Gas turbine engine nozzle configurations

In one embodiment, a gas turbine engine exhaust nozzle comprises a housing having a length which extends along a central longitudinal axis and comprising an interior surface and an exterior surface, and a row of chevrons extending from an aft end of the housing, the chevrons having a root region and a tip, wherein at least a portion of at least one of the interior surface or the exterior surface is scalloped proximate the root region of a chevron. Other embodiments may be described.

RELATED APPLICATIONS

FIELD OF THE DISCLOSURE

The subject matter described herein relates to gas turbine engines, and more particularly to nozzle configurations for gas turbine engines.

BACKGROUND

Aircraft engines have been made quieter as a result of advanced high bypass ratio engines. High bypass ratio engines derive a substantial fraction of their total thrust from bypass air which is propelled around the core of the engine by an engine-driven forwardly mounted fan. This approach results in less engine noise than pure turbojet engines or low bypass ratio engines.

One approach to further reducing engine noise is to increase the amount of mixing between the high velocity gases exiting the engine, and the surrounding freestream air. In that regard, the use of geometric structures known as chevrons may reduce low-frequency noise by increasing the rate at which the engine flow streams mix with the surrounding freestream air in the aft region of the nozzle. However, in some circumstances existing chevron designs may increase the drag of the duct, thereby decreasing engine efficiency. Accordingly, additional chevron designs may find utility.

SUMMARY

In various aspects, gas turbine nozzle configurations are provided. In some embodiments, gas turbine nozzle configurations as described herein include features to reduce drag associated with the nozzle or to tailor airflow through the nozzle.

Thus, in one aspect there is provided a gas turbine engine exhaust nozzle. In one embodiment, the gas turbine engine exhaust nozzle comprises a housing having a length which extends along a central longitudinal axis and comprising an interior surface and an exterior surface and a row of chevrons extending from an aft end of the housing, the chevrons having a root region and a tip. At least a portion of at least one of the interior surface or the exterior surface is scalloped proximate the root region of a chevron.

In another aspect there is provided a gas turbine engine assembly. In one embodiment, the assembly comprises an engine assembly disposed about a longitudinal axis, a first housing surrounding portions of the engine assembly and having a length which extends along the longitudinal axis, an interior surface and an exterior surface, and defining a core flow aperture at an aft end of the housing, a second housing surrounding portions of the first housing and having a length which extends along the longitudinal axis, an interior surface and an exterior surface, the exterior surface of the first housing and the interior surface of the second housing defining a fan flow aperture at an aft end of the second housing. In one embodiment at least one of the first housing or the second housing comprises a row of chevrons extending from an aft end of the housing, the chevrons having a root region and a tip, and at least a portion of at least one of the interior surface or the exterior surface is scalloped proximate the root region of a chevron.

In another aspect, there is provided a method of operating an aircraft engine assembly. In one embodiment, the method comprises generating a flow of exhaust gas in an aircraft engine, and directing the flow of exhaust gas through an exhaust nozzle exit aperture of a first housing surrounding at least a portion of the aircraft engine. In one embodiment the aperture has a perimeter with a row of chevrons extending from an aft end of the housing, the chevrons have a root region and a tip, and at least a portion of at least one of the interior surface or the exterior surface is scalloped proximate the root region of a chevron.

In another aspect, there is provided an aircraft. In one embodiment, the aircraft comprises a fuselage, wings, and a gas turbine engine assembly. The engine assembly, in turn, comprises an engine assembly disposed about a longitudinal axis, a first housing surrounding portions of the engine assembly and having a length which extends along the longitudinal axis, an interior surface and an exterior surface, and defining a core flow aperture at an aft end of the housing, a second housing surrounding portions of the first housing and having a length which extends along the longitudinal axis, an interior surface and an exterior surface, the exterior surface of the first housing and the interior surface of the second housing defining a fan flow aperture at an aft end of the second housing. In one embodiment at least one of the first housing or the second housing comprises a row of chevrons extending from an aft end of the housing, the chevrons having a root region and a tip, and at least a portion of at least one of the interior surface or the exterior surface is scalloped proximate the root region of a chevron.

The features, functions and advantages discussed herein can be achieved independently in various embodiments described herein or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

DETAILED DESCRIPTION

Described herein are exemplary gas turbine engine nozzle configurations and methods to operate gas turbine engines, and aircraft incorporating such nozzles. In some embodiments, a gas turbine engine exhaust nozzle comprises a housing having a row of chevrons extending from an aft end of the housing. The chevrons may be generally triangular in shape having a tip and defining a root region proximate the base of adjacent chevrons. As described herein, portions of at least one of the interior surface or the exterior surface of the housing are removed proximate the root regions of the chevrons to define regions referred to herein as “scalloped” root regions. Some or all of the root regions may be scalloped. In some embodiments, introducing scalloped root regions into an exhaust nozzle may reduce the drag coefficient of the nozzle, which in turn may increase the efficiency of the engine. Alternatively, or in addition, scalloped regions may tailor airflow through the engine.

In the following description, numerous specific details are set forth to provide a thorough understanding of various embodiments. However, it will be understood by those skilled in the art that the various embodiments may be practiced without the specific details. In other instances, well-known methods, procedures, components, and circuits have not been illustrated or described in detail so as not to obscure the particular embodiments.

FIG. 1is a schematic illustration of an exemplary jet engine nozzle, according to embodiments. Referring toFIG. 1, a nozzle20has chevrons extending from an aft section of the nozzle20. Chevrons generally include certain types of serrations on the nozzle lip, typically, triangular in shape having some curvature in the lengthwise cross-section, which slightly immerses them in the adjacent flow. A chevron can project either inwardly or outwardly, by an amount that is on the order of the upstream boundary layer thickness on the inner or outer surface, respectively. In general, the chevron planform shape can also be trapezoidal or rectangular. The nozzle20includes a core flow duct40through which the engine core flow is directed, and a fan flow duct30arranged annularly around the core flow duct40, through which the fan air passes. The exit aperture of the fan flow duct30can include fan flow chevrons35, and the exit aperture of the core flow duct40can include core flow chevrons45.

FIG. 2is a schematic illustration of an aircraft200having a nozzle configured according to embodiments. Referring toFIG. 2, a commercial jet transport aircraft200comprises wings202, a fuselage201, and a propulsion system203. The illustrated propulsion system203comprises at least one gas turbine engine, which may be implemented as a turbofan engine206carried by the wings202. Each engine206is housed in a nacelle204, which includes an inlet205and a nozzle220. The nozzles220include chevrons having features, discussed in greater detail below, to reduce the coefficient of drag associated with the nozzle. In other embodiments, the aircraft200can include a different number of engines and/or engines carried by different portions of the aircraft, along with nozzles220that are tailored to the particular installation.

FIGS. 3A-3Coffer various views of a gas turbine engine nozzle configured according to embodiments.FIG. 3Ais a schematic, perspective view of a jet engine nozzle configured according to embodiments. Referring first toFIG. 3A, in some embodiments a gas turbine engine exhaust nozzle300comprises a housing302having a length which extends along a central longitudinal axis310and comprising an interior surface312and an exterior surface314.

A row of chevrons320extends from an aft end of the housing302. The chevrons320may be generally triangular or sinusoidal in shape and have tip324and a base326. Further, the chevrons324define a root region322proximate the base of adjacent triangles. As used herein, the phrase “root region” refers generally to portions of the surface area of the chevron displaced from tip of the chevrons.

In some embodiments the row of chevrons320encompasses the complete annulus of the aft end of the housing302, while in other embodiments the row of chevrons may encompass only a portion of the annulus of the housing302. Further, in the embodiment depicted inFIG. 3A, the various chevrons320are substantially uniform in size and shape, while in other embodiments the various chevrons320may vary in size and shape, e.g., to reduce noise in selected directions.

As illustrated inFIG. 3A, the surface of the annular housing302converges toward the longitudinal axis310proximate the aft end of the housing302, such that the diameter of the housing decreases progressively toward the aft end of the housing302. In some embodiments, the row of chevrons320essentially follows the contoured surface of the housing302such that each of the chevrons320lies in a plane that intersects the longitudinal axis310.

In some embodiments, at least a portion of at least one of the interior surface or the exterior surface is scalloped proximate the root region322of a chevron320. This is illustrated inFIG. 3B, which is a schematic, perspective view of a scalloped chevron nozzle surface, according to embodiments. Referring toFIG. 3B, portions of the root regions322are removed to define a scalloped surface area in the root regions322. The scalloped root regions322inFIG. 3Bare depicted by contoured lines analogous to topographical lines on a map. The scalloped root regions are generally laterally displaced from an axis340extending longitudinally along the surface302of the nozzle300and through the tip324of adjacent chevrons320, and extend from the base326of the chevron. In some embodiments, the chevrons measure between 10 centimeters and 60 centimeters from the base to the tip, and the scalloped root regions322measure between approximately 5 and 75 centimeters in width and 5 and 90 centimeters in length. Of course, one skilled in the art will recognize that the specific measurements may vary both as a function of the engine size and as a function of engine load.

As a result of the scalloped root regions322, the thickness of the annular housing varies in a cross-sectional plane drawn through the root regions322of the housing302. This is illustrated inFIG. 3C, which is a schematic, perspective, close-up view of a section of a scalloped chevron nozzle, according to embodiments. Referring toFIG. 3C, the thickness of the housing302is depicted by contour lines350and352, which follow the interior surface312of housing302and the exterior surface314of housing302, respectively. The thickness of the housing302varies between a maximum thickness at a point along a longitudinal axis354extending through the tip324of the chevron320to a minimum at a point along a longitudinal axis356extending through the base326of the chevron. In some embodiments, the thickness of the housing varies between a maximum thickness of 2.5 centimeters and a minimum thickness of 0.25 centimeters. Of course, ones skilled in the art will understand that the thickness of the housing varies both as a function of the engine size and as a function of engine load.

Differences between the surface contours of a conventional, constant-thickness housing and a contoured housing that implements scalloped root regions are illustrated inFIGS. 4 and 5.FIG. 4is a schematic, perspective line view of a scalloped chevron nozzle surface, according to embodiments. InFIG. 4the scalloped surface is indicated by solid contour lines and the conventional surface is indicated by dashed lines. The scalloped root region is indicated generally by reference numeral322. The contour lines410,412,414,416,418,420,422, and424represent lateral cross-section contour lines at various positions along the longitudinal axis356of the housing302.

The first contour line410represents a lateral cross-section taken outside the scalloped root region322. In this region the contour lines are coextensive. However, the contour lines diverge as they approach the base326of the chevron. Thus, the surfaces begin to diverge when the contour line412crosses the scalloped region322. Successive contour lines414,416,418, show increasing greater divergence between the surface contours. The divergence is at a maximum along the longitudinal axis356that extends through the base326of the chevron and the contour lines converge at a point along a longitudinal axis354extending through the tip324of the chevron.

FIG. 5is a schematic, perspective line view of a scalloped chevron nozzle surface, according to embodiments. InFIG. 5the scalloped surface is indicated by solid contour lines and the conventional surface is indicated by dashed lines. The scalloped root region is indicated generally by reference numeral322. The contour lines510,512,514are taken in a longitudinal direction, rather than a lateral direction. Thus, the contour lines510,514, taken along a longitudinal axis through the peak324of a chevron are substantially coextensive, indicating that the surfaces are of substantially equal thicknesses along those axes. By contrast, the contour lines512, taken along a longitudinal axis through the base326of a chevron diverge as the lines approach the base326, illustrating the contoured surface of a scalloped chevron root region322.

FIG. 6is a flowchart illustrating operations in a method to operate an aircraft engine assembly, according to embodiments. Referring toFIG. 6, at operation610an exhaust flow is generated. In some embodiments, operation610may be implemented by a gas turbine engine such as, e.g., a jet engine. At operation615the exhaust flow is directed through an exhaust nozzle have at least one scalloped root region, such as the nozzles described herein.

Thus, as described herein a gas turbine engine nozzle may be provided with chevrons having scalloped root regions. The root regions may be scalloped on at least one of the interior surface, the exterior surface, or both. In some embodiments, a scalloped root region may decrease the drag coefficient of the nozzle, thereby enhancing the efficiency of the engine. In another embodiment, a scalloped root region may modulate exhaust flow and or may improve the fuel efficiency of the engine and exhaust system.

Reference in the specification to “one embodiment” or “some embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least an implementation. The appearances of the phrase “in one embodiment” in various places in the specification may or may not be all referring to the same embodiment.