Restraint Mechanism for Rotor Blades of a Turbo Engine, an Assembly Method and a Turbo Engine

Abstract

A restraint mechanism for rotor blades of a turbo engine on a rotor disk having blade root receptacles for radial guidance of the rotor blades is disclosed. The restraint mechanism has a plurality of axial securing elements, each having at least one web for positioning in a blade root receptacle, such that each web has a retaining section at one end for establishing a form-fitting design to a mating brace of another axial securing element. A method for axially securing rotor blades on a rotor disk and a turbo engine are also disclosed.

Description

This application claims the priority of European Patent Document No. EP 12179777.3, filed Aug. 9, 2012, the disclosure of which is expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a restraint mechanism for rotor blades of a turbo engine on a rotor disk, a method for axially securing rotor blades on a rotor disk of a turbo engine, and the turbo engine.

Rotor blades 1, which are arranged with their root 2 inserted into an axial groove 4 of a rotor disk 6 of a turbo engine, as illustrated in FIGS. 1 and 2, are usually secured by a restraint mechanism in the axial direction. A known restraint mechanism has a plurality of securing elements 8, each of which is arranged in the groove 4 between the root 2 and the base of the groove. Each securing element 8 has a web 10 to be placed in the grooves 4 and has two securing sections 12, 14 extending away from the web 10 on the end, becoming wider with respect to the groove 4, so that, when installed, they are in contact with a front disk area 16 and a rear disk area 18. Because of the widened securing sections 12, 14 in comparison with the grooves 4, the securing elements 8 are positioned in the grooves 4 in front of the blades on the rotor disk 6. However, if a securing section 12, 14 is damaged when bent over, all the blades on the entire rotor disk 6 must be removed to replace the defective securing element 8. Additional web-type securing elements with widened securing sections are disclosed in U.S. Patent Application Publication U.S. 2009/0060746 A1 as well as in European Patent Application EP 1 057 973 A2. Alternative restraint mechanisms also provide curved plate elements which together form a closed ring. They are used in the area of the rear disk face between the sections of the rotor disk and the blades, each extending over several rotor blades. Such restraint mechanisms are disclosed in European Patent Application EP 0 761 930 A1, German Patent Application DE 199 60 896 A1, U.S. Patent Application Publication U.S. 2004/0062643 A1 and European Patent Application EP 1 650 406 A2, for example. One disadvantage of all these plate-type restraint mechanisms is that corresponding rotor disk sections and blade sections are provided for holding the plate elements. In addition, the assembly and dismantling of the individual plate elements to form a closed ring are complex.

The object of the invention is to create a restraint mechanism for rotor blades of a turbo machine on a rotor disk which will eliminate the aforementioned disadvantages and will permit a favorable transfer of force between the rotor blades and the rotor disk. In addition, another object of the present invention is to create an improved method for axially securing rotor blades on a rotor disk of a turbo engine as well as a turbo engine having an improved means of axially securing rotor blades.

A restraint mechanism according to the invention for rotor blades of a turbo engine on a rotor disk having blade root receptacles for placement of the rotor blades has a plurality of axial securing elements, each of which has at least one web for positioning in a blade root receptacle. According to the invention, each web has a retaining section at the end to establish a form-fitting design with a mating brace of an opposing axial securing element.

Due to the fact that each of the securing elements is connected in a form-fitting manner to the securing element on the opposite side, they are supported mutually, thereby resulting in a torque-free outward transfer of force. Furthermore, a defined flow of force is ensured. The securing elements can be installed from the front or from the rear, as seen in the axial direction, regardless of the direction of installation.

To permit an exchange of the securing elements in the bladed state of the rotor disk, the retaining sections may be narrower than the blade root receptacles in the area of placement of the securing elements and may assume an installed position, which is different from a secured position. When installed, the retaining sections are aligned as flatly and/or almost as flatly as the webs, so that the retaining sections and the webs have the same or almost the same height. The retaining sections may be plastically deformable, in which case they are then bent out of the flat assembly position into the upright secured position. Alternatively, the retaining sections are prestressed into their upright secured position and then can be deformed elastically out of this position and into the flat assembly position. In this way, accidentally damaged securing elements can be replaced at any time, so that corresponding repairs can be performed rapidly.

The mating braces are preferably offset in the vertical direction of the securing elements and have an elongated shape extending in the transverse direction of the securing elements, where they have an extent such that, when installed, they extend beyond at least one neighboring blade root receptacle and/or they bridge a neighboring blade root receptacle. The mating braces are therefore always situated in the secured position and need not first be moved into this position. In addition, the mating braces run onto the rotor disk in assembly and thus define a definite axial securing position of the securing elements in the blade root receptacles.

In a preferred exemplary embodiment, two securing elements form a securing element pair. Preferred securing elements each have a web from which a mating brace extends on one side in the transverse direction. Each of the two securing elements of this pair has the same, i.e., identical, L-shaped design. Two neighboring rotor blades can be secured quickly and reliably in this way. The pair of securing elements may be used as a repair part, for example, when a traditional web-type securing element has been damaged. The defective securing element and a neighboring securing element can be removed and replaced by a pair of securing elements.

However, the restraint mechanism may also have at least one pair of securing elements, such that one securing element has a web with a mating brace extending on both sides of the web, while the other securing element has two webs spaced a distance apart from one another, connected by a mating brace. When installed, the web of the T-shaped securing element is placed between the webs of the U-shaped securing element, and the retaining sections each form a form-fitting design with the mating braces. Three neighboring rotor blades can be secured on the rotor disk by the U-shaped securing element and the T-shaped securing element, so that the restraint mechanism may be used with rotor disks having an even number of rotor blades or used with rotor disks having an odd number of rotor blades in the combination of the two pairs of securing elements (2 L-shaped securing elements yield one pair of securing elements, 1 T-shaped securing element and 1 U-shaped securing element yield a pair of securing elements). For example, it is conceivable that the pair of securing elements consisting of the U-shaped securing element and the T-shaped securing element with an odd number of rotor blades may be used more or less as the closure of the restraint mechanism.

In another exemplary embodiment, the securing elements do not form a self-contained pair of securing elements but instead identical securing elements are assembled in a chain. Preferred securing elements to form the securing element chain each have a U-shaped design and have two webs joined together by a mating brace and spaced a distance apart from one another, so that two securing elements may be placed with one of their two webs between the webs. Thus each securing element extends over four rotor blades.

For closing the securing element chain in the case of rotor blade numbers that are not divisible by four, a U-shaped securing element and an I-shaped securing element may be provided, each being installed one or more times. Instead of a mating brace, the I-shaped securing element has a body section, which is wider than the respective blade root receptacle in the placement area of the securing element and is free of engagement of a retaining section when installed. The I-shaped securing element is positioned between two U-shaped securing elements having the same orientation, so that the opposite U-shaped securing element has a widened mating brace, so that three webs may be placed between its two webs.

The respective form-fitting design can be improved and/or manufactured more simply if the retaining sections each have a catch nose with dimensional stability for reaching around the respective mating brace in some sections.

In a preferred method for axially securing rotor blades of a turbo engine on a rotor disk, which are inserted with their roots into axial blade root receptacles on the rotor disk, axial securing elements are inserted into the blade root receptacles and are interconnected by at least one form-fitting design. In this way, the securing elements are each connected to a securing element on the opposite side and are thus mutually supported, so that there is a transfer of force to the outside without any torque. Furthermore, a defined flow of force is ensured.

The mutual support can be further improved if the securing elements are connected to one another by a mutual form-fitting design.

A preferred turbo engine has a bladed rotor disk, whose rotor blades are inserted into their blade root receptacles and are secured in the axial direction by a restraint mechanism according to the invention.

Preferred exemplary embodiments of the invention are explained in greater detail below on the basis of schematic diagrams.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show a known axial means of securing a rotor blade on a rotor;

FIG. 3 shows an assembly diagram of a pair of securing elements of a restraint mechanism according to the invention;

FIG. 4 shows a single diagram of an L-shaped axial securing element of the pair of securing elements;

FIG. 5 shows an exploded diagram of a pair of securing elements having a U-shaped securing element and a T-shaped securing element;

FIG. 6 shows an assembly diagram of a chain of securing elements of a restraint mechanism according to the invention;

FIG. 7 shows a single diagram of a U-shaped axial securing element of the chain of securing elements; and

FIG. 8 shows an exploded diagram of a pair of securing elements having a lengthened U-shaped securing element and an I-shaped securing element.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 3 shows a securing element pair 20 of a restraint mechanism according to the invention for axially securing rotor blades (not shown) on a rotor disk (not shown). The root of each rotor blade is inserted into an axial blade root receptacle and/or a rotor groove on the rotor disk. The rotor blades are secured radially in the rotor grooves by a form-fitting contour of the rotor grooves and roots. The restraint mechanism has a plurality of securing element pairs 20, in this embodiment each having two identical axial securing elements 22, 22′, each forming mutually a form-fitting connection.

The securing elements 22, 22′ have, as in FIG. 4 for the securing element 22, for example, a web 24, which has a retaining section 26 on the end and a mating brace 28 on the end. The web 24 has a plate-type contour and extends in the transverse direction y and/or has a width corresponding to the rotor groove in the placement area of the securing element 22. The web 24 thus has mainly a width that is equal to or narrower than the base of a groove.

The mating brace 28 is designed to be rigid and is arranged with an offset in the vertical direction z with respect to the web 24. It has an elongated extent in the transverse direction y of the securing element 22 and therefore has an elongated extent in the circumferential direction of the rotor disk. It is thus arranged at a distance from the web 24 in the vertical direction z and is designed as a one-sided arm in the exemplary embodiment shown here. It has an extent in the transverse direction y such that it bridges a neighboring rotor groove.

The retaining section 26 is plastically deformable and is set back at one end in comparison with the flanks of the web which are not labeled with numbers. It is thus narrower than the rotor groove in the placement area of the securing element 22. It can be converted from a shallow assembly position to the upright securing position shown here. Due to the narrow design and the flat assembly position of the retaining section 26, the rotor disk can be bladed before the securing elements 22 are inserted into the rotor grooves because the retaining section 26 can be pushed between the base of the groove and the blade roots. The retaining section 26 preferably has a catch nose 30 to form a radially outer bordering face for a mating brace 28′ of a neighboring securing element 22′ (see FIG. 3).

When installed on the rotor disk, two securing elements 22, 22′ are each oriented so they are offset in relation to one another in the axial direction x. With their webs 24, 24′ they each pass through a rotor groove and are in contact with a front side face and/or a rear side face of the rotor disk with their mating braces 28, 28′. The mating braces 28, 28′ are offset in relation to one another in the circumferential direction of the rotor disk and they each bridge the rotor groove in which the web 24, 24′ of the opposite securing element 22, 22′ is placed and/or protrudes and/or out of which the retaining section 26, 26′ of the opposite securing element 22, 22′ protrudes. The retaining sections 26, 26′ are shaped around the mating brace 28, 28′ of the opposite securing element 26, 26′ until the latter extend around the mating braces 28, 28′ with their catch noses 30, 30′. The securing elements 22, 22′ are then joined to one another mutually by a form-fitting design and the rotor blades placed in these rotor grooves are releasably secured on the rotor disk in the axial direction.

Due to the fact that the securing elements 22, 22′ are mutually secured, the rotor blades are double secured. If, for example, the retaining section 26 is inadvertently released from the form-fitting design with the mating brace 28′ or even breaks away from it, the respective rotor blade is still axially secured by the mating brace 28′ bridging the rotor groove.

To also be able to cover the odd rotor blade numbers, a securing element pair 32, illustrated in FIG. 5, is provided; three rotor blades can be secured on one rotor disk by this pair. This securing element pair 32 consists of two different securing elements 34, 36, namely a T-shaped securing element 34 and a U-shaped securing element 36, which are installed opposite one another in the axial direction x.

The T-shaped securing element 34 has a web 24 which is placed at the center of a mating brace 28. The mating brace 28 thus extends on both sides of the web 24 and more or less has two arm halves 38, 40. The arm halves 38, 40 have an extent in the transverse direction y, such that, when installed, they each bridge a neighboring rotor groove. At the end, the web 24 has a plastically deformable retaining section 26 with one catch nose 30.

The securing element 36 is designed in a U-shaped design with two webs 24′ spaced a distance apart from one another in the transverse direction y, each having a retaining section 26′ with a catch nose 30′ and being connected to one another via a mating brace 28′. The webs 24′ are spaced a distance apart from one another so that, when installed, they are not accommodated in the respective neighboring rotor groove but instead in the next-but-one rotor groove. In other words, when installed, an empty groove is formed between the webs to receive the web 24 of the T-shaped securing element 34.

When installed on the rotor disk, the T-shaped securing element 34 and the U-shaped securing element 36 are oriented oppositely from one another in the axial direction x. With their webs 24, 24′ they each sit in a rotor groove and are in contact at their mating braces 28, 28′ with a front side face and/or a rear side face of the rotor disk. The T-shaped securing element 34 is placed with its web 24 in the empty groove between the webs 24′ of the U-shaped securing element. The retaining sections 26, 26′ are placed around the mating braces 28′, 28 and/or the mating braces 28′ and the arm halves 38, 40 of the opposite securing element 36, 34, which are thereby connected to one another by their mutual form-fitting design.

Thus through a combination of the securing element pairs 20 consisting of the L-shaped securing elements 22, 22′ with the securing element pairs 32 consisting of the T-shaped securing element 34 and the U-shaped securing element 36, all the rotor blade number variations can be covered.

FIG. 6 shows a securing element chain 42 of a restraint mechanism according to the invention. The securing element chain 42 is characterized in that a securing element 44′ is connected in a mutually form-fitting manner to both of its neighboring securing elements 44, 44″, so that the restraint mechanism is closed in a ring shape around the circumference of the rotor disk.

The securing elements 44, 44′, 44″ are identical and have a U-shaped design, as shown clearly by the securing element 44 in FIG. 7, for example. They each have two webs 24 spaced a distance apart from one another in the transverse direction y, each of them having a retaining section 26 with a catch nose 30 and connected to one another by a mating brace 28. However, in contrast with the U-shaped securing element 36 according to FIG. 5, the webs 24 with the securing elements 44, 44′, 44″ are spaced so far apart from one another that, when installed, not just one empty groove but two free empty grooves each are formed between them. The U-shaped securing elements 44, 44′, 44″ thus each extend over four rotor blades.

As shown in FIG. 6, two of the U-shaped securing elements 44, 44″ are arranged side by side with the same orientation in the axial direction x when installed on the rotor disk. A third U-shaped securing element 44′ is oriented in the axial direction x opposite the two U-shaped securing elements 44, 44″ which are oriented in the same way. The opposite securing element 44′ bridges with its mating brace 28′ two empty grooves in which the identically oriented securing elements 44, 44″ are each arranged with one web 24, 24″. The retaining sections 26, 26′, 26″ are placed in a form-fitting manner around the respective mating braces 28, 28′, 28″ of the securing elements 44, 44′, 44″ and are thus connected to same by a mutual form-fitting design. This placement is continued until the securing element chain 42 is closed.

For closing the chain, in the case of blade numbers not divisible by four (4), a securing element pair 46 shown in FIG. 8 is installed one or more times as a closure, because in the case of blade numbers not divisible by four (4), at least one empty groove is formed between the securing elements 44, 44″ on the end and is aligned equally in the axial direction x. The securing elements 44, 44″ on the end are thus spaced a distance apart from one another in the circumferential direction and can no longer be connected to an identical securing element 44′ because its mating brace 28′ has a transverse extent y that is too short.

The securing element pair 46 thus comprises a U-shaped securing element 48, whose two webs 24′ are spaced a distance apart from one another, such that its mating brace 28′ may extend over three empty grooves. The U-shaped securing element 48 is thus broadened in the transverse direction y in comparison with the U-shaped securing elements 44, 44′, 44″ according to FIGS. 6 and 7. The webs 24′ each have a retaining section 26′ with a catch nose 30′ at the end.

To secure the rotor blade placed in the central empty groove, the securing element pair 46 has an approximately I-shaped securing element 50. The I-shaped securing element 50 has a web 24″ which has a retaining section 26′ with a catch groove 30′″. Instead of a mating brace 28, the I-shaped securing element 50 has a body section 52 at the end. The body section 52 is arranged with an offset in the vertical direction z in comparison with the web 24″ and has an extent on both sides of the web 24″ such that, when installed, it is in contact with the side faces of the rotor disk.

When installed, the widened U shape securing element 48 is oriented in the axial direction x opposite the U-shaped securing elements 44, 44″ at the ends and bridges the empty groove. The retaining sections 26′, 26′ of the widened U-shaped securing element 48 reach around the mating braces 28, 28″ of the securing elements 44, 44″ on the ends. The retaining sections 26, 26″ of the securing elements 44, 44″ on the ends reach around the mating brace 28′ of the widened U-shaped securing element 48 with their catch noses 30, 30″. The securing elements 44, 44″, 48 are now situated in mutual form-fitting engagement. For axially securing the rotor blade arranged in the empty groove, the I-shaped securing element 50 is inserted into the empty groove opposite the widened U-shaped securing element 48. With its body section 52, it is then in contact at the sides with the empty groove on the side faces of the rotor disk, and it extends around the mating brace 28′ of the U-shaped securing element 48 in a form-fitting manner with its retaining section 26′″ and its catch nose 30′″.

The securing elements 22, 34, 36, 44, 48, 50 are each made of a metallic material, i.e., a metal alloy. The mating braces 28 are preferably curved according to the rotor disk in the transverse direction y of the securing elements and thus also in the circumferential direction of the restraint mechanism and/or the rotor disk.

The present invention discloses a restraint mechanism for rotor blades of a turbo engine on a rotor disk, which has blade root receptacles for radial guidance of the rotor blades, having a plurality of axial securing elements, each having at least one web for positioning in one blade root receptacle such that each web has a retaining section at the end for establishing a form-fitting design to a mating brace of a different axial securing element, as well as a method for axially securing rotor blades on a rotor disk and a turbo engine.

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

List of Reference Numerals

• 1 rotor blade
• 2 root
• 4 groove
• 6 rotor disk
• 8 securing element
• 10 web
• 12 securing section
• 14 securing section
• 16 front disk face
• 18 rear disk face
• 20 securing element pair
• 22, 22′ securing element
• 24, 24′, 24″ web
• 26, 26′, 26″ retaining section
• 28, 28′, 28″ mating brace
• 30, 30′, 30″ catch nose
• 32 securing element pair
• 34 securing element
• 36 securing element
• 38 arm half
• 40 arm half
• 42 securing element chain
• 44, 44′, 44″ securing element
• 46 securing element pair
• 48 securing element
• 50 securing element
• 52 body section
• x axial direction
• y transverse direction
• z vertical direction

Claims

1. A restraint mechanism for rotor blades of a turbo engine on a rotor disk, comprising: a plurality of axial securing elements, wherein each of the plurality of axial securing elements has at least one web for positioning in a respective blade root receptacle of the rotor disk, wherein the at least one web has a retaining section at a first end and a mating brace at a second end, and wherein the retaining section of one of the plurality of axial securing elements connects to the mating brace of an opposite one of the plurality of axial securing elements.

2. The restraint mechanism according to claim 1, wherein the retaining section is narrower than the respective blade root receptacle and has both an installation position and a securing position.

3. The restraint mechanism according to claim 1, wherein the mating brace is offset in a vertical direction of the axial securing element and has an elongated shape extending in a transverse direction of the axial securing element, and wherein the mating brace has an extent such that, when installed, the mating brace extends over at least one neighboring blade root receptacle.

4. The restraint mechanism according to claim 3, wherein two of the plurality of axial securing elements form a securing element pair and wherein the respective mating braces of the two axial securing elements extend in the transverse direction on one end of the respective axial securing element.

5. The restraint mechanism according to claim 3, wherein two of the plurality of axial securing elements form a securing element pair, wherein the mating brace of a first of the two axial securing elements extends on both sides of the respective at least one web, and wherein the mating brace of a second of the two axial securing elements extends between the respective at least one web and a second web of the second of the two axial securing elements.

6. The restraint mechanism according to claim 3, wherein at least one of the plurality of axial securing elements has a second web, wherein the respective mating brace of the at least one of the plurality of axial securing elements extends between the at least one web and the second web, and wherein the respective at least one web of two opposite axial securing elements of the plurality of axial securing elements are disposed between the at least one web and the second web of the at least one of the plurality of axial securing elements.

7. The restraint mechanism according to claim 6, wherein at least one of the plurality of axial securing elements is an I-shaped axial securing element, wherein the I-shaped axial securing element does not have a mating brace and has a body section that is wider than a respective blade root, and wherein the I-shaped axial securing element is disposed between the at least one web and the second web of the at least one of the plurality of axial securing elements.

8. The restraint mechanism according to claim 1, wherein the retaining section has a catch nose and wherein the catch nose connects to the mating brace of the opposite one of the plurality of axial securing elements.

9. A method for axially securing rotor blades on a rotor disk of a turbo engine, comprising the steps of: inserting respective blade roots of the rotor blades into respective axial blade root receptacles of the rotor disk; andinserting securing elements which are connected to one another by at least a form-fitting connection into the blade root receptacles.

10. The method according to claim 9, wherein the securing elements are connected to one another by a mutual form-fitting design.

11. A turbo engine, comprising: a bladed rotor disk, wherein blades of the bladed rotor disk are secured axially by a restraint mechanism according to claim 1.

12. A restraint mechanism for rotor blades of a turbo engine on a rotor disk, comprising: a first axial securing element, wherein the first axial securing element has a first web, a first retaining section at a first end of the first web, and a first mating brace at a second end of the first web, wherein the first web is positioned in a first blade root receptacle of the rotor disk, and wherein the first retaining section is disposed on a first side of the rotor disk and the first mating brace is disposed on a second side of the rotor disk; anda second axial securing element, wherein the second axial securing element has a second web, a second retaining section at a first end of the second web, and a second mating brace at a second end of the second web, wherein the second web is positioned in a second blade root receptacle of the rotor disk, and wherein the second retaining section is disposed on the second side of the rotor disk and the second mating brace is disposed on the first side of the rotor disk;wherein the first blade root receptacle is adjacent to the second blade root receptacle;wherein the first side of the rotor disk is opposite from the second side of the rotor disk;wherein the first retaining section of the first axial securing element disposed on the first side of the rotor disk is connected to the second mating brace of the second axial securing element disposed on the first side of the rotor disk;and wherein the second retaining section of the second axial securing element disposed on the second side of the rotor disk is connected to the first mating brace of the first axial securing element disposed on the second side of the rotor disk.