WO1998054443A1

WO1998054443A1 - A device for a rotary machine

Info

Publication number: WO1998054443A1
Application number: PCT/SE1998/001007
Authority: WO
Inventors: Per Thörnblad; Roland Nilsson
Original assignee: Abb Stal Ab
Priority date: 1997-05-27
Filing date: 1998-05-27
Publication date: 1998-12-03
Also published as: CN1200430A; SE509392C2; SE9701987L; SE9701987D0

Abstract

A device for a rotary machine with a stator part (2) and a rotary part (1) supported therein comprises first support means (5) arranged to absorb forces appearing between the stator part (2) and the rotary part (1), and second support means (7) arranged to absorb forces appearing between the rotary part (1) and the stator part (2) and exceeding a certain level, as the forces absorbed by the first support means (5) reach this level.

Description

A device for a rotary machine

THE FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a device for a rotary machine, the rotary machine comprising a stator part and a rotor part supported thereby, and first support means being arranged to absorb forces appearing _b_© ween the stator part and the rotary part .

Generally seen, such a device is suited for rotary machines where, by normal operation conditions, forces of a relatively low level, normally the gravitation force of the rotor, appear between the rotor part and the stator part but where, at exceptional circumstances, much higher force levels may appear therebetween. As the device according to the invention is particularly applicable to rotary machines of the type flown through by a medium with a temperature that differs from the environment, which in its turn leads to the appearance of temperature-induced tensions between the rotary part and the stator part, the invention will, however, particularly be described with reference to an application by such machines, though not in any delimiting purpose .

By the rotary machine of the defined type it is, according to prior art, known to arrange elastically deformable portions between the stator part and the rotary part, said portions on the first hand being capable of carrying the rotor and holding it in a centred position in the rotary machine without being subjected to any particular deformation, on the other hand being able to absorb by their deformation the geometrical changes of parts included in the rotary machine obtained due to temperature differences and thermal expansion phenomena associated thereto. Of course, it is important that the rotor is kept centred also by such deformations of said portions due to temperature differences. Such elastically deformable portions have, according to prior art, for example been constituted by bodies that are elastically deformable, conical and annularly constructed, and arranged between and connected to the bearing housing in which the rotary part is supported and the stator. However, forces between the rotary part and the stator part that substantially exceed the normal forces and that, thereby, also must be absorbed by said elastically deformable portions some times appear. Such a case is for example when blade loss, that is when a rotary blade is loosened during operation, occurs by rotary machines of the turbine type, whereby exceptionally high forces appear between the stator part and the rotary part. If the elastically deformable portions should be capable of absorbing also these forces, a significant overdimensioning thereof in relation to the dimension which, by given materials and a given geometrical design, is required only for the absorption of the gravitation force of the rotor is required. Such an overdimensioning leads, amongst others, to a reduced ability of the portions to absorb through elastic deformation the forces caused by the temperature-induced dimensional changes, as they thereby offer a higher resistance against such a deformation and thus do not permit a different expansion of the stator and the rotor.

Under no circumstances said portions can be allowed to be so weak as to their dimension that they are not able to absorb those significant forces which, for instance, appear in connection to blade losses, as this could lead to very costly and serious breakdowns in rotary machine, for instance of the turbine type arranged to be driven by a medium such a combustion gas or steam of high or very high temperature. Therefore, according to prior art, overdimensioning of the elastically deformable portions is a necessity.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device of the type initially defined, which makes it possible to absorb extremely high forces by a rotary machine, for example in connection to a blade loss.

According to the invention this object is obtained as the device comprises second support means arranged to absorb forces exceeding a certain level and appearing between the rotary part and the stator part as the forces absorbed by the first support means reach this level.

According to a preferred embodiment the first support means comprise a first support element which is arranged to absorb through elastic deformation forces caused by dimensional changes of at least one of the stator part and the rotary part, and the second support means comprise a second support element which is rigid in relation to the first support element in a load absorbing direction.

Thereby, the advantage of having the second support means absorb significant forces or stresses without any particular deformations is obtained thanks to their rigidity in the load absorbing direction. Also in cases of very significant radial forces, such as those appearing in a rotary machine at blade losses, those very significant forces striving to displace the rotary shaft radially in relation to its normal operation position are thereby counteracted. Nevertheless, during normal operation, when no such exceptional radial forces appear, there is an advantage obtained as insignificant dimensional changes between the rotary part and the stator part caused by a temperature influence may be smoothly, that is elastically, transferred by way of the elastic deformation of the first support elements without any participation of the function of the second support means .

According to another embodiment, the first and second support means are arranged in parallel. Thereby, the forces between the rotary part and the stator part, which are not absorbed by the first means due to the elastic deformation thereof, are automatically transferred to the second support means. The parallel arrangement also permits a simple construction of the first and second support means in order to guarantee that the second support means execute the operation as soon as the first support means have absorbed a certain force level and, thereby, obtained a certain degree of elastic deformation.

According to another preferred embodiment, the first support means are arranged to absorb forces caused by dimensional changes of at least one of the rotary part and the stator part and appearing between the stator part and the rotary part due to a temperature influence present in the rotary machine, and said level of the stresses corresponds to a level which is equal to the sum of the gravitation force of the rotor acting on the first support means, and the forces appearing between the rotary part and the stator part due to a temperature influence existing in the rotary machine.

Thereby, one particularly obtains the advantage of being able to dimension the first support means only in order to keep the rotor centred in the rotary machine in the most effective way and absorb forces up to the level defined above, whether these are caused by temperature affection or by other affection, and the first support means, accordingly, do not need to be made unnecessarily rigid because of running the risk of being subjected to more significant forces.

According to another preferred embodiment the first support means are connected to the stator at a first surface, and connected to a bearing device at a second surface, said bearing device being rotatably supported in the rotary part.

Thereby, the first support means form a direct link between the stator part and the rotary part, and operate as a support means for the bearing device by which the rotary part is rotatably supported. Thereby, the first support means may be constructed in one single piece with the stator part and/or the bearing device.

According to another preferred embodiment, the second support means are arranged between the stator part and a bearing device by which the rotary part is rotatably supported, the support means being arranged with a distance to at least one of the stator part and the bearing device when the second support means are in their unloaded condition.

Accordingly, as said distance exists, the second support means will not contribute with any load absorption between the rotary part and the stator part as long as this distance exists. Such an embodiment permits a simple construction which permits a reduction of the distance to an extent corresponding to the increase of the elastic deformation of the first support means . According to another preferred embodiment the second support means are arranged between the stator part and a bearing device by which the rotary part is rotatably supported, and in order to bear on both of these in their active, force- absorbing condition.

Thereby, it is possible to construct and dimension the first and the second support means respectively in such a way that the second support means succeeds in bearing on the bearing device and the stator part respectively at the same time as the first support means are elastically deformed to an extent corresponding to their absorbtion of forces of the level previously defined.

According to another preferred embodiment the second support means comprise an annular support element, and are arranged around a bearing device for the rotary part.

The annular design is advantageous as it, amongst others, permits absorbtion of radial forces between the rotary part and the stator part in all directions in the rotational plane of the rotary part. An evenly distributed force absorbtion is thereby obtained. Alternatively, the second support means may comprise a plurality of segments, for example heals departed from each other, which together define a ring, arranged around the bearing device.

According to another preferred embodiment, the stator part is provided with channels for the passage of a hot medium flowing through the rotary machine, the first and second support means being arranged at portions of the stator part that extend radially, crossing the channels. This means that the first and second support means are arranged at portions of the stator part where the latter is subjected to a significant temperature influence and that their function, accordingly, becomes particularly important as it is regarded as important to absorb the forces between the rotary part and the stator part caused by dimensional changes in that specific area, said changes being caused by, for example, temperature affection, as well as absorbing smaller forces caused by the gravitation force of the rotor, or more significant forces caused by, for example, blade loss by the rotary part.

Preferably, the rotary machine is a turbine, driven by means of one of the media comprised by steam and combustion gas.

Further advantages and advantageous features of the invention will appear in the following description and the other, independent patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, a detailed description follows of preferred embodiments of the invention, referred to by way of example and with reference to the annexed drawings, on which:

Fig 1 is a cross-sectional view which schematically shows the device according to the invention, arranged between the rotary part and the stator part of a rotary machine,

Fig 2 is a cross-sectional view, similar to the one of Fig 1, which shows the device according to the invention, arranged at a stator portion provided with channels, and

Fig 3 is a cross-sectional view according to III-III in Fig 2, showing the device in the rotational plane of the rotor. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In Fig 1-3 a preferred embodiment of the inventive device is shown. The device is arranged in a rotary machine which comprises a rotary part 1 and a stator part 2. The rotary part 1 is, via a bearing device in the shape of a bearing house 3 and a bearing 4 arranged therein, rotatably arranged in the stator part 2.

Preferably, the rotary machine is a turbine driven by means of one of the media comprised by steam and combustion gas . However, it is also possible that the rotary machine in question is of some other type.

First support means 5 are arranged between the stator part 2 and the bearing house 3. Here, the support means 5 comprise an annular body which, at two opposite ends thereof, is connected to the bearing device 3, 4 and the stator part 2 respectively, and which presents at least one conically designed portion and extends around the rotor shaft 6 and is generally concentric therewith. The conical portion has a wall thickness which is substantially smaller than the size of the extension of the body in radial direction. It is also substantially smaller than the size of the extension of said portion between the ends thereof.

The support means 5 is connected to the bearing house 3 at a surface at one of its ends, and connected to the stator part 2 at a surface at its other end. Dimensional changes of the rotary part 1 and the stator part 2 due to, for example, temperature differences between these are absorbed by the support means 5. Particularly, the support means 5 may absorb radial dimension changes of the rotary part and the stator part 2, as its conical construction and the dimensioning thereof permits it to be elastically deformed. Meanwhile, via the support means 5, the normal forces acting on the bearing device 3, 4 due to its own weight and the weight of the rotor are transferred. This must take place in such a way that deformations in the support means do not substantially change the position of the rotor centre in relation to the stator 6. However, in certain cases, extreme forces can be expected to appear between the rotary part 1 and the stator part 2. One example of such occasions are those that appear in connection to so called blade loss, by which an unbalance of the rotary part 1 rotating at high rotational speed appears, and the radial forces thereby produced must be transferred from the rotary part 1 to the stator part 2, preferably with a deviation as small as possible of the shaft of the rotary part 1 in relation to the position which said shaft occupies during normal operation when no such extreme forces appear. In order to transfer those further forces thereby appearing in addition to the level which is expected to be absorbed by the first support means 5 at maximum, the device comprises second support means 7 which are rigid in the radial direction in relation to the support means 5, and transfer these further forces between the rotary part 1 and the stator part 2 while presenting deformations as small as possible in the radial direction. By the preferred embodiment, the second support means 7 are formed by an annular body which is connected to the bearing device 3, 4 and extends around the latter. Thereby, the support means 7 are generally concentric to the bearing device 3, 4 as well as to the rotational axis 6 of the rotary part. Between the surface of the support means 7 which is directed towards the stator part 2 and the latter, and as long as there are forces between the rotary part 1 and the stator part 2 that goes under the maximum force level which is expected to be absorbed by the first support means 5, there is a distance e between this surface 8 and an opposite surface 9 of the stator part 2. This means that, as the first support means 5 are deformed to such an extent in the radial direction that a contact is obtained between the surfaces 8 and 9 all further forces or stresses between the rotary part 1 and the stator part 2 will be transferred between these via the second support means 7.

The support means 7 may also be regarded as a surface of the bearing device 3 or a part connected thereto, which part, when the support means are in their inactive condition, presents a distance to a corresponding surface of the stator part 2 or a part connected thereto, and this distance being eliminated during the active condition of the second support means 7 such that there is a contact between the surfaces.

It should be noted that the distance e in the case where the rotary machine is constituted by, for example, a gas turbine is very small in relation to the diameter of the rotary part, including its rotor blades. Preferably, the distance e is in the order of a few tenths of a millimetre as said diameter is in the order of one meter.

Furthermore, it can be seen from Fig 3 that the stator part 2 is provided with channels 10 for the passage of an operating medium flowing through the rotary machine. This medium may be any of the media comprised by steam and gas, which are expected to have a high temperature. Thereby, it is easy to realise that dimensional changes induced by a temperature affection will appear by the rotary part 1 and the stator part 2 because the flowing medium heats portions 11 of the stator part 2 adjacent to the channels 10 as it passes through these channels. The invented device is particularly well suited for application at a rotary machine of this type.

Of course, a plurality of modifications and varieties of the described device are possible within the frame of the invention without thereby departing from the scope of the invention. As an example it can be mentioned that a plurality of different constructions of the first and second means 5 and 7 respectively may exist and that the construction thereof as a body in the shape of a truncated cone and an annular body respectively are preferred embodiments for the moment, however shown here only by way of example. Of course, it is also possible that the second support means 7 when these are constituted by an annular body as has been shown, are connected to the stator part or a part connected thereto in their inactive condition and present a distance to the bearing device 3, and that they bear on the bearing device 3 or a part connected thereto in their active condition, thereby forming a force transferring unit between the stator part 2 and the rotary part 1.

Claims

1. A device for a rotary machine, the rotary machine comprising stator part (2) and a rotary part (1) supported thereby, and first supporting means (5) being arranged to absorb forces appearing between the stator part (2) and the rotary part (1) , characterized in that it comprises second support means (7) arranged to absorb forces exceeding a certain level and appearing between the rotary part (1) and the stator part (2) , as the forces absorbed by the first support means (5) reach this level.

2. A device according to claim (1), characterized in that the first (5) and second (7) means are arranged between the rotary part (1) and the stator part (2) .

3. A device according to claim 1 or 2, characterized in that the first support means (5) comprises a first support element which is arranged to absorb through an elastic deformation forces caused by dimensional changes of at least one of the stator part and the rotor part.

4. A device according to any one of the preceding claims, characterized in that the second support means (7) comprise a second support element which is rigid in relation to the first support element (5) in a load absorbing direction.

5. A device according to any one of the preceding claims, characterized in that the first and second support means (5 and 7 respectively) are arranged in parallel.

6. A device according to any one of the preceding claims, characterized in that the first support means (5) are arranged to absorb forces caused by dimensional changes of at least one of the rotary part (1) and the stator part (2) due to a temperature affection present in the rotary machine .

7. A device according to any one of the preceding claims, characterized in that said level of the forces corresponds to a level which is equal to the sum of the gravitation force of the rotor acting on the first support means (5) , and the forces appearing between the rotary part (1) and the stator part (2) due to a temperature influence appearing in the rotary machine.

8. A device according to any one of the preceding claims, characterized in that the first support means (5) are connected to the stator part (2) at one surface, and are connected to a bearing device (3, 4) at a second surface, the rotary part (1) being rotatably supported in said bearing device.

9. A device according to any one of the preceding claims, characterized in that the second support means (7) are arranged between the stator part (2) and a bearing device (3, 4) by which the rotary part (1) is rotatably supported, the second support means presenting a distance (e) to at least one of the stator part (2) and the bearing device (3, 4) as the second support means (7) are in an unloaded condition.

10. A device according to any one of the preceding claims, characterized in that the second support means (7) are arranged between the stator part (2) and a bearing device (3, 4) by which the rotary part (1) is rotatably supported, and arranged to bear on both of these as the second support means are in their active, stress-absorbing condition.

11. A device according to any one of the preceding claims, characterized in that the first support means comprise an annular body arranged between the stator part (2) and a bearing device (3, 4) , said body being connected to the bearing device (3, 4) and the stator part (2) respectively at its opposite ends and presenting at least one conically designed portion.

12. A device according to any one of the preceding claims, characterized in that the second support means (7) comprise an annular support element and are arranged around a bearing device (3, 4) for the rotary part (1) .

13. A device according to any one of the preceding claims, characterized in that the stator part (2) is provided with the channels (10) for the passage of a hot medium flowing through the rotary machine.

14. A device according to claim 13, characterized in that the first (5) and second (7) support means are arranged at portions (11) of the stator part (2) , said portions extending radially and crossing the channels (10) .

15. A device according to any one of the preceding claims, characterized in that the rotary machine is a turbine, driven by means of one of the media comprised by steam and a combustion gas.