Guide vane ring with wear elements

Description

[0001] The invention relates to a guide vane ring which is divided into an upper and a lower guide vane ring half, with an at least two-part inner ring which has a substantially U-shaped cross-section and forms a circumferentially extending, radially outwardly open flow channel which is delimited by an inner ring bottom wall and two inner ring side walls, and a plurality of guide vane platforms which are arranged along the outer circumference of the inner ring and which accommodate guide vanes and each have radially inwardly projecting retaining webs which are spaced apart from one another in the axial direction and which engage around the inner ring side walls from the outside.

[0002] Guide vanes are used in axial-flow turbines. A guide vane ring arranged on the stator, together with a rotor blade ring provided on the rotor, forms a turbine stage. The task of the guide vanes is to direct the medium flowing through the turbine as effectively as possible onto the assigned rotor blades. A guide vane ring normally has an inner ring, an outer ring and a plurality of guide vanes extending between the inner ring and the outer ring. For assembly reasons, the guide vane ring is divided into a lower and an upper guide vane ring half, which is why the inner ring and the outer ring are also designed in at least two parts. The guide vanes comprise outer and inner blade platforms, between which the blades extend. The outer blade platforms are attached to the outer ring via radially outward-projecting blade roots.In a guide vane ring design, the inner blade platforms of at least the upper guide vane ring half have radially inward-projecting, axially spaced-apart retaining webs which engage around the inner ring from the outside. When the upper and lower guide vane ring halves are joined, these retaining webs are pushed from above onto the inner ring with slight clearance, normally around 2-3 mm, so that they hold the inner ring between them. The inner ring has a substantially U-shaped cross-section and forms a circumferentially extending, radially outwardly open flow channel which is defined by an inner ring bottom wall and two inner ring side walls. During turbine operation, a cooling medium flowing out of the airfoils of the guide vanes is introduced into this flow channel in order to then pass it on towards the rotor blades to cool the rotor blades.The inner ring, which serves as a coolant distributor, is often referred to as a preswirler in practice.

[0003] During turbine operation, turbine components wear out and must be reconditioned or replaced during maintenance. This also applies to the inner ring. For example, the outer surface areas of the inner ring sidewalls facing the guide vane retaining webs regularly show signs of wear due to deformations and / or stresses occurring during operation. Repairing these components is very costly and results in significantly increased maintenance times.

[0004] Document GB 2 298 680 discloses a guide vane ring having the features of the preamble of claim 1.

[0005] Based on this prior art, it is an object of the present invention to provide a guide vane ring with an alternative structure with which the problems described above are at least partially eliminated.

[0006] To achieve this object, the present invention provides a guide vane ring of the type mentioned above, in which wear elements are inserted into the gaps present between the retaining webs and the immediately adjacent inner ring sidewalls. Such wear elements compensate for the play existing between the retaining webs and the immediately adjacent inner ring sidewalls and prevent direct contact between the retaining webs and the inner ring sidewalls, which can occur without such wear elements due to vibrations of the individual components excited during turbine operation. On the one hand, wear is reduced by the use of wear elements according to the invention. On the other hand, it is primarily the wear elements that wear out and can be replaced quickly, easily, and inexpensively during maintenance work. Repair of the inner ring in the area of ​​the retaining webs is thus completely eliminated or only minimally required.

[0007] The wear elements are plate-shaped in order to distribute the mechanical loads over as large an area as possible, thereby further reducing wear and damage to the inner ring.

[0008] It is advantageous if the wear elements are made of the same material as the inner ring or of a softer material in order to concentrate the wear primarily on the wear elements.

[0009] According to one embodiment of the present invention, each wear element is detachably connected to a retaining web or to an inner ring sidewall. Accordingly, the wear elements can be quickly and easily replaced during maintenance work.

[0010] Preferably, each wear element is attached to a retaining web or to an inner ring sidewall using a screw connection. This creates a simple, detachable connection. Advantageously, each wear element has at least one welded threaded bolt, which can be guided, for example, through an opening in a retaining web or the inner ring sidewall and secured with a nut on the other side.

[0011] Recesses accommodating the wear elements can be provided on the inner surfaces of retaining webs and / or on the outer surface of at least one inner ring side wall in order to ensure a defined positioning of the wear elements during their assembly.

[0012] According to one embodiment of the present invention, wear elements are inserted into gaps present between retaining web guide projections and immediately adjacent inner ring sidewalls, with the retaining web guide projections each projecting radially inward. Such guide projections significantly facilitate the assembly of the guide vane ring.

[0013] Further features and advantages of the present invention will become clear from the following description of an embodiment of a guide vane ring according to the invention with reference to the accompanying drawing. Figure 1 is a schematic front view of an upper half of a guide vane ring according to an embodiment of the present invention; Figure 2 is a perspective schematic partial view of the Figure 1illustrated guide vane ring in the partially assembled state, showing a wear element designed according to a first variant of the invention; Figure 3 is a perspective schematic front view of the Figure 2 shown wear element; Figure 4 a perspective schematic rear view of the Figure 2 shown wear element Figure 5 a perspective schematic sectional view of the in Figure 1 illustrated guide vane ring, showing a wear element formed according to a second variant of the invention; Figure 6 is a perspective schematic front view of the Figure 5 shown wear element; Figure 7 a perspective schematic rear view of the Figure 5 shown wear element and Figure 8 a perspective schematic partial view of an inner ring of the Figure 5 arrangement shown.

[0014] The same reference numbers indicate the same or similar components or component sections.

[0015] Figure 1 schematically shows an upper half of a guide vane ring 1 divided into an upper half and a lower half according to an embodiment of the present invention, which is such a guide vane ring for a turbine.

[0016] The guide vane ring 1 in the present case has a two-part inner ring 2, a two-part outer ring 3 and a plurality of guide vanes 4 extending between the inner ring 2 and the outer ring 3.

[0017] The guide vanes comprise outer and inner vane platforms 5, between which the blades 6 extend. In the present case, an inner vane platform 5 and an outer vane platform 5 each accommodate two blades 6 between them, whereby the number of blades 6 extending between two vane platforms 5 can vary. The outer vane platforms 5 are attached to the outer ring 3 via radially outwardly projecting blade roots 7.

[0018] The inner blade platforms 5 of at least the upper guide vane ring half have radially inwardly projecting retaining webs 8 which are spaced apart from one another in the axial direction and which surround the inner ring 2 from the outside. These retaining webs 8 are pushed onto the inner ring 2 from above with a small clearance, which is normally about 2-3 mm, when the upper guide vane ring half and the lower guide vane ring half are joined together, in such a way that they accommodate the inner ring 2 between them. The inner ring 2, which in practice is also referred to as a preswirler, has, as shown in Figure 2shown, has a substantially U-shaped cross-section and forms a radially outwardly open flow channel 9 extending in the circumferential direction U, which is delimited by an inner ring bottom wall 10 and two inner ring side walls 11. During turbine operation, a cooling medium flowing radially inward from the blades 6 of the guide vanes 4 is introduced into this flow channel 9 in order to then conduct this cooling medium in the direction of the rotor blades for cooling the rotor blades.

[0019] Wear elements 12 are inserted into the gaps present between the retaining webs 8 and the immediately adjacent inner ring side walls 11, which, as previously mentioned, normally each have a gap width of approximately 2-3 mm. More precisely, the wear elements 12 are each inserted in the gaps extending between radially inwardly projecting retaining web guide projections 13 of the retaining webs 8 and the immediately adjacent inner ring side walls 11. In the illustrated embodiment, the retaining webs 8 of the inner blade platform 5 each comprise two retaining web guide projections spaced apart from one another in the circumferential direction U, although the number can fundamentally vary.

[0020] The wear elements 12, one of which is in the Figures 3 and 4shown, are each plate-shaped and have a ring-segment-like outer contour that follows the shape of the inner ring 2. They are made of the same material from which the inner ring 2 is made.

[0021] Alternatively, the wear elements 12 can also have a softer material than the inner ring 2.

[0022] Each wear element 12 is detachably connected to an inner ring side wall 11. For this purpose, each wear element 12 is provided on the rear side with two welded threaded bolts 14, which extend through through holes 15 of the inner ring 2 and are secured on the rear side with a nut (not shown in detail).

[0023] The Figures 5 to 8 show a guide vane ring 1 according to a further embodiment of the present invention, which differs from the previously described embodiment primarily in the type of wear elements 12 used.

[0024] Two wear elements 12 are used per retaining web 8, each positioned between one of the retaining web guide projections 13 and the immediately adjacent inner ring side wall 11. The contour of the front surface of each wear element 12 follows the contour of the facing surface of the associated retaining web guide projection 13. On the rear side, each wear element 8 is provided with a welded or otherwise fastened threaded bolt 14. The inner ring side walls 11 are each provided with recesses 16 that positively receive the wear elements 12, in each of which a through hole 15 is positioned to receive a threaded bolt 14.

[0025] Furthermore, the structure of the Figures 5 to 8 shown guide vane ring 1 corresponds to the one previously described with reference to the Figures 1 to 4 described structure.

[0026] The wear elements 12 according to the invention compensate for the play existing between the retaining webs 8 and the immediately adjacent inner ring side walls 11 and prevent direct contact between the retaining webs 8 and the inner ring side walls 11, which can occur without such wear elements 12 due to vibrations of the individual components excited during turbine operation.

[0027] On the one hand, wear is reduced by the use of wear elements 12 according to the invention. On the other hand, it is primarily the wear elements 12 that wear, and these can be replaced quickly, easily, and inexpensively during maintenance work. Repair of the inner ring 2 in the area of ​​the retaining webs 8 is thus completely eliminated or very minimal.

[0028] The wear elements 12 can be provided during the manufacture of a new guide vane ring 1. They can also be added to an existing guide vane ring 1 during maintenance or repair work.

[0029] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the claims.

Claims

1. Guide vane ring (1) which is divided into an upper and into a lower guide vane ring half, with an inner ring (2) which is split at least in two, has a substantially U-shaped cross section, and forms a radially outwardly open flow duct (9) which extends in the circumferential direction and is delimited by an inner ring bottom wall (10) and two inner ring side walls (11), and with a multiplicity of vane platforms (5), which receive guide vanes (4), are arranged along the outer circumference of the inner ring (2), and each have retaining webs (8) which project radially inwards, are spaced apart from one another in the axial direction, and fit around the inner ring side walls (11) from the outside, wherein wear elements (12) are inserted into gaps which are present between the retaining webs (8) and the inner ring side walls (11) arranged directly adjacent, characterized in that the wear elements (12) are of plate-shaped design.

2. Guide vane ring (1) according to Claim 1, characterized in that the wear elements (12) are produced from the material from which the inner ring is manufactured or from a softer material.

3. Guide vane ring (1) according to either of the preceding claims, characterized in that each wear element (12) is detachably connected to a retaining web (8) or to an inner ring side wall (11).

4. Guide vane ring (1) according to Claim 3, characterized in that each wear element (12) is fastened to a retaining web (8) or to an inner ring side wall (11) using a screw connection.

5. Guide vane ring (1) according to Claim 4, characterized in that each wear element (12) has at least one welded-on threaded bolt (14).

6. Guide vane ring (1) according to one of Claims 3 to 5, characterized in that depressions (16) that receive the wear elements (12) are provided on inner surfaces of retaining webs (8) and / or on the outer surface of at least one inner ring side wall (11).

7. Guide vane ring (1) according to one of the preceding claims, characterized in that wear elements (12) are inserted into gaps which are present between the retaining web guide projections (13) and the inner ring side walls (11) arranged directly adjacent, wherein the retaining web guide projections (13) each project radially inwards.