Engine casing treatment for reducing circumferentially variable distortion

A rotary component for a gas turbine engine defining a central axis extending along an axial direction, a radial direction extending perpendicular to the axial direction, and a circumferential direction perpendicular to both the central axis and the radial direction. The rotary component includes a plurality of rotor blades operably coupled to a rotating shaft extending along the central axis and an outer casing arranged exterior to the plurality of rotor blades in the radial direction and defining an annular gap between a tip of each of the plurality of rotor blades and the outer casing. The outer casing includes a plurality of features on an interior surface of the outer casing. A first feature of the feature(s) defines a first casing thickness, and a second feature positioned at least partially circumferentially or axially from the first feature defines a second casing thickness different than the first casing thickness.

FIELD

The present subject matter relates generally to engine casing treatments, more particularly, to engine casing treatments for reducing circumferentially variable distortion at the rotating blades of a gas turbine engine.

BACKGROUND

A gas turbine engine generally includes a fan and a core arranged in flow communication with one another. Additionally, the core of the gas turbine engine generally includes, in serial flow order, a compressor section, a combustion section, a turbine section, and an exhaust section. In operation, air is provided from the fan to an inlet of the compressor section where one or more axial compressors progressively compress the air until it reaches the combustion section. Fuel is mixed with the compressed air and burned within the combustion section to provide combustion gases. The combustion gases are routed from the combustion section to the turbine section. The flow of combustion gases through the turbine section drives the turbine section and is then routed through the exhaust section, e.g., to atmosphere. Turbofan gas turbine engines typically include a fan assembly that channels air to the core gas turbine engine, such as an inlet to the compressor section, and to a bypass duct. Gas turbine engines, such as turbofans, generally include fan cases surrounding a fan assembly including the fan blades. The compressor section typically includes one or more compressors with corresponding compressor casings.

As is known, an axial compressor for a gas turbine engine may include a number of stages arranged along an axis of the compressor. Each stage may include a rotor disk and a number of compressor blades, also referred to herein as rotor blades, arranged about a circumference of the rotor disk. In addition, each stage may further include a number of stator blades, disposed adjacent the rotor blades and arranged about a circumference of the compressor casing. During operation of a gas turbine engine using a multi-stage axial compressor, a turbine rotor is turned at high speeds by a turbine so that air is continuously induced into the compressor. The air is accelerated by the rotating compressor blades and swept rearwards onto the adjacent rows of stator blades. Each rotor blade/stator blade stage increases the pressure of the air.

In addition, during operation, the fan blades and the first stage of the axial compressor may each include an inlet. The air passing through these inlets may include distortion, such as pressure gradients, velocity gradients, and/or swirl or angular variations. Further, such distortion may be circumferentially varying around the inlet of the fan blades or the compressor blades. Moreover, such distortion may propagate through each subsequent stage of the compressor. Additionally, distortion may be created at the fan blades and/or stages of the compressor and propagate to subsequent stages of the compressor. Such distortion may affect the stall point of the compressor or the fan assembly. Stall on the compressor and/or fan blades may generally reduce the efficiency of the engine. For example, compressor stalls may reduce the compressor pressure ratio and reduce the airflow delivered to a combustor, thereby adversely affecting the efficiency of the gas turbine. A rotating stall in an axial-type compressor typically occurs at a desired peak performance operating point of the compressor. Following rotating stall, the compressor may transition into a surge condition or a deep stall condition that may result in a loss of efficiency and, if allowed to be prolonged, may lead to failure of the gas turbine.

As such, a need exists for an improved engine casing treatment for reducing circumferentially variable distortion at the rotating blades of a gas turbine engine.

BRIEF DESCRIPTION

Aspects and advantages will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one aspect, the present subject matter is directed to a rotary component for a gas turbine engine defining a central axis extending along an axial direction, a radial direction extending perpendicular to the axial direction, and a circumferential direction perpendicular to both the central axis and the radial direction. The rotary component includes a plurality of rotor blades operably coupled to a rotating shaft extending along the central axis. The rotary component further includes an outer casing arranged exterior to the plurality of rotor blades in the radial direction and defining an annular gap between a tip of each of the plurality of rotor blades and the outer casing. Further, the outer casing includes a plurality of features on an interior surface of the outer casing. A first feature of the feature(s) defines a first casing thickness, and a second feature of the feature(s) positioned at least partially circumferentially or axially from the first feature defines a second casing thickness different than the first casing thickness.

In one embodiment, the first and second features may each include an axial slot or a circumferential groove. In a further embodiment, the first casing thickness may be greater than the second casing thickness. In such an embodiment, the first casing thickness may be positioned at location of a first distortion level on the interior surface of the outer casing, and the second casing thickness may be positioned at a location of a second distortion level less than the first distortion level. In another embodiment, the first feature may further define a first characteristic, and the second feature may further define a second characteristic. Moreover, the first characteristic may be different than the second characteristic. In one such embodiment, the first and second characteristics may each include a radial height, axial dimension, circumferential dimension, separation from an adjacent feature, and/or internal angle for each of the first and second features.

In an additional embodiment, the first feature may be a first circumferential groove at a first axial location. The second feature may be a second circumferential groove at a second axial location positioned downstream of the first axial location. Moreover, the first and second characteristics may each include a radial height, circumferential length, and/or an axial width. In one such embodiment, a first radial height, first circumferential length, and/or first axial width of the first characteristic maybe greater than a second radial height, second circumferential length, and/or second axial width of the second characteristic.

In another embodiment, the first feature may be a first axial slot at a first circumferential location, and the second feature may be a second axial slot at a second circumferential location. Moreover, the first and second characteristics may each include a radial height, circumferential width, orientation, and/or axial length. In one such embodiment, the first casing thickness may be greater than the second casing thickness. Further, a first separation from an adjacent feature of the first characteristic may be less than a second separation from an adjacent feature of the second characteristic. In another embodiment, a first radial height, circumferential width, orientation, and/or axial length of the first characteristic may be greater than a second radial height, circumferential width, orientation, and/or axial length of the second characteristic.

In additional embodiments, each of the features may be positioned radially outward from one or more of the rotor blades. Further, each of the features may be positioned axially between a leading edge and a trailing edge of the rotor blade(s). In another embodiment, one or more of the features may be positioned at least partially radially outward from one or more of the rotor blades. Further, the feature(s) may be positioned at least partially axially forward of a leading edge or at least partially axially rearward of trailing edge of the rotor blade(s). In one embodiment, the rotary component may be a fan section or compressor of the gas turbine engine. As such, the rotor blade(s) may include a plurality of fan blades or compressor blades, respectively.

In another aspect, the present subject matter is directed to another rotary component for a gas turbine engine defining a central axis extending along an axial direction, a radial direction extending perpendicular to the axial direction, and a circumferential direction perpendicular to both the central axis and the radial direction. The rotary component includes a plurality of rotor blades operably coupled to a rotating shaft extending along the central axis. The rotary component further includes an outer casing arranged exterior to the plurality of rotor blades in the radial direction. The outer casing defines an annular gap between a tip of each of the plurality of rotor blades and the outer casing. Further, the outer casing includes a plurality of features on an interior surface of the outer casing. The features include one or more circumferential grooves extending along the circumferential direction. The circumferential groove(s) defines a first characteristic at a first circumferential position and a second characteristic at a second circumferential position. Moreover, the first characteristic is different than the second characteristic.

In one embodiment, the first and second characteristics may each include a casing thickness, radial height, axial width, orientation, separation from an adjacent feature, and/or an internal angle. In one such embodiment, at least one of a first casing thickness, radial height, axial width, or separation from an adjacent feature of the first characteristic may be greater than a second casing thickness, radial height, axial width, or separation from an adjacent feature of the second characteristic. Moreover, in such an embodiment, the first characteristic may be positioned at a location of a first distortion level on the interior surface of the outer casing, and the second characteristic may be positioned at a location of a second distortion level on the interior surface of the outer casing less than the first distortion level.

In a further embodiment, one circumferential groove may be positioned radially outward from one rotor blade of the rotor blades. As such, the circumferential groove may be positioned axially between a leading edge and a trailing edge of the rotor blade. In another embodiment, one circumferential groove may be positioned at least partially radially outward from one rotor blade of the plurality of rotor blades and at least partially axially forward of a leading edge or at least partially axially rearward of trailing edge of the rotor blade. In one embodiment, the rotary component may be a fan section or compressor of the gas turbine engine. As such, the rotor blade(s) may include a plurality fan blades or compressor blades, respectively. It should be further understood that the rotary component may further include any of the additional features as described herein.

These and other features, aspects and advantages will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain certain principles of the invention.

DETAILED DESCRIPTION

The terms “communicate,” “communicating,” “communicative,” and the like refer to both direct communication as well as indirect communication such as through a memory system or another intermediary system.

A rotary component is generally provided including a plurality of rotor blades connected to a rotating shaft and surrounded by an outer casing. The rotor blades and outer casing define an annular gap extending therebetween. Further, the outer casing includes one or more features on an interior surface of the outer casing. For example, the feature(s) may be positioned at least partially within the annular gap. Further, a first feature may define a first casing thickness while a second feature positioned axially, circumferentially, or both from the first feature may define a second casing thickness different than the first casing thickness. In certain embodiments, the first feature may further define a first characteristic different than a second characteristic of the second feature. As such, the difference in the first casing thickness and second casing thickness and/or the difference in the first characteristic and second characteristic may reduce a circumferentially varying distortion at one of the first or second features.

Referring now to the drawings,FIG. 1illustrates a cross-sectional view of one embodiment of a gas turbine engine10that may be utilized within an aircraft in accordance with aspects of the present subject matter. More particularly, for the embodiment ofFIG. 1, the gas turbine engine10is a high-bypass turbofan jet engine, with the gas turbine engine10being shown having a longitudinal or axial centerline axis12extending therethrough along an axial direction A for reference purposes. The gas turbine engine10further defines a radial direction R extending perpendicular from the centerline12. Further, a circumferential direction C (shown in/out of the page inFIG. 1) extends perpendicular to both the centerline12and the radial direction R. Although an exemplary turbofan embodiment is shown, it is anticipated that the present disclosure can be equally applicable to turbomachinery in general, such as an open rotor, a turboshaft, turbojet, or a turboprop configuration, including marine and industrial turbine engines and auxiliary power units.

In general, the gas turbine engine10includes a core gas turbine engine (indicated generally by reference character14) and a fan section16positioned upstream thereof. The core engine14generally includes a substantially tubular outer casing18that defines an annular inlet20. In addition, the outer casing18may further enclose and support a low pressure (LP) compressor22for increasing the pressure of the air that enters the core engine14to a first pressure level. A multi-stage, axial-flow high pressure (HP) compressor24may then receive the pressurized air from the LP compressor22and further increase the pressure of such air. The pressurized air exiting the HP compressor24may then flow to a combustor26within which fuel is injected into the flow of pressurized air, with the resulting mixture being combusted within the combustor26. The high energy combustion products60are directed from the combustor26along the hot gas path of the gas turbine engine10to a high pressure (HP) turbine28for driving the HP compressor24via a high pressure (HP) shaft or spool30, and then to a low pressure (LP) turbine32for driving the LP compressor22and fan section16via a low pressure (LP) drive shaft or spool34that is generally coaxial with HP shaft30. After driving each of turbines28and32, the combustion products60may be expelled from the core engine14via an exhaust nozzle36to provide propulsive jet thrust.

Additionally, as shown inFIGS. 1 and 2, the fan section16of the gas turbine engine10generally includes a rotatable, axial-flow fan rotor38configured to be surrounded by an annular fan casing40. In particular embodiments, the LP shaft34may be connected directly to the fan rotor38or rotor disk39, such as in a direct-drive configuration. In alternative configurations, the LP shaft34may be connected to the fan rotor38via a speed reduction device37such as a reduction gear gearbox in an indirect-drive or geared-drive configuration. Such speed reduction devices may be included between any suitable shafts/spools within the gas turbine engine10as desired or required. Additionally, the fan rotor38and/or rotor disk39may be enclosed or formed as part of a fan hub41.

It should be appreciated by those of ordinary skill in the art that the fan casing40may be configured to be supported relative to the core engine14by a plurality of substantially radially-extending, circumferentially-spaced outlet guide vanes42. As such, the fan casing40may enclose the fan rotor38and its corresponding fan rotor blades (fan blades44). Moreover, a downstream section46of the fan casing40may extend over an outer portion of the core engine14so as to define a secondary, or by-pass, airflow conduit48that provides additional propulsive jet thrust.

During operation of the gas turbine engine10, it should be appreciated that an initial airflow (indicated by arrow50) may enter the gas turbine engine10through an associated inlet52of the fan casing40. The air flow50then passes through the fan blades44and splits into a first compressed air flow (indicated by arrow54) that moves through the by-pass conduit48and a second compressed air flow (indicated by arrow56) which enters the LP compressor22. The LP compressor22may include a plurality of rotor blades (LP rotor blades45) enclosed by the outer casing18. The pressure of the second compressed air flow56is then increased and enters the HP compressor24(as indicated by arrow58). Additionally, the HP compressor24may include a plurality of rotor blades (HP rotor blades47) enclosed by the outer casing18. After mixing with fuel and being combusted within the combustor26, the combustion products60exit the combustor26and flow through the HP turbine28. Thereafter, the combustion products60flow through the LP turbine32and exit the exhaust nozzle36to provide thrust for the gas turbine engine10.

Referring now toFIGS. 3-4, illustrated schematically is rotary component61of the gas turbine engine10. Specifically, the rotary component61is configured as a portion of the LP compressor22, but it should be appreciated that the rotary component61may be configured as the HP compressor24, the fan section16, the HP turbine28, the LP turbine32, and/or any other rotary component61of the gas turbine engine10. As indicated,FIG. 4is taken along section line4-4ofFIG. 3. The rotary component61includes a one or more sets of circumferentially spaced rotor blades62, such as the LP rotor blades45, which extend radially outward towards an outer casing64from a hub66. As such, the rotor blades62may be coupled to a rotating shaft (such as the HP shaft30or LP shaft34as shown inFIG. 1). Further, the outer casing64may be arranged exterior to the rotor blades62in the radial direction R. It should be appreciated that the outer casing64may be a part of the outer casing18or fan casing40or a standalone component coupled thereto. One or more sets of circumferentially-spaced stator blades68(of which only a single stator blade68is shown inFIG. 3) may be positioned adjacent to each set of rotor blades62, and in combination form one of a plurality of stages70(of which only a single stage70is shown inFIG. 3). However, in other embodiments, such stator blades68may be absent, such as when the rotary component61is the fan section16. Each of the stator blades68may be securely coupled to the outer casing64and extends radially inward to interface with the hub66. Each of the rotor blades62may be circumscribed by the outer casing64, such that an annular gap72is defined between the outer casing64and a rotor blade tip63of each rotor blade62. Likewise, the stator blades68are disposed relative to the hub66, such that an annular gap72is defined between the hub66and a stator blade tip69of each of the stator blades68.

During operation, an operating range of the rotary component61is generally limited due to leakage flow, as indicated by directional arrows74, proximate the rotor blade tips63. In addition to leakage flow74, the initial airflow50traveling through the inlet52and/or the second compressed airfoil56traveling through the annular inlet20may include circumferential flow non-uniformities75. Such flow non-uniformities75may be present in the initial airflow50passing through the inlet52, and/or the fan section16may form such circumferential flow non-uniformities75. In other situations, the stator blades68and/or rotor blades62may form such circumferential flow non-uniformities75that propagate downstream. As best illustrated inFIG. 4, the circumferential flow-non-uniformities75are present in the form of a plurality of wakes71.

Referring now toFIG. 5, a cross-section of the core engine14is illustrated along the radial direction R and circumferential direction C. More specifically,FIG. 5illustrates a cross-section of the core engine14taken at the annular inlet20of the core engine14. Further, as illustrated, the inlet20is defined between the fan hub41and/or fan rotor38and the outer casing18of the core engine14. As such, the second compressed airfoil56may be directed through the annular inlet20and into the core engine14. As shown, the second compressed airflow56may contain flow non-uniformities (illustrated as shaded triangles75inFIG. 5) such as but not limited to pressure, temperature, velocity, and/or swirl or angular variations. As shown, the flow non-uniformities75may vary along the circumferential direction C of the inlet20. As such, the compressed airflow56may define one or more high distortion locations88and one or more low distortion level location90. Further, the high distortion locations88may propagate downstream of the inlet20and affect the stall margins and/or efficiency of the compressors22,24. It should be appreciated that such high distortion locations88may be present in the initial airflow50passing through the inlet52of the gas turbine engine10. Additionally, or alternatively, the high distortion location(s)88may be introduced in the second compressed airflow56by the fan section16and propagate downstream to the inlet20of the core engine14.

Though the inlet20is illustrated inFIG. 5, it should be appreciated that such high distortion level locations88may be present in the initial airflow50entering the inlet52and further affect the stall margins and efficiency of the fan section16, the LP compressor22, and/or the HP compressor24. Further, such high distortion level locations88may be introduced by one or more stages70of the rotary component(s)61and affect stages70of the rotary component(s)61downstream thereof. For example, high distortion level locations88may be introduced by the fan section16and affect the LP compressor22and HP compressor24downstream of the fan section16. Further, high distortion level locations88flowing through annular inlet20may affect the LP compressor22and HP compressor24. Further, high distortion locations88may be introduced by the LP compressor22(such as by the upstream stages70of the LP compressor22) and affect later stages70of the LP compressor22or the HP compressor24. In addition, high distortion locations88may be introduced by the HP compressor24(such as by the upstream stages70of the HP compressor24) and affect later stages70of the HP compressor24.

A specific rotor stall point is determined by the operating conditions and the rotary component design. To increase the range of this operation, some previous rotary components have included endwall treatments, such as circumferential grooves82, in an attempt to provide an increase in the operating range by redirecting and/or minimizing leakage flow74. Due to these endwall treatments being formed geometrically identical circumferentially about the entire annulus, previous known endwall treatments have failed to additionally address the circumferential flow non-uniformities75introduced by the upstream airflow50,56and/or by upstream rotor blades62or stator blades68. Disclosed herein are novel features78for the outer casing64that address the circumferential flow non-uniformities75described herein and improve stall margins.

Referring now specifically toFIG. 3, the outer casing64may define an interior surface76. As such, the annular gap72may be defined between the rotor blades62and the interior surface76. Further, the interior surface76may include a plurality of the features78. For instance, the features78may include one or more axial slots80extending generally along the axial direction A and/or circumferential grooves82extending generally along the circumferential direction C. Such features78may be formed in the outer casing64after manufacturing the outer casing64(e.g., the features78may be machined in the interior surface76of the outer casing64). However, in other embodiments, the feature(s)78may be formed integrally with the outer casing64(e.g., the features78may be formed in the outer casing64during an additive manufacturing process or casting process).

As further illustrated inFIG. 3, one or more of the features78, such as each of the features78, may be positioned radially outward from one or more of the rotor blades62. Further, the feature(s)78may be positioned axially between a leading edge84and a trailing edge86of the rotor blade(s)62. For instance, each of the features78may be positioned between the leading edges84and trailing edges86of the rotor blades62of a stage70of the rotary component61. As such, the feature(s)78may be positioned in one or more of the annular gaps72positioned between the rotor blade tips63of a stage70and the outer casing64. In further embodiments, one or more of the features78of may be positioned at least partially radially outward from one or more of the rotor blades62on the interior surface76of the outer casing64. For instance, the feature(s)78may be positioned at least partially axially forward of the leading edge84or at least partially axially rearward of trailing edge86of the rotor blade(s)62, such as the rotor blades62of a stage70. As such, one or more of the features78may be positioned partially within one or more of the annular gaps72.

Referring to now generally toFIGS. 6-8, multiple views of rotary components61including features78on the interior surface76of the outer casing64are illustrated in accordance to aspects of the present subject matter. Particularly,FIG. 6illustrates a cross-sectional view of one embodiment of a stage70of a rotary component61according to aspects of the present disclosure taken along the radial direction R and the circumferential direction C illustrating a plurality of features78configured as axial slots80.FIGS. 7 and 8illustrate multiple, cross-sectional views of one embodiment of a rotary component61according to aspects of the present disclosure taken along the axial direction A and radial direction R illustrating a plurality of features78configured as circumferential grooves82. Particularly,FIG. 7illustrates the rotary component61at a high distortion location88. Whereas,FIG. 8illustrates the rotary component61at a low distortion location90. It should be recognized that the rotary component61may be the fan section16, a compressor22,24, or a turbine28,32as described herein or any other suitable rotary component61. Further, the airflow passing though the annular gap72may include one or more high distortion locations88and one or more low distortion locations90(as described in regards toFIG. 5).

As shown, the outer casing64may define a casing thickness91. Further, the casing thickness91may be circumferentially varying along the circumferential direction C. Further, the casing thickness91may additionally, or alternatively, be axially varying along the axial direction A (FIG. 7). As such, the annular gap72defined between the interior surface76of the outer casing64and the rotor blade tips63of the stage70may also be circumferentially and/or axially varying. More particularly, the annular gap72may be larger where the casing thickness91is smaller, and the annular gap72may be smaller where the casing thickness91is larger.

Still referring generally toFIGS. 6-8, a first feature92of the feature(s)78may define a first casing thickness96, and a second feature94of the feature(s)78positioned at least partially circumferentially or axially from the first feature92may define a second casing thickness98different than the first casing thickness96. Further, as illustrated, the first casing thickness96may be defined around a plurality of first features92. Similarly, the second casing thickness98may be defined around a plurality of second features94.

Additionally, the outer casing64may include a location of a first distortion level on the interior surface76of the outer casing64and a location of a second distortion level on the interior surface76of the outer casing64. For instance, the interior surface76of the outer casing64may define a first distortion level100at the first feature(s)92. Or, more particularly, the airflow passing though the annular gap72between the interior surface76of the outer casing64and the rotor blade tips63at the first feature(s)92may define the first distortion level100at or upstream of the stage70of the rotary component61. Similarly, the interior surface76of the outer casing64may define a second distortion level102at the second feature(s)94. Or, more particularly, the airflow passing through the annular gap72between the interior surface76of the outer casing64and the rotor blade tips63at the second feature(s)92may define the second distortion level102at or upstream of the stage70of the rotary component61.

It should be appreciated that the first distortion level100may be defined at a high distortion location88whereas the second distortion level102may be defined at a low distortion location90. As such, the second distortion level102at the second feature(s)94may be less than the first distortion level100at the first feature(s)92. Additionally, the first casing thickness96may be greater than the second casing thickness98in order to reduce the size of the annular gap72and thus reduce the distortion level of the airflow passing through the high distortion location(s)88.

As shown generally inFIGS. 6-8, the first feature(s)92may further define one or more first characteristics, and the second feature(s)94may further define one or more second characteristics. Moreover, the first characteristic(s) may be different than the second characteristic(s). In one such embodiment, the first and second characteristics may each include one or more radial heights, axial dimensions, circumferential dimensions, separations from an adjacent feature78, and/or internal angles for each of the first and second features92,94as described in more detail below.

Referring now specifically toFIG. 6, in the illustrated embodiment, the first feature(s)92may include one or more first axial slots104at a first circumferential location106. Further, the second features(s)94may include one or more second axial slots110at a second circumferential location108. It should be appreciated that the first circumferential location106may correspond to a high distortion location88while the second circumferential location108may correspond to a low distortion location90.

Moreover, the first and second characteristics of the first axial slot(s)104and second axial slot(s)110may each include a radial height112and/or circumferential width114. As described above, the first casing thickness96at the first circumferential location106may be greater than the second casing thickness98at the second circumferential location108. In certain embodiments, the first and/or second characteristics of the first and second axial slot(s)104,110may include a circumferential separation113from an adjacent feature78(such an adjacent axial slot80or circumferential groove82). Further, a first circumferential separation115from an adjacent feature78of the first characteristic may be less than a second circumferential separation116from an adjacent feature78of the second characteristic. In further embodiments, a first radial118height and/or first circumferential width120of the first characteristic may be greater than a second radial height122and/or second circumferential width124of the second characteristic.

Further, one or more of the first and/or second axial slots104,110may define one or more internal angles, such as a first angle126, defined between a circumferential sidewall128and the radial direction R. The first angle126(as well as other internal angles included herein, such as third angle158) is defined here to be positive if the circumferential sidewall128causes the feature78to expand as the feature78extends outward in the radial direction R; the first angle126is defined here to be negative if the circumferential sidewall128causes the feature78to contract as the feature78extends outward in the radial direction R. As such, a first angle126of at least one of the first axial slots104may be larger than a first angle126of at least one of the second axial slots110. It should also be appreciated that although the second axial slots110are illustrated extending along the radial direction R, the second axial slot(s)110may define one or more positive or negative first angles126.

It should be appreciated that the first axial slot(s)104with a thicker casing thickness91, smaller circumferential separation113, taller radial height112, larger first angle126, and/or longer circumferential width114compared to the second axial slot(s)110may reduce the distortion level of the airflow at the first circumferential location106. More particularly, such first axial slot(s)104may reduce or eliminate flow non-uniformities75(see, e.g.,FIGS. 3 and 4) at the first circumferential location106.

Referring now toFIG. 9, another view of the rotary component61ofFIG. 6is illustrated according to aspects of the present disclosure. More particularly,FIG. 9illustrates a top view looking down on the features78(e.g., the axial slots80) defined in the interior surface76of the outer casing64. For example, first axial slots104may be positioned at the first circumferential location106and may be positioned where the airflow is at the first distortion level100, such as the high distortion location88. Further, second axial slots110may be positioned at the second circumferential location108and may be positioned where the airflow is at the second distortion level102, such as the low distortion location90.

As illustrated inFIG. 9, each of the axial slots80may include an axial length130. For instance, the first characteristic of the first axial slot(s)104may include one or more first axial lengths132. Similarly, the second characteristic of the second axial slot(s)110may include one or more second axial lengths134. In certain embodiments, a first axial length(s)132of the first axial slot(s)104may be longer than the second axial length(s)134of the second axial slot(s)110. As further illustrated inFIG. 9, one or more of the axial slots80may be arranged at an orientation relative to the axial direction A. For instance, the first and/or second characteristics of one or more of the axial slots80may define a second angle136relative to the axial direction A. Moreover, in certain embodiments, the second angle136of the first axial slot(s)104may be greater than the second angle136of the second axial slot(s)110. It should be appreciate that, although the second axial slots110are illustrated parallel to the axial direction A inFIG. 9, one or more of the second axial slots110may define the second angle136relative to the axial direction A. As such, first axial slots104with longer axial lengths134and/or greater second angles136may reduce the distortion level of the airflow at the first circumferential location106. More particularly, such first axial slot(s)104may reduce or eliminate flow non-uniformities75(see, e.g.,FIGS. 3 and 4) at the first circumferential location106.

Referring again toFIG. 7, in certain embodiments, the first feature92may be a first circumferential groove150at a first axial location152. In one such embodiment, as shown, the second feature94may be a second circumferential groove154at a second axial location156positioned downstream of the first axial location152. In certain embodiments, the first feature/first circumferential groove92,150may include two or more first features/first circumferential grooves92,150configured generally the same, such as with the same first characteristics described below. Similarly, the second feature/second circumferential groove94,154may include a two or more second features/second circumferential grooves94,154configured generally the same, such as with the same second characteristics described below. It should be recognized that in certain embodiments, three or more features78may be defined in the interior surface76of the outer casing64at three or more different casing thicknesses91. For instance, one or more features78may be positioned on the outer casing64at the first casing thickness96(e.g., the second circumferential groove154). One or more features78may be positioned on the outer casing64at the second casing thickness98(see, e.g., the features78ofFIGS. 8 and 6). Further, one or more features78may be positioned on the outer casing64at a third thickness162different than the first and second thicknesses96,98(e.g., the first circumferential groove150ofFIG. 7). However, it should be recognized that the rotary component61may include four or more features78positioned at four or more different casing thicknesses91.

As shown inFIG. 7, the first and second circumferential grooves150,154(e.g., the first and second features92,94) may each include one or more first and second characteristics, respectively, such as a radial height112, an axial width138, an axial separation144from an adjacent feature78, and an internal angle (e.g., a third angle158defined between an axial sidewall160and the radial direction R). For example, the first circumferential groove(s)150may define a first radial height118, a first axial width140, a first axial separation146, and/or a first internal angle (e.g., zero degrees in the embodiment ofFIG. 7). Further, the second circumferential groove(s)154may define a second radial height122, a second axial width142, a second axial separation148, and/or a second internal angle (e.g., the third angle158) different than the first radial height118, axial width140, first axial separation146, and internal angle.

In certain embodiments, at least one of the first radial height118, axial width140, axial separation146, and/or first internal angle may be larger than the second radial height122, axial width142, axial separation148, and/or second internal angle. However, in other embodiments, at least one of the first radial height118, axial width140, and/or first internal angle may be smaller than the second radial height122, axial width142, and/or second internal angle. It should be appreciated that the first and second circumferential grooves150,154may be positioned at one or more first circumferential locations106where the airflow passing through the rotary component61has the first distortion level100(e.g., the high distortion level location88). As such, the first and second circumferential grooves150,154with at least one changing characteristic down the axial direction A may reduce the distortion level of the airflow passing through the high distortion location(s)88. It should also be appreciated that the first and second circumferential grooves150,154may define the same, or approximately the same, circumferential length164(seeFIG. 10). However, in other embodiments, one of circumferential grooves150,154may define a longer or shorter circumferential length164.

It should be recognized that although the first a second features92,94are described as the same type of feature (e.g. both as axial slots80or circumferential grooves82), in other embodiments the first and second features92,94may include different types of features. For instance, the first feature92may be an axial slot80while the second feature94may be a circumferential groove82. Further, the first feature92configured as an axial slot80and the second feature94configured as a circumferential groove82may be positioned within the same stage70of the rotary component61. However, in other embodiments, the second feature94may be positioned in a stage70axially upstream or downstream of the first feature92. As described generally above, the first feature92may define a first casing thickness96and/or one or more first characteristics different than a second casing thickness98and/or one or more second characteristics of the second feature94as described generally above. In a still further embodiment, a single stage70may include first and second axial slots104,110including different casing thicknesses96,98and/or different characteristics as well as first and second circumferential grooves150,154including different casing thicknesses96,98and/or different characteristics.

Referring now toFIG. 10, another embodiment of the feature78is illustrated according to aspects of the present disclosure. Particularly,FIG. 10illustrates a circumferential groove150extending along the circumferential direction C through high and low distortion locations88,90. As shown, the circumferential groove150may intersect one or more first circumferential locations106and second circumferential locations108. Further, the interior surface76of the outer casing64may include a location of a first distortion level100(e.g., the high distortion location88) at the first circumferential location(s)106higher than a location of a second distortion level102(e.g., the low distortion location90) at the second circumferential location(s)108. More particularly, the airflow passing through the annular gap72at the first circumferential location106may define the first distortion level100higher than an airflow passing through the annular gap72at the second circumferential location108at the lower, second distortion level102.

In certain embodiments, the casing thickness91of the outer casing64may be different at the first circumferential location106than at the second circumferential location108. For instance, the outer casing64may define a first casing thickness96at the first circumferential location106greater than a second casing thickness98at the second circumferential location108, as described generally in regards toFIGS. 6 and 7. As shown, the circumferential groove150may define one or more first characteristics at the first circumferential location106. For instance, the circumferential groove150may define a first radial height118, a first axial separation146, a first axial width140, and a first internal angle (e.g., the third angle158) as described generally in regards toFIG. 7. Further, the circumferential groove150may define one or more second characteristics at the second circumferential location108. For example, the circumferential groove150may define a second radial height122, a second axial separation148, a second axial width142, and a second internal angle (e.g., the third angle158) as described generally in regards toFIG. 7. Furthermore, at least one of the first characteristics may be different than at least one of the second characteristics.

More particularly, in one embodiment, a first casing thickness96, radial height118, axial width140, internal angle, and/or axial separation146from an adjacent feature78of the first characteristic may be greater than a second casing thickness98, radial height122, axial width142, internal angle, and/or axial separation148from an adjacent feature78of the second characteristic. However, in other embodiments, at least one second characteristic may be greater than at least one of the first characteristics. For instance, the second axial separation148may be greater than the first axial separation146. It should also be appreciated that at least one of the first characteristics of the circumferential groove150at the first circumferential location(s)106different than at least one of the second characteristics (including the casing thickness91) may reduce or eliminate flow non-uniformities75(see, e.g.,FIGS. 3 and 4) at the first circumferential location106. It should further be recognized that the first characteristic(s) at the first circumferential location(s)106may transition to the second characteristic(s) at the second circumferential location108. For instance, the first characteristic(s) may transition linearly or non-linearly to the second characteristic(s).

In one embodiment, the rotor blade(s)62and/or the outer casing64may include at least one of a metal, metal alloy, or composite material. For instance, the rotor blade(s)62may be formed at least partially from a ceramic matrix composite. For instance, the rotor blades62and/or outer casing64may be formed at least partially from a ceramic matrix composite. More particularly, in certain embodiments, the rotor blades62and/or outer casing64may be formed from one or more ceramic matrix composite prepreg plies. In another embodiment, the rotor blades62and/or outer casing64may be formed from a ceramic matrix composite woven structure (e.g., a 2D, 3D, or 2.5D woven structure). In still other embodiments, the rotor blades62and/or outer casing64may be formed at least partially from a metal, such as but not limited to, steel, titanium, aluminum, nickel, or alloys of each. For instance, in certain embodiments, the rotor blades62and/or outer casing64may be cast. Though, it should be recognized that the rotor blades62and/or outer casing64may be formed from multiple materials, such as a combination of metals, metal alloys, and/or composites. Further, in certain embodiments, the interior surface76of the outer casing64may include a spray on abradable coating.

Composite materials may include, but are not limited to, metal matrix composites (MMCs), polymer matrix composites (PMCs), or ceramic matrix composites (CMCs). Composite materials, such as may be utilized in the rotor blade(s)62, generally comprise a fibrous reinforcement material embedded in matrix material, such as polymer, ceramic, or metal material. The reinforcement material serves as a load-bearing constituent of the composite material, while the matrix of a composite material serves to bind the fibers together and act as the medium by which an externally applied stress is transmitted and distributed to the fibers.

Exemplary CMC materials may include silicon carbide (SiC), silicon, silica, or alumina matrix materials and combinations thereof. Ceramic fibers may be embedded within the matrix, such as oxidation stable reinforcing fibers including monofilaments like sapphire and silicon carbide (e.g., Textron's SCS-6), as well as rovings and yarn including silicon carbide (e.g., Nippon Carbon's NICALON®, Ube Industries' TYRANNO®, and Dow Corning's SYLRAMIC®), alumina silicates (e.g., Nextel's 440 and 480), and chopped whiskers and fibers (e.g., Nextel's 440 and SAFFIL®), and optionally ceramic particles (e.g., oxides of Si, Al, Zr, Y, and combinations thereof) and inorganic fillers (e.g., pyrophyllite, wollastonite, mica, talc, kyanite, and montmorillonite). For example, in certain embodiments, bundles of the fibers, which may include a ceramic refractory material coating, are formed as a reinforced tape, such as a unidirectional reinforced tape. A plurality of the tapes may be laid up together to form a preform component. The bundles of fibers may be impregnated with a slurry composition prior to forming the preform or after formation of the preform. The preform may then undergo thermal processing, such as a cure or burn-out to yield a high char residue in the preform, and subsequent chemical processing, such as melt-infiltration with silicon, to arrive at a component formed of a CMC material having a desired chemical composition. In certain embodiments, the thermal processing may take place in an autoclave.

Similarly, in various embodiments, PMC materials may be fabricated by impregnating a fabric or unidirectional tape with a resin (prepreg), followed by curing. For example, multiple layers of prepreg plies may be stacked to the proper thickness and orientation for the part, and then the resin may be cured and solidified to render a fiber reinforced composite part. As another example, a die may be utilized to which the uncured layers of prepreg may be stacked to form at least a portion of the composite component. The die may be either a closed configuration (e.g., compression molding) or an open configuration that utilizes vacuum bag forming. For instance, in the open configuration, the die forms one side of the blade (e.g., a pressure side or a suction side). The PMC material is placed inside of a bag and a vacuum is utilized to hold the PMC material against the die during curing. In still other embodiments, the rotor blade62may be at least partially formed via resin transfer molding (RTM), light resin transfer molding (LRTM), vacuum assisted resin transfer molding (VARTM), a forming process (e.g. thermoforming), or similar.

Prior to impregnation, the fabric may be referred to as a “dry” fabric and typically comprises a stack of two or more fiber layers. The fiber layers may be formed of a variety of materials, non-limiting examples of which include carbon (e.g., graphite), glass (e.g., fiberglass), polymer (e.g., Kevlar®) fibers, and metal fibers. Fibrous reinforcement materials can be used in the form of relatively short chopped fibers, generally less than two inches in length, and more preferably less than one inch, or long continuous fibers, the latter of which are often used to produce a woven fabric or unidirectional tape. Other embodiments may include other textile forms such as plane weave, twill, or satin.

In one embodiment, PMC materials can be produced by dispersing dry fibers into a mold, and then flowing matrix material around the reinforcement fibers. Resins for PMC matrix materials can be generally classified as thermosets or thermoplastics. Thermoplastic resins are generally categorized as polymers that can be repeatedly softened and flowed when heated and hardened when sufficiently cooled due to physical rather than chemical changes. Notable example classes of thermoplastic resins include nylons, thermoplastic polyesters, polyaryletherketones, and polycarbonate resins. Specific examples of high performance thermoplastic resins that have been contemplated for use in aerospace applications include polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherimide (PEI), and polyphenylene sulfide (PPS). In contrast, once fully cured into a hard rigid solid, thermoset resins do not undergo significant softening when heated but, instead, thermally decompose when sufficiently heated. Notable examples of thermoset resins include epoxy, bismaleimide (BMI), and polyimide resins.

In general, the exemplary embodiments of the rotor blades62and/or outer casing64described herein may be manufactured or formed using any suitable process. However, in accordance with several aspects of the present subject matter, the rotor blades62and/or outer casing64may be formed using an additive-manufacturing process, such as a 3D printing process. The use of such a process may allow the rotor blades62and/or outer casing64to be formed integrally, as a single monolithic component, or as any suitable number of sub-components. In particular, at least one feature78may be formed in the outer casing64via an additive-manufacturing process. Forming the feature(s)78via additive manufacturing may allow the feature(s)78to be integrally formed and include a variety of characteristics not possible when using prior manufacturing methods. For example, the additive manufacturing methods described herein enable the manufacture of feature(s)78having any suitable size and shape with one or more configurations, some of these novel features are described herein.

As used herein, the terms “additively manufactured,” “additive manufacturing techniques or processes,” or the like refer generally to manufacturing processes wherein successive layers of material(s) are provided on each other to “build-up,” layer-by-layer, a three-dimensional component. The successive layers generally fuse together to form a monolithic component which may have a variety of integral sub-components. Although additive manufacturing technology is described herein as enabling fabrication of complex objects by building objects point-by-point, layer-by-layer, typically in a vertical direction, other methods of fabrication are possible and within the scope of the present subject matter. For instance, although the discussion herein refers to the addition of material to form successive layers, one skilled in the art will appreciate that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or manufacturing technology. For example, embodiments of the present invention may use layer-additive processes, layer-subtractive processes, or hybrid processes.

Suitable additive manufacturing techniques in accordance with the present disclosure include, for example, Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjets and laserjets, Sterolithography (SLA), Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS), Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), Laser Net Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), Digital Light Processing (DLP), Direct Selective Laser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal Laser Melting (DMLM), and other known processes.

In addition to using a direct metal laser sintering (DMLS) or direct metal laser melting (DMLM) process where an energy source is used to selectively sinter or melt portions of a layer of powder, it should be appreciated that according to alternative embodiments, the additive manufacturing process may be a “binder jetting” process. In this regard, binder jetting involves successively depositing layers of additive powder in a similar manner as described above. However, instead of using an energy source to generate an energy beam to selectively melt or fuse the additive powders, binder jetting involves selectively depositing a liquid binding agent onto each layer of powder. The liquid binding agent may be, for example, a photo-curable polymer or another liquid bonding agent. Other suitable additive manufacturing methods and variants are intended to be within the scope of the present subject matter.

The additive manufacturing processes described herein may be used for forming components using any suitable material. For example, the material may be plastic, metal, concrete, ceramic, polymer, epoxy, photopolymer resin, or any other suitable material that may be in solid, liquid, powder, sheet material, wire, or any other suitable form. More specifically, according to exemplary embodiments of the present subject matter, the additively manufactured components described herein may be formed in part, in whole, or in some combination of materials including but not limited to pure metals, nickel alloys, chrome alloys, titanium, titanium alloys, magnesium, magnesium alloys, aluminum, aluminum alloys, iron, iron alloys, stainless steel, and nickel or cobalt based super alloys (e.g., those available under the name Inconel® available from Special Metals Corporation). These materials are examples of materials suitable for use in the additive manufacturing processes described herein, and may be generally referred to as “additive materials.”

In addition, one skilled in the art will appreciate that a variety of materials and methods for bonding those materials may be used and are contemplated as within the scope of the present disclosure. As used herein, references to “fusing” may refer to any suitable process for creating a bonded layer of any of the above materials. For instance, if an object is made from polymer, fusing may refer to creating a thermoset bond between polymer materials. If the object is epoxy, the bond may be formed by a crosslinking process. If the material is ceramic, the bond may be formed by a sintering process. If the material is powdered metal, the bond may be formed by a melting or sintering process. One skilled in the art will appreciate that other methods of fusing materials to make a component by additive manufacturing are possible, and the presently disclosed subject matter may be practiced with those methods.

Moreover, the additive manufacturing process disclosed herein allows a single component to be formed from multiple materials. Thus, the components described herein may be formed from any suitable mixtures of the above materials. For example, a component may include multiple layers, segments, or parts that are formed using different materials, processes, and/or on different additive manufacturing machines. In this manner, components may be constructed that have different materials and material properties for meeting the demands of any particular application. Further, although the components described herein may be constructed entirely by additive manufacturing processes, it should be appreciated that in alternate embodiments, all or a portion of these components may be formed via casting, machining, and/or any other suitable manufacturing process. Indeed, any suitable combination of materials and manufacturing methods may be used to form these components.

An exemplary additive manufacturing process will now be described. Additive manufacturing processes fabricate components using three-dimensional (3D) information, for example, a three-dimensional computer model, of the component. Accordingly, a three-dimensional design model of the component may be defined prior to manufacturing. In this regard, a model or prototype of the component may be scanned to determine the three-dimensional information of the component. As another example, a model of the component may be constructed using a suitable computer aided design (CAD) program to define the three-dimensional design model of the component.

The design model may include 3D numeric coordinates of the entire configuration of the component including both external and internal surfaces of the component. For example, the design model may define the rotor blades62, outer casing64, and/or internal or external passageways such as the features78, openings, support structures, etc. In one exemplary embodiment, the three-dimensional design model is converted into a plurality of slices or segments, e.g., along a central (e.g., vertical) axis of the component or any other suitable axis. Each slice may define a thin cross section of the component for a predetermined height of the slice. The plurality of successive cross-sectional slices together forms the 3D component. The component is then “built-up” slice-by-slice, or layer-by-layer, until finished.

In this manner, the components described herein may be fabricated using the additive process, or more specifically each layer is successively formed, e.g., by fusing or polymerizing a plastic using laser energy or heat or by sintering or melting metal powder. For instance, a particular type of additive manufacturing process may use an energy beam, for example, an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt a powder material. Any suitable laser and laser parameters may be used, including considerations with respect to power, laser beam spot size, and scanning velocity. The build material may be formed by any suitable powder or material selected for enhanced strength, durability, and useful life, particularly at high temperatures.

Each successive layer may be, for example, between about 10 μm and 200 μm, although the thickness may be selected based on any number of parameters and may be any suitable size according to alternative embodiments. Therefore, utilizing the additive formation methods described above, the components described herein may have cross sections as thin as one thickness of an associated powder layer, e.g., 10 μm, utilized during the additive formation process.

In addition, utilizing an additive process, the surface finish and features of the components may vary as needed depending on the application. For instance, the surface finish may be adjusted (e.g., made smoother or rougher) by selecting appropriate laser scan parameters (e.g., laser power, scan speed, laser focal spot size, etc.) during the additive process, especially in the periphery of a cross-sectional layer that corresponds to the part surface. For example, a rougher finish may be achieved by increasing laser scan speed or decreasing the size of the melt pool formed, and a smoother finish may be achieved by decreasing laser scan speed or increasing the size of the melt pool formed. The scanning pattern and/or laser power can also be changed to change the surface finish in a selected area.

While the present disclosure is not limited to the use of additive manufacturing to form these components generally, additive manufacturing does provide a variety of manufacturing advantages, including ease of manufacturing, reduced cost, greater accuracy, etc. In this regard, utilizing additive manufacturing methods, even multi-part components may be formed as a single piece of continuous metal, and may thus include fewer sub-components and/or joints compared to prior designs. The integral formation of these multi-part components through additive manufacturing may advantageously improve the overall assembly process. For instance, the integral formation reduces the number of separate parts that must be assembled, thus reducing associated time and overall assembly costs. Additionally, existing issues with, for example, leakage, joint quality between separate parts, and overall performance may advantageously be reduced.

Also, the additive manufacturing methods described above may enable much more complex and intricate shapes and contours of the outer casing64described herein. For example, such components may include thin additively manufactured layers and unique fluid passageways or cavities, such as the features78. In addition, the additive manufacturing process enables the manufacture of a single component having different materials such that different portions of the component may exhibit different performance characteristics. The successive, additive nature of the manufacturing process enables the construction of these novel features. As a result, the rotary component61described herein may exhibit improved performance and reliability.