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.
- Top of Page
- Top of Page
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
- Top of Page
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.
- Top of Page
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.