Patent Publication Number: US-9903205-B2

Title: Impeller for a rotor of a turbomachine, and rotor and turbomachine having an impeller of said type

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/EP2013/053738, filed on 25 Feb. 2013, which claims priority to the German Application No. 10 2012 203606.7, filed 7 Mar. 2012, the content of both incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an impeller for a rotor of a turbomachine, a rotor for a turbomachine equipped with such an impeller and a turbomachine having a rotor equipped with such an impeller. 
     2. Description of the Related Art 
     An impeller, a rotor and a turbomachine of the type mentioned at the outset are each known from DE 196 03 388 C1. In the case of the impeller described in this document, the moving blades are each fixed by a rivet both axially and also radially in their respective axial groove. During the mounting of the respective moving blade, such a rivet requires a widening of a closing head of the rivet and during the dismounting of the respective moving blade, working away (e.g., drilling away) of the closing head. These procedures are time-consuming and realize a defined radial clamping action of the moving blades in their respective axial grooves only conditionally during the mounting. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an impeller such that the moving blades of that impeller can be mounted and dismounted with reduced time expenditure and can be fixed in their respective axial grooves with defined radial clamping action. Other objects of the invention are to provide a rotor for a turbomachine equipped with such an impeller and a turbomachine having a rotor equipped with such an impeller. 
     The above mentioned objects are achieved with an impeller, a rotor and a turbomachine as described herein. 
     According to a first aspect of the invention an impeller is provided for a rotor of a turbomachine, the impeller comprising: a wheel disc, which is to be provided on a rotor shaft of the rotor and which has a plurality of grooves, which are arranged distributed along an outer circumference of the wheel disc and each of which extends in a thickness direction of the wheel disc running axially of the rotor shaft; wherein on two groove sides located opposite one another and running parallel to the thickness direction of each groove a tooth profile each is formed; a plurality of moving blades, of which each comprises a blade root with two blade root sides facing away from one another and running parallel to the thickness direction, on which a tooth profile each is formed; wherein each moving blade subject to forming a moving blade-groove combination is inserted with its blade root into a respective groove of the grooves, so that the tooth profiles of the blade root sides are in engagement with the tooth profiles of the groove sides; and wherein each moving blade-groove combination comprises a fixing device, which is equipped to fix the moving blade against movement in the groove both in thickness direction and also in a radial direction of the wheel disc. The impeller according to the invention is characterized in that each fixing device comprises a recess which is closed on both sides at least in thickness direction in a underside of the moving blade facing a base of the groove and a bar, which is moveably received in the base of the groove, so that the bar is adjustable in radial direction in a controlled manner between an unlocking position in which the bar does not engage in the recess of the moving blade, and a locking position, in which the bar radially engages in the recess of the moving blade, so that it presses the moving blade radially to the outside with a predetermined force. 
     Because the recess at least in thickness direction is closed on both sides with side walls, the bar in the locking position provides a stop in the thickness direction on both sides for the side walls of the recess so that the moving blade is fixed against movement in thickness direction. 
     Because the bar in the locking position presses the moving blade radially to the outside with a predetermined force, a play provided in the tooth profiles of the groove sides and the blade root sides for mounting and dismounting the moving blade in the groove is used up and the moving blade subject to being loaded with a predetermined preload force in radial direction (radially to the outside) is fixed against movement in this direction. Through the controlled adjusting of the bar, the predetermined force or the predetermined preload force (radial clamping action) radially to the outside can be predefined in a simple and repeatable manner. 
     Because the bar can be sunk into its unlocking position, in which it is out of engagement with the recess of the moving blade, the play in the tooth profiles of the groove sides and the blade root sides can be enabled again, so that the moving blade, both during its mounting and also during its dismounting from the wheel disc, can be slid easily and quickly axially into the groove or out of the groove. 
     According to an embodiment of the impeller according to the invention, the recess is in the form of a depression in the lower side of the moving blade enclosed on all sides by material of the moving blade, such that a radial outermost end of the bar provided for engagement in the recess is formed complementarily to the recess. 
     With this configuration of the impeller according to the invention, fixing of the moving blade in the groove against a possible movement in a circumferential direction of the wheel disc is advantageously realized in addition. 
     According to a further embodiment of the impeller according to the invention, the recess is formed as a negative to the outer contour of a spherical dome, with the radially outermost end of the bar having a shape corresponding to the outer contour of this spherical dome. 
     With this configuration of the impeller according to the invention, a self-centering of the bar in the recess, and thereby a more accurate fixing of the moving blade and an easier introducing of the bar in the recess, is advantageously realized. 
     According to yet another embodiment of the impeller according to the invention, each fixing device in the wheel disc has a first passage running in radial direction, which opens into the groove at a first longitudinal end of the passage and in which the bar is fitted preferably with a clearance fit. 
     The first passage provides a sliding guide for moving the bar in a simple and sturdy manner. Preferably, the first passage is embodied as a bore that is easily produced. 
     According to yet a further embodiment of the impeller according to the invention, each fixing device comprises an actuating device, which is arranged on a second longitudinal end of the first passage for the controlled adjusting of the bar, the actuating device being equipped so that it can be activated from a lateral side of the wheel disc facing in the thickness direction for adjusting the bar. 
     Because the adjusting device can be activated from the lateral side of the wheel disc, this activation position is easily accessible to a mounting or dismounting person, as a result of which the respective time expenditure can be further reduced and the embodiment accuracy further improved. 
     According to an embodiment of the impeller according to the invention, the actuating device comprises a second passage, which running in the thickness direction of the wheel disc is formed in the wheel disc with an internal thread, so that the first passage with its second longitudinal ends opens into the second passage and a first longitudinal end of the second passage opens into the lateral side of the wheel disc, and a screw element, which from the lateral side of the wheel disc is screwed into the second passage and which is in contact with a radial innermost end of the bar, so that a moving of the screw element in the thickness direction of the wheel disc brings about a moving of the bar in the radial direction. 
     Realizing the actuating device with the screw element screwed into the second passage, which is preferably formed as a bore that is easy to produce, is particularly simple and sturdy, so that production costs for the actuating device are relatively low and service life and reliability are long and high respectively. 
     According to a further embodiment of the impeller according to the invention, a longitudinal end of the screw element provided for the contact with the bar is formed having a first cone shape, the radially innermost end of the bar being formed with a second cone shape, so that between respective outer surfaces of the first and of the second cone shape a line contact is realized. 
     This configuration of the impeller according to the invention provides a wedge slider arrangement, which in a particularly simple and sturdy manner realizes a directional change of the actuating movement. 
     According to yet another embodiment of the impeller according to the invention, the first cone shape has a cone angle of approximately 20 degrees. 
     This size of the cone angle provides a particularly advantageous compromise between self-locking, actuating force and actuating travel of the actuating device. 
     Provided according to a second aspect of the invention is a rotor for a turbomachine, wherein the rotor comprises at least one impeller according to any one, multiple or all of the embodiments of the invention described above in any conceivable combination. 
     Provided according to a third aspect of the invention is a turbomachine with a rotor, comprising at least one impeller according to any one, multiple or all of the embodiments of the invention described above in any conceivable combination. 
     The invention expressly extends also to such embodiments as are not defined by feature combinations from explicit references to the claims, as a result of which the disclosed features of the invention—insofar as this is technically practical, can be combined with one another as required. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention is explained in more detail with the help of a preferred embodiment and making reference to the attached figures. 
         FIG. 1  shows a sectioned part view of an impeller of a rotor of a turbomachine according to an embodiment of the invention, viewed in an axial direction of the rotor; and 
         FIG. 2  shows a view of the impeller from  FIG. 1 , viewed as a section along a section line A-A in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  and  FIG. 2  show sectioned part views of an impeller  20  of a rotor  10  of a turbomachine  1  according to an embodiment of the invention. 
     The rotor  10  comprises a rotor shaft (not designated), on which multiple impellers  20  as shown in  FIG. 1  and  FIG. 2  are arranged one behind the other in an axial direction AR of the rotor shaft. The turbomachine  1  comprising the rotor  10  is preferably designed as a turbine, such as for example a steamed turbine or as a turbo compressor. In addition to this, the turbomachine  1  is preferably designed as an axial flow machine. 
     As is shown in  FIG. 1  and  FIG. 2 , each impeller  20  comprises a wheel disc  30 , a plurality of moving blades  40  (only one shown) and a plurality of fixing devices  50  (only one shown). 
     The wheel disc  30  is arranged either integrally therewith or as a separate part on the rotor shaft of the rotor  10  in a rotationally fixed manner and comprises a plurality of grooves (only one shown), which are arranged evenly distributed along an outer circumference  31  of the wheel disc  30  and which extend each in a thickness direction (which corresponds to the axial direction AR) of the wheel disc  30  running axially of the rotor shaft. 
     A tooth profile  33  is formed on each of the two groove sides of each groove  32 , running parallel to the thickness direction or axial direction AR and located opposite one another. 
     Each moving blade  40  has a blade root  41  with two blade root sides facing away from one another and running parallel to the thickness direction or the axial direction AR, on each of which a tooth profile  43  is formed. 
     Each moving blade  40  is inserted with its blade root  41  into a respective one of the grooves  32  so as to form a moving blade-groove combination, so that the tooth profiles  43  of the blade root sides are in engagement with the tooth profiles  33  of the groove sides. In this way, the moving blades  40  are held on the wheel disc  30  in a radial direction RR of the wheel disc  30  or of the rotor shaft in a failsafe manner. 
     As is evident from  FIG. 1 , the tooth profiles  33 ,  43  of the groove sides and of the blade root sides, respectively, are preferably formed as multiple tooth profiles. Even more preferably, the blade roots  41  of the respective moving blades  40  are each designed as a blade root  41 , also known in the art as a Christmas tree root. Accordingly, the grooves  32  of the wheel disc  30  are more preferably designed in their form as an envelope contour or negative to the form of a Christmas tree root. 
     Each combination of groove  32  and moving blade  40  fitted therein includes one of the fixing devices  50 . Each fixing device  50  is configured to fix the associated moving blade  40  against movement in the associated groove  32  both in thickness direction or axial direction AR as well as in radial direction RR of the wheel disc  30 . 
     For this purpose, each fixing device  50  comprises a recess  51 , which is closed on both sides at least in thickness direction or axial direction AR in a underside  44  of the moving blade  40  facing a base  32   a  of the groove  32 , and a bar  52 , which is preferably designed in the form of a circle-cylindrical pin, which is moveably or shiftably received in the base  32   a  of the groove  32 . 
     Each fixing device  50  additionally includes a first passage  53  running in the wheel disc  30  in the radial direction RR, which at a first longitudinal end  53   a  of the same opens into the groove  32  on the base  32   a  and in which the bar  52  is fitted with a clearance fit. 
     Each fixing device  50  additionally includes an actuating device  60 , which is arranged at a second longitudinal end  53   b  of the first passage  53  for the controlled adjusting of the bar  52 . The actuating device  60  is equipped so that it can be activated for adjusting the bar  52  from a lateral side  30   a  of the wheel disc  30  facing in the thickness direction or the axial direction AR. 
     In the illustrated embodiment, the actuating device  60  includes a second passage  61 , which, running in the thickness direction or the axial direction AR of the wheel disc  30 , is formed in the same with an internal thread (not designated) so that the first passage  53  with its second longitudinal end  53   b  opens into the second passage  61  and a first longitudinal end  61   a  of the second passage  61  opens into the lateral side  30   a  of the wheel disc  30 . 
     In the illustrated embodiment, the actuating device  60  additionally including a screw element  62  configured in the form of a grub screw with internal hexagon (not designated), which from the lateral side  30   a  of the wheel disc  30  is screwed into the second passage  61  and which is in a sliding contact with a radially innermost end of the bar  52   b , so that moving of the screw element  62  in the thickness direction or the axial direction AR of the wheel disc  30  causes moving of the bar  52  in the radial direction RR. 
     Expressed more precisely, a longitudinal end  62   a  of the screw element  62  provided for the contact with the bar  52  is configured with a first cone shape, wherein the radially innermost end  52   b  of the bar  52  is configured with a second cone shape, so that between respective outer surfaces of the first and of the second cone shape a line contact is realized. Preferably, the first cone shape has a cone angle α of approximately 20 degrees. Accordingly, the second cone shape preferably has a cone angle (not designated) of approximately 70 degrees. 
     Through the construction described above, the bar  52  is adjustable in the radial direction RR in a controlled manner between an unlocking position (not shown in the  FIGS. 1 and 2 ) in which the bar  52  does not engage in the recess  51  of the moving blade  40 , and a locking position (as shown in the  FIGS. 1 and 2 ), in which the bar  52  radially engages in the recess  51  of the moving blade  40 , so that it presses the moving blade  40  radially to the outside with a predetermined force. 
     Because the recess  51  is closed at least in the thickness direction or the axial direction AR on both sides with side walls, the bar  52  forms a stop on both sides in the thickness direction or the axial direction AR in the locking position for the side walls of the recess  51 , so that the moving blade  40  is fixed against movement in the thickness direction or the axial direction AR. 
     Because the bar  52  in the locking position presses the moving blade  40  radially to the outside with a predetermined force, a play, which is provided in the tooth profiles  33 ,  43  of the groove sides and the blade root sides for the mounting and dismounting of the moving blade  40  in the groove  32 , is used up and the moving blade thus fixed is subject to preloading with a predetermined preload force in radial direction RR (radially to the outside) against movement in this direction. 
     Through the described configuration of the actuating device  60 , the predetermined force or the predetermined preload force (radial clamping action) radially to the outside can be predefined in a simple and repeatable manner, for example by a torque wrench for actuating the screw element  62 . 
     Because bar  52  can be sunk into its unlocking position, in which it is out of engagement with the recess  51  of the moving blade  40 , the play in the tooth profiles  33 ,  43  of the groove sides and of the blade root sides can be enabled again, so that the moving blade  40 , both during its mounting and also during its dismounting from the wheel disc  30 , can be slid easily and quickly axially into the groove  32  and out of the groove  32 . 
     As is evident from viewing  FIGS. 1 and 2  together, the recess  51  is preferably formed in the underside  44  of the moving blade  40  in the form of a depression that is enclosed on all sides by material of the moving blade  40  or of side walls, wherein a radially outermost end  52   a  of the bar  52  provided for the engagement in the recess  51  is designed complementarily in its shape to the shape of the recess  51 . In the illustrated embodiment of the invention, the recess  51  is formed as an enveloping contour or negative to the outer contour of a spherical coupling (spherical segment or spherical portion), wherein the radially outermost end  52   a  of the bar  52  has a shape corresponding to the outer contour of this spherical dome. In other words, the recess  51  is configured as a spherical seat for the approximately semi-spherical radial outermost end  52   a  of the bar  52 . 
     In conclusion, the impeller  20  according to the invention is configured so that its moving blades  40  can be mounted and dismounted with less time expenditure and can be fixed in their respective axially running grooves  32  with a defined radial clamping action. 
     Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.