Patent Description:
Bleed air is provided by a gas turbine engine to be used for engine functions (such as cooling of turbines and to help seal bearing cavities, for example) and, as the case may be, for aircraft functions (such as wing de-icing, cabin pressurization, cabin climate control, liquid tank pressurization, etc.). Depending on the type of engine and on the levels of pressure and temperature needed, bleed air can be derived from an air intake duct or compressor cavity. While typical conventional bleed air systems may be suitable for their intended purposes, aerodynamics and/or performance of such existing systems may nevertheless be improved upon.

A prior art gas turbine engine having the features of the preamble of claim <NUM> is disclosed in <CIT>.

In an aspect of the present invention, there is provided a gas turbine engine in accordance with claim <NUM>.

In an embodiment, the outer-duct wall defines a relief opening extending from the interior-duct surface to the exterior-duct surface, and the conduit outlet is in fluid communication with inside the duct via the relief opening.

In an embodiment of any of the above, the relief opening includes a plurality of bores.

In an embodiment of any of the above, a portion of the tube and a portion of the air line have cylindrical shapes that are coaxial to one another.

In an embodiment of any of the above, the tube defines at least one lateral opening in fluid communication between inside the tube and inside the conduit.

In an embodiment of any of the above, the outer-duct wall has a boss projecting into the duct, the boss defining the offtake opening and a relief opening, the conduit outlet in fluid communication with inside the duct via the relief opening.

In an embodiment of any of the above, the boss has a fore-facing side defining the offtake opening and an aft-facing side defining the relief opening.

In an embodiment of any of the above, the gas turbine engine is a turbofan gas turbine engine and the duct is a bypass duct.

In an embodiment of any of the above, the duct has a duct inlet upstream of the offtake opening and the relief location is downstream of the offtake location relative to the duct inlet.

In an embodiment of any of the above, the gas turbine engine is a turboshaft gas turbine engine having a first stage compressor and a second stage compressor downstream of the first stage compressor, and the duct defines a bleed air cavity of the second stage compressor.

In an embodiment of any of the above, the gas turbine engine is a turboprop gas turbine engine having a compressor and the duct defines a bleed air cavity of the compressor.

<FIG> illustrates a gas turbine engine 10A being of a turbofan type preferably provided for use in an aircraft for subsonic flight, generally comprising in serial flow communication along a centerline CL a fan <NUM> through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases. The compressor section <NUM> and the turbine section <NUM> form part of an engine core <NUM>. The engine core <NUM> defines a main fluid path <NUM> in which the combustor <NUM> is provided. The engine core <NUM> has an annular wall facing radially outwardly relative to the centerline CL, referred to as a core wall <NUM>. The core wall <NUM> is positioned coaxially and radially inwardly of a nacelle <NUM> of the engine 10A. The nacelle <NUM> has an annular wall facing radially inwardly relative to the centerline CL, referred to as an engine wall <NUM>. The core wall <NUM> and the engine wall <NUM> together define an annular bypass duct <NUM> for directing an air flow F (the flow F) drawn by the fan <NUM> such that the flow F bypasses the main fluid path <NUM>. Hence, the core wall <NUM> and the engine wall <NUM> can also be respectively referred to as inner and outer walls of the duct <NUM>. A bleed air offtake assembly <NUM> (the offtake assembly <NUM>) is fluidly connected to the duct <NUM> such that some of the air flow F may be drawn from the duct <NUM> by the offtake assembly <NUM> to drive and/or supply one or more pneumatically-driven aircraft systems <NUM> connected thereto. Stated otherwise, the offtake assembly <NUM> is operatively connected to the duct <NUM>. In this case, the offtake assembly <NUM> is connected to an annular outer-duct wall <NUM> (the outer-duct wall <NUM>) of the duct <NUM> being a portion of the engine wall <NUM> spaced aft from an inlet of the duct <NUM>. Depending on the implementation, the outer-duct wall <NUM> to which the offtake assembly <NUM> is located can be located between a fan outer bypass vane and a bypass air-exhaust gas mixer of the engine <NUM>.

The offtake assembly <NUM> generally includes an air line <NUM> (the line <NUM>) having a first-line end defining a line inlet <NUM> in fluid communication with inside the duct <NUM> via the outer-duct wall <NUM> and a second-line end opposite the first-line end, a valve <NUM> located outside the duct <NUM> and fluidly connected to the line <NUM> via the second-line end, and a pressure-relief conduit <NUM> (the conduit <NUM>, <FIG>) having opposite ends respectively in fluid communication with inside the line <NUM>, at a location between the first-line end and the second-line end upstream of the valve <NUM>, and with inside the duct <NUM>. In some implementations, the valve <NUM> is fluidly connected between the line <NUM> and a pre-cooler being a part of the one or more aircraft systems <NUM>.

While the engine 10A is of a turbofan type and the offtake assembly <NUM> is located radially outward of the duct <NUM>, the offtake assembly <NUM> may be employed with any other suitable engine type and at any suitable location thereof. For instance, referring to <FIG>, another gas turbine engine 10B is shown. In this example, the engine 10B is a turboshaft engine generally comprising in serial flow communication a low pressure compressor section (or first stage compressor) 12B and a high pressure compressor section (or second stage compressor) 14B for pressurizing air, a combustor 16B in which the compressed air is mixed with a fuel flow delivered to the combustor 16B via fuel nozzles of a fuel system (not depicted) and ignited for generating a stream of hot combustion gases, a high pressure turbine section 18B for extracting energy from the combustion gases and driving the high pressure compressor section 14B via a high pressure shaft 20B, and a low pressure turbine section 22B for further extracting energy from the combustion gases and driving the low pressure compressor section 12B via a low pressure shaft 24B. The offtake assembly <NUM> is operatively connected to a duct or air plenum 30B defining a compressor bleed cavity of the high pressure compressor section 14B.

Turning now to <FIG>, another gas turbine engine 10C is shown. In this example, the engine 10C is a turboprop engine generally comprising in serial flow communication an air inlet 12C through which ambient air enters the engine, a compressor section 14C for pressurizing the air, a combustor 16C in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section 18C for extracting energy from the combustion gases. The turbine section 18C includes a compressor turbine section 20C driving the rotor(s) of the compressor section 14C through a compressor shaft 22C, and a free power turbine section 24C driving a propeller 26C through a power shaft 28C. The offtake assembly <NUM> is operatively connected to a duct or air plenum 30C defining a compressor bleed cavity of the compressor section 14C.

It shall be noted that whereas implementations of the offtake assembly <NUM> described henceforth relate specifically to the engine 10A, such implementations also apply, mutatis mutandis, to other engines such as for example the engines 10B and 10C.

In <FIG>, portions of the offtake assembly <NUM> proximate to the outer-duct wall <NUM> are shown, including a portion of the line <NUM> having the line inlet <NUM> and including the conduit <NUM>, whereas the valve <NUM> and a portion of the line <NUM> proximate to the valve <NUM> have been removed. The line <NUM> is a tubular structure which, in this embodiment, features the line inlet <NUM> having a cylindrical shape projecting outwardly from an exterior-duct surface 32e of the outer-duct wall <NUM>. In this example, the line <NUM> extends from line inlet <NUM> at an angle α to the exterior-duct surface 32e so as to be inclined relative to the flow F. Depending on the implementation, the line <NUM> can be inclined rearwardly (i.e., cocurrent relative to the flow F), at a right angle or forwardly (i.e., crosscurrent relative to the flow F). Other shapes and orientations for the line inlet <NUM> are possible, so long as suitable aerodynamics are attained. Indeed, the flow F must be partially drawn into the line <NUM> from inside the duct <NUM> such that a bleed air flow Fb (the bleed flow Fb, <FIG>) having suitable aerodynamic properties is delivered to the valve <NUM>. For this purpose, as depicted in <FIG>, the line <NUM> is in fluid communication with an offtake location L1 inside the duct <NUM> via an offtake opening <NUM> defined through the outer-duct wall <NUM>. The offtake opening <NUM> extends from an interior-duct surface 32i (<FIG>) of the outer-duct wall <NUM> to the exterior-duct surface 32e. The offtake location L1 adjoins a fore, high-pressure side of the offtake opening <NUM>. In the present embodiment, the outer-duct wall <NUM> has a boss <NUM> projecting into the duct <NUM>. The offtake opening <NUM> is defined at least partially onto an upstream, fore-facing side of the boss <NUM> such that the offtake opening <NUM> at least partially faces the flow F. Stated otherwise, the boss <NUM> and the offtake opening <NUM> are arranged relative to the interior-duct surface 32i such that as the flow F runs along the interior-duct surface 32i at the offtake location L1, a portion of the flow F is incident relative to the offtake opening <NUM>. Outside the duct <NUM>, the line inlet <NUM> is joined to the exterior-duct surface 32e so as to surround the offtake opening <NUM>, forming a seal therewith preventing air entering the offtake opening <NUM> from bypassing the line <NUM>.

With reference to <FIG>, characteristics of the offtake assembly <NUM> pertaining to the conduit <NUM> will now be described. In this embodiment, the conduit <NUM> is provided in the form of an elongated volume partitioned inside the line <NUM>. The conduit <NUM> has opposite open ends, respectively a conduit inlet <NUM> in fluid communication with a resonance location L2 inside the line <NUM> distanced from both the line inlet <NUM> and the valve <NUM>, and a conduit outlet <NUM> in fluid communication with a relief location L3 (<FIG>) inside the duct <NUM>. As an example, the relief location L3 adjoins an aft, low-pressure side of the offtake opening <NUM>. The relief location L3 is thus located aft of the offtake location L1, although it does not have to be the case, as will be explained hereinbelow. A tube <NUM> of the offtake assembly <NUM> is received inside the line <NUM> in an overlaid yet spaced positioning relative to the line <NUM>. The line <NUM> surrounds the tube <NUM> as the line <NUM> extends away from the exterior-duct surface 32e so as to define the conduit <NUM> between an interior-line surface 60i of the line <NUM> and an exterior-tube surface 90e of the tube <NUM>. A distal-tube end <NUM> of the tube <NUM> is located at the resonance location L2 and is surrounded by the interior-line surface 60i. A proximal-tube end <NUM> of the tube <NUM> opposite the distal-tube end <NUM> is joined to the exterior-duct surface 32e so as to follow a periphery of the offtake opening <NUM> and be surrounded by the interior-line surface 60i. The proximal-tube end <NUM> forms a seal with the exterior-duct surface 32e proximate to the periphery of the offtake opening <NUM>, forcing air having exited the duct <NUM> via the offtake opening <NUM> to travel through the tube <NUM> before it may pressurize the line <NUM> at the resonance location L2 and enter the conduit <NUM>. At the distal-tube end <NUM>, an exterior-tube surface 90e of the tube <NUM> defines an inner boundary of the conduit inlet <NUM>. At the proximal-tube end <NUM>, the exterior-tube surface 90e defines an inner boundary of the conduit outlet <NUM>. Outer boundaries of the conduit inlet <NUM> and conduit outlet <NUM> are respectively defined by the interior-line surface 60i. It shall be noted that the line <NUM> and the tube <NUM> are shaped and positioned relative to one another such that a portion of the conduit <NUM> located at the resonance location L2 is annular in shape. Indeed, at the resonance location L2, the line <NUM> and the tube <NUM> respectively have cylindrical shapes that are coaxial to one another. However, other shapes are contemplated, insofar as the conduit <NUM> forms a fluid passage from the conduit inlet <NUM> to the conduit outlet <NUM> for a relief flow Fr to travel via the conduit <NUM> from the resonance location L2 to the relief location L3. For example, the line <NUM> and the tube <NUM> may be routed so as to follow different paths as they extend outward of the duct <NUM>, imparting the conduit <NUM> with a non necessarily annular shape. For example, one of the line <NUM> and the tube <NUM> may follow a straight path and the other a curvilinear path. One or both of the line <NUM> and the tube <NUM> may have a non-circular cross-section. Depending on the implementation, the line <NUM> and the tube <NUM> may be constructed of composite and/or metallic materials, such as stainless steel or titanium. In some embodiments, for instance those implemented in a hot engine section (<FIG>), the line <NUM> is constructed of a metallic material suitable for withstanding high temperatures and for shielding the tube <NUM> from such high temperatures. In some such embodiments, the tube <NUM> is constructed of a composite material. In some embodiments implemented in a cold engine section (<FIG>), the line <NUM> and the tube <NUM> are constructed of composite materials.

With reference to <FIG>, the conduit <NUM> is in fluid communication with the relief location L3 inside the duct <NUM> via a relief opening <NUM> defined through the outer-duct wall <NUM> from the exterior-duct surface 32e to the interior-duct surface 32i. In this example, the relief opening <NUM> is provided in the form of a plurality of bores 38A positioned so as to be in communication between the conduit outlet <NUM> and the relief location L3. The bores 38A are distributed arcuately next to one another peripherally to the proximate-tube end <NUM> and so as to be surrounded by the line inlet <NUM>. Such a multi-opening arrangement for the relief opening <NUM> can advantageously assist the relief flow Fr from migrating from inside the conduit <NUM> to inside the duct <NUM> while maintaining the structural integrity of the duct <NUM>. The relief opening <NUM> is defined at least partially onto a downstream, aft-facing side of the boss <NUM> so as to direct the relief flow Fr concurrently to the flow F away from the offtake opening <NUM>. Other shapes and spatial arrangements for the relief opening <NUM> are possible.

Referring to <FIG>, in operation, the air flow F flows inside the duct <NUM> from the inlet to the offtake location L1 on the high-pressure side of the offtake opening <NUM>, and supplies the bypass flow Fb into the offtake assembly <NUM>. As air enters through the offtake opening <NUM>, flow separation and vortex shedding of the bypass flow Fb occur proximate to the line inlet <NUM>, leading to cyclical pressurization (i.e., pressure amplitude spikes, or dashes) inside the line <NUM> upon the valve <NUM> being closed. Such pressurization builds up upstream of the valve <NUM> and is maximized at the resonance location L2 along the interior-line surface 60i. The resonance location L2 encompasses a portion of the interior line surface 60i most solicited by the pressurization, and is referred to as such due to the vibration of the line <NUM> and resulting acoustic tones emitted thereby under certain operating conditions of the engine 10A. It shall be noted that the tube <NUM> is sized and arranged such that the conduit <NUM> extends to the resonance location L2, i.e., the conduit inlet <NUM> is located proximate to the resonance location L2. As such, the pressure building up at the resonance location L2 is maintained under a certain desired maximum level, or built-up pressure, by allowing pressure in excess of the built-up pressure to be relieved via the conduit <NUM>. Indeed, by circulating a relief flow Fr from inside the line <NUM> at the resonance location L2, through the conduit <NUM> and into the duct <NUM> via the relief opening <NUM>, air which would otherwise be trapped in the line <NUM>, dash against the interior line surface 60i and cause vibration at the resonance location L2 to be amplified, is instead released from the line <NUM>.

The line <NUM> is sized and arranged relative to the duct inlet such that upon the duct <NUM> being at an intake pressure at the duct inlet and the valve <NUM> being closed, an offtake pressure at the offtake location L1 is less than the intake pressure, and built up pressure at the resonance location L2 is greater than the offtake pressure. Upon the valve <NUM> being closed, the built up pressure at the resonance location L2 is greater than a relief pressure inside the duct <NUM> at the relief location L3. This creates a positive pressure differential between inside the line <NUM> at the resonance location L2 and inside the duct <NUM> at the relief location L3, allowing the relief of the excess pressure to occur via the conduit <NUM>. It should be noted that the built up pressure is also greater than an offtake pressure inside the duct <NUM> at the offtake location L1. Hence, in other embodiments, the relief location L3 and the offtake location L1 (and, conversely, the relief opening <NUM> and the offtake opening <NUM>) may be at a same distance from the inlet, or the relief location L3 may even be upstream of the offtake location L1, so long as a suitable positive pressure differential is attained. Upon the valve <NUM> being open, the resonance location L2 is at a pressure that is less than inside the duct <NUM> at either the offtake location L1 or the relief location L3.

Referring to <FIG> (<FIG> are outside the wording of the claims), a description of other embodiments of the offtake assembly <NUM> will now be provided, in which elements alike those described hereinabove bear like numerals. In <FIG>, there is shown another embodiment of the offtake assembly <NUM> in which the tube <NUM> has lateral openings <NUM> extending from an interior-tube surface 90i of the tube <NUM> to the exterior-tube surface 90e so as to be in fluid communication between inside the tube <NUM> and inside the conduit <NUM>. The lateral openings <NUM> are positioned at or proximate to the resonance location L2 inside the line <NUM>. Quantity, size, shape (e.g., bore(s), slot(s)), and spatial arrangement of such lateral openings <NUM> are determined with respect to high pressure amplitude areas of the resonance location L2 so as to assist migration of the bleed flow Fb away from the resonance location L2 via the conduit <NUM> and thereby assist migration of the relief flow Fr from inside of the conduit <NUM> to inside of the duct <NUM>. In this example, a density of the lateral openings <NUM> varies along the length of the tube <NUM>, and is greatest alongside a portion of the resonance location L2 being the closest to the conduit inlet <NUM>. The density of the lateral openings <NUM> increases along the tube <NUM> toward the distal-tube end <NUM>.

In some embodiments including the one shown in <FIG>, the line inlet <NUM> flares as it meets the boss <NUM> near a periphery thereof so as to surround the proximal-tube end <NUM> as well as the relief opening <NUM>. The boss <NUM>, the line inlet <NUM> and the proximal-tube end <NUM> can be shaped such that the conduit <NUM> increases in size as it nears the conduit outlet <NUM>, and thus can advantageously allow to optimize the configuration of the relief opening <NUM>. For example, a plurality of openings 38A can be distributed next to one another, for example radially outwardly relative to the offtake opening <NUM>.

Turning now to <FIG>, an example of the offtake assembly <NUM> outside the wording of the claims is shown, in which the conduit <NUM> is alternatively formed by an interior of the tube <NUM>. In such embodiments, the proximal-tube end <NUM> defines the conduit outlet <NUM>, and meets the outer-duct wall <NUM> so as to follow a periphery of the relief opening <NUM>. The distal-tube end defines the conduit inlet <NUM>.

Referring to <FIG>, there is shown yet another example of the offtake assembly <NUM> outside the wording of the claims, in which the conduit <NUM> is formed by an interior of a tube <NUM> provided outside the line <NUM>. A distal end <NUM> of the tube <NUM>, which defines the conduit inlet <NUM>, is fluidly connected to the line <NUM> at the resonance location L2. A proximal end <NUM> of the tube <NUM> defines the conduit outlet <NUM> and is fluidly connected to the relief opening <NUM> in the duct <NUM> such that the resonance location L2 inside the line <NUM> is in fluid communication with inside the duct <NUM>. In this example, the relief opening <NUM> is located proximate to the offtake opening <NUM> and the tube <NUM> runs alongside the line <NUM>. In alternate implementations, the relief opening <NUM> may be defined in the outer-duct wall <NUM> at a location remote from the offtake opening <NUM>, for example further downstream and away from the boss <NUM>, or even upstream of the offtake opening <NUM>, so long as a suitable pressure differential is attainable between inside the line <NUM> at the resonance location L2 and inside the duct <NUM> at the location of the relief opening <NUM>.

Claim 1:
A gas turbine engine (10A; 10B; 10C) comprising:
a duct (<NUM>) extending about an axis (CL), the duct (<NUM>) including an outer-duct wall (<NUM>) having an interior-duct surface (32i) circumscribing an interior of the duct (<NUM>) and an exterior-duct surface (32e) radially outward of the interior-duct surface (32i) relative to the axis (CL), the outer-duct wall (<NUM>) defining an offtake opening (<NUM>) extending from the interior-duct surface (32i) to the exterior-duct surface (32e), the offtake opening (<NUM>) in fluid communication between an offtake location (L1) inside the duct (<NUM>) and outside the duct (<NUM>); and
a bleed air offtake assembly (<NUM>) including:
an air line (<NUM>) in fluid communication with inside the duct (<NUM>) via the offtake opening (<NUM>), the air line (<NUM>) having a first-line end defining a line inlet (<NUM>) proximate to the outer-duct wall (<NUM>) and a second-line end spaced from the first-line end;
a valve (<NUM>) located outside the duct (<NUM>) and fluidly connected to the air line (<NUM>) via the second-line end; and
a conduit (<NUM>) having a conduit inlet (<NUM>) in fluid communication with inside the air line (<NUM>) at a resonance location (L2) between the first-line end and the second-line end upstream of the valve (<NUM>), and a conduit outlet (<NUM>) in fluid communication with inside the duct (<NUM>) at a relief location (L3) spaced from the offtake location (L1),
characterised in that:
the conduit (<NUM>) is located inside the air line (<NUM>), the bleed air offtake assembly (<NUM>) includes a tube (<NUM>) extending from the exterior-duct surface (32e) to the resonance location (L2) inside the air line (<NUM>), the tube (<NUM>) having an exterior-tube surface (90e), the air line (<NUM>) has an interior-line surface (60i) surrounding the exterior-tube surface (90e), and the conduit (<NUM>) has an annular shape circumscribed inwardly by the exterior-tube surface (90e) and outwardly by the interior-line surface (60i).