Support For Rotor Blades In A Rotor

Abstract

The blades are held in slots of the rotor along with baffle elements which are placed between each pair of blades. Each element is elastically connected in a yieldable manner to each blade of a pair of blades at points on opposite sides of the element while simultaneously filling the slot to prevent leakage between the blades. The elements can be slotted or provided with elevations at opposite ends to enhance the yieldability.

Description

This invention relates to a support for rotor blades in a rotor. More particularly, this invention relates to a support for rotor blades of a turboengine rotor.

Turboengine rotors have been known wherein a plurality of turbine blades have been mounted in slots within the rotor with wedgelike baffle elements therebetween. For example, blades have been constructed with a baseplate, a necklike extension below the baseplate and a base below the extension which has been shaped to mate within an axial or oblique slot in the rotor. In order to prevent leakage between these blades, the baffle elements have been sized to fit within the space between the necklike extension of two adjacent blades. Further, such baffle elements have been sized and fitted so as to obtain as smooth as possible a transition between the baseplates and rotor.

However, it has been found that under the influence of centrifugal force, the heretofore used baffle elements have been pressed with such force against the baseplates as to behave in a manner as if they were rigidly interconnected with the baseplates. Such rigid connections have frequently exerted unfavorable influence on the vibration behavior of the rotor in that the natural vibration frequency of a row of blades has become excessively high.

Accordingly, it is an object of the invention to mount the blades of a rotor in place in an elastic manner.

It is another object of the invention to permit vibration of a turbine blade with respect to a baffle element adjacent the blade within a rotor.

It is another object of the invention to reduce the natural vibration frequency of a blade secured in a rotor.

Briefly, the invention provides a baffle element for turbine blades in a rotor which is situated between a pair of blades and contacts each blade at a point in an elastic yieldable manner opposite the contact point of the other blade. This allows the blades to vibrate more or less freely with respect to the baffle element. In effect, an elastic yieldable section is provided in the baffle element between the contact points with the respective turbine blades. As a result, the blades are able to oscillate more or less freely with respect to the baffle element while their natural frequency is reduced. Depending on the configuration of the intermediate baffle elements, the natural vibration frequency of the blades can be adjusted to a desired value within certain limits. Also, depending on the vibration form of particular interest, various configurations of the baffle elements can likewise be elastically effective.

These and other objects and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a fragmentary side view of a rotor having blades mounted in place by baffle elements according to the invention;

FIG. 2 illustrates a view taken on line A-B of FIG. 1;

FIG. 3 illustrates a perspective view of the baffle element of FIG. 1;

FIGS. 4 to 6 respectively illustrate perspective views of modified baffle elements according to the invention; and

FIG. 7 illustrates a view similar to FIG. 1 of another modified baffle element according to the invention.

Referring to FIG. 1, the rotor 1 is provided with a plurality of circumferentially spaced axial or oblique slots 2 each of which receives a complementary shaped base 3 of a turbine blade 4. In addition to the shaped base 3, each blade 4 has a baseplate 5 and a necklike extension 6 between the base 3 and baseplate 5. The necklike extensions 6 of each pair of adjacent blades 4 are spaced apart to provide an interspace for a baffle element 7. Each baffle element 7 serves to fill up the interspace between the blade extensions 6.

Referring to FIG. 3, each baffle element 7 has a pair of plates 8, which are joined together in spaced relation by a crosspiece 9 of substantially T-shaped cross section. In addition, elevations 11, 16 are provided at either end of the crosspiece 9 to extend over a part of the length of the crosspiece 9, for example, one-quarter of the crosspiece length. The elevations 11, 16 are further disposed diagonally opposite each other on the top of the crosspiece 9. Thus, one elevation 11 comes in contact with the baseplate 3 of one turbine blade 4 while the other elevation 16 comes in contact with the baseplate 3 of the other turbine blade 4 of an adjacent pair of blades. Also, one of the plates 8, i.e., the front plate, of each baffle element 7 has a lug 18 extending therefrom in the same plane which abuts the side of a blade 4 so as to prevent axial displacement of the baffle element 7. Since each of the baffle elements 7 contacts the baseplates 5 of adjacent blades 4 at separated points and is of a shape to elastically yield under stress, the baseplates 5 can move with respect to one another, for example, under a torsional vibration.

Referring to FIG. 4 in order to increase the elastic yieldability, the baffle element 7 is provided with a slot 14 substantially in the center of the crosspiece 9 which passes upwardly through the upper part of the cross section of the crosspiece 9. Alternatively, a plurality of slots (not shown) can be distributed uniformly or nonuniformly over the length of the crosspiece 9.

Referring to FIG. 5, the elastic yieldability of the baffle element 7 can also be increased by reducing the cross-sectional area of the center of the crosspiece 9 in the upper part. For example, as shown, the flat horizontal upper part of the crosspiece can be centrally interrupted.

Referring to FIG. 6, the elastic yieldability of the baffle element can be increased by positioning the two elevations 12 on the same side of the crosspiece 9. This allows the baffle element 7 to bear against only one of the two adjacent blades 4 during operation while the contact point of the baffle element 7 with the other blade 4 lies between the plates 8 and the necklike extension 6 substantially in the area 13, as shown, opposite the lug 18.

Referring to FIG. 7, a baffle element 7' having an axial slot 20 can also be fitted between the necklike extensions 6 of a pair of blades 4. This allows an elastic yieldable connection to be formed at the contact points 19 between the upper surfaces of the element 7' on opposite sides of the slot 20 and the baseplates 5 of the blades 4.

Claims

What is claimed is:

1. The combination of a rotor having a plurality of circumferentially spaced slots; a plurality of turbine blades mounted in respective slots of said rotor, each blade having a base received in a respective slot, a baseplate and a necklike extension between said base and baseplate; and a plurality of elements, each said element being of approximately the same axial length as said necklike extensions and positioned between a pair of adjacent blades between said necklike extensions, each said element having a pair of spaced-apart elevations projecting therefrom, one of said elevations contacting one blade at a first contact point and the other of said elevations contacting the other blade of said pair of blades at a second contact point, and each said element being elastically yieldable between said points of contact and said elevations.

2. The combination as set forth in claim 1, wherein said element includes a pair of spaced plates between said pair of blades and a crosspiece joining said plates.

3. The combination as set forth in claim 2, wherein each baseplate is disposed radially over said elements and wherein said crosspiece mounts said elevations on an upper surface thereof with each said elevation extending along not more than one-quarter of the length of said crosspiece.

4. The combination as set forth in claim 3, wherein said crosspiece includes at least one slot therein between said contact points.

5. The combination as set forth in claim 3, wherein said crosspiece has a reduced cross section centrally thereof.

6. The combination as set forth in claim 2, wherein one of said plates of each element has a lug projecting therefrom in contact with the side of an adjacent blade.

7. The combination as set forth in claim 1, wherein said element includes an axial slot in the upper part between said contact points.

8. The combination as set forth in claim 1, wherein said slots are obliquely disposed in said rotor.

9. The combination as set forth in claim 1 wherein said slots are axially disposed in said rotor.