Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Casing with axial flow runner
Reexamination Certificate
2000-08-30
2002-11-12
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Casing with axial flow runner
C415S223000, C415S232000
Reexamination Certificate
active
06478539
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a blade ring or blade structure for a gas turbine engine, especially an aircraft engine. A ring or disk forms a carrier for at least one blade, that forms an airfoil with its surface and is fixed to the carrier.
BACKGROUND INFORMATION
Blade rings for gas turbine engines usually comprise a carrier such as a disk, or ring, or a housing part, or a shroud to which normally several blades are attached in corresponding holes in the carrier.
When rotor blade rings of fabricated rotors are used in a gas turbine, static flexural torque arises in the blades due to centrifugal forces and due to the force of the gas. Additionally, dynamic flexural torque arises due to blade vibration. To avoid damage, it is important to reduce the resulting mechanical stress at the transition from the blade to the carrier. This stress reduction is also important for rotors with integral blades at the transition of the respective blade to the peripheral surface of the carrier.
Fabricated guide vane rings are blade rings that, as carriers for attaching the blades, generally comprise an annular outer shroud and sometimes an annular inner shroud, and are mounted to an integral component. The vanes are inserted through a recess in the shroud and, e.g. attached by soldering or welding. The annular shroud can be segmented or a closed ring and extends along the longitudinal axis of the gas turbine. The vanes of blade rings basically extend in a radial direction.
As mentioned, when a fabricated guide vane ring is used in a gas turbine, static flexural torque arises in the blades due to the force of the gas, and dynamic flexural torque arises due to blade vibrations. The resulting mechanical stress at the transition between the blade and shroud or carrier must be kept as low as possible.
European Patent Publication EP 0 945 594 A1 diskloses a cooled rotor blade for a gas turbine that has a platform and an inner cooling air passage, whereby the transition from the platform to the blade surface first runs elliptically along the entire perimeter, then in a straight line, then curved to the blade tip.
Japanese Patent Publication JP 8 177 401 A diskloses a turbine rotor with a disk and numerous blades on the perimeter extending essentially in a radial direction. The structure is such that the center of gravity of the blades is offset to the intake side of the blade, and the transition between the blade surface and the peripheral surface of the blade extends radially or elliptically.
The above object has been achieved according to the invention in that a transition area between the surface of the airfoil and trhe platform of the blade carrier such as a ring or disk or shroud has a limited number of at least two radii of different length and with different midpoints or center points. The first radius neighboring the surface of the airfoil is the largest, and the limited number of radii in the direction toward the platform may be part of the blade or of the carrier are successively smaller than the first radius.
SUMMARY OF THE INVENTION
It is an object of the present invention to create a rotor and/or stator construction for a gas turbine engine, wherein the mechanical stress due to flexural torque is very low in the transition area between a blade and its support, while simultaneously keeping the overall axial length of the present blade mountings optimally short. The construction of the present invention is equally applicable to rotor rings or rotor disks and to stator disks or shrouds carrying guide blades. The support is either a ring or disk or shroud or housing wall.
An advantage of such a transition area construction also referred to herein as fillet is that the axial length of the blade carrier is less than it would be if the transition area has a circular transition under corresponding conditions due to the curvature that narrows toward the platform or the peripheral section of the carrier neighboring the airfoil at the transition between the surface of the airfoil and the platform or the peripheral section which may form the platform as part of the carrier rather than as part of the blade. In addition, the mechanical stress is less from the flexural torque than if there was no fillet or a fillet with a circular curvature surface forming the transition area. The narrowing curvature or its path can be realized using any kind of suitable tool means.
The present transition area or fillet is constructed with at least two different radii, whereby the radii toward the platform become successively smaller. The transition is hence comparatively easy to manufacture. In comparison to a circular fillet, the mechanical stress is less due to flexural torque with the same volume of the fillet. In addition, the overall axial length of the ring platform carrying the blades is reduced by this feature of the invention.
Given the same stress level at the transition, the volume of the fillet with a curvature according to the invention may be less than that of a fillet having a circular transition curvature. In addition, any deviations from an aerodynamically optimal design are small. Furthermore, not only is the axial platform length reduced, the mass of the ring is also reduced.
In an alternative embodiment, the transition curvature between a curvature neighboring the platform and a curvature neighboring the surface of the airfoil, can be any continuous function, or it can even be a straight line or several sections of a straight line joining one curvature with the other.
The blade ring can be a rotor blade ring, especially for a fabricated rotor where the blade is a rotor blade and the carrier is a rotor carrier such as a disk or ring.
The rotor with integral blades can have rotor blades that extend in an essentially radial direction and are affixed to the peripheral surface of a rotor carrier such as a disk or ring. The platform is formed by a section of the peripheral surface or portion of the rotor carrier neighboring the radially inner blade end, or blade foot and the transition from the surface of the rotor blade in this peripheral carrier portion is defined by a narrowing curve with a radius smaller than the radius of the curvature next to the blade surface. When mounted, the surface of the platform forms a section of the peripheral surface otherwise formed by the shroud. This feature is provided even in a guide blade ring.
Alternatively, the blade ring can be constructed as a fabricated stator guide vane ring that comprises a carrier with at least one inner or outer shroud with at least one recess for attaching the blade constructed as a vane. Alternatively, a vane ring can be produced by casting or milling so that the recesses are not necessary, and the transition changes into a peripheral section on the carrier side. Such a guide blade ring can be constructed of several segments each with three or four guide blades and the corresponding number of perforations or recesses in the shroud, or it can be a circular ring.
REFERENCES:
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patent: 3890062 (1975-06-01), Hendrix et al.
patent: 5284421 (1994-02-01), Chlus et al.
patent: 5292385 (1994-03-01), Kington
patent: 5562419 (1996-10-01), Crall et al.
patent: 0900920 (1999-03-01), None
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patent: 514430 (1939-11-01), None
patent: 1233022 (1971-05-01), None
patent: 8177401 (1996-07-01), None
patent: 556238 (1977-05-01), None
patent: WO94/12765 (1994-06-01), None
patent: WO96/15356 (1996-05-01), None
“Kleine Enzyklopädie der Mathematik” (Little Encyclopaedia of Mathematics), Nachdruck, der2, v{umlaut over (v)}llig überarbeiteten Auflag, 1984, Verlag Harri Deutsch, pp. 192 to 195.
“Taschenbuch der Mathematik” (Pocket Book of Mathematics); 1987; German Democratic Republic, pp. 220 to 223.
Fasse W. F.
Fasse W. G.
Look Edward K.
McAleenan James M
MTU Aero Engines GmbH
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