EP2352905A1

EP2352905A1 - Assembly mechanism comprising a tension anchor and corresponding method for a rotor system of an axial turbo engine

Info

Publication number: EP2352905A1
Application number: EP09801389A
Authority: EP
Inventors: Werner Humhauser
Original assignee: MTU Aero Engines GmbH
Current assignee: MTU Aero Engines AG
Priority date: 2008-12-04
Filing date: 2009-12-02
Publication date: 2011-08-10
Anticipated expiration: 2029-12-02
Also published as: US20110225822A1; CA2742868A1; US8764390B2; DE102008060571A1; WO2010063272A1; EP2352905B1

Abstract

The invention relates to a device (1) and to a method associated with an assembly mechanism for a rotor system of an axial turbo engine having a central tension anchor, as is particularly known from engine technology. To this end, the invention provides a tensioning tool that pre-tensions the tension anchor prior to and during the insertion of the same in the rotor assembly. After inserting the pre-tensioned tension anchor in the rotor assembly, the tension anchor is relaxed such that the same exerts a compressive force on the rotor assembly. According to a preferred embodiment, the rotor assembly is also pre-tensioned (compressed) and relaxed after assembling the tension anchor, so that a desired nominal pre-tension Sigma_Nenn can be particularly easily achieved. The use of a shaft lock nut is no longer necessary for the device according to the invention, thus avoiding the difficulties associated with the use of the same, such as complexity and safety problems. The invention further relates to a method for assembling a tension anchor (2) for a rotor system (6) using the assembly mechanism according to the invention.

Description

ASSEMBLY DEVICE WITH A ZUGANKER AND CORRESPONDING PROCESS FOR A ROTOR SYSTEM OF AN AXIAL FLOW MACHINE

The invention relates to a device and a method for mounting a rotor system of an axial flow machine with a central tie rod, as is known in particular from engine technology.

For assembling a plurality of successive rotor disks of an axial flow machine, which are to be assembled into a composite (rotor disk assembly), various devices are known from the prior art. If the connections need not be solvable, for example, welding techniques are used. For the reasons of serviceability more common case of a detachable connection of the components, for example, screw connections, radial clamping bolts, radially toothed couplings, or so-called tie rods are used, as disclosed for example in the document US 5,537,814. Combinations of central (tie rod) and decentralized (screw) connections are known, for example from the document EP 1 321 626 Al. The tie rod is basically guided through a central bore, which passes through all the slices to be joined, and has components at both its ends, by means of which it is positively or non-positively connected to the first or the last of the discs. The joining of the slices to be joined is then effected by a compressive stress exerted by the tie rod on both sides of the composite. Such tie rods have a number of advantages. Radial piercing of the discs and the notch points associated therewith are eliminated, as well as the presence of welds with the usually necessary reworking; also the possibility of a slight disassembly is given.

As also disclosed, for example, in US Pat. No. 5,537,814 or DE 10 2005 052 819 A1, a certain preload must be applied to the tie rod during installation, which is then introduced as compressive stress into the rotor disk assembly. This compressive stress is usually generated so that the tie rod with one end of the composite positively or non-positively connected such as is screwed, and at its other end has a shaft nut. By tightening this shaft nut of the tie rod is stretched, and thus braces the composite of zusammenzusügenden discs.

However, this approach has a number of disadvantages, particularly with regard to the peculiarities of the field of engine technology. So are in such Drives the tie rods and with them the shaft nut joints mechanically very high load because in addition to the high voltages that act on them, even transient loads occur, so that the components must have a correspondingly high alternating strength. In addition, it comes in engines to temperature fluctuations resulting in a corresponding thermal stress. The stresses which result from the vibrations in conjunction with the high temperatures or the temperature changes when switching off and on again or load changes of the engine, initially lead to an alternating bias of the tie rods, for example, by varying degrees of heating and accordingly varying degrees of expansion components. In extreme cases, the bias voltage can drop below a minimum necessary value, so that the rotor disks are released from the composite, or the voltage can rise above a maximum value, so that the tie rod breaks. The document DE 10 2005 052 819 A1 deals with this problem, but here too a conventional shaft nut is used for pretensioning the multi-part tie rod.

Especially in the area of the shaft nut, however, there are special signs of wear, such as the increased susceptibility to cracking due to the notch effects on the thread root, and the so-called "fretting", in which the mechanical wear is accompanied by corrosion, which in turn reinforces the mechanical wear even more on possibly existing additional shaft nuts, which are arranged in the assembly of multi-stage and therefore longer engines not only at the end, but also in the central region of the tie rod The discs (rotors) to be joined are the complexity, the weight, the required space, the number of parts and thus the cost, and at the same time represent a problem due to the tendency to crack.

The object of the invention is therefore to provide an apparatus and a method which overcomes the disadvantages of the prior art. In particular, the disadvantages of high wear, high numbers of parts and corresponding costs should be avoided.

The object is achieved by the features of the device according to the invention according to claim 1 and the features of the method according to claim 10. Accordingly, according to the invention can be dispensed with the use of a shaft nut, as they usually for assembly and in particular for the operation of a erfϊndungsgemäß assembled composite rotor disks is necessary when the inventive mounting device described below and used in the following.

Further preferred embodiments can be found in the dependent claims and the following detailed description and the figure.

The device according to the invention is a mounting device for a composite consisting of several successive disks, in particular for a rotor system of an axial flow machine, using a tie rod. This tie rod has a front and a rear end, each having a force introduction component. The front end has in the case of an engine in the suction direction, and the rear end points in the ejection direction. The composite of disks to be produced may preferably be a rotor system with a rotor disk assembly of at least two successive disks (rotors). These must be clamped in the assembled state so that a nominal prestress Sigma _{nominal is} applied to the composite by the tie rod. This Nemivorspannung presses the composite together, so that during operation no change in position of the rotors relative to each other longer possible.

According to the invention, a stretching tool is now provided for assembling the composite, which comprises at least the following components:

a push rod having front and rear ends disposed coaxially within the hollow tie rod; With

- A printing device for applying a compressive force on one of the ends of the push rod.

The push rod is connected to the pressure device at the front and at the rear end of the tie rod in such a way that when generating a compressive force with the pressure device of the tie rod by applying a mounting bias Sigma _Mo ntag _{e is} stretched. The push rod is therefore used together with the pressure device to stretch the tie rod, so that adjusts a certain tensile stress in its cross section. Preferably, the push rod is designed so that it extends substantially over the entire length of the tie rod. The printing device has to make up only a small part of this length, because the increase in length, which imprints the pressure device by their extension to the tie rod is limited and is for example only a few millimeters. The push rod therefore serves to extend the printing device. Preferably, the push rod is designed interchangeable, so that depending on the specific assembly task push rods of different lengths and / or with different diameters, etc. can be used.

According to the invention, the tie rod must have force introduction components at both ends, so that the tensile forces acting axially on it and on the discs to be clamped can be introduced or deflected.

According to a preferred Ausfülirungsform is provided that the tie rod has at one end as Kraftumleitungskomponente a Zugankergewinde for screwing into the corresponding arranged at this end disc of the rotor system. This thread is therefore according to the invention preferably an external thread. Particularly preferably, the tie rod exclusively on this Zugankergewinde as force introduction component at this end. It is further provided that the printing device is arranged at the other end of the tie rod. In other words, it is in principle irrelevant whether the Zugankergewinde is located at the front and the printing device at the rear end of the tie rod or vice versa. However, it is preferred that the two components are arranged at different ends of the tie rod. Preferably, the tie rod at its other end as a force introduction component on a radial shoulder for positive connection with the disc arranged at this end of the rotor system, which preferably has a corresponding end-side mating surface. Particularly preferably, the tie rod has exclusively this radial shoulder as a force introduction component at this end. A conventional shaft nut is therefore not necessary. In this way, so by dispensing with a conventional shaft nut, the disadvantages described above can be avoided. The radial shoulder is designed and arranged so that the tie rod contracts when relieving the applied by means of the push rod and the printing device mounting bias Sigma _Monta g _e , but only so far until the radial shoulder comes into contact with the preferably present counter surface, which is located on the disc which is arranged at the corresponding end of the tie rod. Subsequently, the tensile force inherent in the tie rod exerts a compressive force of the same magnitude on the corresponding opposing surface, so that the composite of the discs is compressed. If the tie rod can relax even slightly, the resulting force is smaller than the mounting preload SigmaMontage and preferably corresponds exactly to the nominal preload Sigma _nominal - The power flow runs in the assembled state as a tensile force through the tie rod, at its one end over the Zugankergewinde in the rotor assembly, as a compressive force therethrough, and is returned at the other end by means of the mating surface of the last disc to the radial shoulder of the corresponding end of the tie rod in this. A tightening a shaft nut is no longer necessary, if it is ensured by the dimensioning of the components and the correct dimension of the mounting prestressing Sigma _Monta g _e that the desired nominal bias Sigma _N hen sets. However, this dimensioning is easily possible for any skilled person and therefore need not be further elaborated at this point.

Preferably, it is further provided that the mounting system according to the invention also includes a connector for releasably, positively and / or non-positively connecting the printing device to the other end of the tie rod. This connector is located at the end of the printing device facing away from the tie rod.

Also preferably, the connector has a pressure surface that contacts the pressure device and a mounting area that can be connected to the tension anchor. Particularly preferably, this attachment region is designed as a screw thread, wherein the tie rod an external thread, the connector carries an internal thread. Given a deflection of the printing device can now by means of axial rotation of the connecting piece on the tie rod up or be unscrewed from it, so that in this way a fine adjustment of the position is possible. Further, by using the connecting piece, it is particularly easy to assemble and disassemble the mounting device consisting of push rod, pressure device and connecting piece.

According to a preferred embodiment, the printing device according to the invention is designed as a hydraulic cylinder. Such devices can generate the necessary forces in a small space, which are necessary for the Vorrecken invention of the tie rod. Of course, the printing device can alternatively be designed as a pneumatic, mechanical or electrical device.

It is also preferred that the push rod according to the invention is designed as a hollow body. In this way, the weight of the same can be kept so low that the assembly of the push rod can be accomplished without special aids of one or two people. Of course, it must be ensured that the stability required for the application is ensured. Therefore, in particular Push rods with the largest possible, but thin-walled as possible cross-section, since they have a smaller cross-sectional area at the same area moment of inertia.

According to another Ausführungsforai it is provided that the tie rod on its outer wall comprises one or more radial support surfaces for supporting the tie rod surrounding components thereto. This can be particularly advantageous for very long tie rods. While too large a number of radial support surfaces can lead to excessive friction during assembly, too small a number can lead to a running at operating speed in the rotor dynamic supercritical speed range tie rods.

According to a particularly preferred Ausfülirungsform the mounting device according to the invention further comprises components for pre-upsetting the rotor system to nominal prestress Sigma _N e _m - These components can be hydraulically, pneumatically, mechanically or electrically driven and serve to the initially loosely assembled rotor disk assembly under an axially acting compressive stress set so that it is compressed and at the same time held by means of the contact surfaces of the discs frictional forces. The components are designed so that they do not interfere with insertion and use of the tie rod, the push rod and the printing device in accordance with the invention, and in turn are not hindered by the other components of the device according to the invention. The components must also be capable of applying at least the nominal preload Sigma _K enn required for safe assembly to the composite.

According to the invention it is provided that the components for pre-compression of the rotor disc composite initially compress, and in these then the biased with push rod and pressure device tie rod is introduced. After screwing in the tie rod, both this and the prestressed or pre-compressed rotor disk assembly are relaxed. If the tie rod and the rotor disk assembly were each prestressed or pre-compressed to nominal prestress Sigma _Nen n, this tension is maintained in the system, so that a pre-tension corresponding to the specifications is ensured. The invention also discloses a method for mounting a tie rod for a rotor system with a mounting device according to claim 1. This is subdivided into the following steps:

First, the push rod is introduced together with the pressure device in the tie rod, so introduced axially centrally in the designed as a hollow shaft tie rods.

Thereafter, the one, for example, the front end of the push rod is connected to the corresponding end of the tie rod. This happens depending on the embodiment force and / or positive fit, with a purely positive connection is preferred. For this purpose, the tie rod, for example, have a radial inner shoulder, which abuts the one end of the push rod. The tie rod is now connected on one side with the push rod and thus able to absorb at least compressive forces.

Unless already done in advance, now the other, for example, the rear end of the push rod with the printing device force and / or positively connected. This step is omitted if push rod and printing device can be seen as a structural unit or a separation of the same is not provided. In principle, the provision of a corresponding, sufficiently dimensioned front-side contact surface on both components suffices here since the pressure rod and the pressure device are only subjected to pressure. For reasons of operational safety, however, it may be desirable to bolt the components together, for example.

Subsequently, a positive and / or positive connection of the printing device with the other end of the tie rod. It must therefore be ensured that the pressure forces which are to be applied by the pressure device and the pressure rod to the two ends do not "run into space." For this purpose, an adjustable connecting piece of the type described above can be used to particular advantage the power flow between the inner pressure rod with pressure device and the outer tie rod closed.

Then, by means of the printing device, a compressive force is applied to the push rod, so that the tie rod is stretched to a mounting bias SigmaMontage, where SigmaMounting is greater than or equal to the nominal bias SigmaNenn.

In the next step, the assembly device of push rod with pressure device and tie rod is introduced in the stretched, biased state in the rotor system. The Rotor system must be at least loosely assembled; it is preferably secured accordingly, so that during the introduction of the mounting device no unintentional Relatiwerschiebungen the components of the rotor system can occur.

Next, the one, for example, front end of the prestressed tie rod force and / or form-fitting connected to the disc arranged at this end of the rotor system, which is particularly preferably done by means of screwing. The screwing takes place only so far that the other, for example, rear end of the tie rod gets a Foπnschluss with the disposed at this other end of the rotor system disc. This form fit must now be suitable only for absorbing compressive forces, which later lead to a compression of the rotor disk assembly by means of the tie rod. Accordingly, here is a simple radial paragraph sufficient, which cooperates with a corresponding counter-surface, which is located at the front side of the disposed at this end of the rotor system disc.

Thereafter, by relaxing the printing device, the mounting bias Sigma _M ontage is reduced to zero, so that the tie rod now in turn relaxes by exerting a compressive force on the rotor system. Preferably, this is done until the remaining bias voltage is just sigma _rated . The actual preload is achieved by a balance between a possible preload (compression, immediately) of the rotor system and the mounting bias of the tie rod.

Finally, in a final step, the relaxed push rod with the pressure device is removed from the tie rod. Since the pressure device and possibly the connector no longer exert pressure on the tie rod, this only the connection on the pressure device opposite end of the tie rod, for example by unscrewing the corresponding thread, solved and the push rod to be pulled out of the hollow tie rod.

It will be understood that the steps described herein may also be partially practiced in a changed order while still retaining the substance of the invention. Possibly. If necessary, the steps can be repeated in the event that the nominal prestressing voltage obtained is too small or too large, with appropriate spacers having to be inserted or removed from a suitable location.

According to a further preferred Ausföhrungsform before the first step described above, the rotor disk assembly is biased or compressed by means of appropriate components for pre-upsetting. Particularly preferably, this compression takes place precisely on the nominal preload SigmaNenn- To carry out this step, reference is made to the above statements regarding the components for prewesting. Also according to this embodiment closes after the last step still a withdrawal of the pre-compression by relaxing the rotor system and a decrease in the components for pre-ups.

It is also particularly preferred that the mounting bias of the tie rod Sigma _Mon ntage is just equal to the nominal bias Sigma _N enn. In this way, it is ensured that during joint relaxation of the prestressed (stretched) tie rod and the prestressed (compressed) rotor system, a balance of power is established, in which just the desired nominal bias SigmaNenn adjusts itself. For this purpose, it must be ensured when introducing the prestressed tie rod in the rotor system that the tie rod "screwed", for example, up to a radial shoulder (stop collar), so that a relaxation of the tie rod directly to exerting a compressive force on the rotor system without the Tie rod initially "relaxed" into the void.

By using the mounting device according to the invention and the concomitant renouncement of the use of shaft nuts for biasing a tie rod, the complexity of the construction is reduced. Due to a smaller number of parts, the weight and the required installation space also decrease, which in turn has a positive effect on the costs. Safety problems due to the notch effect on corresponding, to be provided for a shaft nut threads are also avoided.

Figure 1 shows a schematic longitudinal half-section through a part of a very simplified axial flow machine shown with the mounting device according to the invention.

FIG. 2 shows the detail of an alternative fastening in the form of a shaft nut 10. In order to illustrate the invention, reference is made to FIG. 1, which shows a schematic longitudinal half-section through a part of an axial flow machine, in particular a composite of rotor disks shown in a very simplified manner, and a tie rod for tensioning the same. The axis of rotation is symbolized by the dot-dash line.

Shown is the mounting device I ₅ which is composed of the components tie rod 2, which is designed as a hollow shaft, and the push rod 3 and the printing device 4 and a connecting piece 5.

The tie rod 2 has at its one end, shown on the left in the picture, a radial shoulder 7. This is able to absorb compressive forces exerted by the push rod 3 on the tie rod 2. At its other end, shown on the right in the image, the tie rod 2 has a threaded connection G, which engages with the connecting piece 5. Furthermore, the tie rod 2 comprises a further radial shoulder 8, which is designed and arranged such that it abuts or abuts against a corresponding mating surface of the rotor system 6 shown schematically and greatly simplified.

The rotor system 6 has at its end, which is arranged opposite this Gegenfiäche, an internal thread, which together with a corresponding external thread of the tie rod a threaded connection G 'results. The tie rod 2 is screwed at this point in the rotor system 6, and indeed so far, until it abuts with the radial shoulder 8 (stop) to the rotor system 6.

At the radial shoulder 7 facing away from the end of the push rod 3, the printing device 4 connects. The latter serves to generate a compressive force, which is required for biasing the tie rod 2; the push rod 3 is merely the extension of the printing device 4. In the illustrated embodiment, the printing device 4 is designed as a hydraulic cylinder. On its one side (in the picture on the left) it has a threaded connection G '' with the push rod 3, so that these two components can be treated as a structural unit. At its other end (in the picture on the right), the printing device 4 has a Druckfiäche 9, which serves the pressure force transmission to the connector 5.

The connecting piece 5 finally serves to initiate the compressive force of the printing device 4 in the tie rod 2, in which it leads to a longitudinal expansion. This must be the Connector 5 have the possibility of a corresponding Verbindbaxkeit, which is made possible in the dargstellten embodiment by means of the above-mentioned thread G.

For mounting the mounting device 1, first the tie rod 2 by means of the push rod 3 with printing device 4, which are non-positively and / or positively connected thereto, pre-stretched, wherein it stretches.

Subsequently, the tensioned tie rod 2 is thus introduced into the rotor system 6, which is preferably in turn pre-immersed (not shown). The tie rod 2 is fixed with the threaded connection G 'on one side in the rotor system 6, by means of screwing to the point where the radial shoulder 8 abuts against the rotor system 6.

Finally, the tie rod 2 is relaxed by canceling the compressive stress applied by the printing device 4, thereby trying to contract. However, if the tie rod 2 already has positive contact with the rotor system 6, this contraction is inhibited by the rotor system 6. The existing tension in the tie rod 2 is now used to compress the rotor system 6 (to brace).

According to this embodiment, the mounting bias Sigma _M ontage, which is applied during mounting, is reduced by relaxation by a specific value, so that the value for sigma mounting must be correspondingly higher in order to achieve a desired nominal bias SigmaNom.

According to an embodiment not shown, the rotor system 6 is biased by means also not shown components for pre-upsetting (compressed), and preferably straight to the value of sigma _N to which the tie rod 2 is biased. When relaxing after inserting and screwing in the prestressed tie rod 2, the desired nominal prestressing sigma _Nen n is then set.

FIG. 2 shows the detail of an alternative fastening in the form of a shaft nut 10. The shaft nut 10 has an internal thread, which produces a threaded connection G with the tie rod 2. By tightening the shaft nut 10 of the tie rod, which is at its other end not shown form and / or non-positively attached to the corresponding end of the rotor assembly, stretched in its longitudinal direction, so that the compressive stress, with which the composite is compressed, increases accordingly ,

Claims

claims

1. Mounting device (1) for a rotor system of an axial flow machine, wherein at least one tie rod (2) is provided with a front and a rear end, each having a force introduction component, and wherein the rotor system (6) comprises a rotor disk assembly of at least two successive slices which, in the mounted state, have a tensioning anchor (2) with a nominal prestress Sigma _N , characterized in that a stretching tool is provided for assembly, which comprises at least the following components:

- A push rod (3) having a front and a rear end, which is arranged coaxially within the hollow tie rod (2); With

- A printing device (4) for applying a compressive force on one of the ends of the push rod (3); wherein the push rod (3) is connectable to the pressure device (4) at the front and rear ends of the tie rod (2) such that when a compressive force is applied to the pressure device (4) the tie rod (2) is stretched applying a mounting bias Sigma assembly ,

2. Mounting device (1) according to claim 1, characterized in that the tie rod (2) at one end as a force introduction component Zugankergewinde (G ') for screwing into the corresponding disposed at this end disc of the rotor system (6), and that the Printing device (4) is arranged at the other end of the tie rod (2).

3. Mounting device (1) according to claim 1 or 2, characterized in that the tie rod (2) at its other end as a force introduction component has a radial shoulder (8) for positive connection with the disc arranged at this end of the rotor system (6), and that this disc has a corresponding counter surface.

4. Mounting device (1) according to one of claims 1 to 3, further comprising a connecting piece (5) for releasably, positively and / or non-positively connecting the printing device (4) with the other end of the tie rod (2).

5. Mounting device (1) according to claim 4, wherein the connecting piece (5) has a pressure surface (9) for receiving the forces of the printing device (4), and a thread (G) for screwing onto the corresponding end of the tie rod (2).

6. Mounting device (1) according to one of the preceding claims, wherein the printing device (4) is a hydraulic cylinder.

7. Mounting device (1) according to one of the preceding claims, wherein the push rod (3) is hollow.

8. Mounting device (1) according to any one of the preceding claims, wherein the tie rod (2) on its outer wall, one or more Radial Stützfiächen for supporting the tie rod (2) surrounding components on the same.

9. Mounting device (1) according to any one of the preceding claims, further comprising components for pre-upsetting the rotor system (6) to nominal bias SigmaNenn-

10. A method for assembling a tie rod (2) for a rotor system (6) with a mounting device (1) according to claim 1, comprising the following steps:

- Introducing the push rod (3) with the printing device (4) in the tie rod (2);

- Force and / or positive connection of the one end of the push rod (3) with the corresponding end of the tie rod (2);

- Force and / or positive connection of the other end of the push rod (3) with the printing device (4);

- Force and / or positive connection of the printing device (4) with the other end of the tie rod (2);

- Applying a compressive force by means of the printing device (4) on the push rod (3), so that the tie rod (2) is stretched to a mounting bias Sigma _Mo nt _a g _e , where Sigma _Mθ ntage is greater than or equal to Sigma ^ m;

- Introducing the mounting device (1) of push rod (3) with pressure device (4) and tie rod (2) in the stretched state in the rotor system (6);

- Force or positive connection of the one end of the tie rod (2) arranged at this one end disc of the rotor system (6) such that the other end of the tie rod (2) form-fitting with the disc arranged at this other end of the rotor system (6) gets; Sigma Mont _a g _e so that the tie rod (2) now in turn relaxes canceling the mounting prestressing to zero by relaxing the pressure device (4), by exerting a pressure force on the rotor system (6) until Sigma _N hen -;

- Removing the relaxed push rod (3) with the pressure device (4) from the tie rod (2).

11. The method of claim 10, wherein before the first step, the rotor disk assembly is biased by means for pre-upsetting to the nominal bias Sigma _nominal , and after the last step, the pre-compression is reduced by relaxing and removing the components for pre-upsetting.