated as well. In addition, each of the shown outer end face compressed air outlets 45a and inner end face compressed air outlets 45b are angled to deliver the compressed air to the mixing site <NUM> at various locations and angles, for instance to promote mixing. Various numbers, sizes, angles and positions for the end face compressed air outlets 45a, 45b may be contemplated, for instance based on the fuel types(s), their combustion requirements and/or the required gas pressure. In the shown case, as best seen in <FIG>, the outer end face compressed air outlets 45a are directed inwardly towards the longitudinal axis L in the mixing site <NUM>, while the inner end face compressed air outlets 45b are directed both inwardly towards the longitudinal axis L and circumferentially in a directions towards an adjacent inner end face compressed air inlet 45b.

In the shown embodiment, the inner fuel swirler <NUM> is disposed inside the outer fuel swirler <NUM>. Illustratively, the inner fuel swirler <NUM> also engages with the stops <NUM> of the stem <NUM> for axial positioning and retaining purposes. The inner fuel swirler <NUM> includes an inner fuel swirler interior chamber <NUM> for receiving the swirler core <NUM>, as will be discussed in further detail below. The shown inner fuel swirler interior chamber <NUM> includes an inner fuel swirler upstream end <NUM> and a frustoconically-shaped inner fuel swirler downstream end <NUM>.

When assembled, the inner fuel swirler <NUM> sits concentrically within the outer fuel swirler <NUM> and defines a first axial fuel passage <NUM> between the outer fuel swirler <NUM> and the inner fuel swirler <NUM>. As such, the shown first axial fuel passage <NUM> is said to be annular. The first axial fuel passage <NUM> is in fluid communication with the first fuel supply <NUM> via a first aperture <NUM>, i.e. a first inlet, in the outer fuel swirler <NUM> and extends towards the downstream end D. until a first fuel outlet <NUM>. The shown inner fuel swirler <NUM> also includes a second aperture <NUM> for directing the second fuel F2, as will be discussed in further detail below.

In the shown case, the first fuel outlet <NUM> is operable to deliver the first fuel F1, for instance a gaseous fuel such as hydrogen, to the mixing site <NUM>. The first fuel outlet <NUM> is positioned on an outermost surface of the fuel swirler relative to the longitudinal axis L, as will be discussed in further detail below. The illustrated first fuel outlet <NUM> is an annular fuel outlet disposed about the longitudinal axis L and is circumferentially inward of the inner end face compressed air outlets 45b, although other arrangements may be contemplated as well. The thickness of the first axial fuel passage <NUM> and the sizing of the first fuel outlet <NUM> may vary, for instance based on the type of fuel flow delivered via the first fuel supply <NUM>, its properties (for instance viscosity) and its effects on mixing and combustion. The fuel delivery angle of the first fuel outlet <NUM> may vary as well.

In the shown case, the first fuel outlet <NUM> is positioned on an outermost surface of the fuel swirler towards the downstream end D. relative to the longitudinal axis L, i.e. on the annular end face <NUM>. This outermost surface of the fuel swirler borders the mixing zone <NUM>, i.e. it is acts as a boundary between the fuel swirler and the mixing zone <NUM>. As such, the first fuel outlet <NUM> leads directly into the mixing site <NUM> so that it delivers the first fuel F1 directly to the mixing site <NUM> where it mixes with compressed air, i.e. there is no pre-mixing zone for the first fuel F1. For gaseous F1 fuels such as hydrogen that auto-ignite upon mixing with the compressed air, any pre-mixing with air within the fuel nozzle <NUM> may result in early ignition that may damage the fuel nozzle <NUM> or other components. As such, by injecting the F1 fuel directly into the mixing site <NUM> via the first fuel outlet <NUM>, the durability of the fuel nozzle <NUM> may be improved. Other flame propagation prevention means may be contemplated, as will be discussed in further detail below.

The swirler core <NUM> has an internal bore <NUM> extending longitudinally through the swirler core <NUM> along the longitudinal axis L through which compressed air is transported, as will be discussed in further detail below. According to the illustrated embodiment, the internal bore <NUM> is a central bore coaxial to the centerline of the swirler core <NUM>. As best shown in <FIG>, the swirler core <NUM> includes a swirler core upstream end <NUM> and a swirler core downstream end <NUM> relative to a general direction of fuel and air flow through the fuel nozzle <NUM>. As will be discussed in further detail below, compressed air stream A3 from a compressed air source (not shown) flows through the internal bore <NUM> and exits the swirler core <NUM> at a swirler core compressed air outlet <NUM> at the swirler core downstream end <NUM> towards the mixing site <NUM>. In the shown case, the swirler core compressed air outlet <NUM> is circular. In various cases, the sizing and shape of the swirler core compressed air outlet <NUM> as well as the sizing and shape of the internal bore <NUM> may vary, for instance based on the required quantity of compressed air for mixture with the fuel and combustion. In the shown case, compressed air is thus delivered to the mixing site <NUM> via outer end face compressed air outlets 45a and inner end face compressed air outlets 45b, as well as via the swirler core compressed air outlet <NUM>, for optimal fuel and air mixture. The quantity and direction of air delivery may vary, for instance based on the fuel type(s) and the desired combustion characteristics.

The swirler core <NUM> further includes a shank portion <NUM> forming the exterior profile of the swirler core <NUM> and extending from the swirler core upstream end <NUM> to the swirler core downstream end <NUM>. In the shown case, the shank portion <NUM> incudes an annular shoulder portion <NUM> and a pair of axially spaced-apart annular protrusions <NUM>, illustratively protrusions 67a, 67b with respective circumferentially disposed fuel-directing apertures 68a, 68b. As shown in <FIG>, the fuel-directing apertures 68a, 68b may be disposed through the annular protrusions 67a, 67b at an angle relative to the central longitudinal axis L for directing and mixing a flow of fuel, as will be discussed in further detail below. Various angles may be contemplated, for instance based on the type of fuel selected and its viscosity. In the shown case, the fuel-directing apertures referenced by 68a are in the form of holes while the fuel-directing apertures referenced by 68b are in the form of cutouts, although other forms and combinations may be contemplated as well. In other cases, the swirler core <NUM> may include other numbers of annular protrusions with circumferentially disposed fuel-directing apertures. An additional shoulder <NUM> may further aid in directing a flow of fuel and/or accelerate the flow of compressed air A passing through the internal bore <NUM>.

As best shown in <FIG>, a second axial fuel passage <NUM> is radially formed between the swirler core <NUM> and the inner swirler <NUM>, and thus in the shown case is said to be annular. The second axial fuel passage <NUM> is in fluid communication with the second fuel supply <NUM> via the second aperture <NUM> and extends towards the downstream end D. until a second fuel outlet <NUM>. In the shown case, the annular protrusions 67a, 67b radially extend between the swirler core <NUM> and the inner fuel swirler <NUM>, only allowing fuel to pass through the fuel-directing apertures 68a, 68b. As the second fuel F2 flows through the second axial fuel passage <NUM>, it passes through fuel-directing apertures 68a, 68b in annular protrusions 67a, 67b. The angles of these fuel-directing apertures 68a, 68b, cause the second fuel F2 to mix and swirl as it flows towards the second fuel outlet <NUM>. Other mixing and swirling features within the second axial fuel passage <NUM> may be contemplated as well. may be contemplated as well.

In the shown case, the second fuel outlet <NUM> is operable to deliver the second fuel F2, for instance a liquid fuel such as kerosene, to the mixing site <NUM>. The illustrated second fuel outlet <NUM> is an annular fuel outlet disposed about the longitudinal axis L and is circumferentially inward of the first fuel outlet <NUM> and circumferentially outward of the swirler core compressed air outlet <NUM>, although other arrangements may be contemplated as well. The thickness of the second axial fuel passage <NUM> and the sizing of the second fuel outlet <NUM> may vary, for instance based on the type of fuel flow delivered via the second fuel supply <NUM>, its properties (for instance viscosity) and its effects on mixing and combustion. The fuel delivery angle of the second fuel outlet <NUM> may vary as well. In the shown case, although the second fuel outlet <NUM> is annular in nature, the exiting fuel will not exit uniformly due to the mixing and swirling caused by the fuel-directing apertures 68a, 68b, as discussed above. Due to the proximity of the first and second fuel outlets <NUM>, <NUM>, fuels from two independent circuits may be atomized at close radial locations to each other relative to the longitudinal axis L, reducing the impact that a fuel change may have on downstream hot section components in terms of thermal profiles. In addition, the delivery of different compressed air streams A1, A2, A3 from various directions may aid in atomizing the fuel.

In an exemplary embodiment, the fuel nozzle <NUM> may be assembled via the following process in a clearance fit-type fashion. First, the inner fuel swirler <NUM> is inserted into the stem interior chamber <NUM> via the downstream opening <NUM> until it hits a stop <NUM>, ensuring the second aperture <NUM> is aligned with an outlet of the second fuel supply <NUM>. Then, the outer fuel swirler <NUM> is slipped over the inner fuel swirler as it is inserted into the interior chamber <NUM> via the downstream opening <NUM> until it hits a stop <NUM>, ensuring that the first aperture <NUM> is aligned with an outlet of the first fuel supply <NUM>. Then, the swirler core <NUM> is inserted into the inner fuel swirler interior chamber <NUM> via the inner fuel swirler upstream end <NUM> until the annular protrusion 67b abuts the frustoconical inner fuel swirler downstream end <NUM> and/or the shoulder portion <NUM> engages the interior wall of the inner fuel swirler <NUM>. The above-describes steps may be carried out in different orders. In other cases, various steps may be added or omitted. Other assembly processes may be contemplated as well.

In the shown case, the fuel nozzle <NUM> includes a plurality of brazing joints <NUM>, <NUM>, illustratively in the outer fuel swirler <NUM> and inner fuel swirler <NUM>, which are used to secure the various components of the fuel nozzle <NUM> together upon assembly. A brazing joint may be added to the shoulder portion <NUM> as well (not shown), which may also aid in sealing. In an exemplary process, a brazing compound may be applied to the various brazing joints upon assembly. Then, the fuel nozzle <NUM> may be inserted into an oven to harden the brazing compound and secure and seal the various components together. Additionally or alternatively, welding may be employed to secure and seal various components together. In other cases, some or all of the various components may engage in a press fit-type connection for secure engagement. Other securing techniques may be contemplated as well.

In another embodiment, as discussed above, the fuel swirler <NUM> may be a unitary fuel swirler rather than a two-part fuel swirler having an outer fuel swirler <NUM> and an inner fuel swirler <NUM>. In such a case, the unitary fuel swirler may include an interior chamber for mounting the swirler core <NUM> with an upstream end and a frustoconically-shaped downstream end with an end face such as an annular end face at the downstream end. The first axial fuel passage <NUM> may be integrated within the unitary fuel swirler while the second axial fuel passage <NUM> may be formed between the swirler core <NUM> and the unitary fuel swirler. Other fuel swirler arrangements may be contemplated as well.

Various manufacturing processes may be utilized to produce the fuel nozzle <NUM>. Traditional manufacturing and removal techniques using machines such as lathes and mills may be implemented. Other manufacturing techniques such as additive manufacturing, metal injection moulding and casting may be contemplated as well. As discussed above, various brazing or welding procedures may be utilized to fix the various components of the fuel nozzle <NUM> together. A given fuel nozzle <NUM> may be manufactured based on the specific fuel types to be utilized. For instance, the shown fuel nozzle <NUM> is operable to receive hydrogen through the first axial fuel passage <NUM> and kerosene through the second axial fuel passage <NUM>. The first and second fuel outlets <NUM>, <NUM> may be dimensioned to optimize the delivery of these fuels to the mixing site <NUM> based on the unique properties of each fuel and the desired combustion performance indicators. For instance, the cross-sectional area of the first fuel outlet <NUM> may be optimized based on the desired hydrogen pressure, while the cross-sectional area of the second fuel outlet <NUM> may be optimized based on the viscosity of the kerosene. Similarly, the number, size and area of the various end face compressed air outlets 45a, 45b, <NUM> may be optimized to achieve a desired fuel-to-air ratio for ignition and operation. Other parameter optimizations may be contemplated as well.

Various operating modes for the fuel nozzle <NUM> may be contemplated. As discussed above, the shown fuel nozzle <NUM> is operable to deliver two different fuels to the combustor <NUM>, either alternatingly or simultaneously. One or both of the fuel circuits are said to be powered during operation, indicating that they are providing a given fuel to the mixing site <NUM> and then to the combustor <NUM>. For instance, an aircraft employing the fuel nozzle <NUM> may utilize a first fuel, for instance hydrogen, for a first flight and then utilize a second fuel, for instance kerosene, for a second flight immediately after the first flight. No modifications to the fuel nozzle <NUM> would be required to switch from the first fuel source S1 to the second fuel source S2 as the fuel nozzle's <NUM> various fuel and compressed air outlets are already optimized for both fuel types. As such, the aircraft operators would simply have to select a different fuel supply before departing on the second flight rather than having to switch to a different fuel nozzle for the second fuel F2. Similarly, in other embodiments, the fuel type delivered to the combustor may be switched mid-flight without requiring any modifications to the fuel nozzle <NUM>.

In other cases, a hybrid combustor (not shown) may be employed that is operable to receive and combust two types of fuel, for instance hydrogen and kerosene, simultaneously. In such cases, the fuel nozzle <NUM> would be operable to deliver both fuel types through their respective fuel passages <NUM>, <NUM> to the mixing site <NUM> and then to the combustor <NUM>. Various combinations of fuel mixtures without having to remove and replace the fuel nozzle <NUM> may be contemplated.

In cases where the second fuel F2, for instance a liquid fuel such as kerosene, flows through the second axial fuel passage <NUM> while no fuel flows through the first axial fuel passage <NUM> (i.e. the first fuel supply <NUM> is inactive while the second fuel supply <NUM> is powered), the first axial fuel passage <NUM> may act as an air gap insulating layer for the second fuel F2. As such, the first axial fuel passage <NUM> may shield the second fuel F2 flowing through the second axial fuel passage <NUM> from various heat sources in the engine such as convection and radiation effects from combustion. Similarly, in cases where the first fuel F1, for instance a gaseous fuel such as hydrogen, flows through the first axial fuel passage <NUM> while no fuel flows through the second axial fuel passage <NUM> (i.e. the second fuel supply <NUM> is inactive while the first fuel supply <NUM> is powered), the second axial fuel passage <NUM> may act as an air gap insulating layer for the first fuel F1. As such, the second axial fuel passage <NUM> may shield the fuel flowing through the first axial fuel passage <NUM> from the hot compressed air A3 flowing through the internal bore <NUM> of the swirler core <NUM>. Other insulating means may be contemplated as well. Such insulation techniques may reduce the temperature of the fuel flowing through the various fuel passages, which may improve the durability of the fuel nozzle <NUM>.

In another embodiment, an exemplary fuel nozzle (not shown) may include three fuel passages. For instance, two fuel passages may be dedicated to a first fuel type, for instance a liquid fuel, in a duplex nozzle-type arrangement whereby a first fuel path is optimized for engine startup while the second fuel path is optimized for steady-state operation and acceleration. The third fuel path may then be dedicated to a second fuel type, for instance a gaseous fuel such as hydrogen. As such, this fuel nozzle with three fuel paths may be operable to deliver two fuel types either simultaneously or sequentially. In other cases, fuel nozzles with three or more fuel paths carrying three or more fuel types may be contemplated as well. Single fuel nozzles with a single, gaseous fuel path may be contemplated as well, as will be discussed in further detail below.

The present disclosure further teaches systems, devices and methods for preventing flame propagation, for instance from the combustor <NUM> or mixing site <NUM>, upstream into the fuel nozzle <NUM>. As discussed above, gaseous fuels such as hydrogen are prone to ignite upon mixing with air at the mixing site <NUM>. As such, various embodiments of the fuel nozzle <NUM> taught by the present disclosure include a flashback arrestor to prevent such flames, as well as other flames from the combustor <NUM>, from propagating upstream through the axial fuel passage <NUM> towards the gaseous fuel source S1. Such a flashback arrestor also serves as a flow metering device for controlling the flow rate of the gaseous fuel towards the mixing site <NUM>. In various cases, the combined flashback arrestor and flow restrictor may resemble a corrugated screen, although other options may be contemplated as well.

Flashback arresting, or flame quenching, may be accomplished by ensuring that a potential flame loses heat to a surrounding wall (assuming there is sufficient metal thermal mass), for instance the walls of the fuel nozzle <NUM>, such that there is insufficient heat to maintain the flame's chemical reaction. The dimensions of the passageway through which the gaseous fuel travels may also play a role in the flame quenching, as too narrow a passageway in combination with sufficient heat loss to the surrounding walls would quench the flame before it propagated upstream. As will be discussed in further below, some embodiments include a combined flashback arresting and flow restricting device disposed about a circumference of a fuel swirler <NUM>, the device having a plurality of apertures operable to prevent a flame from the mixing site <NUM> from traveling upstream towards the gaseous fuel supply S1 and to selectively restrict a flow of gaseous fuel F1 from the gaseous fuel supply S1 towards the mixing site <NUM>.

Referring to <FIG>, an additional embodiment of an outer fuel swirler <NUM>' is shown. In this case, the first fuel outlets <NUM>' are individual holes rather than the single annular fuel outlet shown above. In this case, the outer fuel swirler <NUM>' includes a combined flashback arrestor and flow restrictor integrated with the first fuel outlets <NUM>' in the annular end face <NUM>'. The first fuel outlets <NUM>' additionally aid in controlling the flow of gaseous fuel towards the mixing site <NUM>, as well as controlling the direction and swirl of the gaseous fuel as it exits the fuel nozzle <NUM> to achieve the desired mixing characteristics within the mixing site <NUM>. The first fuel outlets <NUM>' are circumferentially disposed about the longitudinal axis L' on the outer fuel swirler <NUM>', more particularly on the annular end face <NUM>'. In the shown case, the first fuel outlets <NUM>' are evenly distributed about the circumference of the annular end face <NUM>', although uneven distributions may be contemplated as well. In other cases, the first fuel outlets <NUM>' may be disposed on the inner fuel swirler downstream end (not shown) or formed by a combination of the annular end face <NUM>' and the inner fuel swirler downstream end. While the illustrated first fuel outlets <NUM>' are shown to be circular, other shapes such as squares or slots may be contemplated as well.

The number, shape and size of the first fuel outlets <NUM>' may vary, for instance based on flashback arresting requirements, flow restricting requirements, and the required mixing and combustion characteristics. In the shown case, the outer end face compressed air outlets 45a' are directed inwardly towards the longitudinal axis L' in the mixing site, while the inner end face compressed air outlets 45b' are directed both inwardly towards the longitudinal axis L' and circumferentially in a directions towards an adjacent inner end face compressed air inlet 45b'. The angles and directions of the first fuel outlets <NUM>' and compressed air outlets 45a', 45b' may vary, for instance to optimize mixing and combustion. For instance, the first fuel outlets <NUM>' may be angled to swirl the gaseous fuel in a clockwise or counter-clockwise direction, depending on the flow of compressed air.

In the illustrated embodiment, the first fuel outlets <NUM>' include circular holes or apertures with cross-sectional diameters of <NUM> inches (<NUM>) or less. In some embodiments, the cross-sectional diameters may be <NUM> inches (<NUM>). The cross-sectional diameter of the discrete fuel outlets <NUM>' is selected so that the flames from the mixing site <NUM> will be unable to travel upstream through the first fuel outlets <NUM>' due to the restricted passage size. Such apertures may prevent flames from propagating into the first elongated axial fuel passage towards the gaseous first fuel source S1, for instance hydrogen or methane. Rather, the flames will be quenched as heat is lost to the surrounding metal, i.e. the annular end face <NUM>'. The cross-sectional diameter of the circular apertures and the number of holes <NUM>' may additionally vary to control the flow of the gaseous fuel to the mixing site <NUM>, without exceeding a maximum cross-sectional diameter for flame quenching needs. For instance, in the shown case, if the maximum cross-sectional diameter of the holes <NUM>' is <NUM> inches (<NUM>) yet additional fuel flow is required, additional holes <NUM>' may be added to increase the fuel's flow rate. Similarly, the cross-sectional diameter of the holes <NUM>' and/or the number of holes <NUM>' may be reduced to decrease the flow rate of the gaseous fuel.

The mass of the annular end face <NUM>' may also vary, for instance to increase or decrease the metal thermal mass for flame quenching. The annular end face <NUM>' may be made from various materials based on the flame-quenching needs of the fuel nozzle <NUM>. For instance, various nickel-based materials or stainless steel-based materials may be selected based on the required metal thermal mass. In addition, as the temperature of the compressed air flowing both around and through the fuel nozzle <NUM> is much lower than a potential flame temperature would be, this compressed air temperature would aid in allowing the metals surrounding the gaseous fuel passage <NUM> to act as a quenching heat sink.

The shown annular end face <NUM>' with integrated combined flashback arrestor and flow restrictor may be operable for use in a single fuel nozzle with a gaseous fuel source such as hydrogen or in a dual fuel nozzle with a liquid fuel source and a gaseous fuel source. In the latter case, the integrated combined flashback arrestor and flow is operable to prevent flashback and meter the flow rate of the gaseous fuel.

Referring to <FIG>, a dual fuel nozzle <NUM> is shown similar to the dual fuel nozzle <NUM> of <FIG> but with an integrated combined flashback arrestor and flow restrictor. In the depicted case, the combined flashback arrestor and flow restrictor is integrated with the outer fuel swirler <NUM> and positioned at a junction between the housing <NUM> and the outer fuel swirler <NUM>, i.e. at the first inlet of the outer fuel swirler <NUM>. In particular, the combined flashback arrestor and flow restrictor is integrated with a radially exterior surface of the outer fuel swirler <NUM> relative to the longitudinal axis L. In the depicted case, the first fuel source S1 provides a gaseous fuel F1 such as hydrogen that is prone to early combustion when mixed with hydrogen, while the second fuel source S2 is a liquid fuel F2 such as kerosene. As such, the combined flashback arrestor and flow restrictor is positioned in the path of the gaseous fuel F1.

Referring additionally to <FIG>, in the shown case the combined flashback arrestor and flow restrictor includes a plurality of discrete apertures 46a disposed about a circumference of the outer fuel swirler <NUM>. In the shown case, the apertures 46a are arranged in an evenly spaced, two row staggered formation and act as inlets for the gaseous fuel into the first elongated axial fuel passage <NUM>. Other arrangements for the apertures 46a, both evenly and unevenly spaced with varying numbers of rows, may be contemplated as well. In the depicted case, the housing <NUM> includes an annular gallery <NUM> that is axially aligned with the apertures 46a to deliver gaseous fuel from the first fuel supply <NUM> evenly through the apertures 46a and into the first elongated axial fuel passage <NUM>. The width and/or shape of the housing <NUM> may vary based on the functional requirements of the fuel nozzle <NUM>, for instance based on the required number of apertures 46a.

A gaseous fuel pathway with the combined flashback arrestor and flow restrictor in the shown case thus includes the first fuel supply <NUM>, the annular gallery <NUM>, the apertures 46a, the first elongated axial fuel passage <NUM>, and the first fuel outlet <NUM>. In the depicted case, the outer fuel swirler <NUM> includes an additional annular collar <NUM> abutting against the housing <NUM> and a curved or recessed portion <NUM> to improve the flow of compressed air flowing towards the inner compressed air outlets 45b. In addition, a plurality of inlets 62a divert compressed air into the internal bore <NUM> of the swirler core <NUM>. In the shown case, the first fuel outlet <NUM> is positioned on an outer surface of the outer fuel swirler <NUM> bordering the mixing site <NUM> downstream of the outer fuel swirler <NUM>, the first fuel outlet <NUM> leading directly to the mixing site <NUM>. This may aid in preventing early ignition of the gaseous fuel, as discussed above.

Referring to <FIG>, a single fuel nozzle <NUM> is shown with an integrated combined flashback arrestor and flow restrictor. Similarly to the fuel nozzle <NUM> depicted in <FIG>, the combined flashback arrestor and flow restrictor is integrated with the fuel swirler of the fuel nozzle <NUM>. In particular, the combined flashback arrestor and flow restrictor is integrated with a radially exterior surface of the single fuel swirler <NUM> relative to the longitudinal axis L. However, in the depicted case, the fuel nozzle <NUM> is operable to inject a single gaseous fuel F1 to the mixing site. As such, the discrete apertures 46a are disposed in a single fuel swirler <NUM>, as there is a single elongated axial fuel passage <NUM> formed between the single fuel swirler <NUM> and the swirler core <NUM>. The apertures 46a thus act as inlets for the gaseous fuel into the single elongated axial fuel passage <NUM>. In the depicted case, the swirler core <NUM> includes brazing joints 69a for assembly purposes with the single fuel swirler <NUM>. A gaseous fuel pathway with the combined flashback arrestor and flow restrictor thus includes the gaseous fuel supply <NUM>, the annular gallery <NUM>, the apertures 46a, the elongated axial fuel passage <NUM>, and the fuel outlet <NUM>. In the shown case, the fuel outlet <NUM> is positioned on an outer surface of the fuel swirler <NUM> bordering the mixing site <NUM> downstream of the fuel swirler <NUM>, the fuel outlet <NUM> leading directly to the mixing site <NUM>. This may aid in preventing early ignition of the gaseous fuel, as discussed above.

Referring to <FIG>, the apertures 46a in the outer fuel swirler <NUM> (in the case of a dual fuel nozzle <NUM>) or single fuel swirler <NUM> (in the case of a single fuel nozzle <NUM>) may be sized to prevent flame propagation upstream towards the first fuel source S1. In the shown case, the apertures are circular apertures with cross-sectional diameters of at most <NUM> inches (<NUM>). In some embodiments, the cross-sectional diameters may be <NUM> inches (<NUM>). Other shapes (such as slots or squares) and sizes for the apertures may be contemplated as well. In addition, the number, shape, arrangement and size of the apertures 46a may vary to control the flow rate of the gaseous fuel F1 towards the mixing zone <NUM>. The material, mass and wall thickness of the swirler <NUM> may also vary to achieve a desired metal thermal mass for flame quenching.

Referring to <FIG> and <FIG>, in another embodiment, the combined flashback arrestor and flow restrictor <NUM> is a sleeve or washer-like insert or add-on component that is positioned at the junction between the of the housing <NUM> and the outer fuel swirler <NUM>. In this case, the housing <NUM> is dimensioned to accommodate the inserted combined flashback arrestor and flow restrictor <NUM> in a concentric arrangement between the housing <NUM> and outer fuel swirler <NUM>, as shown in <FIG>. The combined flashback arrestor and flow restrictor <NUM> has an annular body <NUM> with an inner circumferential surface <NUM> and an outer circumferential surface <NUM>. A plurality of discrete apertures <NUM> extend from the inner circumferential surface <NUM> to the outer circumferential surface <NUM>, allowing the gaseous fuel F1 to flow from the first fuel supply <NUM>, into the annular gallery <NUM>, through the apertures <NUM>, through the first aperture <NUM> (i.e. the inlet to the first elongated axial fuel passage <NUM>) and into the first elongated axial fuel passage <NUM>. In other cases, the combined flashback arrestor and flow restrictor <NUM> may be insertable into a single fuel nozzle <NUM> between the housing <NUM> and the single fuel swirler <NUM>. Other locations for the combined flashback arrestor and flow restrictor <NUM> may be contemplated as well, for instance at the downstream end D. of the fuel nozzle <NUM> adjacent the first fuel outlet <NUM>. The widths of the housing and the annular gallery <NUM> may vary, for instance based on the size of the combined flashback arrestor and flow restrictor <NUM>.

The apertures <NUM> in the combined flashback arrestor and flow restrictor <NUM> may be sized to prevent flame propagation upstream towards the first fuel source S1. In the shown case, the apertures are circular apertures with cross-sectional diameters of at most <NUM> inches (<NUM>). In some embodiments, the cross-sectional diameters may be <NUM> inches (<NUM>). Other shapes (such as slots or squares) and sizes may be contemplated as well. In addition, the number, shape and size of the apertures <NUM> may vary to control the flow rate of the gaseous fuel F1 towards the mixing zone <NUM>. In the shown case, the apertures <NUM> are evenly spaced in a single row formation, although other arrangements for the apertures <NUM>, both evenly spaced and unevenly spaced, may be contemplated as well. The material, mass, width and thickness of the combined flashback arrestor and flow restrictor <NUM> may also vary to achieve a desired metal thermal mass for flame quenching.

In the embodiment shown in <FIG>, the gaseous fuel pathway with the combined flashback arrestor and flow restrictor <NUM> thus includes the first fuel supply <NUM>, the annular gallery <NUM>, the apertures <NUM>, the first aperture <NUM> (in the outer swirler <NUM>), the first elongated axial fuel passage <NUM>, and the first fuel outlet <NUM>. In the shown case, the first fuel outlet <NUM> is positioned on an outer surface of the outer fuel swirler <NUM> bordering the mixing site <NUM> downstream of the outer fuel swirler <NUM>, the first fuel outlet <NUM> leading directly to the mixing site <NUM>. This may aid in preventing early ignition of the gaseous fuel, as discussed above.

Claim 1:
A fuel supply system for an aircraft engine, comprising:
a gaseous fuel source (S1); and
a fuel nozzle (<NUM>) including:
a housing (<NUM>) having a housing interior chamber (<NUM>); and
a fuel swirler (<NUM>, <NUM>; <NUM>') disposed inside the housing interior chamber (<NUM>),
the fuel swirler (<NUM>, <NUM>; <NUM>') fluidly connected to the gaseous fuel source (S1) for directing gaseous fuel to a combustor (<NUM>) of an aircraft engine,
the fuel swirler (<NUM>, <NUM>; <NUM>') defining a gaseous fuel path (<NUM>) extending from a fuel inlet (<NUM>) to a fuel outlet (<NUM>),
the gaseous fuel path (<NUM>) including a plurality of discrete apertures (46a; <NUM>) distributed around a circumference of the fuel swirler (<NUM>, <NUM>),
characterized in that
the plurality of discrete apertures (46a) are defined through a radially exterior surface of the fuel swirler (<NUM>) relative to a longitudinal axis (L) of the fuel swirler (<NUM>),
wherein the plurality of discrete apertures (46a) are positioned at the fuel inlet (<NUM>) of the fuel swirler (<NUM>),
wherein each of the plurality of discrete apertures (46a; <NUM>) has a cross-sectional area selected to prevent a flame from propagating in an upstream direction through the gaseous fuel path (<NUM>) towards the gaseous fuel source (S1), and
wherein the plurality of discrete apertures (46a; <NUM>) have cross-sectional diameters of at most <NUM> (<NUM> inches).