Patent application title: ROTOR FOR A TURBO-MACHINE
Norbert Wagner (Bottrop, DE)
IPC8 Class: AF01D514FI
Class name: Fluid reaction surfaces (i.e., impellers) specific blade structure (e.g., shape, material, etc.)
Publication date: 2012-11-01
Patent application number: 20120275923
A radial compressor includes a rotor arrangement having a rotating shaft,
a rotor wheel that is arranged on the shaft and corotates with the shaft,
and a shaft bearing arranged on the shaft. To achieve improved rotor
dynamics, the rotor wheel has a recess toward the shaft, in which the
shaft bearing is at least partially arranged.
9. A radial compressor, comprising: a rotor arrangement, comprising: a rotating shaft, a corotating rotor wheel arranged on the shaft, and a shaft bearing arranged on the shaft, wherein the rotor wheel has a recess toward the shaft, in which the shaft bearing is at least partially arranged.
10. The radial compressor as claimed in claim 9, wherein the rotor wheel is part of an overhung stage.
11. The radial compressor as claimed in claim 9, wherein the shaft bearing is a radial bearing.
12. The radial compressor as claimed in claim 9, wherein the recess is arranged on the wheel-disk side in the rotor wheel.
13. The radial compressor as claimed in claim 9, wherein an axial center of the shaft bearing is arranged in the recess.
14. The radial compressor as claimed claim 9, wherein a seal is arranged in the recess, between the shaft bearing and the rotor wheel.
15. The radial compressor as claimed in claim 9, wherein a stator-side bearing receptacle of the shaft bearing projects into the recess.
16. The radial compressor as claimed in claim 14, wherein the stator-side bearing receptacle also carries the seal.
CROSS REFERENCE TO RELATED APPLICATIONS
 This application is the US National Stage of International Application No. PCT/EP2010/067184, filed Nov. 10, 2010 and claims the benefit thereof. The International Application claims the benefits of German application No. 10 2009 052 931.4 DE filed Nov. 12, 2009. All of the applications are incorporated by reference herein in their entirety.
FIELD OF INVENTION
 The invention relates to a radial compressor having a rotor arrangement, which has a rotating shaft, a corotating rotor wheel arranged on the shaft, and a shaft bearing arranged on the shaft.
BACKGROUND OF INVENTION
 In a turbomachine for industrial installations, one or more rotor wheels rotates on a shaft as rotating wheels which perform fluid-dynamic work in order, for example, to compress a gaseous medium in a compressor or to drive a generator in a steam turbine. In this arrangement, the shaft is supported at at least two locations. One example that may be mentioned is a radial compressor, in which the rotor wheels are arranged between the bearing locations and possibly also as an overhung stage at the free shaft end. Owing to a high overhang moment, there may be considerable vibration and, as a result, a maximum possible speed of rotation may be undesirably low.
SUMMARY OF INVENTION
 It is an object of the present invention to indicate a radial compressor for a turbomachine which can be moved at a high speed of rotation.
 This object is achieved by a radial compressor of the type stated at the outset on which, according to the invention, the rotor wheel has a recess toward the shaft, in which the shaft bearing is at least partially arranged. This makes it possible to support the shaft close to the rotor wheel. By virtue of the short distance between the support and the mass-bearing rotor wheel, the rotor is less sensitive to vibrational excitation and can therefore be moved at a high speed of rotation.
 The invention can be employed to particular advantage if the rotor wheel is part of an overhung stage. In the case of an overhung stage, the absence of an obstruction in the region of the shaft axis makes it possible to achieve an enlarged intake cross section in comparison with radial induction of the air with a rotor wheel of the same diameter.
 Since the shaft expediently ends in the rotor wheel, a free, i.e. unsupported, shaft end is necessarily formed. If the rotor wheel is arranged at the free shaft end, it is not possible for bending of the shaft to be counteracted there by a bearing, in particular a radial bearing. Consequently, moments which are critical in terms of bending and hence speeds of rotation which are critical in terms of bending can arise, imposing a disadvantageous restriction on the operating range of the turbomachine. By means of the invention, corresponding vibration can be reduced and the speed of rotation which can be achieved can be kept high. The advantage of the embodiment according to the invention of the support for the shaft additionally lies in a reduction in the length of the shaft made possible by the design and, in particular, a reduction in the length of the free shaft end, thereby making it possible to achieve advantageous rotor dynamics
 It is advantageous if the recess is arranged on the wheel-disk side in the rotor wheel. Here, the wheel-disk side of a rotor wheel is the side facing away from the flow. In contrast, the rotor wheel has an oppositely situated shroud ring side which faces axially outward. In such an embodiment, a large intake cross section of the rotor wheel is maintained in combination with a short shaft end and good rotor dynamics
 It is advantageous if part of the axial extent of the shaft bearing and, in particular, an axial center of the shaft bearing is arranged in the recess, with the result that the majority of the bearing area is positioned within the recess and hence a considerable reduction in the length of the free shaft end can be achieved.
 Particularly in the case of a radial compressor, a seal can be arranged between the shaft bearing and the rotor wheel, advantageously being arranged in the recess, in particular completely within the recess. The seal can be a labyrinth seal for sealing off bearing oil from the outside and/or for sealing off from the outside a working pressure built up within the compressor.
 The size of the recess is advantageously dimensioned in such a way that a stator-side bearing receptacle of the shaft bearing projects into the recess. Stable support for the shaft close to the shaft end can thereby be achieved.
 A sturdy construction and reliable sealing can be achieved if the stator-side bearing receptacle also carries the seal in addition to the shaft bearing.
DETAILED DESCRIPTION OF INVENTION
 The invention is explained in greater detail with reference to an illustrative embodiment, which is shown in the drawing. The single figure of the drawing shows a scrap view of a turbomachine 2 embodied as a radial compressor. The illustration shows a schematic section along the shaft 4 of the turbomachine 2. The shaft 4 is part of a rotor 6 of the turbomachine 2 and, at one end, carries a rotor wheel 8 for inducing external air in the axial direction 10 and compressing the induced air in a radially outward direction.
 The turbomachine 2 is a radial compressor having an overhung stage, i.e. a compressor stage with a rotor wheel 8 which is arranged at one axial end of the shaft 4. The radial compressor is of particularly large design and is used for air compression at volume flows of between 100,000 m3/h and 800,000 m3/h and compression from atmospheric pressure to between 4 bar and 8 bar.
 The shaft 4 is supported by a first shaft bearing 12 embodied as a radial bearing and a second shaft bearing 14 embodied as an axial bearing. The shaft 4 is supported by another radial shaft bearing, but this is arranged outside the area illustrated in the figure and is therefore not shown. A shaft seal 16 in the form of a labyrinth seal is arranged between the radial shaft bearing 12 and the rotor wheel 8 in order to seal off the bearing oil from the outside.
 The rotor wheel 8 ends radially toward the outside in blade segments 18, which form a recess 20 toward the shaft 4. A boundary of this recess 20 on the wheel-disk side is represented by a dashed line 22. The radial shaft bearing 12 is arranged partially within this recess 20, namely to an extent such that an axial center line 24 of the shaft bearing 12 is arranged in the recess 20. Here, the axial center line 24 is formed by a section extending parallel to the shaft 4 in an imaginary axial central area of the shaft bearing 12 which intersects the shaft bearing 12 centrally in the axial direction 10. More than half of a bearing area of the radial shaft bearing 12 is thus in the recess 20 of the rotor wheel 8. The shaft bearing 16 arranged around the shaft 4 is completely in the recess 20.
 In this arrangement, the recess is arranged on the wheel-disk side of the rotor wheel 8, i.e. on the side which faces away from the side from which the medium to be compressed, in this illustrative embodiment external air, is induced. The expression "wheel-disk side" accordingly means on the side of the hub and facing away from the axial side of the rotor wheel which guides the flow.
 The shaft seal 16 and the radial shaft bearing 12 are fixed on the stator of the turbomachine 2 by a stator-side bearing receptacle 26, thereby fixing the shaft 4 in the desired position thereof within the stator. In this arrangement, the bearing receptacle 26 projects by a certain amount into the recess 20 of the rotor wheel 8 and surrounds the outside of the shaft bearing 12 and the shaft seal 16 at least partially for the purpose of fixing. In this arrangement, the bearing receptacle 26 supports both the radial shaft bearing 12 and the shaft seal 16 by means of an element of integral design.
 Arranging the radial bearing 12 at least partially within the recess 20 enables the shaft 4 to be designed with a shorter length than known shafts, thereby making it possible to achieve rotor dynamics which are favorable in respect of vibration. In this arrangement, the projecting part of the rotor wheel 8, the part extending in the circumferential direction and situated radially on the outside, which comprises the blade segments 18, projects at least partially beyond the radial bearing 12 on the wheel-disk side, and therefore the fixing of the radial bearing 12 is passed out of the recess 20 in a direction facing laterally away from the rotor wheel 8. Accordingly, the bearing receptacle 26 of the shaft bearing 12 projects into the recess 20 together with the shaft bearing 12.
 Arranging the shaft bearing partially in the recess 20 achieves a reduction in the length of the overhang and, as a result, a reduction in sensitivity to vibration. In particular, rotor dynamics are thereby improved, with an increase in the speed of rotation critical in terms of bending at the free end, thus allowing the radial compressor to be operated at higher speeds of rotation as compared with conventional embodiments of overhung stages.
Patent applications by Norbert Wagner, Bottrop DE
Patent applications in class SPECIFIC BLADE STRUCTURE (E.G., SHAPE, MATERIAL, ETC.)
Patent applications in all subclasses SPECIFIC BLADE STRUCTURE (E.G., SHAPE, MATERIAL, ETC.)