Patent Abstract:
A turbomachine, especially a gas turbine, includes a rotor having rotating blades and a stator having a housing and guide blades. The rotating blades form at least one rotating blade ring, which at one radially outward lying end adjoins an inner ring or casing ring of the housing, thereby defining a gap therebetween. The casing ring is connected to a support ring via curved walls, which together with the casing ring and the support ring bound a cavity and form a bellowslike structure. By changing the pressure prevailing in the cavity of the respective bellowslike structure, the gap between the casing ring and the radially outward lying ends of the respective rotating blade ring can be pneumatically adjusted.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase application submitted under 35 U.S.C. §371 of Patent Cooperation Treaty application serial no. PCT/DE2007/001946, filed Oct. 30, 2007, and entitled TURBO ENGINE, which application claims priority to German patent application serial no. DE 10 2006 052 786.0, filed Nov. 9, 2006, and entitled TURBOMASCHINE, the specifications of which are incorporated herein by reference in their entireties. 
     TECHNICAL FIELD 
     The invention concerns a turbo engine, especially a gas turbine. 
     BACKGROUND 
     From DE 10 2004 037 955 A1 there is a known turbo engine with a stator and a rotor, wherein the rotor has rotating blades and the stator has a housing and guide blades. The rotating blades at the rotor side form at least one rotating blade ring, which at one radially outward lying end adjoins a radially inward lying wall of the housing, by which it is surrounded and with which it bounds a radial gap. The radially inward lying wall of the housing is also known as the inner ring or casing ring and serves in particular as the substrate for a run-in coating. Furthermore, from DE 10 2004 037 955 A1 it is known that the gap between the casing ring of the housing and the radially outward lying end of the rotating blade ring or each rotating blade ring can be adjusted or adapted in its size by servomechanisms to provide a so-called Active Clearance Control, so as to automatically influence the gap and ensure an optimal gap maintenance over all operating conditions. According to DE 10 2004 037 955 A1, the radially inward lying housing wall or the casing ring is segmented in the circumferential direction, and preferably each segment is assigned a separate servomechanism. The servomechanisms are preferably electromechanical actuators. 
     DE 101 17 231 A1 discloses a turbo engine with a stator and a rotor, wherein the gap between radially outward lying ends of the rotating blades and the radially inward lying housing wall can be adjusted by means of a pneumatic, i.e., pressurized air-operated, actuator unit of a rotor gap control module. The pneumatic actuator unit of the rotor gap control module disclosed there has an actuator chamber, a pressure chamber, and valves connecting the actuator chamber and the pressure chamber, and depending on the pressure prevailing in the actuator chamber sealing elements of the rotor gap control module are inflated so as to adjust or adapt the size of the gap between radially outward lying ends of rotating blades and the casing ring of the housing in the sense of a pneumatic Active Clearance Control. 
     DE 29 22 835 C2 and U.S. Pat. No. 5,211,534 disclose further turbo engines with a pneumatic or pressurized air-operated Active Clearance Control. 
     Thus, the turbo engine of DE 29 22 835 C2 has a stator and a rotor, while the gap between radially outward lying ends of the rotating blades and an inner ring or casing ring of a housing wall can be pneumatically adjusted. For this, the casing ring is connected to a support ring via flexible sidewalls, with the casing ring, the support ring and the side walls forming a bellows-like structure. By adjusting the pressure in a cavity defined by the bellows-like structure, the gap between radially outward lying ends of the rotating blades and the casing ring can be adjusted. The flexible sidewalls of DE 29 22 835 C2 are curved several times. Accordingly, seen in the axial direction, the sidewalls of DE 29 22 835 C2 curve inward into the cavity for some segments and outward from the cavity for some segments. 
     SUMMARY 
     Starting from the previously discussed background, the problem of the present invention is to create a new kind of turbo engine with a pneumatic Active Clearance Control. 
     According to a first aspect of the invention, a turbo engine is provided, wherein, in the region of the bellows-like structure or each bellows-like structure, the wall connecting the casing ring to the support ring is curved only once inwardly into the respective cavity, looking in the axial direction. 
     According to a second aspect of the invention, a turbo engine is provided, wherein, in the region of the bellows-like structure or each bellows-like structure, the wall connecting the casing ring to the support ring is curved only once outwardly from the respective cavity, looking in the axial direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred modifications of the invention will emerge from the subclaims and the following description. Sample embodiments of the invention are explained more closely by means of the drawing, without being restricted to these. This shows: 
         FIG. 1 , a cross section through subassemblies at the stator side of a turbo engine according to the invention; 
         FIG. 2 , a schematic representation of a bellows-like structure of the turbine per  FIG. 1 ; 
         FIG. 3 , a schematic representation of an alternative bellows-like structure of a turbo engine; and 
         FIG. 4 , a cross section of a turbo engine in according with an alternative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a partial cross section through a stator of a compressor  10  of a turbo engine, wherein the stator comprises a housing  11  as well as several stationary guide blades  12 . The guide blades  12  on the stator side form so-called guide blade rings, which are arranged one behind the other looking in the axial direction.  FIG. 1  shows a total of four stationary guide blade rings  13 ,  14 ,  15  and  16  at the stator side. 
     Besides the stator, the compressor  10  contains a rotor  40  not shown in  FIG. 1 , the rotor being formed from several rotor disks, not shown, arranged one behind the other in axial direction  42 , each rotor disk carrying several rotating blades  44 , likewise not shown, alongside each other in the circumferential direction (see FIG  4 ). The rotating blades assigned to one rotor disk and arranged alongside each other in the circumferential direction form so-called rotating blade rings, while between every two neighboring guide blade rings  13  and  14 ,  14  and  15 , and  15  and  16 , there is arranged a respective rotating blade ring  46 , not shown. 
     Besides the stator, the compressor  10  contains a rotor  40  not shown in  FIG. 1 , the rotor being formed from several rotor disks, not shown, arranged one behind the other in axial direction  42 , each rotor disk carrying several rotating blades  44 , likewise not shown, alongside each other in the circumferential direction (see  FIG. 4 ). The rotating blades assigned to one rotor disk and arranged alongside each other in the circumferential direction form so-called rotating blade rings  46 , while between every two neighboring guide blade rings  13  and  14 ,  14  and  15 , and  15  and  16 , there is arranged a respective rotating blade ring  46  (see  FIG. 4 ). 
     The housing  11  of the stator of the compressor  10  comprises a radially inward lying housing wall, while the radially inward lying housing wall forms a so-called inner ring or casing ring in the region of each rotating blade ring  46  at the rotor side, not shown in  FIG. 1 , and encloses the respective rotating blade ring  46  radially on the outside. Besides the casing rings  17  of the radially inward lying housing wall, the housing  11  further comprises a radially outward lying housing wall  18 . 
     As already mentioned, the radially inward lying housing wall forms a so-called casing ring  17  in the region of each rotating blade ring at the rotor side (not shown), which encloses the rotating blade ring radially on the outside. Thus, between the radially outward lying ends of the rotating blades  44  of each rotating blade ring  46  and the respective casing ring  17  is formed a radial gap  48  ( FIG. 4 ), which is subject to considerable changes during the operation of the compressor, since on the one hand the rotating blades and the respective casing rings have different thermal behavior and on the other hand the rotating blades undergo a change in length  50  due to the centrifugal forces at work during operation. 
     It is quite difficult to maintain definite dimensions of the respective gap between the radially outward lying ends of the rotating blades of a rotating blade ring and the respective casing ring  17  during operation, yet it is of critical importance for optimized efficiency. 
     The present invention concerns only those details which can be used to exactly maintain radial gaps between radially outward lying ends of rotating blade rings and the respective casing ring  17 . 
     Per  FIG. 1 , the casing rings  17  which extend between the guide blade rings  13  and  14 , as well as  15  and  16 , are connected by curved and elastically flexible walls  19  to a support ring  20 , the respective support ring  20  being arranged between the respective casing ring  17  and the radially outward lying housing wall  18 . The respective casing ring  17 , the support ring  20 , and the curved walls  19  extending between the respective casing ring  17  and the respective support ring  20  form a bellows-like structure  21 , having a cavity  22 . The bellows-like structure  21  and thus the cavity  22  fully surrounds and thereby encloses the rotating blade ring, looking in the circumferential direction. 
     By changing a pressure prevailing in the respective cavity  22  of the bellows-like structure  21 , the gap  48  between the respective casing ring  17  and the radially outward lying end of the respective rotating blade ring  46  can be adjusted pneumatically. If the pressure is increased in the cavity  22  of the respective bellows-like structure  21 , the respective radially inward lying casing ring  17  can be forced radially inward and the respective radially outward lying support ring  20  radially outward. By reducing the pressure in the cavity  22  of the respective bellows-like structure  21 , an opposite deformation of the respective bellows-like structure  21  can be accomplished. 
     In the preferred embodiment of  FIG. 1 , the curved and elastically flexible walls  19  of the bellows-like structures  21  are curved only one time inward into the respective cavity  22 , looking in the axial direction. In the region of a vertex of the curve, wall segments of the respective wall  19  subtend a relatively obtuse angle α larger than 90 degrees. This is described hereafter in reference to  FIG. 2 , which shows a schematic representation of a bellows-like structure  21 . 
     Thus,  FIG. 2  shows that in the region of a vertex  29  of the curve, the wall segments of the respective wall  19  subtend an obtuse angle α. For such curved walls  19 , two effects are superimposed when the pressure increases in the respective cavity  22  of the respective bellows-like structure  21 . 
     First, due to the pressure rise in the cavity  22 , the respective casing ring  17  and the respective support ring  20  are forced apart, looking directly in the radial direction. Secondly, this radial forcing apart of the casing ring  17  and support ring  20  is supported or at least not hindered by a toggle-like effect of the curved walls  19 . The curved walls  19  are essentially subjected only to compressive forces. 
     According to  FIGS. 1 and 2 , the bellows-like structure  21  has a greater radial dimension than its axial dimension. Preferably, the walls  19  of the bellows-like structure  21  have a greater radial dimension than their axial dimension. 
     In the sample embodiment shown in  FIG. 1 , the curved walls  19  of each bellows-like structure  21  have a roughly constant wall thickness, looking in the radial direction. In contrast to this, it is also possible for the curved walls  19  to have a variable wall thickness, looking in the radial direction. 
     As can likewise be seen from  FIG. 1 , the radially inward lying casing ring  17  of each bellows-like structure  21  has a smaller wall thickness that the respective radially outward lying support ring  20 . The support ring  20  of each bellows-like structure  21  is accordingly designed with a greater wall thickness than the respective casing ring  17 . This ensures that deformations of the bellows-like structure  21  brought about by change of pressure prevailing in the particular cavity  22  act primarily on the casing ring  17 . 
     Moreover, one can infer from  FIG. 1  that the casing ring  17  of each bellows-like structure  21  has a radially outward curved contour  23 , protruding into the respective cavity  22 , in a middle region, looking in the axial direction. 
     Thanks to this, upon deformation of the casing ring  17  due to a pressure change in the cavity  22  of the respective bellows-like structure  21 , an outer contour  28  of the casing ring  17  is displaced essentially only parallel, looking in the radial direction, so that a gap between the casing ring  17  and the rotating blade ring can be adjusted exactly. 
     Each bellows-like structure  21  is coordinated with at least one pressurized air line  24 , in order to either bring pressurized air into the cavity  22  of the respective bellows-like structure  21  or drain pressurized air from it. For an easier representation,  FIG. 1  shows one such pressurized air line  24  only for the bellows-like structure  21  positioned between the two guide blade rings  13  and  14 , looking in the axial direction. Each bellows-like structure  21  is coordinated with at least one such pressurized air line  24 . The more such pressurized air lines  24  are present per bellows-like structure  21 , the quicker pressurized air can be taken to or drained from the respective cavity  24 . 
     In the sample embodiment of  FIG. 1 , one bellows-like structure  21  is arranged between the two guide blade rings  13  and  14 , and also between the two guide blade rings  15  and  16 , while no such bellows-like structure is present between the two guide blade rings  14  and  15 . Instead, according to  FIG. 1 , a sensor unit  25  is arranged between the two guide blade rings  14  and  15  and, thus, in the region of a rotating blade ring arranged between the former. 
     With the sensor unit  25 , one can measure at least the radial dimension of the gap  48  between the corresponding rotating blade ring  46  and the casing ring  17  surrounding this rotating blade ring. Via a signal line  26 , the sensor unit  25  transmits the corresponding actual value to a feedback control mechanism  52  ( FIG. 4 ) where the feedback control mechanism compares the actual value against a setpoint and, depending on this, adjusts the pressure prevailing in the cavities  22  of the bellows-like structures  21  so that the actual value comes near the setpoint. 
     It can be provided that the pressurized air feed to the cavities  22  and the pressurized air drain from the cavities  22  of the bellows-like structures  21  can be adjusted by individual valves, in order to individually adjust the pressure prevailing in the cavities  22  of the two bellows-like structures  21  and thus individually adjust the dimension of the radial gap between the casing ring  17  and the corresponding rotating blade ring as a function of the respective radial dimension of the rotating blade ring. 
     Alternatively, as best seen in  FIG. 4 , it can be provided to adjust the pressurized air feed  24  to the cavities  22  of the bellows-like structures  21  and the pressurized air drain from same by a common valve  54 . Different deformations of the bellows-like structures  21  required due to different radial dimensions  50  of the particular rotating blade ring  46  of the compressor  10  can then be achieved by an adapted curvature of the curved walls  19  and/or an adapted wall thickness of the curved walls  19  and/or by an adapted radial dimension of the bellows-like structures  21 . For example, in the embodiment shown in  FIG. 4 , the profiles of the first curved walls  19  disposed between guide rings  13  and  14  are adapted to produce a different deformation of the associated bellows-like structure  21  (denoted by deformed casing ring  17 ′, shown in broken line) than the profiles of the second curved walls  19  disposed between guide rings  15  and  16  produce in the associated bellows-like structure  21 . In particular, the curvature of the curved walls  19  of the bellows-like structure  21  disposed between guide rings  13  and  14  is different (i.e., greater than) than the curvature of the curved walls  19  of the bellows-like structure  21  disposed between guide rings  15  and  16 . Further, the wall thickness of the curved walls  19  of the bellows-like structure  21  disposed between guide rings  13  and  14  is different (i.e., less than) than the wall thickness of the curved walls  19  of the bellows-like structure  21  disposed between guide rings  15  and  16 . These differences between the profiles of the first curved walls  19  disposed between guide rings  13  and  14  and the profiles of the second curved walls  19  disposed between guide rings  15  and  16  result in different deformations of the respective bellows-like structures  21 . 
     According to  FIG. 1 , the two bellows-like structures  21  are divided in the axial direction by dividing planes extending in the radial direction, and the two axial halves of the bellows-like structures  21  are welded together during the fabrication process. Alternatively, it is also possible to divide the bellows-like structures  21  in the radial direction. 
     According to  FIGS. 1 and 2 , each wall  19  in the region of each bellows-like structure  21  is curved only once inward into the respective cavity  22 , looking in the axial direction. 
     In contrast with this, it is also possible, as diagrammed in  FIG. 3 , for each curved, elastically flexible wall  19  in the region of each bellows-like structure  30  to be curved only once outward from the respective cavity  22 , looking in the axial direction. Wall segments of the respective wall  19  in the region of a vertex  29  of the curvature subtend a relatively acute angle β smaller than 90 degrees. 
     According to  FIG. 3 , the wall segments of the wall  19  subtending the angle β extend basically in the axial direction. Like the casing ring  17  and the support ring  21 , they are exposed to the pressure prevailing in the cavity  22  and thereby support a radial moving apart of the casing ring  17  and support ring  20  when pressure increases in the cavity  22 . A negative toggle effect in this variant is also totally eliminated by the acute angle β. 
     The bellows-like structure  30  per  FIG. 3  has a larger axial dimension than its radial dimension; in particular, the walls  19  of the bellows-like structure  30  have a larger axial dimension than their radial dimension.

Technology Classification (CPC): 5