Patent Application
20100300113
The present application relates to gas turbine engines and, more particularly, to an anti-vortex structure for a compressor.
Conventional compressor bleed arrangements typically consist of a relatively complex assembly of parts, such as discs, plates, sheet metal guide vanes, conical members, shafts and rotors. All these parts are cumbersome and add to the overall weight and cost of the engine. Space limitations as well as the needs for not disrupting the airflow in the main gaspath of the engine also render the installation of multi-parts bleeding arrangement challenging. Multi-part assemblies also suffer from non-negligible pressure drops notably at the joints between differently oriented parts. They may also affect the balance of the compressor rotor when mounted thereto.
Therefore, in accordance with one aspect of the present application, there is provided a compressor rotor assembly mounted for rotation about a central axis of a gas turbine engine, comprising an anti-vortex device having a peripheral rim surface defining an inner boundary of a primary gas path of the engine, the anti-vortex device defining circumferentially spaced-apart radial passageways extending from respective axially extending central passages to an outer peripheral rim surface of the device, each said radial passageway receiving bleed air from the primary gas path and directing it to an associated one of said axially extending passages.
Another general aspect of the present application is to provide a gas turbine engine comprising a compressor having at least two rotors mounted for joint rotation about a central axis, a combustor and a turbine section; the compressor has an anti-vortex device secured between said at least two rotors, the anti-vortex device having a solid body portion, circumferentially spaced-apart radial passageways defined in said solid body portion, each said radial passageway extending from an axial passage extending through the solid body portion in a central area thereof to an outer peripheral rim surface of the solid body portion, the outer peripheral rim surface being spaced inwardly of an air bleed gap formed between said at least two rotors and in communication with a gaspath of the engine, the anti-vortex device channelling air from the gaspath in non-interference therewith through said air bleed gap and into said radial passageways and said axial passage, said axial passage redirecting said air under pressure in two opposite axial directions.
In accordance with a further general aspect, there is provided a method of reducing total pressure drop and the formation of free vortex in a flow of compressed air bled inwardly from a compressor of a gas turbine engine, the method comprising: providing circumferentially spaced-apart radial passageways extending from an axial passage extending through the compressor in a central area thereof to an outer peripheral rim of a compressor hub; bleeding compressed air from a gas path of the compressor through said radial passageways and directing said compressed air to said axial passage when said compressor rotor assembly is rotating; and directing at least some of the compressed air bled from said axial passage, via a central axially-extending passage of the compressor rotor assembly, to a turbine section of said gas turbine engine to cool turbine components in said turbine section.
Reference is now made to the accompanying figures, in which:
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The anti-vortex device 20 is formed from a solid mass, herein titanium, and the radial passageways 26 and axial passages 27 are machined from this mass. Also machined are cone-shaped cavities 32 disposed between the radial passageways 26 and of like transverse configuration but with the exception that the cavities 32 do not communicate with an axial passage. These cavities are formed to reduce the weight of the device 20. Tie-rod holes 33 are provided in the solid mass between the radial passageways 26 and the cone-shaped cavities 32 to receive corresponding tie rods 37 (
From a geometrical point of view, the anti-vortex device 20 channels some of the compressed air towards a small outlet area along the engine axis and in a compressor rotating at high r.p.m. Since most of the pressure drop occurs in the low radius region near the engine axis 40, the structural shape and disposition of the radial passageways 26 provides for reduced pressure drops. As herein shown, these radial passageways 26 are disposed along radius portions of transversely intersecting diametrical axes 30 and thus form an “X” structural shape (generally speaking, though it is understood that the “X” may have more or less than 4 legs, and as such the shape may be more akin to a star or wheel spokes than an “X” per se; thus it is understood that the shape is not strictly speaking limited to an arrangement which has the shape of the letter X) which helps to distribute the flow of compressed air as it facilitates the change of direction of the bled compressed air from radial to axial direction without allowing the air to mix. That is to say, each radial passage 26 has an associated axial passage 27 to redirect its flow, to reduce the swirl level of the bled air at that location to that of the rotating speed of the disc. Otherwise, there would be a higher pressure drop than is present with the anti-vortex device. The independent passageways and their transverse passages orient the channelling of the bled air and keep the stress at an acceptable level. These designs also satisfy the requirements of aerodynamics, stress and manufacturing requirements in a gas turbine engine. Although the anti-vortex device 20 is hereinshown being secured in the rotor assembly of a turbofan gas turbine engine, it is not restricted to such engines and may be incorporated in an auxiliary prime unit, a turboshaft engine, a turboprop engine or other turbine power plant where there is a need to bleed air from the high pressure gas path for cooling a turbine section of the power plant.
Briefly describing the method of operation of the example of the anti-vortex device described above, the device 20, when in operation, rotates at high speeds, reduces total pressure drop and prevents the formation of free vortex of compressed air flowing from a compressed air path of a high pressure rotor towards an axial central passage of the rotor assembly and the engine. The method comprises securing the anti-vortex device 20 between opposed rotor elements of a compressor rotor assembly, whereby high pressure air from the primary gas path 24 of the compressor is bled through the air bleed gap 23 between the rotor elements and enters the anti-vortex device 20 at the outer peripheral rim surface 31 thereof and led towards the center of the compressor through the radial passageways 26 and transverse passages 27. The airflow in the radial passages 26 is split axially by the transverse passages 27 associated with each of the radial passageways 26, in two opposite directions; to further minimize the pressure drop. A first portion of the re-directed air flow can be utilized to pressurize a buffer seal, not shown, with this redirected air flow herein indicated by arrow 41 (
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, although the anti-vortex device has a “disc” or “drum” geometry in the above example, any suitable configuration may be employed which achieves the taught result. For example, the device need not be one-piece as described, but may have multiple pieces. The device need not be machined from solid as described, but may be provided in any suitable manner. Also, in will be understood in light of the above description that the anti-vortex device need not be provided as a separate component as described above, but rather it may be integrated where suitable into another component, such as a rotor disc, impeller, stub-shaft, etc. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
