Patent Description:
Duct assemblies are provided about the turbine engine and include conduits for providing the flow of various operating fluids to and from the turbine engine and between stages of the turbine engine. One of the operating fluids is bleed air. In the compressor stages, bleed air is produced and taken from the compressor via feeder ducts. Bleed air from the compressor stages in the gas turbine engine can be utilized in various ways. For example, bleed air can provide pressure for the aircraft cabin, keep critical parts of the aircraft ice-free, or can be used to start remaining engines. Configuration of the feeder duct assembly used to take bleed air from the compressor requires rigidity under dynamic loading, and flexibility under thermal loading.

The complexity and spacing requirements of the turbine engine often require particular ducting paths in order to accommodate other engine components. However, duct assemblies and conduits thereof are limited by manufacturing capabilities and costs, which can lead to increased weight or inefficient duct assemblies.

<CIT> describes a steam valve device and steam turbine plant. <CIT> describes a flexural interface for bellowed ball-joint assemblies for controlled rotational constraint. <CIT> describes thermal isolating service tubes and assemblies thereof for gas turbine engines. The Wikipedia page for "Funnel" defines a funnel as a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening.

<CIT> discloses a prior art bleed air duct for a turbine engine.

The present invention provides a bleed air duct according to claim <NUM>.

The present invention will be described with respect to a gas turbine engine. Gas turbine engines have been used for land and nautical locomotion and power generation, but are most commonly used for aeronautical applications such as for airplanes, including helicopters. In airplanes, gas turbine engines are used for propulsion of the aircraft. It will be understood, however, that the invention is not so limited and can have general applicability in non-aircraft applications, such as other mobile applications and non-mobile industrial, commercial, and residential applications. Additionally, the described embodiments will have equal applicability to any ducting system experiencing high system loading or large thrust and shear loads requiring a flex joint to connect elements.

As used herein, the term "forward" or "upstream" refers to moving in a direction toward the engine inlet, or a component being relatively closer to the engine inlet as compared to another component. The term "aft" or "downstream" used in conjunction with "forward" or "upstream" refers to a direction toward the rear or outlet of the engine relative to the engine centerline. Additionally, as used herein, the terms "radial" or "radially" refer to a dimension extending between a center longitudinal axis of the engine and an outer engine circumference.

All directional references (e.g., radial, axial, proximal, distal, upper, lower, upward, downward, left, right, lateral, front, back, top, bottom, above, below, vertical, horizontal, clockwise, counterclockwise, upstream, downstream, aft, etc.) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and can include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to one another. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto can vary.

<FIG> is a schematic cross-sectional diagram of a gas turbine engine <NUM> for an aircraft. The engine <NUM> has a generally longitudinally extending axis or centerline <NUM> extending from forward <NUM> to aft <NUM>. The engine <NUM> includes, in downstream serial flow relationship, a fan section <NUM> including a fan <NUM>, a compressor section <NUM> including a booster or low pressure (LP) compressor <NUM> and a high pressure (HP) compressor <NUM>, a combustion section <NUM> including a combustor <NUM>, a turbine section <NUM> including a HP turbine <NUM>, and a LP turbine <NUM>, and an exhaust section <NUM>.

The fan section <NUM> includes a fan casing <NUM> surrounding the fan <NUM>. The fan <NUM> includes a set of fan blades <NUM> disposed radially about the centerline <NUM>. The HP compressor <NUM>, the combustor <NUM>, and the HP turbine <NUM> form a core <NUM> of the engine <NUM>, which generates combustion gases. The core <NUM> is surrounded by core casing <NUM>, which can be coupled with the fan casing <NUM>.

A HP shaft or spool <NUM> disposed coaxially about the centerline <NUM> of the engine <NUM> drivingly connects the HP turbine <NUM> to the HP compressor <NUM>. A LP shaft or spool <NUM>, which is disposed coaxially about the centerline <NUM> of the engine <NUM> within the larger diameter annular HP spool <NUM>, drivingly connects the LP turbine <NUM> to the LP compressor <NUM> and fan <NUM>. The portions of the engine <NUM> mounted to and rotating with either or both of the spools <NUM>, <NUM> are also referred to individually or collectively as a rotor <NUM>.

The LP compressor <NUM> and the HP compressor <NUM> respectively include a set of compressor stages <NUM>, <NUM>, in which a set of compressor blades <NUM> rotate relative to a corresponding set of static compressor vanes <NUM>, <NUM> (also called a nozzle) to compress or pressurize the stream of fluid passing through the stage. In a single compressor stage <NUM>, <NUM>, multiple compressor blades <NUM>, <NUM> can be provided in a ring and can extend radially outwardly relative to the centerline <NUM>, from a blade platform to a blade tip, while the corresponding static compressor vanes <NUM>, <NUM> are positioned downstream of and adjacent to the rotating blades <NUM>, <NUM>. It is noted that the number of blades, vanes, and compressor stages shown in <FIG> were selected for illustrative purposes only, and that other numbers are possible. The blades <NUM>, <NUM> for a stage of the compressor can be mounted to a disk <NUM>, which is mounted to the corresponding one of the HP and LP spools <NUM>, <NUM>, respectively, with stages having their own disks. The vanes <NUM>, <NUM> are mounted to the core casing <NUM> in a circumferential arrangement about the rotor <NUM>.

The HP turbine <NUM> and the LP turbine <NUM> respectively include a set of turbine stages <NUM>, <NUM>, in which a set of turbine blades <NUM>, <NUM> are rotated relative to a corresponding set of static turbine vanes <NUM>, <NUM> (also called a nozzle) to extract energy from the stream of fluid passing through the stage. In a single turbine stage <NUM>, <NUM>, multiple turbine blades <NUM>, <NUM> can be provided in a ring and can extend radially outwardly relative to the centerline <NUM>, from a blade platform to a blade tip, while the corresponding static turbine vanes <NUM>, <NUM> are positioned upstream of and adjacent to the rotating blades <NUM>, <NUM>. It is noted that the number of blades, vanes, and turbine stages shown in <FIG> were selected for illustrative purposes only, and that other numbers are possible.

In operation, the rotating fan <NUM> supplies ambient air to the LP compressor <NUM>, which then supplies pressurized ambient air to the HP compressor <NUM>, which further pressurizes the ambient air. The pressurized air from the HP compressor <NUM> is mixed with fuel in the combustor <NUM> and ignited, thereby generating combustion gases. Some work is extracted from these gases by the HP turbine <NUM>, which drives the HP compressor <NUM>. The combustion gases are discharged into the LP turbine <NUM>, which extracts additional work to drive the LP compressor <NUM>, and the exhaust gas is ultimately discharged from the engine <NUM> via the exhaust section <NUM>. The driving of the LP turbine <NUM> drives the LP spool <NUM> to rotate the fan <NUM> and the LP compressor <NUM>.

Some of the air from the compressor section <NUM> can be bled off via one or more bleed air duct assemblies <NUM>, and be used for cooling of portions, especially hot portions, such as the HP turbine <NUM>, or used to generate power or run environmental systems of the aircraft such as the cabin cooling/heating system or the deicing system. In the context of a turbine engine, the hot portions of the engine are normally downstream of the combustor <NUM>, especially the turbine section <NUM>, with the HP turbine <NUM> being the hottest portion as it is directly downstream of the combustion section <NUM>. Air that is drawn off the compressor and used for these purposes is known as bleed air.

A plurality of ducts are described herein having different cross-sectional shapes, areas, and profiles, which can further include varying thicknesses, or bends with small radiuses of curvature. Such form, shape, physical dimensions or organizations of the ducts can be collectively described as a geometry of the ducts, and can include one or more of the physical dimensions or organizations. Additionally, the ducts, or metal tubular elements thereof, can also be a fluid delivery system, for routing a fluid through the engine <NUM>, such as through the bleed air duct assemblies <NUM>.

For example, the bleed air duct assemblies <NUM>, or other ducting assemblies leading either internally to other portions of the turbine engine <NUM> or externally of the turbine engine <NUM>, can include one or more metal tubular elements or metallic tubular elements forming ducts or conduits. Referring to <FIG>, such a duct <NUM> can include a metal tubular element <NUM> with a first end <NUM> and a second end <NUM>. A passage <NUM> is defined within the duct <NUM> between the first end <NUM> and the second end <NUM>.

A variable profile having a variable thickness and a variable cross-section between the first and second end <NUM>, <NUM> can be included in the duct <NUM>. In <FIG>, taken along section <NUM>-<NUM> of <FIG>, the first end <NUM> includes a rounded-edge-square profile <NUM> having an outer wall <NUM> with four linear sides <NUM> and rounded corners <NUM>. The outer wall <NUM> includes a first thickness <NUM> that is uniform around the entire outer wall <NUM>.

In <FIG>, taken along section <NUM>-<NUM> of <FIG>, the second end <NUM> of the duct <NUM> includes a circular profile <NUM> with the outer wall <NUM> including a second thickness <NUM> where the second thickness <NUM> is different from the first thickness <NUM>. The second thickness <NUM> is uniform about the entirety of the second end <NUM>. The second thickness <NUM> can be less than the first thickness <NUM>, resultant of the second end <NUM> having a greater cross-sectional area than the first end <NUM>. However, it is contemplated that the second thickness <NUM> can alternatively be greater than or equal to the first thickness <NUM>.

In <FIG>, a third profile <NUM> of the duct <NUM> is illustrated as a cross-sectional cut taken along section <NUM>-<NUM> of <FIG>. The third profile <NUM> includes an exterior having a rounded-square shape, with an interior having a rounded-trapezoidal shape. The profile <NUM> includes a first side <NUM> having a third thickness <NUM> and a second side <NUM> having a fourth thickness <NUM>. Two connecting sides <NUM> connect the first side <NUM> and the second side <NUM>. The connecting sides <NUM> have been illustrated as including a thickness that transitions between the third thickness <NUM> of the first side <NUM> and the fourth thickness <NUM> of the second side <NUM>. The third thickness <NUM> can be equal to the first thickness <NUM> of the first end <NUM>, for example. The fourth thickness <NUM> can be greater than the third thickness <NUM>. However, it will be understood that the thicknesses can be alternatively sized. In one non-limiting example, the third thickness <NUM> can be <NUM> millimeters or <NUM> inches and the fourth thickness <NUM> can be <NUM> millimeters or <NUM> inches.

It should be appreciated that the duct <NUM> as shown can represent only a portion of the duct, and can be shorter or longer, including more or different profiles, thicknesses, turns, or cross-sectional areas.

It should be further appreciated that the duct <NUM> of <FIG>, or any duct described herein, can include a variable thickness along one or more portions of the duct. The variable thickness can have increased thicknesses locally to increase strength or durability of the duct, such as at portions encountering heightened operational temperatures or stresses, or at turns along the duct <NUM>. Such variable thicknesses can provide for a duct having variable thermal or mechanical properties. For example, a duct having an increased thickness can provide for improved structural integrity in order to operate under heightened stresses or loads. In another example, the duct can have a decreased thickness, which can provide for improved heat transfer along the duct. Such an implementation may be beneficial in the use of heat exchangers. Furthermore, the variable profiles and thicknesses can include dimples, or structures that can enhance thermal transfer of the fluid at the duct. For example, the variable profile can include helical ribs to turbulate a fluid travelling within or around the duct. Additionally, the variable thickness can also include lesser thicknesses to decrease engine weight, or even increase local convective transfer. Furthermore, the ducts as described herein can have a transitional thickness as a varying thickness along a portion of the profile of the duct. Such a transitional thickness is illustrated by the sides <NUM> of <FIG>.

Additionally, it should further be appreciated that the duct <NUM>, or any duct described herein, can include any suitable type of varying profile. Such a varying profile can include different profile shapes, different cross-sectional areas, different thicknesses, or a combination thereof. The varying profiles can improve local strength, can be adapted based upon local thermal needs, or can be adapted to fit into crowded areas of the engine.

Referring to <FIG>, the duct <NUM> is illustrated in an alternative bent configuration and can define a passage diameter D. The duct <NUM> includes four bends <NUM> shown as a first bend <NUM>, a second bend <NUM>, a third bend <NUM>, and a fourth bend <NUM>. The first bend <NUM> and the third bend <NUM> have been illustrated as being "tight bends," defining a first angle <NUM> and a second angle <NUM>, respectively. Furthermore, the term "tight bend" can include a radius of curvature that is less than twice the diameter D of the duct <NUM>. In non-limiting examples, the tight bend can include a radius of curvature that is equal to the diameter D, or one-half of the diameter D. The tight bends as described herein provide for increased maneuverability and a greater bending range for the duct <NUM>. Such tight bends can provide for providing ducting through crowded or complex regions of the engine, where accommodating space is important or necessary. Additionally, the improved maneuverability can provide for decreased engine weights, as the improved maneuverability can provide for duct geometries to snake through the crowded engine areas, requiring less total ducting. It should be understood that the second bend <NUM> is not a tight bend in order to illustrate that other bends in the duct <NUM> are not required to be tight bends, but can be any bend. It should be further understood that the "tight bend" as described herein cannot be made by traditional machine bending of a metal tube or duct. Traditional bending causes excessive stress on the duct or tube that causes fracture or breakage, thus limiting the potential to bend to a radius of curvature twice the diameter of the duct. The duct <NUM> having the first bend <NUM> and the third bend <NUM> as described are not subject to such limitations.

It should be appreciated that the unique profiles, the variable profiles, the variable thicknesses, and the tight bends as described herein can be used alone or in combination with one another to develop a particular duct adapted to the particular needs of the engine. For example, the unique profiles can be used to accommodate the duct along other shaped areas of the engine, aligning at least partially complementary to one another. For example, providing four cylindrical ducts next to one another necessarily requires a gap between them. Utilizing a unique profile can minimize or eliminate such a gap, which can improve efficient use of valuable space within an engine. Additionally the unique profiles can provide for increased surface area to improve heat transfer at the duct. Furthermore, the unique profiles can provide for improved strength or durability for the ducts operating under mechanical and thermal stresses.

It should be further appreciated that the variable profiles can be used to adapt a single duct to changing needs for the duct along the engine. For example, a forward portion of the duct may be susceptible to greater engine stresses, while an aft portion of the duct may be susceptible to a greater range of engine temperatures. Varying the profile can be used to adapt a single duct to varying factors along the length of the duct. Similarly, the varying profiles can be used to fit the duct into crowded engine areas. For example, at a forward portion of the duct, it may be advantageous to use a circular profile, while an aft portion of the duct may require a squared profile. The variable profile can accommodate such needs.

It should be further appreciated that the variable thicknesses can be used to balance engine weight with local strength and durability. For example, the duct at a junction or connection to another component may need increased durability. The increased thickness can be provided adjacent the junction or connection to provide the increased durability. Away from the areas requiring increased durability and strength, the thickness can be decreased in order to minimize engine weight, having a positive impact on engine efficiency. As such, the thickness of the duct can be varied locally in order to maximize strength and minimize engine weight.

It should be further appreciated that tight bends can be used to adapt the geometry of the duct to snake through complex crowded areas, minimizing total duct length and improving flow rates while minimizing engine weight. The tight bends can be supplemented with the variable profiles or thicknesses to ensure that local strength requirements are met for the tight bends.

Referring to <FIG>, a flow chart illustrates a method of forming a metallic tubular element such as any of the ducts described herein. At <NUM>, the method can optionally include, modelling and designing a desired metallic tubular element. Such a metallic tubular element can be adapted for a particular use and location within a turbine engine. At <NUM>, the method can include forming, using additive manufacturing, a three-dimensional (3D) mandrel having an outer surface with a predetermined geometry. The 3D mandrel can be a sacrificial mandrel made of plastic, for example, or any other removable material such as wax. At <NUM>, the mandrel can be prepared for metal deposition. Such preparation can include surface treatments to facilitate uniform deposition along the mandrel.

The method can further include, at <NUM>, depositing metal on the outer surface of the sacrificial mandrel. Depositing metal on the sacrificial mandrel can form a metallic tubular element where depositing metal occurs at a temperature that does not damage the outer surface having the predetermined geometry of the sacrificial mandrel. Depositing metal on the outer surface can be accomplished, in non-limiting examples, by electrochemical deposition or cold metal spray deposition. The metallic tubular element can include at least one of a varying wall thickness or a varying cross-section along at least a portion of its length, or it can include both a varying wall thickness and a varying cross-section, such as that of FISG. <NUM>-<NUM>. The metal deposition can further include depositing metal to a predetermined thickness. The predetermined thickness, in one non-limiting example, can include a thickness more than <NUM> millimeters (mm). The metallic tubular element can further include a non-circular cross section, such as, in non-limiting examples, a rounded square, teardrop, cross, corkscrew, or any other profile suitable to the particular needs of the duct or metallic tubular element. Furthermore, the metallic tubular element can have at least one curve that includes a radius of curvature that is less than twice the diameter or greatest cross-sectional distance of the metallic tubular element.

The method can further include, at <NUM>, removing the sacrificial mandrel from the metallic tubular element. Removal of the sacrificial mandrel can include, in non-limiting examples, melting or chemically etching the sacrificial mandrel. In essence the sacrificial mandrel is destroyed during this process.

At <NUM>, the metallic tubular element can pass through optional post-processing that can include, in non-limiting examples, operations such as polishing, stress relieve, shaping, or insertion of a bellows within the metallic tubular element. At <NUM>, the final product can be optionally inspected.

The ducts, metallic tubular elements, and bellows can all be formed utilizing a sacrificial mandrel formed by additive manufacturing in combination with low temperature metal deposition processes. The electrochemical deposition or low temperature metal deposition utilizing cold metal spray technologies on the mandrel can be used to form the ducts and bellows as described above. Utilizing the mandrel can provide for improved yields and improve product precision.

Referring to <FIG>, at least a portion of an alternative duct <NUM> includes a metal tubular element <NUM> with a variable profile having a uniform thickness along its length. The duct <NUM> includes a first end <NUM> and a second end <NUM>, defining a passage <NUM> there between. In <FIG>, taken across section <NUM>-<NUM> of <FIG>, the first end <NUM> includes a first cross-sectional shape, formed as a circular profile <NUM>. In <FIG>, taken across section <NUM>-<NUM> of <FIG>, the second end <NUM> includes a second cross-sectional shape, formed as a rounded, rectangular profile <NUM>. The first end <NUM> can include a cross-sectional area that is less than that of the second end <NUM>. A fluid passing within the duct <NUM> can decrease in velocity extending from the first end <NUM> toward the second end <NUM> with the increase in cross-sectional area of the fifth duct <NUM>. The variable profiles <NUM>, <NUM> can be used to tailor the duct <NUM> to fit within particular crowded areas or spaces, while particularly affecting a flow of fluid passing through the duct <NUM>. In addition to velocities, the variable cross-sectional shapes or areas can be used to vary the pressures, flow rates, or temperatures of the fluids passing through the duct <NUM>.

Additional exemplary alternative profiles for the ducts are described herein. It should be understood that the alternative profiles as shown are non-limiting, and the ducts and metallic tubular elements can include any profile suitable for the particular duct, any transitional shape between two profiles, or having any thickness or variable thickness at the particular profile. Referring to <FIG>, at least a portion of a duct <NUM> includes a metal tubular element <NUM> with a first end <NUM> and a second end <NUM> opposite of the first end <NUM> defining a passage <NUM> there between. In <FIG>, the duct <NUM> includes a cross-shaped profile <NUM> taken along section <NUM>-<NUM> of <FIG>, having four convex sides <NUM> interconnected by four concave, rounded corners <NUM> surrounding an interior <NUM> of the first duct <NUM>. While four convex sides <NUM> interconnected by four corners <NUM> are shown, any number of sides <NUM> and complementary corners <NUM> are contemplated.

Referring to <FIG>, at least a portion of another duct <NUM> includes a metal tubular element <NUM> having a first end <NUM> and a second end <NUM> opposite the first end <NUM>, defining a passage <NUM> there between. A rib in the form of a helical wrap <NUM> winds around the exterior of the second duct <NUM>. In <FIG>, the duct <NUM> includes a circular profile <NUM>, taken along section <NUM>-<NUM> of <FIG>. The helical wrap <NUM> can be formed integral with the second duct <NUM>. While only one helical wrap <NUM> is shown, any number of helical wraps are contemplated. Alternatively, ribs can be formed as a plurality of concentric rings that are not interconnected with one another. Furthermore, while the rib has a circular profile, any shape or size profile is contemplated. The rib can further define a varying wall thickness for the second metal tubular element <NUM> or a varying cross-section rotating about the duct <NUM>.

Referring to <FIG>, at least a portion of yet another duct <NUM> includes a metal tubular element <NUM> with a first end <NUM> and a second end <NUM> opposite of the first end <NUM>, defining a passage <NUM> there between. In <FIG>, taken across section <NUM>-<NUM> of <FIG>, the duct <NUM> includes a rounded, cross-shaped profile <NUM> having four peaks <NUM> separated by four complementary valleys <NUM>. In alternative examples, the third duct <NUM> can have any number of peaks <NUM> separated by any number of complementary valleys <NUM>.

Referring to <FIG>, at least a portion of yet another duct <NUM> includes a metal tubular <NUM> element having a first end <NUM> and a second end <NUM> opposite of the first end <NUM>, defining a passage there between <NUM>. In <FIG>, taken across section <NUM>-<NUM> of <FIG>, the duct <NUM> includes a teardrop profile <NUM> having a first radiused portion <NUM> and a second radiused portion <NUM>, with the first radiused portion <NUM> having a greater radius of curvature that the second radiused portion <NUM>. Two flat portions <NUM> interconnect the first radiused portion <NUM> and the second radiused portion <NUM>. While the profile <NUM> of the fourth duct <NUM> includes two radiused portions, any number of radiused portions having differing radiuses of curvature are contemplated.

The aforementioned exemplary profiles are illustrative of different examples of ducts, and metal tubular elements thereof, having differing profiles. As such, it should be understood that the duct, conduits, and metal tubular elements used in the duct assembly can have differing profiles, that are beyond standard cylindrical or squared conduits. Such conduits can include, in non-limiting examples, conduits having one or more of the convex sides <NUM>, concave corners <NUM>, wrap <NUM>, peak <NUM>, valley <NUM>, first radiused portion <NUM>, second radiused portion <NUM>, or the flat portions <NUM>, in any combination. Thus, it should be appreciated that the conduits can have variable or unique profiles. Such profiles can be advantageous for providing sufficient ducting within crowded areas within a turbine engine where space is limited.

The ducts, or metal tubular elements thereof, as described herein can include a bellows provided on the interior of the duct facilitating the adjoining of two or more ducts or fluidly coupling sections of a duct at a flexible joint. Indeed, the duct of the invention includes bellows as described below. The bellows can provide for carrying the flow of fluid within the duct, as well as influencing the flow of fluid. <FIG> illustrates a duct <NUM>, which can be similar to the duct <NUM> of <FIG>. The duct <NUM> includes a first end <NUM> and a second end <NUM> defining a passage <NUM> there between. An interior <NUM> can be defined within the passage <NUM>. The duct <NUM> can be separated into two portions including a first portion <NUM> and a second portion <NUM>. A bellows <NUM> can be provided in the interior <NUM> at a junction between two portions <NUM>, <NUM> for adjoining the two portions and fluidly coupling the interior <NUM> of the first and second portions <NUM>, <NUM>. The bellows permits expansion and contraction of the first and second portions <NUM>, <NUM> at joints while fluidly coupling the two portions <NUM>, <NUM>. Additionally, the bellows <NUM> can permit dampening loading or similar operational forces for an engine.

Referring to <FIG>, the bellows <NUM> as used in the duct of the invention is illustrated including a convolution <NUM> and one or more grooves <NUM> provided in an outer wall <NUM> extending between a first end <NUM> and a second end <NUM>. The length of the bellows <NUM> as illustrated is exemplary. The convolution <NUM> is formed in the outer wall <NUM> and helically wraps around the bellows <NUM> having a greater radius than the remainder of the outer wall <NUM>. While only one helical convolution <NUM> is shown, any number of intertwined helical convolutions are contemplated. The grooves <NUM> are formed as a plurality of spaced grooves <NUM> in the helical convolution <NUM>. Referring now to <FIG>, the grooves <NUM> can be organized in a patterned manner to be aligned about the helical convolution <NUM>. As shown, the grooves <NUM> are spaced every <NUM>-degrees relative to the cylindrical shape of the outer wall <NUM> to form ten rows <NUM> of grooves about the bellows <NUM>. Alternatively, any spacing of grooves <NUM> is contemplated. The bellows <NUM> including the helical convolution <NUM> with the grooves <NUM> can provide for improved strength or resiliency for the bellows <NUM>. Additionally, the particular grooves <NUM> can be used to tailor the movement of the bellows <NUM>, such as the force required for the bellows <NUM> to expand or contract. Furthermore, the particular grooves <NUM> or convolution(s) <NUM> can be used to affect a flow of fluid passing through the bellows <NUM>, such as, in non-limiting examples, decreasing velocity or increasing turbulence of the fluid.

Referring to <FIG>, another exemplary bellows <NUM> includes a first end <NUM> and a second end <NUM> defining a passage <NUM> there between. The bellows <NUM> includes a profile <NUM> having alternating linear portions <NUM> interconnecting alternative arcuate portions <NUM>. The arcuate portions <NUM> are convex, extending radially outward, while it is contemplated that the arcuate portions <NUM> can be concave, or a combination of convex and concave. While it is shown as having ten linear portions <NUM> separating ten arcuate portions <NUM>, any number of linear portions <NUM> and arcuate portions are contemplated. It is further contemplated that the profile of the bellows <NUM> can be variable, having some areas with or without the linear portions <NUM> or the arcuate portions <NUM>. The arcuate portions <NUM> can include spaced grooves <NUM>, while it is contemplated that the grooves <NUM> can be positioned on the linear portions <NUM>, or a combination of the linear portions <NUM> and the arcuate portions <NUM>.

The bellows <NUM> including the arcuate portions <NUM> and the grooves <NUM> can provide improved strength. Additionally, the profile and grooves <NUM> can be used to tailor the bellows <NUM> to flex in a particular manner. For example, a greater number of grooves <NUM> can be positioned at one portion of the bellows <NUM> to improve local strength, while another portion of the bellows <NUM> can have a lesser number of grooves <NUM> to encourage local flexion.

Referring now to <FIG>, another exemplary bellows <NUM> includes an outer wall <NUM> having a first end <NUM> and a second end <NUM>. The outer wall <NUM> includes five helical convolutions <NUM> intertwined with one another. The five helical convolutions <NUM> provide for a twisting of the bellows <NUM> during flexion. The number of helical convolutions <NUM> can be used to increase or decrease the strength of the bellows <NUM>. Additionally, the helical convolutions <NUM> can be used to tailor flexion of the convolutions to rotate the bellows <NUM>. Such rotation can be advantageous for bellows <NUM> within a curved or arcuate metallic tubular element.

Referring now to <FIG>, another exemplary bellows <NUM> includes an outer wall <NUM> extending between a first end <NUM> and a second end <NUM> and defines a passage <NUM> there between. The outer wall <NUM> includes a variable cross-sectional area defining a concave portion <NUM>. Convolutions <NUM> are provided along the extent of the bellows <NUM>, and follow the concave geometry of the outer wall <NUM>.

Similarly, <FIG> includes another exemplary bellows <NUM> including an outer wall <NUM> extending between a first end <NUM> and a second end <NUM> and defines a passage <NUM> there between. The outer wall <NUM> includes a variable cross-sectional area defining a convex portion <NUM>, with convolutions <NUM> provided about the convex portion <NUM>.

With regard to <FIG>, it should be appreciated that the bellows as described herein can have a variable cross-sectional area without consideration to convolutions provided in the bellows. For example, the bellows can have an outer wall that varies in cross-sectional area or shape, and includes convolutions further including a variable cross-sectional area provided within the variable outer wall.

Referring to <FIG>, yet another exemplary bellows <NUM> has an outer wall <NUM> having a curved cylindrical shape. A first end <NUM> is spaced from a second end <NUM> defining a passage <NUM> there between. The bellows <NUM> can include a plurality of convolutions <NUM>. The convolutions <NUM> can be arranged around the curved outer wall <NUM>. The convolutions <NUM> can be utilized to improve flexion as well as stability of the bellows extending through curved portions of a duct. For example, the curved bellows <NUM> can be adapted to fit into the first bend <NUM> or the third bend <NUM> of <FIG>, having a radius of curvature that is less than twice the diameter of the duct around the bellows <NUM>.

Referring now to <FIG>, an exemplary duct assembly <NUM> is illustrated having a concentric tube geometry with a tube-in-tube design. A first duct <NUM> of the duct assembly <NUM> defines a first interior <NUM>. A second duct <NUM> is provided in the interior <NUM> of the first duct <NUM>, having a diameter that is smaller than that of the first duct <NUM>. A second interior <NUM> is defined within the second duct <NUM> and can be fluidly isolated from the first interior <NUM>. In an alternative example, the second duct <NUM> can have apertures or an open end to fluidly couple the ducts <NUM>, <NUM> to one another.

The ducts <NUM>, <NUM> can couple to a common end or mount, in order to maintain the second duct <NUM> spaced within the first duct <NUM>. Alternatively or additionally, it is contemplated that spokes <NUM> or other fixed structural elements can optionally be used to space the second duct <NUM> from the first duct <NUM>.

Referring now to <FIG>, a sectional view of the duct assembly <NUM> is illustrated taken across section <NUM>-<NUM>. The ducts <NUM>, <NUM> can have similar thicknesses and circular profiles. Alternatively, it is contemplated that one or more of the ducts <NUM>, <NUM> can have a variable cross-section area or shape, or a variable thickness, as described herein. Furthermore, while only two ducts <NUM>, <NUM> are shown in the duct assembly <NUM>, any number of ducts is contemplated. In yet another example, multiple ducts can be provided within the interior of an outer duct, without being provided within the interior of one another.

It should be appreciated that the duct assembly <NUM> provides for passing multiple fluids within a single duct assembly <NUM>. Providing multiple fluids within the duct assembly <NUM> provides for a compact duct arrangement, minimizing the space required to duct multiple fluids throughout the engine, as well as providing thermal insulation, cooling, or heating. In one example, the duct assembly <NUM> can operate as a heat exchanger.

Referring now to <FIG>, an exemplary first method <NUM> of forming the duct assembly <NUM> without the spokes <NUM> of <FIG> is described. At <NUM>, the second duct <NUM> can be provide or pre-formed. For instance, prefabricated tube stock can be used. At <NUM>, a mandrel layer <NUM> can be provided around the exterior of the second duct <NUM>. The mandrel layer <NUM> can be formed over the second duct <NUM> by any suitable method, or can be pre-formed and provided over the second duct <NUM>, such as slid along the exterior of the second duct <NUM>. The mandrel layer <NUM> can be made of plastic, in one non-limiting examples, or any other readily removable material such as a material having a melting point lower than the duct assembly <NUM>. Optionally, the spokes can be formed by 3D printing or any other suitable method during formation of the mandrel <NUM>. Eventual removal of the mandrel <NUM> leaves the spokes remaining to space the first and second ducts <NUM>, <NUM>.

At <NUM>, the mandrel layer <NUM> can be prepared, such as by providing a coating <NUM> over the exterior of the mandrel layer <NUM>. The coating <NUM>, in one non-limiting example, can be a conductive paint to facilitate bonding of a metal along the mandrel layer <NUM>. At <NUM>, the first tube <NUM> can be formed over the mandrel <NUM> and the coating <NUM>. The first tube <NUM> can be formed by additive manufacturing, such as utilizing a cold spray or electroforming that will not deform or destroy the mandrel layer <NUM> during formation.

At <NUM>, the mandrel layer <NUM> can be removed from the duct assembly <NUM>. The mandrel layer <NUM> can be removed by any suitable method, such as heating or chemical etching. Similarly, any remnant material from the coating <NUM> can be removed from the ducting assembly <NUM> by any suitable method such as chemical etching. After removal of the mandrel layer <NUM>, the duct assembly <NUM> including the first and second ducts <NUM>, <NUM> remains with the first duct <NUM> formed around the second duct <NUM>.

In an alternative example, the second duct <NUM> can be formed having a variable thickness, variable cross-sectional area, or variable shape, such as that described herein. The mandrel layer <NUM> can be provided over the second duct <NUM> and the first duct <NUM> can be formed complementary to the unique shape of the second duct <NUM>. Additionally, the first duct <NUM> during formation can have an alternative variable thickness or cross-sectional area or shape.

Referring now to <FIG>, an alternative exemplary second method <NUM> of forming the duct assembly <NUM> without the spokes <NUM> of <FIG>. At <NUM>, a mandrel <NUM> can be provided having the profile, shape, and diameter for the second duct <NUM>. The mandrel <NUM> can be made by any suitable method, and can be made of a readily removable material such as plastic. At <NUM>, the mandrel <NUM> can be prepared with a coating <NUM> for forming the second duct <NUM> around the mandrel <NUM>. At <NUM>, the second duct <NUM> can be formed around the mandrel <NUM>. The second duct <NUM> can be formed, in non-limiting examples, by electroforming or cold metal spray. The second duct <NUM> can be formed by any means that will not deform or destroy the mandrel <NUM> during formation. Time can pass to allow the second duct <NUM> to solidify.

At <NUM>, after solidification of the second duct <NUM>, a mandrel layer <NUM> can be provided over the second duct <NUM>. The mandrel layer <NUM> can be made of a removable material, such as plastic, and can be formed to define a cross-sectional area and shape for the first duct <NUM>. At <NUM>, a second coating <NUM> can be applied to the mandrel layer <NUM> to prepare the mandrel layer <NUM> for formation of the first duct <NUM>. Optionally, the spokes <NUM> of <FIG> can be formed by 3D printing or any other suitable manner during formation of the mandrel <NUM>. Eventual removal of the mandrel <NUM> leaves the spokes remaining to space the first and second ducts <NUM>, <NUM>.

At <NUM>, the first duct <NUM> can be formed around the mandrel layer <NUM>. The first duct <NUM> can be formed similar to the second duct <NUM>, such as by cold metal spray or electroforming in non-limiting examples. The first duct <NUM> can be formed to have a variable cross-sectional area or shape, or a variable profile, as described herein.

At <NUM>, the mandrel <NUM> and the mandrel layer <NUM> can be removed by any suitable method, such as heating or chemical etching. Similarly, any remnant material from the coatings <NUM>, <NUM> can be removed from the ducting assembly <NUM> by any suitable method such as chemical etching, leaving the duct assembly <NUM> with the first and second ducts <NUM>, <NUM> remaining.

The ducts and bellows as described herein can be formed utilizing additive manufacturing, such as with 3D printing, Direct Metal Laser Melting (DMLM), Direct Metal Laser Sintering (DMLS), electroforming, electroplating, or cold metal spray in non-limiting examples. As such, it is contemplated that the ducts and bellows can be formed without the use of a mandrel.

The ducts provided herein provide for multi-functional monolithic fluid delivery systems. The ducts provide for the freeform of lighter and more compact systems that can use localized mechanical and thermal properties with improved routing schemes. The ducts as described herein provide for utilizing ducts with novel cross-sectional dimensions, areas, and profiles, which can provide for improved structural integrity, affecting a flow of fluid within the duct, or fitting into crowded engine spaces. Additionally, the cross-sectional dimensions, areas, and profiles can be varies with a single tube, without requiring the interconnection of multiple tubes with variable cross-sections and transition elements there between. The variable cross-sections can provide a balance of structural integrity, with a need to minimize engine weight. Furthermore, the ducts provide for a small bending radius, which can provide for fitting the duct in a tight, crowded engine space, which can increase room in the crowded spaces, while reducing engine weight with shorter duct paths.

Additionally, the bellows as described herein can be utilized with the ducts as described, in order to provide improved strength or determinative vectors for flexion of the bellows within the particular ducts. Furthermore, the bellows can influence a flow of fluid passing through them.

To the extent not already described, the different features and structures of the various embodiments can be used in combination as desired. That one feature is not illustrated in all of the embodiments is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different embodiments can be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described. All combinations or permutations of features described herein are covered by this disclosure. However, the duct of the invention is defined by the claims.

Claim 1:
A bleed air duct (<NUM>) for carrying bleed air in a turbine engine (<NUM>), the bleed air duct (<NUM>) comprising:
a metal tubular element (<NUM>), the metal tubular element being configured to convey fluid from a first portion to another portion;
wherein the metal tubular element (<NUM>) includes both a varying wall thickness and a varying cross-section along at least a portion of a length of the metal tubular element (<NUM>);
wherein the metal tubular element (<NUM>) has at least one bend (<NUM>) with a radius of curvature (<NUM>) that is less than twice a greatest cross-sectional distance of the metal tubular element (<NUM>); and
wherein the bleed air duct (<NUM>) further comprises a bellows (<NUM>), wherein the bellows (<NUM>) comprises a convolution (<NUM>) and one or more grooves (<NUM>) provided in an outer wall (<NUM>) extending between a first end (<NUM>) and a second end (<NUM>), wherein the convolution (<NUM>) is formed in the outer wall (<NUM>) and helically wraps around the bellows (<NUM>) having a greater radius than the remainder of the outer wall (<NUM>), wherein the one or more grooves (<NUM>) are formed as a plurality of spaced grooves (<NUM>) in the convolution (<NUM>).