WO2015188954A1

WO2015188954A1 - Tilting-pad radial bearing

Info

Publication number: WO2015188954A1
Application number: PCT/EP2015/055060
Authority: WO
Inventors: Andreas Hofmann
Original assignee: Siemens Aktiengesellschaft
Priority date: 2014-06-12
Filing date: 2015-03-11
Publication date: 2015-12-17
Also published as: DE102014211255A1

Abstract

The invention relates to a tilting-pad radial bearing (1) for supporting a shaft (2), comprising a plurality of tilting pads (3) distributed over the circumference of the bearing (1) and spaced apart from each other. The individual tilting pads (3) have a profile (Ψ_υ) adapted to the shaft (2). The tilting pads (3) are formed from a bimetal, which is arranged and designed in such a way that the bimetal counteracts a change in the profile (Ψ_υ) as a result of thermal and/or mechanical load during bearing operation. The invention further relates to a turbomachine having at least one such tilting-pad radial bearing (1) according to the invention.

Description

description

The invention relates to a radial tilting pad bearing according to the preamble of independent claim 1 and a Turboma ^¬ machine, in particular a steam turbine, with a radial tilting pad bearing according to claim 5. For the radial storage of rotating shafts Usually used bearings with fixed bearings that completely enclose the shaft. The oil for lubrication of the bearing is supplied via one or more distributed over the bearing circumference, axially extending grooves. Plain bearings in which the bearing shell is divided along the circumference by axial grooves in partial storage areas, referred to as a multi-surface bearing with a fixed segment. If such multi-surface bearings are to be designed for high peripheral speeds, then relatively large lubrication gaps are required, since otherwise an inadmissible heating of the bearing would occur. However, large lubrication gap widths lead, especially at high circumferential speeds of the shaft, to a turning over of the laminar flow in the lubrication gap into a turbulent gap flow, which is accompanied by a high increase in the bearing friction. In addition, the shaft is insufficiently guided in a large bearing clearance which can lead to instability ^¬ ren.

For high-speed shafts, therefore, radial tilting pad bearings are often used in which the shaft circumference is not completely enclosed by the bearing. The shaft is held in the radial tilting pad bearing by several, usually 3 to 5, tilting bearing segments, which have equal or unequal circumferential lengths depending on the load and intended use of the bearing. The sliding surfaces of the tilting bearing segments are usually formed circular cylindrical. Such Kippsegmentlager are well known from the prior art, for example from DE 10 2011 105762 AI. A known from the prior art Radial Kippsegment- bearing is shown in Figure 1. The radial Kippsegment- bearing here consists of 4 tilting segments 3, wherein the lower two tilting elements have a shorter circumferential length than the two overhead tilting segments 3. The rotating in the radial tilting pad bearing shaft 2 is asymmetrical to the axis of the radial Kippsegment- Warehouse arranged. The individual tilt ^¬ segments 3 are spaced from each other, being formed in the interim ^¬ rule evacuate nozzle holes through which the lubricant, preferably a hydraulic oil, can be injected into the bearing. A characteristic of the Radi ^¬ al-tilting pad bearing is the profiling Ψ. The Profilie ^¬ tion significantly influenced the damping behavior of the radial tilting pad bearing. Basically, it can be said that the smaller the profiling, the better the damping property of the radial tilting pad bearing. Typical values for the profiling of radial tilting pad bearings lie in a value range between 1.5 and 3.

During operation, the radial tilting pad bearing and thus each individual tilting segment is bent open by the mechanical (hyd ^¬ rodynamic pressure distribution) and the thermal Beanspru ^¬ chung. This increases the profiling Ψυ, whereby the damping property of the tilting segment decreases ^¬ . The thermal and mechanical bending of the tilting segment can be counteracted only to a very limited extent by the choice of a smaller initial profile, since too low a selected initial profiling can lead to instabilities and in particular to segment flutter, especially when the shaft is raised to rated speed.

Based on the present state of the art, it is therefore an object of the present invention to provide a radial Kippsegment- bearing in which prevents the bending of the segments and the associated increase in the profiling, due to mechanical and thermal stress on the Kippsegmente, during operation or at least significantly ver is ^¬ Ringert. Another object of the invention is to provide a turbomachine with such a radial tilting pad bearing.

The object is achieved with respect to the radial tilt pad bearing by the features of independent claim 1 and with respect to the turbomachine by the features of the inde- pendent claim ^¬. 5

Advantageous embodiments and further developments, which can be used individually or in combination with one another, are the subject matter of the subclaims.

The radial tilting pad bearing according to the invention for supporting a shaft, comprising a plurality of tilting segments distributed over the circumference of the bearing and spaced from each other, wherein the individual tilting segments have a profiling adapted to the shaft, which changes as a result of thermal and / or mechanical stress in the bearing operation, is characterized in that at least one tilting segment has a bimetal, which is arranged and designed so that it counteracts the change in the profiling, in particular in a widening of Kippsegmens (increase the profiling) in storage operation.

Since the bimetal is arranged and designed so that it counteracts a change in the profiling in the bearing operation, the decrease in damping, in particular due to an enlarged profiling, counteracted and a constant damping during operation ensured ^¬ tet. Improving the bearing damping improves the running performance of the rotor. The improved

Running behavior of the rotor is reflected in a lower shaft amplitude and a greater system damping during storage operation. An embodiment of the invention provides that the bimetal is arranged such that the bimetallic layers are arranged radially over ^¬ nander and the coefficient of linear expansion 0 (i of the radially inner layer, smaller than that Linear expansion coefficient n of the radially outer layer. Such an arrangement of the bimetallic layers ensures that the bimetallic layer deforms concavely when heated, that is, assumes a greater curvature and thus a smaller profiling. As a result, the magnification ^¬ tion of the profiling due to thermal and mechanical stress is effectively counteracted.

A further embodiment of the invention prefers that the ratio between the coefficient of expansion οίι / oin the radially outer bimetallic layer to the radially inner bimetallic layer at Kippsegmenten, which are more thermally and / or mechanically loaded in the bearing operation, greater than in the Kippsegmenten, which in storage operation are less thermally and / or mechanically loaded. This makes it possible for the profiling to be largely constant during operation for all tilting segments of the radial tilting-pad bearing. Tilting segments with greater thermal and mechanical stress experience due to the larger ratio between the coefficients of linear expansion a greater curvature than Kippsegmente which are exposed to lower thermal and / or mechanical stress.

A further embodiment of the invention provides that the bimetal is selected such that the profiling for ei ^¬ nen predetermined operating point, within a predetermined range of values for the profiling Ψ, preferably between a profiling Ψ _υ = 1.5 to Ψ = 3. In this way, si is ^¬ chergestellt that for a good storage damping is achieved, but at the same instability at start-up of the rotor as a result of Seg ^¬ ment flutter is counteracted.

The turbomachine according to the invention, in particular steam turbine, is characterized in that the turbomachine has at least one radial tilting pad bearing according to one of the preceding claims. The turbomachine according to the invention offers, due to the radial tilting-pad bearing used, a lent improved bearing damping and thus improved running behavior of the rotor, which allows smaller shaft amplitudes and greater system damping. This as ^¬ derum enables lower bearing and seal gaps leading to an increase in the efficiency of the turbine engine and a higher reliability.

Reference to an embodiment, further advantages of the invention are explained below. It shows:

Figure 1 is a radial tilting pad bearing according to the prior

Technique in radial section;

Figure 2a) a radial tilting pad bearing with a profiling towards infinity;

Figure 2b) a radial tilting pad bearing with a profiling of 1;

Figure 3 shows a single tilting pad bearing in the installed state and under thermal and / or mechanical stress;

Figure 4 shows an inventive radial tilting pad bearing.

In the figures, each is a greatly simplified representation, in which only the essential components necessary to describe the invention are shown. Identical or functionally identical components are throughout the figures provided with Densel ^¬ reference symbols.

Figure 1 shows a radial tilting pad bearing according to the prior art. The radial tilting pad bearing 1 for supporting a shaft 2 comprises a plurality of, in the example four, distributed over the circumference of the bearing and spaced from each other segments 3, which are angeord ^¬ net in a bearing housing, not shown. In the embodiment, the two bottom hinged ^¬ tilting pads 3 have a smaller circumferential length than the two above arranged Kipplagersegmente. 3 Grund ^¬ addition, the tilting bearing segments may have the same or unequal circumferential surfaces. Often, however, smaller circumferential lengths are used for the tilting segments, and those for a higher one Exposure are exposed, since the deflection is smaller at the lower ^¬ ren circumferential lengths. The lubricant, preferably hydraulic oil, is injected into the storage space via a nozzle 4, which is arranged in the intermediate space 5 between two individual tilting bearing segments 3. The heated hydraulic oil is subsequently removed via one or more ^further interspaces 5, between the individual tilting bearing segments 3. The damping property of the radial tilting pad bearing 1 depends to a large extent on the profiling Ψ. The smaller the profiling Ψ, the better usually is the damping of the radial tilting pad bearing 1. Too small a profiling Ψ but when starting up the rotor 1 to its rated speed to instabilities and in particular ^¬ special to a segment flutter, which must be avoided ,

FIG. 2 a) shows a profiling Ψ which runs counter to infinity. The tilting segment 3 is substantially flat, that is, formed without a curvature.

FIG. 2 b) shows a profiling with Ψυ = 1. Here, the lubrication gap between the shaft and tilting segment is not substantially divergent.

In principle, no uniform optimum value for the profiling Ψ can be specified for all radial tilting pad bearings. Rather, the optimum profiling Ψ depends on a large number of parameters, for example the bearing load, the bearing temperature, the viscosity, the bearing diameter, the shaft diameter, the rotational speed, etc. Usually, the values for profiling Ψ are between Ψυ = 1.5 to Ψ = 3. In individual cases, however, the value can deviate significantly from this.

The profiling Ψ does not remain constant during storage operation. Due to the thermal and mechanical loads of the individual tilting segments, in particular due to the hydro- dynamic pressure distribution within the lubrication gap and by an increase in temperature due to friction occurs, as shown schematically in Figure 3, to a

Expansion and thus to an increase in profiling Ψ. The widening of the tilting segment 3 is shown by the dashed lines in FIG. Due to the widening or enlargement of the profiling Ψ there is a decrease in the damping properties during storage operation. To a lesser extent, it is possible to counteract a reduction in attenuation by making the initial pronunciation somewhat smaller. However, too small an initial profile leads to the mentioned instabilities and to the problematic segment flutter when the rotor is raised to rated speed.

FIG. 4 shows a radial tilting-pad bearing 1 according to the invention, in which the tilting segments 3 comprise a bimetal, the bimetallic layers I and II of the bimetal being arranged and configured in such a way that, in the bearing operation, they are in particular subject to an increase in the profiling Ψ Act. The bimetal layers I, II are arranged radially one above the other and the coefficient of linear expansion 0 (i of the radially inner layer I is smaller than the coefficient of linear expansion n of the radially outer layer II. If it comes due to the bearing load and the ^¬ associated with increasing storage temperature to an increase the temperature of the bimetal, so the outer bimetallic layer II expands more than the inner bimetallic layer I. This results in a greater curvature and thus an increase in the profile Ψ of the tilting segment 3, whereby the expansion of the profiling Ψ is effectively counteracted . Due to the optimum for the respective application range of bimetal, therefore, the pro ^{¬-regulation} can be kept constant during the storage operation. This results in a significantly improved damping of the bearing-rotor system, and there are small amplitudes and large system attenuations achieved. The bimetal can thereby be preferably selected before ^¬ that the profiling of egg NEN predetermined operating point an optimal value, preferably a value between

indicates. In individual cases, the optimum value may also be outside the value range of 1.5 to 3. This must be determined on a case-by-case basis. The radial tilt pad bearing of the invention is suitable in particular ^¬ sondere fast running for any kind of high-speed rotors particular turbomachinery as well as gear pinions and the like.

The individual tilting segments can be designed so that the ratio between the coefficients of linear expansion ι to n of the radially outer bimetallic layer II to radi ^¬ al inner bimetal layer I at tilting segments, which are more thermally and / or mechanically loaded in the bearing operation, is greater than tilting segments, which are less thermally and / or mechanically loaded in the warehouse operation. Usually, the lower tilting pads are stressed by the weight force of the rotor and by the dynamic pressure ^¬ distribution within the lubricant in the lubricating gap Staer ^¬ ker. Due to the different choice of bimetals for the more heavily loaded Kippsegmente a constant profiling for all tilting segments of the Kippsegmentlagers he be ^¬ aims, resulting in a more uniform flow in the bearing and thus a smooth running of the rotor. In this way, in particular, a turning of the laminar flow into a turbulent flow can be avoided.

In summary it can be said therefore that by Ver ^¬ application of bimetallic for rocking segments of the inventive SEN tilt pad bearing results in a constant or largely konstan ^¬ te profiling of the tilt pad bearing over the entire operational purpose of the camp. The widening of the tilting segments due to thermal and / or mechanical stress is effectively counteracted by the bimetal, whereby a decrease in the damping in bearing operation is largely prevented.

Claims

claims

1. Radial tilting pad bearing (1) for supporting a shaft (2) comprising a plurality of, over the circumference of the bearing (1) distributed te and spaced apart tilting segments (3), wherein the individual tilting segments (3), one of Shaft (2) adapted profiling Ψυ, which changes as a result of thermal and / or mechanical stress in storage operation,

characterized in that

the tilting segments (3) have a bimetal, which is arranged and designed so that it counteracts the change in the profiling Ψυ in storage operation.

2. Radial tilting pad bearing (1) according to claim 1,

characterized in that

the bimetal is arranged so that the bimetallic layers (I, II) are arranged radially one above the other and the Län ^¬ genausdehnungskoeffizient α, ι the radially inner layer (I) is smaller than the Längenausdehnungskoeffi ^¬ zient on the radially outer layer (II ).

3. Radial tilting pad bearing (1) according to claim 1 or 2,

characterized in that

the ratio between the coefficients of linear expansion α, ι / α, ιι the radially outer bimetallic layer (II) for radially inner bimetallic layer (I) in tilt ^¬ segments (3) which are more thermally and / or mechanically loaded in the bearing operation, is greater than in the tilting segments (3) which are less thermally and / or mechanically loaded in the bearing operation.

4. Radial tilting pad bearing (1) according to one of the preceding claims,

characterized in that

the bimetal is selected such that the profiling Ψυ for a given operating point a predetermined NEN value, preferably a value between Ψυ = 1.5 and Ψυ = 3 assumes.

5. Turbomachine, in particular steam turbine,

characterized in that

the turbomachine has at least one radial tilting pad bearing (1) according to one of the preceding claims.