Abstract:
A rotor for a thermal turbomachine, in particular a gas turbine, is configured to conduct a medium in its interior. In order to conduct the medium in the interior with low flow losses, it is provided that a rotor disk of the compressor has holes, in order to feed the medium from outside into the rotor interior. For improved temperature control of the rotor disk, the holes conduct the medium through the rotor disk counter to the flow direction in the compressor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation and claims the benefit of pending U.S. application Ser. No. 14/904,542 filed Jan. 12, 2016, which is the US National Stage and claims the benefit of International Application No. PCT/EP2014/063561 filed Jun. 26, 2014. The International Application claims the benefit of European Application No. EP13176855 filed Jul. 17, 2013. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention relates to a rotor for a thermal turbomachine, which rotor is configured in the interior for conducting a medium. 
       BACKGROUND OF INVENTION 
       [0003]    Rotors for thermal turbomachines such as axial compressors and gas turbines are known in different designs from the comprehensively available prior art. For example, welded rotors are known for gas turbines, in the case of which welded rotors drums of different width are welded to one another to form a monolithic rotor. Secondly, it is known to stack a plurality of disk-shaped elements (also known as rotor disks) and to brace them with the aid of one or more tie rods to form a fixed structure. Even combinations of said designs are known. Rotor blades are mounted on the outside of all rotors, which rotor blades can be assigned in the case of gas turbines, for example, either to the compressor or to the turbine unit. Regardless of the design, a medium can be introduced into the interior of the rotors via holes which are arranged in the rotor shell, in order to conduct said medium from the feed position to a second axial position, where the medium is removed from the rotor again. This method is used, in particular, in gas turbines, in order to remove cooling air from the main flow path of the compressor of a gas turbine on the rotor side and to conduct it to the turbine unit, where, guided out of the rotor interior again, it can be used for cooling air purposes and/or sealing air purposes. 
         [0004]    In order to make an aerodynamically efficient removal of air from the compressor of a gas turbine and efficient conducting of the air in the rotor interior possible, different constructions are known. 
         [0005]    The aim here is first of all to guide the cooling air out of the flow path in the compressor to the rotor interior. To this end, removal holes are as a rule arranged in at least one rotor disk of the compressor, which removal holes in the simplest case run through the rotor disk radially perpendicularly with respect to the rotor axis. As an alternative to this, embodiments are known, for example from DE 198 52 604 A1, in which the removal hole is arranged in the rotor disk in an inclined manner with respect to the radial direction, the cooling air being removed from an upstream side upstream of the compressor blades which are arranged on the rotor disk and exiting out of the rotor disk in the interior of the rotor again on a downstream side close to the rotor axis. 
         [0006]    By means of the cooling air from the main flow path being conducted through the rotor disk, the temperature control of the rotor disk is improved and a thermal equilibrium is achieved more rapidly. 
         [0007]    Although the known cooling air routing through the rotor disk provides a suitable solution for cooling air routing and at the same time for the temperature control of the rotor disk, there is nevertheless the requirement to make the cooling air routing more effective on account of a general performance increase in gas turbines. 
       SUMMARY OF INVENTION 
       [0008]    An object of the invention is achieved by way of a rotor and by way of a rotor disk in accordance with the features of the claims. The rotor according to the invention comprises at least one rotor disk in accordance with certain claims. 
         [0009]    Advantageous refinements are specified in the dependent claims, the features of which can be combined with one another in accordance with the back-references. 
         [0010]    It is to be noted that the terms “axial” and “radial” and “outside” and “inside” always relate to the rotational axis of the rotor disk or the rotor. In addition, the rotor interior is to be understood as that cavity in the interior of the rotor which is delimited by the rotor disks. 
         [0011]    A rotor which is assembled from disks, regardless of whether the disks are later welded to one another or are braced with one another via one or more tie rods, comprises at least a first rotor disk which has a circumferential disk web and, at its radially outer end, a ring region for receiving rotor blades and, on both sides between the ring region and the disk web, an axially widened collar for bearing against adjacent disks. At its radially inner end in relation to the rotational axis, the disk web comprises a hub region with a central opening which is concentric with respect to the rotational axis. Furthermore, the rotor disk has holes, in order to transfer the medium from the outside into the rotor interior. 
         [0012]    According to the invention, the holes which extend through the disk web are inclined in such a way that, in the ring region, the holes open on a downstream side of the first rotor disk, in relation to the throughflow direction of the medium in the main flow path of the turbomachine. Therefore, the removal position for the medium to be extracted lies downstream of the rotor blades which are supported by the relevant rotor disk. In other words: the holes are inclined in a downstream manner in relation to their inner end. 
         [0013]    The inclined holes assist the homogeneous heating of the rotor disk, which reduces thermal stresses in the rotor disk. At the same time, the removal of a medium from the main flow of the turbomachine takes place at an axial position, in which the circumferential speed of the medium in the main flow path of the turbomachine corresponds substantially to the circumferential speed of the rotor. This facilitates the flow of the medium into the holes, which reduces aerodynamic losses. Therefore, positive inflow conditions for the medium which is to be removed from the main flow are thus provided. In an advantageous way, the first rotor disk has a multiplicity of ribs for forwarding the flow of the medium which can flow through the holes. On the inner side of the rotor, the holes open in a ring face of the rotor, which ring face is arranged obliquely with respect to the radial direction. The ribs end immediately adjacently with respect thereto radially on the inside. 
         [0014]    In an advantageous manner, a second rotor disk for the rotor according to the invention comprises a circulating disk web which, at its radially inner end in relation to the rotational axis, has a hub region with a central opening which is concentric with respect to the rotational axis and, at its radially outer end, has an axially widened ring region for bearing against the adjacent disks and for receiving rotor blades, the hub region being widened on both sides in the axial direction in comparison with a thickness of the disk web, with the result that an outwardly pointing freely ending annular auxiliary web is provided on at least one of the projecting lengths which are formed in this way, with the formation of an annular recess between the disk web and the auxiliary web. 
         [0015]    Here, the extent of the ribs, which can be detected in the radial direction, and that of the auxiliary web including the projecting length are adapted to one another in such a way that they are approximately identically great, that is to say the ribs and the auxiliary web or the projecting length advantageously end at the same radius on the outside and on the inside. 
         [0016]    In the case of the first rotor disk, the ribs can extend along the radial direction from the inside toward the outside. This leads to particularly effective deswirling of the medium which flows in from the outside, which reduces the flow losses. 
         [0017]    Further, at least one of the ribs, in particular all the ribs, has/have a freely ending extension at their radially outwardly pointing ends, as a result of which the spacing between the hole opening on the rotor inner side and the radially outer end of the respective rib can be reduced further. The reduction of said spacings leads to improved guidance of the medium which exits from the holes, which further reduces the flow losses. 
         [0018]    In the ring region on both disk sides, both rotor disks advantageously comprise a transversely projecting collar with a collar height which can be detected in the axial direction of the rotational axis, the collar height of which is slightly greater than the height, which can be detected in an analogous manner, of the relevant projecting length or the ribs. With the aid of the slightly greater collars, the rotor disks have a greater axial width on their radially outer regions than radially on the inside, which prevents the auxiliary web coming into contact with the ribs when both rotor disks bear against one another. Said contact might lead to mechanical wear which can be avoided thus, however. The heights and the axial widths of the rotor disks in the ring region are advantageously selected in such a way that the axial spacings between the ribs and the lateral surface of the auxiliary web which lies opposite are kept as small as possible, with consideration of the thermal expansions which occur during operation. 
         [0019]    The invention relates overall to a rotor for a thermal turbomachine, in particular a gas turbine, which rotor is configured to conduct a medium, for example compressor air, in its interior. In order to conduct said medium in the interior with low flow losses, it is provided that a pair of rotor disks is provided which bear against one another and of which the first of the two rotor disks of the pair has holes, in order to feed the medium from the outside into the rotor interior. In an advantageous manner, the first rotor disk has rib-shaped ribs, in order to guide the medium further in the direction of the rotational axis, and the second rotor disk being configured with the aid of an auxiliary web in such a way that the flow passages which are formed between the ribs as viewed in the circumferential direction are delimited axially at least over the large part of the radial extent of the ribs. 
         [0020]    Further advantages and features of the invention will be explained using a single exemplary embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In the drawing: 
           [0022]      FIG. 1  shows a longitudinal section through a rotor of a turbomachine and 
           [0023]      FIG. 2  shows a detail through the longitudinal section of a rotor according to the invention of a turbomachine with essentially two rotor disks. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0024]    Identical features are provided with the same designations in both figures. 
         [0025]      FIG. 1  shows the principal diagrammatic construction of a rotor  10  of a thermal turbomachine which, in the assembled state, is mounted such that it can be rotated about its rotational axis  13 . In the exemplary embodiment which is shown, this is the rotor  10  of a stationary gas turbine. The rotor  10  might also be used in an aircraft gas turbine. On account of the use in a gas turbine, the rotor  10  comprises a compressor section  12  and a turbine section  14 . A tube  16  is provided between the two sections  12 ,  14 . Both the compressor section  12  and the turbine section  14  are of disk-type design. In the exemplary embodiment which is shown, the compressor section  12  comprises sixteen rotor disks  18  and the turbine section  14  comprises four rotor disks  18 . A tie rod  20  extends through all rotor disks  18  and the tube  16 , onto the two ends of which tie rod  20  what is known as a front hollow shaft  22  and what is known as a rear hollow shaft  24  are screwed. The two hollow shafts  22 ,  24  brace all the rotor disks  18  and the tube  16  with one another, with the result that relative movements in the circumferential direction are avoided as far as possible. In detail, this is by way of Hirth toothing systems which are arranged on the contact faces  23 . They are not shown in further detail, however. 
         [0026]    The features according to the invention are not shown in  FIG. 1 . Reference is made in this regard to  FIG. 2  which shows a detail of two arbitrary rotor disks  18  of the compressor section  12  from  FIG. 1  which form a disk pair  25 , however, on an enlarged scale. 
         [0027]    In the operating state, air flows as a medium outside the rotor  10  in a main flow path (not shown in further detail) in the arrow direction  27 , which air is compressed during this by the compressor. 
         [0028]    Each rotor disk  18  has a disk web  26  which runs endlessly about the rotational axis  13 . At its radially inner end, the disk web  26  has a hub region  28  with a central opening  30  which is concentric with respect to the rotational axis and, at its radially outer end, a rim region  32 . The rim region serves to fasten rotor blades  31  ( FIG. 1 ) and comprises collars  33  which are arranged on both sides and on which the adjacent rotor disks  18  bear against one another. The rotor disk  18  which is shown on the right-hand side in the middle in  FIG. 2  is called the first rotor disk  34  in the following text. In addition, the first rotor disk  34  has holes which extend inward through the disk web  26  from the rim region and are distributed uniformly along the circumference of the disk web  26 . Merely one of the holes is shown and is labeled with the designation  36 . The holes  36  are inclined with respect to the radial direction in such a way that they penetrate the disk web  26  from one side to the other side. The holes  36  open with their radially inner end in a ring face  38  which ring face  38  is arranged obliquely with respect to the radial direction of the rotor disk  34 . A multiplicity of ribs  40  are provided in the hub region  28  immediately adjacently with respect to the ring face  38 . The ribs  40  extend from an outer to an inner end. In addition, the ribs  40  are distributed uniformly along the circumference. The ribs  40  can be welded to the hub region  28  of the first rotor disk  34  or can have been manufactured at the same time as the latter. In relation to the fastened section of the rib  40 , each has an extension at the outer end of the rib  40 , in order to keep the spacing at  41  of the ring face  38  and the openings of the holes  36  as small as possible. In terms of structural mechanics, the key is to avoid the ribs  40  also being fastened in a circumferential hollow channel  50 , but it is likewise necessary in terms of structural mechanics between the ring face  38  and the hub region  28 . 
         [0029]    The ribs  40  serve for flow guidance of the air which flows from the holes  36  and is to flow into the interior of the rotor  10 . That side of the first rotor disk  34 , on which the ribs  40  are provided, is adjoined by a second rotor disk  42  Like every customary rotor disk  18 , the second rotor disk  42  also has a hub region  28 , the axial extent of which is wider on account of two projecting lengths  44  than that of the associated disk web  26 . For reasons of symmetry, an outwardly pointing freely ending annular auxiliary web  46  is provided on both projecting lengths  44 , with the formation of an annular recess  48  between the disk web  26  and the auxiliary web  46 , although only that auxiliary web  46  would be necessary which lies directly opposite the ribs  40 . The auxiliary web  46  in conjunction with the projecting length  44  delimits, over the entire radial extent of the ribs  40 , the flow passages, in which the cooling air which exits from the holes  36  enters and is conducted as far as the tie rod  20 . This avoids swirling of the air at the inlet of each flow passage, which improves the efficiency of the air conducting. 
         [0030]    Since the central openings  30  of the rotor disks  18  are larger than the diameter of the tie rod  20 , annular spaces are formed between the respective hub regions  28  and the tie rod  20 , through which annular spaces the air which is conducted to the tie rod  20  can be conducted in the axial direction along the tie rod  20  from the compressor section  12  to the turbine section  14 . 
         [0031]    It goes without saying that the above-described disk pair  25  can also be used to conduct the air which is conducted along the tie rod  20  toward the outside, as is necessary in the case of rotor disks  18  in the turbine section  14 .