Patent Description:
A gas turbine engine may be used to power aircraft or various other types of vehicles or systems. Such engines typically include: a compressor that receives and compresses incoming gas such as air; a combustor in which the compressed gas is mixed with fuel and burned to produce high-pressure, high-velocity exhaust gas; and one or more turbines that extract energy from the exhaust gas exiting the combustor.

There is an increasing desire to reduce combustion by-product emissions, particularly oxides of nitrogen (NOx), carbon monoxide (CO), and particulates, which may form during the combustion process. Combustion is typically achieved in a combustion chamber over a range of operating conditions. As a result, combustors operate under a variety of pressures, temperatures, and mass flows. These factors change with power requirements and environmental conditions. Controlling the various forms of combustion by-products over the range of operating conditions, thus, provides a number of challenges.

An injector module according to the prior art is known from <CIT>.

As such, it is desirable to provide improved combustion systems in gas turbine engines. It is also desirable to provide an injector module for a combustor that provides effective combustion across a number of different operating conditions and that also reduces emissions of NOx and other combustion by-products. Moreover, it is desirable to provide an injector module that is more robust and maintains effective and efficient fuel injection in a number of different operating conditions. It is also desirable to provide an injector module that is highly manufacturable at reduced costs. Moreover, it is desirable to provide an injector module that provides fuel injection control in a cost-effective manner. Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the present disclosure.

The injector module according to the invention includes an injector stem that extends along an injector longitudinal axis between an inlet end and an outlet end of the injector module. The injector module also includes a first fuel line of a first fuel circuit at least partly extending through the injector stem. The first fuel line has a first outlet disposed at the outlet end of the injector stem. The injector module further includes a second fuel line of a second fuel circuit at least partly extending through the injector stem. The second fuel line has a second outlet disposed at the outlet end of the injector stem. The first outlet and the second outlet are spaced apart and have different orientations relative to the injector longitudinal axis. The first fuel line is thermally coupled to the second fuel line. The first fuel line includes a wrap segment that extends about the second fuel line to thermally couple the first fuel line to the second fuel line. The second fuel line includes an inlet and the second fuel line includes a turn between the inlet and the outlet and the wrap segment wraps about the turn of the second fuel line. The wrap segment is axially curved and wraps about the bulbous portion of the stem, proximate the outlet end. The wrap segment curves from the forward side to the aft side and back toward the outlet segment.

In another embodiment, a method of operating the injector module according to the invention is diclosed.

The method also includes controlling selectively, with a control system of the gas turbine engine, fuel injection by at least one of the first fuel circuit and the second fuel circuit. Moreover, the method includes cooling of the second fuel line by the first fuel line during the fuel injection by the at least one of the first fuel circuit and the second fuel circuit.

In yet another embodiment, a gas turbine engine is disclosed with a combustion section having a combustion chamber that extends about an engine axis of the gas turbine engine. The combustion chamber has an upstream end and a downstream end that are separated along the axis. The gas turbine engine also includes the injector module according to the invention.

Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background.

The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

Broadly, an improved injector module for a gas turbine engine is disclosed according to example embodiments of the present disclosure. The exemplary embodiments discussed herein provide a combustion system and methods of combustion for a gas turbine engine that achieve effective and efficient combustion over a range of operating conditions. The injector module may provide desirable reductions in emissions.

The injector module may include a plurality of fuel outlets to a combustion chamber within the engine. A control system may also be included that selectively controls the outlets independently, for example, based upon certain engine operating conditions (i.e., according to detected operating parameters). Accordingly, emissions may be advantageously reduced.

Also, there may be individual fuel lines that are routed through the injector module to their respective outlets. These fuel lines may be thermally coupled. As such, fuel in one line may provide cooling for the fuel in the other line. The injector module may also include a cooling jacket, a shroud, etc. for further thermal benefits. Accordingly, the injector module may operate across a wide range of operating conditions while maintaining high efficiency, low emissions, and other advantages. Related methods of operating the injector module are also disclosed.

Moreover, methods of manufacturing the injector module are disclosed. For example, in some embodiments, one or more parts of the injector module may be unitary and monolithic, which may increase manufacturing efficiency. Furthermore, in some embodiments, one or more parts may be additively manufactured layer-by-layer to further improve manufacturability.

<FIG> is a cross-sectional view of a combustor area of an engine <NUM> showing a combustion system <NUM> in accordance with exemplary embodiments of the present disclosure. As shown, the engine <NUM> may be a turbofan type of gas turbine engine, with a turbine wheel <NUM> that achieves mechanical energy from combustion of air and fuel in a combustor <NUM>. The combustor <NUM> mixes admitted air with fuel and ignites the resulting mixture to generate high energy combustion gases that are then directed to the turbine wheel <NUM>. The mechanical energy from the turbine wheel <NUM> may be used to drive a compressor wheel <NUM>, which may be embodied in the form of a ducted fan driven by the turbine wheel <NUM> through a shaft <NUM>. The shaft <NUM> defines an axis <NUM> around which the compressor wheel <NUM> and the turbine wheel <NUM> rotate. The compressor wheel <NUM> may pressurize air for use in the combustor <NUM> and generally accelerate air through the engine <NUM>, which may contribute to thrust.

Air may be delivered from the compressor wheel <NUM> to the combustor <NUM> through an air discharge <NUM>. From there, compressed air may be discharged into the combustor's case <NUM>. The case <NUM> may define an expanding diffuser <NUM> that leads to a liner <NUM>. Combustion may be contained within the liner <NUM>. The combustor <NUM> may be an annular type, with the liner <NUM> and the case <NUM> encircling the shaft <NUM>. Accordingly, the liner <NUM> may define a single annular shaped combustion chamber <NUM> that extends around the axis <NUM>. In some embodiments, the liner <NUM> may include a dome <NUM> at its upstream end <NUM>. The liner <NUM> may gradually narrow as it extends further in the downstream direction, and the liner <NUM> may terminate at an exhaust opening <NUM> at its downstream end <NUM>.

The engine <NUM> may also include an injector module <NUM> with an inlet end <NUM> and an outlet end <NUM>. The injector module <NUM> may extend into the case <NUM>, and the outlet end <NUM> may be received within the liner <NUM> via an injector opening <NUM>. As such, the outlet end <NUM> may be disposed in the combustion chamber <NUM>. The inlet end <NUM> may be disposed outside the case <NUM> and may be fluidly connected to at least one fuel source <NUM> (a fuel tank) to receive fuel therefrom. (Although multiple fuel sources <NUM> are illustrated in <FIG>, there may be a single, common fuel source <NUM> in some embodiments. ) The injector module <NUM> may inject this fuel into the chamber <NUM> via the outlet end <NUM> as will be discussed. Although only one injector module <NUM> is shown in <FIG>, it will be appreciated that a plurality of injector modules may be disposed about the axis <NUM> and angularly spaced about the annular combustion chamber <NUM>. In some embodiments, the number of injector modules <NUM> may be sixteen (<NUM>), although the number may be different in different configurations of the engine <NUM>.

During operation, air from the compressor wheel <NUM> may be supplied into the case <NUM> via the air discharger <NUM>. The introduced air may flow between the case <NUM> and the liner <NUM> through an outer air plenum <NUM> and an inner air plenum <NUM>. From these plenums <NUM>, <NUM>, the air may enter the combustion chamber <NUM> through the injector opening <NUM> (and openings in the injector module <NUM> to be discussed), through effusion cooling holes <NUM> distributed across the liner <NUM>, and/or through one or more quench jets <NUM>. In some embodiments, the relative contributions of admitted air may include a majority of the air entering the combustion chamber <NUM> through the injector opening <NUM>, with the quench jets <NUM> providing the second largest inflow, followed by the effusion cooling holes <NUM>. The injector module <NUM> may selectively inject fuel into the chamber <NUM>. Also, an igniter <NUM> may be included, which ignites the air/fuel mixture within the chamber <NUM> for drivingly rotating the turbine wheel <NUM>.

The engine <NUM> may additionally include a control system <NUM>. The control system <NUM> may include a processor <NUM>, a computerized memory device <NUM>, sensors <NUM>, and/or other related components. The injector module <NUM> may be operatively connected to the control system <NUM> such that the control system <NUM> selectively controls injection of fuel into the chamber <NUM> as will be discussed in greater detail below.

Referring to <FIG> and <FIG>, the injector module <NUM> will be discussed in greater detail according to the invention. As mentioned above, the injector module <NUM> includes an inlet end <NUM> and an outlet end <NUM>. The injector module <NUM> may be elongate and extends generally along an injector longitudinal axis <NUM> between the inlet end <NUM> and the outlet end <NUM>. The injector module <NUM> may also define an injector transverse axis <NUM>, which may be normal to the injector longitudinal axis <NUM>, which may intersect the axis <NUM>, and which may extend between a forward side <NUM> and an aft side <NUM> of the injector module <NUM>. As shown, the injector module <NUM> includes an injector stem <NUM> and may include an injector shroud <NUM> as well as other fittings and components that will be discussed in detail below.

As shown in <FIG>, the injector stem <NUM> may also include an exterior surface <NUM>. In some embodiments, a majority of the exterior surface <NUM> may be cylindrical with a circular cross section taken normal to the injector longitudinal axis <NUM>. At the outlet end <NUM>, the exterior surface <NUM> may be bulbous, rounded, and generally semi-spherical.

Also, in some embodiments, the injector stem <NUM> may be made out of a metallic material. In some embodiments, the injector stem <NUM> may be a unitary, one-piece, monolithic member.

The injector stem <NUM> may be formed in a variety of ways without departing from the scope of the present disclosure. In some embodiments, the injector stem <NUM> may be additively manufactured layer-by-layer in an additive manufacturing system (e.g., a direct metal laser sintering (DMLS) system). Accordingly, the injector stem <NUM> may be manufactured conveniently and efficiently despite including complex features described in detail below. It will also be appreciated that the stem <NUM> may be formed via casting processes, may be assembled from a plurality of parts, etc. without departing from the scope of the present disclosure.

The injector stem <NUM> may include a first inlet branch <NUM> and a second inlet branch <NUM> at the inlet end <NUM>. The first and second inlet branches <NUM>, <NUM> may be hollow and tubular. The first inlet branch <NUM> may extend from the inlet end <NUM>, for example, in a direction that is substantially parallel to the transverse axis <NUM> and may extend in a forward direction from the forward side <NUM>. The second inlet branch <NUM> may extend from the inlet end <NUM> and may be directed at an angle but generally along the transverse axis <NUM> in a rearward direction from the aft side <NUM>. The first inlet branch <NUM> and the second inlet branch <NUM> may be coupled to the fuel source <NUM> (<FIG>) via a fluid connector (not shown), or there may be a continuous connection between the inlet branches <NUM>, <NUM> and the fuel source(s) <NUM>.

Moving further along the injector longitudinal axis <NUM> away from the inlet end <NUM>, the injector stem <NUM> may include a flange <NUM>. The flange <NUM> may be relatively flat, platelike, and thin. The flange <NUM> may project substantially perpendicular to the injector longitudinal axis <NUM>. The outboard corners of the flange <NUM> may collectively define a bolt pattern for fixedly attaching the stem <NUM> to the combustor case <NUM> as shown in <FIG>.

Furthermore, the injector stem <NUM> may include a shroud support structure <NUM>. The shroud support structure <NUM> may include at least one projection that projects outward radially from the axis <NUM>. As shown, the shroud support structure <NUM> may include two rounded, cylindrical projections (i.e., arms) that project in an outboard direction from opposite sides of the axis <NUM>. The shroud support structure <NUM> may be attached to the shroud <NUM> to connect the shroud <NUM> to the stem <NUM> as will be discussed in more detail below.

As shown in <FIG>, the injector stem <NUM> includes a first stem outlet <NUM> and a second stem outlet <NUM> at the outlet end <NUM> of the injector module <NUM>. The first stem outlet <NUM> and the second stem outlet <NUM> include respective apertures that are spaced apart angularly about the injector longitudinal axis <NUM> to have different orientations relative to the axis <NUM>. The second stem outlet <NUM> (i.e., the axis of the outlet <NUM>) may be directed substantially normal to the injector longitudinal axis <NUM> (e.g., directed substantially along the axis <NUM> and away from the aft side <NUM>) whereas the first stem outlet <NUM> may be canted away at an angle relative to the axis <NUM> and the axis <NUM>.

Furthermore, the flange <NUM> may be fixedly attached to the exterior of the case <NUM> as shown in <FIG>, and the outlet end <NUM> may be received within the liner <NUM> with the second stem outlet <NUM> directed generally rearward along the engine longitudinal axis <NUM> toward the downstream end <NUM> of the chamber <NUM>. The injector transverse axis <NUM> may be disposed at a slight angle relative to the engine longitudinal axis <NUM>; however, the second stem outlet <NUM> may be directed substantially rearward along the engine longitudinal axis <NUM>. As such, the second stem outlet <NUM> may provide axially directed fuel injection in the downstream direction relative to the axis <NUM> and relative to flow through the chamber <NUM>.

In contrast, the first stem outlet <NUM> may be directed substantially tangentially with respect to the axis <NUM>. In some embodiment, the first stem outlet <NUM> may be directed slightly in the forward-facing direction with respect to the axis <NUM> and primarily tangentially with respect to an imaginary circle that is centered on and normal to the axis <NUM>. As such, the first stem outlet <NUM> may provide tangentially-directed fuel injection into the chamber <NUM> relative to the axis <NUM>.

As shown in <FIG>, the first stem outlet <NUM> may be fitted with a first nozzle member <NUM>, and the second stem outlet <NUM> may be fitted with a second nozzle member <NUM>. The nozzle members <NUM>, <NUM> may atomize and discharge fuel into the chamber <NUM>.

The stem <NUM> includes a first fuel line <NUM> and a second fuel line <NUM> (<FIG>) that extend internally through the stem <NUM> between the inlet end <NUM> and the outlet end <NUM>. The first fuel line <NUM> may fluidly connect the first inlet branch <NUM> to the first stem outlet <NUM>, and the second fuel line <NUM> may fluidly connect the second inlet branch <NUM> to the second stem outlet <NUM>. The first fuel line <NUM> may be referred to as a so-called "pilot fuel line," and the second fuel line <NUM> may be referred to as a so-called "main fuel line" in some embodiments. Also, in some embodiments, the first fuel line <NUM> may have a smaller cross sectional area than the second fuel line <NUM>.

As represented in <FIG>, the injector module <NUM> may define at least part of a first fuel circuit <NUM> of the engine <NUM>. Using the first fuel circuit <NUM>, fuel may flow from the source <NUM>, through the stem <NUM> via the first fuel line <NUM>, and out of the stem <NUM> into the chamber <NUM> via the first stem outlet <NUM>. Also, the injector module <NUM> may define at least part of a second fuel circuit <NUM>, wherein fuel may flow from the source <NUM>, through the stem <NUM> via the second fuel line <NUM>, and out of the stem <NUM> via the second stem outlet <NUM>.

As will be discussed, the control system <NUM> may selectively and independently control fuel injection via the first fuel circuit <NUM> and the second fuel circuit <NUM>. Thus, the control system <NUM> may operate the injector module <NUM> in a manner that provides environmental benefits (e.g., reduced emissions, etc.).

Additionally, the first fuel line <NUM> and the second fuel line <NUM> are thermally coupled within the stem <NUM>. Accordingly, heat in one line <NUM>, <NUM> may transfer to the other to provide cooling. Because of this heat transfer, fuel in the lines <NUM>, <NUM> may be less prone to coking or other problems associated with overheating.

Moreover, as shown in <FIG> and <FIG>, the stem <NUM> may include a heat shield <NUM>. The heat shield <NUM> may be defined by a gap <NUM> (i.e., a heat shield gap) that is offset in an inboard direction from the exterior surface <NUM>. The gap <NUM> may extend about and jacket a majority of the stem <NUM> so as to jacket the first and second fuel lines <NUM>, <NUM>. Also, as shown in <FIG> and <FIG>, the gap <NUM> may be open proximate the outlet end <NUM> so as to encircle the first stem outlet <NUM> (<FIG>) and the second stem outlet <NUM> (<FIG>). The gap <NUM> may insulate and protect the fuel within the fuel lines <NUM>, <NUM> from external heat.

The shroud <NUM> of the injector module <NUM> may be hollow and cup-shaped. The shroud <NUM> may include an exterior surface <NUM>, an internal surface <NUM>, an upper rim <NUM>, and a bottom end <NUM>. The upper rim <NUM> may be circular and its diameter may be slightly less than that of the injector opening <NUM> (<FIG>) to be received therein. The bottom end <NUM> may be rounded (e.g., semi-spherical). The majority of the exterior surface <NUM> and internal surface <NUM> may be rounded and contoured, but the shroud <NUM> may include a substantially flat face <NUM> on one side. The shroud <NUM> may include an array (a plurality) of effusion cooling holes <NUM> extending through the wall thickness of the shroud <NUM> between the exterior surface <NUM> and the internal surface <NUM>. The effusion cooling holes <NUM> may extend at non-perpendicular angles relative to the exterior and internal surfaces <NUM>, <NUM> for directing film cooling air therethrough. The shroud <NUM> may further include a first opening <NUM> for the first stem outlet <NUM> and a second opening <NUM> for the second stem outlet <NUM>. The first and second openings <NUM>, <NUM> may be round (e.g., circular) holes extending through the wall thickness of the shroud <NUM>. The second opening <NUM> may be included on the flat face <NUM> of the shroud <NUM>, whereas the first opening <NUM> may be angularly spaced therefrom with respect to the axis <NUM> and may extend through the bottom end <NUM>.

The shroud <NUM> may be attached to the stem <NUM> via the shroud support structures <NUM>. More specifically, the upper rim <NUM> may receive the shroud support structures <NUM> with pins <NUM> (<FIG>) attaching the shroud <NUM> to the stem <NUM>. As such, the shroud <NUM> may receive the stem <NUM> (at the outlet end <NUM>) and may be spaced in an outboard direction therefrom.

The injector module <NUM> may further include a first swirler <NUM> and a second swirler <NUM>. The first and second swirlers <NUM>, <NUM> may be rounded and disc-shaped. The first swirler <NUM> may include a central hole <NUM> (<FIG>) that receives the first nozzle member <NUM>, and the second swirler <NUM> may include a central hole <NUM> (<FIG>) that receives the second nozzle member <NUM> (<FIG>). Also, the first and second swirlers <NUM>, <NUM> may include a plurality of swirler holes <NUM> (<FIG> and <FIG>) extending therethrough and arrayed around the respective central hole <NUM>, <NUM>.

As shown in <FIG> and <FIG>, the second swirler <NUM> may abut and mate to a circular, flat seat <NUM> surrounding the second stem outlet <NUM>. In some embodiments, the second swirler <NUM> may be welded or brazed to the seat <NUM>; however, the second swirler <NUM> may be attached via fasteners, etc. in other embodiments.

As shown in <FIG> and <FIG>, the first swirler <NUM> may threadably attached to a cylindrical projection <NUM> that surrounds the first stem outlet <NUM>. There may be a sealing ring <NUM> between mating faces of the swirler <NUM> and stem <NUM> as well.

Additionally, with the shroud <NUM> attached to the stem <NUM>, the first and second swirlers <NUM>, <NUM> may be received in the first and second openings <NUM>, <NUM>, respectively. As shown in <FIG>, the second swirler <NUM> may include an outer diameter area <NUM> that opposes an inner diameter area <NUM> of the second opening <NUM>. In some embodiments, this interface may be formed with precision and with corresponding dimensions. More specifically, the outer and inner diameter areas <NUM>, <NUM> may have substantially equal diameters (i.e., a so-called "line-to-line" interface that falls within reasonable manufacturing tolerances). As such, the areas <NUM>, <NUM> may fit closely without further attachment therebetween. In additional embodiments, the outer and inner diameter areas <NUM>, <NUM> may be welded or brazed together, thereby sealing the joint. This joint may also be configured to account for differences in thermal expansion between the swirler <NUM> and the shroud <NUM> during operation. The first swirler <NUM> may be attached to the shroud <NUM> differently. For example, as shown in <FIG>, there may be a resilient sealing ring <NUM> included between the outer diameter surface of the first swirler <NUM> and the inner diameter surface of the first opening <NUM>.

Operations of the injector module <NUM> will now be discussed. As stated, the injector module <NUM> may define the first fuel circuit <NUM> and the second fuel circuit <NUM>. These fuel circuits <NUM>, <NUM> may be fluidly independent (i.e., fluidly disconnected) through the injector module <NUM> with separate and distinct inputs and outputs. Also, fuel injection may be selectively provided independently from the fuel circuits <NUM>, <NUM> into the chamber <NUM> as will be discussed.

To inject fuel via the first fuel circuit <NUM>, fuel may flow from the source <NUM> to be received by the first inlet branch <NUM> and routed through the first fuel line <NUM> (<FIG> and <FIG>) to the first nozzle member <NUM> in the first stem outlet <NUM>. The first swirler <NUM> may swirl the atomized fuel and air mixture further into the chamber <NUM>. Also, due to the orientation of the nozzle member <NUM>, the injector module <NUM> may inject fuel in a substantially tangential direction within the combustion chamber <NUM> relative to the axis <NUM> and slightly toward the dome <NUM>.

Furthermore, to inject fuel via the second fuel circuit <NUM>, fuel may flow from the source <NUM> to be received by the second inlet branch <NUM> and routed through the second fuel line <NUM> (<FIG> and <FIG>) to the second nozzle member <NUM> in the second stem outlet <NUM>. The second swirler <NUM> may swirl the atomized fuel and air mixture further into the chamber <NUM>. Also, due to the orientation of the nozzle member <NUM>, the injector module <NUM> may inject fuel in a longitudinal, rearward direction within the combustion chamber <NUM> along the axis <NUM> and toward the downstream end <NUM>.

The control system <NUM> may control and regulate fuel injection via the first and second fuel circuits <NUM>, <NUM>. In this regard, embodiments of the present disclosure may be described herein in terms of functional and/or logical block components and various processing steps. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any number of systems.

During operation of the combustion system <NUM>, the control system <NUM> may receive sensor input from one or more sensors <NUM>. The sensors <NUM> may be of any suitable type and may detect any one of a number of parameters relating to operation of the engine <NUM> (e.g., operating speed of the engine <NUM>, altitude, etc.). The control system <NUM> may operate the injector module <NUM> according to the sensor input from the sensor <NUM> in some embodiments. Also, in some embodiments, the processor <NUM> may access the memory device <NUM> to obtain stored data corresponding to the sensor input and, thus, control injection from the injector module <NUM> accordingly. Thus, the control system <NUM> may selectively control fuel injection based at least partly on the detected operating conditions of the engine <NUM>.

More specifically, <FIG> graphically illustrates combustion in the combustion chamber <NUM> of the engine <NUM> using the injector module <NUM> at various operating conditions according to example embodiments. Fuel pressure is indicated along the vertical axis <NUM> in pounds per square inch, and fuel flow is indicated along the horizontal axis <NUM> in pounds per hour.

Fuel flow may be divided between the first fuel line <NUM> and the second fuel line <NUM>. In some embodiments, a flow divider valve (not shown) may sequence operation to divide flow between the two fuel lines <NUM>, <NUM>. Also, the control system <NUM> may selectively operate the first fuel line <NUM> and independently operate the second fuel line <NUM>. Accordingly, the first and second fuel lines <NUM>, <NUM> may inject fuel into the chamber <NUM> according to different injection profiles. These respective injection profiles of the first and second fuel lines <NUM>, <NUM> may vary according to those operating conditions of the engine <NUM>.

More specifically, the injection profile of the first fuel line <NUM> (the first injection profile) may be represented by a curve <NUM> of <FIG>, whereas the injection profile of the second fuel line <NUM> (the second injection profile) may be represented by a curve <NUM> of <FIG>. In this example, at start of the engine <NUM>, fuel flow is introduced through the first fuel line <NUM> as indicated by curve <NUM>. The igniter <NUM> may be turned on and light-off may occur at point <NUM>. The introduced fuel may be lit by the igniter <NUM> causing ignition. Speed of the engine <NUM> increases and fuel flow may be increased to a stable idle state at point <NUM>. During this phase, more than fifty percent of the fuel flow may be through the first fuel line <NUM>, and as represented in <FIG>, the fuel flow may be entirely through the first fuel line <NUM> (i.e., second fuel line <NUM> is shut-off). In additional embodiments, a small amount of trickle flow may be delivered through the second fuel line <NUM> during this phase; however, it will be appreciated that the first fuel line <NUM> injects more fuel during this phase than the second fuel line <NUM> in these embodiments. The igniter <NUM> may be turned off at a threshold speed of the engine <NUM>. Above the idle point <NUM>, fuel flow may be initiated and/or increased through the second fuel line <NUM> as shown by the curve <NUM>, while it is decreased through the first fuel line <NUM> as shown by a downward slope of the curve <NUM>. Fuel flow through the first fuel line <NUM> may be decreased to a minimum level <NUM> sufficient to keep the flame initiated from the first fuel line <NUM> from blowing out. The first fuel line <NUM> may maintain flow at the minimum level <NUM> onward. For example, at full power of the engine <NUM>, more than fifty percent, and in the exemplary embodiment, approximately ninety percent of the fuel flow may be provided via the second fuel line <NUM>. Also at full power, less than fifty percent of the total fuel flow may be provided through the first fuel line <NUM>, and in the exemplary embodiment, approximately ten percent may be delivered via the first fuel line <NUM>.

It will be appreciated that these injection profiles may vary based on the power conditions of the engine <NUM>. In the embodiments of <FIG>, the injection profiles of the first and second fuel lines <NUM>, <NUM> is such that more fuel is injected by the first fuel line <NUM> than the second fuel line <NUM> in lower-power operating conditions of the engine, whereas more fuel is injected by the second fuel line <NUM> than the first fuel line <NUM> in comparatively higher-power operating conditions.

There may be additional injection profiles that vary, for example, based on the altitude of the aircraft. For example, at higher altitudes in which the engine <NUM> is in a relatively low-power operating condition, a majority of fuel injection may be provided via the first fuel line <NUM>. In contrast, at lower altitudes in which the engine <NUM> is in a relatively high-power operating condition, a majority of fuel injection may be provided via the second fuel line <NUM>.

Furthermore, the injection profiles of the first and second fuel lines <NUM>, <NUM> may vary dependent on whether a START request is received from an auxiliary power unit (APU). If an APU ignition request is received, then the first fuel line <NUM> may deliver the majority of the fuel into the chamber <NUM> for starting the APU.

Additionally, the processor <NUM> may process the sensor input from the sensor <NUM> to distinguish a high-power operating condition from a comparatively low-power operating condition of the engine <NUM>. The control system <NUM> may operate the first and second fuel circuits <NUM>, <NUM> differently in the high- and low-power conditions. The control system <NUM> may, thus, provide corresponding control signals to the injector module <NUM> for operation based on these detected operating conditions.

Controlling the injector module <NUM> according to the methods of the present disclosure may provide substantial benefits. For example, to cold-start an auxiliary power unit (APU), a majority (e.g., all) fuel may be delivered tangentially via the first fuel circuit <NUM>. This tangential injection may provide high operability, for example, at high-altitude operations. In other conditions (e.g., high-power operating conditions of the engine <NUM>), a majority of the fuel may be injected longitudinally via the second fuel circuit <NUM>. This longitudinally-directed injection may provide low-emission operations at high-power operating conditions, thereby providing environmental benefits.

Additionally, the injector module <NUM> may include a number of features that provide thermal benefits, for example, for allowing the injector module <NUM> to robustly operate in high temperature environments in a number of operating conditions. For example, the shroud <NUM> and may shield the stem <NUM> from high temperature combustion gases in the chamber <NUM>. The array of effusion cooling holes <NUM> in the shroud <NUM> may provide film cooling for the injector module <NUM>. Also, the heat shield <NUM> may thermally insulate the first and second fuel lines <NUM>, <NUM> within the stem <NUM>.

Moreover, as mentioned above, the first and second fuel lines <NUM>, <NUM> are thermally coupled. In some embodiments, the first fuel line <NUM> may be thermally coupled to the second fuel line <NUM> to cool the second fuel line <NUM> at one or more operating conditions of the engine <NUM>. In other words, the first fuel line <NUM> may be thermally coupled as a heat sink to the second fuel line <NUM> in at least one operating condition of the engine <NUM>. For example, in some operating conditions discussed above, the first fuel circuit <NUM> may inject fuel while the second fuel circuit <NUM> remains shut-off. In these conditions, fuel flowing through the first fuel circuit <NUM> may receive heat from (i.e., cool) fuel residing within the second fuel circuit <NUM>. Accordingly, coking within the second fuel circuit <NUM> is less likely.

In the embodiment according to the invention and represented in <FIG>, the first fuel line <NUM> includes a first longitudinal segment <NUM>, a wrap segment <NUM>, and an outlet segment <NUM>. The first longitudinal segment <NUM> may be axially straight and may extend along the injector longitudinal axis <NUM> from the first inlet branch <NUM> (<FIG> and <FIG>) to the wrap segment <NUM> (<FIG>). The first longitudinal segment <NUM> may be disposed closer to the forward side <NUM> of the stem <NUM> than the aft side <NUM> as it extends along the axis <NUM>. Also, the wrap segment <NUM> is axially curved and wraps about the bulbous portion of the stem <NUM>, proximate the outlet end <NUM>. The wrap segment <NUM> curves from the forward side <NUM> to the aft side <NUM> and back toward the outlet segment <NUM>. The outlet segment <NUM> may be axially straight and aligned with the first stem outlet <NUM>.

According to the invention, the second fuel line <NUM> includes a turn <NUM> and may include a longitudinal segment <NUM> and an outlet segment <NUM>. The second longitudinal segment <NUM> may be axially straight and may extend along the injector longitudinal axis <NUM> from the second inlet branch <NUM> to the turn <NUM>. The second longitudinal segment <NUM> may be disposed closer to the aft side <NUM> of the stem <NUM> than the forward side <NUM>. Also, the turn <NUM> may be an approximately ninety degree (<NUM>°) contour that bends normal to the axis <NUM>, toward the axially straight outlet segment <NUM> and toward the second stem outlet <NUM>.

The first and second longitudinal segments <NUM>, <NUM> may both extend substantially parallel to each other and may be separated on opposite sides of the axis <NUM> by an interior barrier <NUM> (<FIG>). The interior barrier <NUM> may have a relatively small thickness <NUM> such that the first and second longitudinal segments <NUM>, <NUM> are in close proximity. The material of the stem <NUM> (e.g., metallic material) may have relatively high thermal conductivity. Thus, the first and second longitudinal segments <NUM>, <NUM> may be thermally coupled together. Heat (indicated schematically as "H" in <FIG>) may transfer, for example, from the second fuel line <NUM> to the first fuel line <NUM> via the interior barrier <NUM> as indicated schematically by arrows <NUM> in <FIG>.

Furthermore, the wrap segment <NUM> extends about the second fuel line <NUM>. At least part of the wrap segment <NUM> wraps about and may extend about the turn <NUM>. In some embodiments, the wrap segment <NUM> may include a helical part <NUM> that extends from the longitudinal segment <NUM> and helically about the second fuel line <NUM> proximate (upstream) to the turn <NUM>. The helical part <NUM> may wrap and helically extend the first fuel line <NUM> from the forward side <NUM> to the aft side <NUM> of the stem <NUM> as well. The wrap segment <NUM> may also include a looping part <NUM> that extends from the helical part <NUM> and that wraps and arcuately loops about the turn <NUM> of the second fuel line <NUM>. The looping part <NUM> may be semi-circular and may lie substantially within a plane, thereby wrapping from the top side of the turn <NUM> to the bottom side of the turn <NUM> proximate the outlet end <NUM>. The looping part <NUM> may arcuately extend at least one-hundred-eighty degrees (<NUM>°) about the second fuel line <NUM>. The looping part <NUM> may also extend generally from the aft side <NUM> toward the forward side <NUM> to connect to the outlet segment <NUM> and the first stem outlet <NUM>. Thus, the wrap segment <NUM> may wrap around to thermally couple to the second fuel line <NUM>. The close proximity of the lines <NUM>, <NUM>, and the wrapped arrangement increases surface area exposure of the first fuel line <NUM> to the second fuel line <NUM>. Thus, heat (indicated schematically as "H" in <FIG>) may transfer, for example, from the second fuel line <NUM> to the wrap segment <NUM> as indicated schematically by arrows <NUM> in <FIG>.

Because of this thermal coupling, fuel within the first fuel line <NUM> may readily receive heat from the fuel in the second fuel line <NUM> (i.e., the first fuel line <NUM> may be a heat sink for the second fuel line <NUM>). Thus, in conditions where fuel flow through the first fuel line <NUM> is higher than that of the second fuel line <NUM> (e.g., up until point <NUM> <FIG>), fuel in the first fuel line <NUM> may effectively cool fuel in the second fuel line <NUM>. This may be effective, for example, in high-power conditions where fuel is injected via the first fuel line <NUM> and fuel flow is shut-off via the second fuel line <NUM>. As such, the engine <NUM> may provide high performance, produce less emissions, and the injector module <NUM> may robustly operate in a number of operating conditions.

Claim 1:
An injector module (<NUM>) for a combustion section of a gas turbine engine comprising:
an injector stem (<NUM>) having a bulbous portion, a forward side (<NUM>) and an aft side (<NUM>), the injector stem extending along an injector longitudinal axis (<NUM>) between an inlet end (<NUM>) and an outlet end (<NUM>) of the injector module;
a first fuel line (<NUM>) of a first fuel circuit at least partly extending through the injector stem, the first fuel line (<NUM>) having a first outlet (<NUM>) disposed at the outlet end of the injector stem (<NUM>);
a second fuel line (<NUM>) of a second fuel circuit at least partly extending through the injector stem (<NUM>), the second fuel line (<NUM>) having a second outlet (<NUM>) disposed at the outlet end of the injector stem (<NUM>);
the first outlet (<NUM>) and the second outlet (<NUM>) being spaced apart and having different orientations relative to the injector longitudinal axis (<NUM>); and
the first fuel line (<NUM>) being thermally coupled to the second fuel line (<NUM>)
wherein the first fuel line (<NUM>) includes a first longitudinal segment (<NUM>), an outlet segment (<NUM>) and a wrap segment (<NUM>) that extends about the second fuel line (<NUM>) to thermally couple the first fuel line (<NUM>) to the second fuel line (<NUM>);
wherein the second fuel line (<NUM>) includes an inlet and the second fuel line (<NUM>) includes a turn (<NUM>) between the inlet and the outlet (<NUM>);
wherein the wrap segment (<NUM>) wraps about the turn (<NUM>) of the second fuel line (<NUM>);
wherein the wrap segment (<NUM>) is axially curved and wraps about the bulbous portion of the stem (<NUM>), proximate the outlet end (<NUM>); and
wherein the wrap segment curves from the forward side (<NUM>) to the aft side (<NUM>) and back toward the outlet segment (<NUM>).