EP0604754A1 - Turbine rotor - Google Patents

Abstract

It is known to produce the rotor of a turbine from individual rotor parts welded together to form a unit. Conventional welding techniques are used and the segments are only pre-machined, so that the rotors have to be reworked according to a full rotor. According to the invention, a standardized modular system is created from rotor parts (1 to 5), which enables a selection corresponding to the respective thermodynamic and rotor dynamic requirements. For this purpose, largely machined rotor parts (1 to 5) including associated rotor disks (2, 3) are used. The rotor parts (1 to 5) are welded by means of electron beam welding and corresponding weld seams (13) are placed as far apart as possible from the central axis (M) of the rotor. <IMAGE>

Description

The invention relates to methods for producing a turbine rotor according to the preamble of claim 1 and a turbine rotor according to the preamble of claim 2.

The rotor of a turbine used to generate electricity, including a steam turbine, is subject to high loads. In order to do justice to this and still achieve a long service life, but on the other hand to keep the manufacturing costs within acceptable limits, a variety of design options have been devised, all of which have certain advantages, but of course also disadvantages.

A particularly solid, but equally complex manufacturing method is to forge a one-piece runner from the solid. The required before manufacturing Material can only be ordered after receipt of the order and often requires a long delivery time, which is not least caused by the small number of suppliers available. Furthermore, prefabrication independent of the order and also no parallel processing of individual parts is possible, so that long production lead times result. Difficulties also arise when inserting impeller blades, insofar as the blade feet can be inserted axially, since a larger axial distance between the impeller disks is required for machining the groove in order to be able to work with appropriate tools. However, wide distances between the impellers degrade the rotor dynamics.

Another construction enables the manufacture of assembled runners with drawn-on, shrunk running disks. When shrinking, however, additional stresses arise in the rotor, and there is also a risk of fretting corrosion at the joints. It is also known to screw toothed washers together using a tie rod, but this is also not unproblematic since loosening of the screw connection must be expected in the long term.

Some of the aforementioned disadvantages can be avoided by forming individual rotor segments and then welding them to form a unit that forms the rotor. Such runners are e.g. B. from the BBC company publication "Welded rotors for steam turbines", publication no. CH-T 060 072 D and from DE 22 35 961 A1 and DE 25 22 277 known. A disadvantage of Läu-

This means that the rotor must be finished as a large and heavy single piece, just like a rotor forged from solid. The runner should be made easier by the segmentation and other measures.

The object of the invention is to provide a method for producing a rotor and a rotor for a turbine according to the preamble of claim 1 and the preamble of claim 2, which enables simple production with a short lead time.

This object is achieved in each case by the features characterized in claims 1 and 2.

Appropriate refinements and developments of the subject matter of the invention are mentioned in the subclaims.

Due to the construction of a modular system consisting of standardized rotor parts, the largely finished machining of the individual parts and the use of electron beam welding when connecting the rotor parts, it is possible to obtain forged washers as stock goods using rod material and to achieve shorter delivery times with a larger supplier selection. The prefabrication can be carried out to a large extent independently of the order and with parallel processing of the individual elements on relatively small machine tools with a reduced throughput time. The simplified, stable individual parts enable NC production. The largely finished machined rotor parts have only a small allowance at the most important fitting points, while flat surfaces, the grooves of the blade roots etc. are finished, so that after radial welding with the electron beam and subsequent heat treatment, the finishing process begins the final turning of the remaining fits is restricted. The steam shaft end can be finished except for the bearings, the compensating piston and, if necessary, the blade attachment. The exhaust steam shaft end can be finished except for the bearings and the coupling connection and the impellers can be finished except for the outer diameter in the weld area. Alternatively, the impellers can also be manufactured entirely as castings, whereby Powdermet can also be used.

Another essential advantage of the method according to the invention is that it is possible to build particularly compact short runners with better dynamic properties due to the reduced weight. Since the largely finished machined disks are already provided with the grooves required for their blading, it is no longer necessary to ensure that their mutual distance is large enough to provide adequate tools for machining the grooves. The distance between the adjoining running disks can thus be minimized from a rotor dynamic point of view.

In a further development of the subject matter of the invention, it is also possible to blade individual or all rotor disks and, if necessary, even to balance them before they are welded together. There is also the possibility of assembling the rotor from parts of different materials for better material utilization and adaptation to the operating conditions.

A double rotor washer has proven to be a particularly advantageous part of the modular system, since it can be used to optimize the modularization. By combining two rotor disks for a double running disk, on the one hand a high stability of the component is guaranteed, and on the other hand good accessibility is achieved, in particular when machining the grooves for the base parts of the blades, and in addition the number of weld seams is reduced by using individual disks. Just as the tools can be brought to the grooves from the outside on both sides, the blades can also be comfortably inserted axially with their blade base into the correspondingly shaped grooves.

The rotor parts expediently have an axial bore which serves to receive an axial tie rod which holds the parts together, so that they can be connected to one another by electron beam welding.

The modular system designed for the manufacture of a rotor includes, in addition to the already mentioned double running disks, single running disks, steam shaft ends, steam shaft ends and condensation end stage drums.

To save material on the one hand, but also to facilitate electron beam welding, on the other hand, a recess is provided in the rotor parts, at least on one side symmetrical to the central axis, through which a ring-shaped sleeve which is symmetrical to the axis is created, which lies against the adjacent rotor part and defines the position of the welding night.

In the case of steels with high mechanical strength, in particular those with a relatively high carbon and / or nickel content, the production of good weld seams is difficult. In order to eliminate this problem, it is provided in a further development of the subject matter of the invention that the annular cuff is made of a lighter welding material, preferably a steel with a lower carbon and / or nickel content than other areas of the rotor part. This can be done by appropriate processing methods such. B. melting in a vacuum or a slag melt can be achieved.

As an alternative to this, it is also possible to produce the region of the rotor disks which is located further away from the central axis and to which the blades are fastened, from a steel of higher mechanical strength. The annular sleeve and possibly also the rest of the rotor disk can be made from a material that is easy to weld.

In order to counteract a reduction in strength in the area of the weld seams, there is also the possibility that toothings are provided on the outer region of the rotor parts which are located towards the central axis and which engage in corresponding toothings of the adjacent rotor part. These gears can absorb at least part of the rotational forces, which relieves the pressure on the weld seams. It is expedient to then produce these toothings from a steel with higher mechanical strength.

An embodiment of the invention is shown in the drawings and will be described in more detail below.

Fig. 1

einen Ausschnitt aus einem geschweißten Dampfturbinenläufer seitlich im Schnitt,

Fig. 2

die obere Hälfte eines Dampfturbinenläufers teilweise im Schnitt,

Fig. 3

die obere Hälfte eines Dampfturbinenläufers in einer zweiten Variante teilweise im Schnitt und wie Fig. 2 in Seitenansicht,

Fig. 4

eine teilweise beschaufelte Läuferscheibe mit axialen Nuten,

Fig. 5

eine der Figur 4 entsprechende Darstellung mit anderen Axialnuten.

Show it:

Fig. 1

a section of a welded steam turbine rotor laterally in section,

Fig. 2

the top half of a steam turbine rotor partly in section,

Fig. 3

the upper half of a steam turbine rotor in a second variant, partly in section and like FIG. 2 in side view,

Fig. 4

a partially bladed rotor disc with axial grooves,

Fig. 5

a representation corresponding to Figure 4 with other axial grooves.

The section of a rotor shown in FIG. 1 corresponds to a section of FIG. 2. According to this, the rotor of this embodiment consists of an inlet steam shaft end 1, two double rotor disks 3, a single rotor disk 2 and an exhaust steam shaft end 4. A control wheel 6 is part of the steam shaft end 1, but it does can also be further divided. In the rotor according to FIG. 3, a condenser output stage drum 5 is added to the rotor parts 1 to 4 already listed.

Symmetrical to the central axis M, the rotor parts 1 to 5 are provided with different recesses 7a, 7b, 7c, which ensure that ring-like sleeves 9a, 9b are formed which overlap one another and thus bring about a concentric alignment with the axis.

All rotor parts have an axial bore through which a tie rod 8 is guided, which is screwed into the steam shaft end 1 and holds the rotor parts 1 to 5 together. Where the ring-like sleeves 9a meet with the adjacent rotor parts, weld seams 13 can now be made by electron beam welding, which ensure that the rotor parts 1 to 5 are connected to a single rotor.

Due to the modularization of the rotor, the tools required for cutting the grooves can be used both for the single discs 2 and for the double discs 3 can be conveniently introduced from the outside. It is thus possible to implement any desired groove shape, as shown in FIGS. 4 and 5, and to insert blades 10 with their blade roots 11 and 12 axially into the rotor disks 2.

This disc construction therefore enables any type of blade attachment and its manufacture can be carried out in a simple manner on smaller machine tools. Processing with welded-on blades or complex pulleys made of powder metal is also possible. Very short throughput times can be achieved through parallel processing.

The illustration of a toothing between the rotor parts that relieves the weld seams has been dispensed with, since it is a matter of customary designs familiar to the person skilled in the art.

Claims (12)

Method for producing the rotor of a turbine, in particular a steam turbine, from individual rotor parts (1 to 5) welded together to form a unit, characterized by the following manufacturing steps essential for the manufacturing process: - Based on a modular system with additional steam shaft ends (1), single running disks (2), double running disks (3), exhaust steam shaft ends (4) and, if necessary, condenser output stage drums (5), to create different rotor variants, the parts of the rotor required for a specific turbine are made in parallel depending on the order manufactured and / or stored parts taken from the warehouse, - The parts are manufactured with the requirement to minimize the rework still required on the assembled rotor, in particular the grooves (14, 15) for receiving the blade feet (11, 12) are finished, the parts are connected with a beam with high power density, preferably an electron beam, with little distortion, the required rotor blades are selected and the rotor disks are bladed before or only after the parts have been connected, - The runner composed of the individual parts is finished. Rotor of a turbine, in particular a steam turbine, which are welded together from individual to a unit runner parts (1 to 5), characterized in that the individual rotor parts (1 to 5), including associated rotor discs (2, 3), largely finished, and in particular Grooves (14, 15) for the blade roots (11, 12) are already finished and belong to a modular system that standardizes the parts of the rotor, which enables a selection to be made according to the respective thermodynamic and rotor dynamic requirements, and that the welding of the rotor parts (1 to 5 ) by a beam of high power density, preferably by electron beam welding, and corresponding weld seams (13) are placed at the greatest possible distance from the central axis (M) of the rotor. Rotor according to claim 2, characterized in that at least one of the rotor disks (2, 3) is completely or partially bladed and optionally also balanced. Rotor according to one of the preceding claims 2 or 3, characterized in that the rotor parts (1 to 5) are made of different materials. Rotor according to one of the preceding claims 2 to 4, characterized in that at least one of its rotor disks is designed as a double rotor disk (3). Rotor according to one of the preceding claims 3 to 5, characterized in that the rotor parts (1 to 5) to be connected to one another by electron beam welding have an axial bore which serves to receive an axial tie rod (8) which holds the parts together during the welding process. Rotor according to one of the preceding claims 2 to 6, characterized in that, in addition to double running disks (3), individual running disks (2), steam shaft ends (1), steam shaft ends (4), and condensation output stage drums (5) also belong to the modular system. Runner according to one of the preceding claims 2 to 7, characterized in that the runner parts (1 to 5) have, at least on one side, a recess (7) which is symmetrical to the central axis (M) and through which an annular sleeve (9) is formed, which adjoins the adjacent one Runner part rests and defines the position of the weld (13). Runner according to claim 8, characterized in that the annular sleeve (9) consists of a material which is easier to weld, preferably a steel with a lower carbon and / or nickel content, than other regions of the runner part (1 to 5). Rotor according to claim 8, characterized in that the outer region of the rotor disks, to which the blades (10) are fastened, which is more distant from the central axis (M), is made of a higher mechanical steel Strength, preferably made of steel with a higher carbon and / or nickel content, exists than other areas of the rotor disk, in particular the annular sleeve (9). Rotor according to one of the preceding claims 2 to 10, characterized in that toothings are provided on the outside on the area of the rotor parts (1 to 5) lying to the central axis (M), which engage in corresponding toothings of the adjacent rotor part (1 to 5). Runner according to claim 11, characterized in that the area of the toothing consists of a steel of higher mechanical strength, preferably of steel with a higher carbon and / or nickel content, than other areas of the rotor disk, in particular the annular sleeve (9).

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