Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Vane or deflector
Reexamination Certificate
1998-08-24
2001-04-17
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Vane or deflector
C415S209300
Reexamination Certificate
active
06217282
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a vane element for a gas turbine, particularly a low-pressure turbine, in which the vane element has a vane blade, which extends between an inner platform and an outer platform, the outer platform being secured to a housing by fastening means, the inner platform being adapted for being coupled to the inner platforms of adjacent vane elements.
The invention relates further to a vane segment assembled from at least three vane elements as well as to a ring of the vane elements formed by assembling the vane segments.
BACKGROUND
Vanes of low-pressure turbines have been made of metal and are generally soldered together first to form segments of three or six vanes and then to form the annular ring. For investigations of aerodynamic dimensioning of the profile of the vane blades as well as for incorporation in an actual gas turbine drive mechanism, a number of vane segments are secured together to form a ring of blades in which individual vane segments are not rigidly connected to one another in order to accommodate thermal expansion. The vanes are fastened by their outer platforms in a drive housing and are detachably connected to one another at their inner platforms by metal clamps or the like. By clamping the vanes at the inner platforms, the vibration behavior of the vane blades is improved. The use of clamps as additional components, however, has the disadvantage of more extensive assembly and higher costs.
For calibrating the aerodynamic dimensioning process and for rapid determination of test data for alternately measuring pressure, velocity and flow quantity, vanes made substantially of carbon-fiber-reinforced plastics are utilized and are tested in so-called aerodynamic “cold” test stands. Such vanes can be produced considerably more rapidly and at lower cost than corresponding vanes made of metal and thus are preferably utilized in these investigations. Vanes of plastic are loaded in the test stand at considerably lower temperatures (approximately 130° C.) compared to actual operation, but are subjected to forces of the same order of magnitude as in the actual drive turbine.
It is thus a problem to adopt the geometry of the outer and inner platforms of the vanes made of metal for those made of plastic, since the latter cannot withstand the high loads produced by the actual gas forces. Gluing or bonding together three or six vane elements into individual vane segments, from which the vane ring is formed has only slightly met this problem. Similarly, securing the vane elements by means of bolts at lateral front surfaces of the inner and outer platforms has not proven effective because the amplitude of vibration of the vanes was too high and led to breakage of the vanes.
SUMMARY OF THE INVENTION
An object of the invention is to provide a vane element of the above type which has an improved dynamic vibration behavior, which limits vibration amplitudes of adjacent vanes and can be produced by manufacturing technology in a simple and cost-favorable manner.
The above and further objects are achieved according to the invention in that at least the inner or outer platform has a projection with a lateral surface at a first lateral front surface, and a recess at an opposite lateral front surface, the recess being shaped to correspond to the projection, such that the projection of one vane element can be form-fit into the recess of an adjacent vane element so that the inner or outer platforms of adjacent vane elements are flush with one another.
This construction has the advantage that vane elements of adjacent vane segments, (formed, for example, by joining three vane elements together) are coupled in a form-fitting manner with one another in the axial direction and a damping effect is produced at the contact surfaces due to friction therebetween. The projections also seal any gaps that occur between the platforms.
In a preferred embodiment, the lateral surfaces of the projection extend at right angles to the first front surface of the outer or inner platform generally extending in the radial direction. The lateral surfaces of the projection therefore extend in the circumferential direction that is intensely loaded by the gas flow and achieve damping as a consequence of friction at the contact surfaces.
Preferably, the lateral surfaces of the projections project at least 3 mm from the first front surface of the inner or outer platform, so that a sufficiently high friction or contact surface is present in the recess of the adjacent vane element.
It is advantageous for the projection to constitute at least 30% and preferably at least 50% of the area of the first front surface in order to limit the vibration amplitude of the vane elements.
Further, it is preferred that the projection fits with a small play in the recess of the adjacent vane element so that, for example, the vane elements of adjacent vane segments can move towards and away from one another to accommodate thermal expansion.
Most preferably, the inner surfaces of the recess at the second front surface extend parallel to the lateral surfaces of the projection, so that secure friction contact is assured between the inner surfaces of the recess and the lateral surfaces of the projection.
It is preferred that the outer platform comprises a flange integral with the vane and an outer reinforcing wall, which are joined by means of two transverse webs extending circumferentially at axially spaced locations, and/or that the inner platform comprises a flange integral with the vane and a reinforcing wall. In this way, resistance to bending and twisting of the platforms is obtained. The resistance to bending and twisting is particularly effective for the outer platform consisting of the flange, the outer reinforcing wall, the two transverse webs, and the fastening means attaching the vane element to the drive housing. Due to this arrangement, the vane element also resists relatively high actual gas forces, even when made from relatively weak materials, such as, for example, fiber-reinforced plastic.
In a preferred embodiment, the vane element is formed as an integral one-piece body so that it can be made inexpensively from metal or by injection molding processes.
It is particularly preferred that the vane element be made of carbon-fiber-reinforced plastic, so that it can be investigated in so-called aerodynamic “cold” test stands. In this way, test data for the calibrating of aerodynamic dimensioning processes can be determined more rapidly and in a more cost-favorable manner, than is the case of the vane elements made of metal. Such test vane elements of plastic also can be joined by bonding or gluing three or six vane elements together to form a vane segment. The lateral surfaces of the projections serve for the application of adhesive, which, in contrast to the first and second front surfaces of the conventional inner or outer platforms, resist the circumferentially applied forces in shear rather than in tension or compression. This is clearly a more favorable form of loading for glued joints.
REFERENCES:
patent: 3442442 (1969-05-01), Seiwert
patent: 3561884 (1971-02-01), Zerlauth
patent: 4832568 (1989-05-01), Roth et al.
patent: 5848874 (1998-12-01), Heumann et al.
patent: 128499 (1950-06-01), None
Daimler-Chrysler AG
Ladas & Parry
Look Edward K.
McAleenan James M
LandOfFree
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