Abstract:
An arrangement is disclosed for the admission of cooling air to the internal walls of a component rotating about a rotation axis, such as a moving blade in a rotary machine. A component root can be fastened to a rotor unit in a rotationally fixed manner and adjoining in a radially extending manner is a one piece component airfoil in which at least one radially extending cooling passage region (K 1 ) is provided which, in the region of the component root, opens out via an opening into a cooling-air supply passage passing at least partly through the component root longitudinally relative to the rotation axis. A distribution plate forms a fluid-tight connection with an opening margin, surrounding the opening of the cooling passage region (K 1 ), at least during the rotation of the component about the rotation axis. The distribution plate provides at least one through-opening in the region of the opening of the at least one cooling passage region (K 1 ), through which through-opening cooling air passes from the axial cooling-air supply passage into the radial cooling passage region (K 1 ).

Description:
RELATED APPLICATION 
   This application is based on and claims priority under 35 U.S.C. §119 to German Application No. 10 2004 015 609.3, filed Mar. 30, 2004 and is a continuation application under 35 U.S.C. §120 of International Application No. PCT/EP2005/051411, filed Mar. 29, 2005 designating the U.S., the entire contents of both of which are hereby incorporated by reference. 

   BACKGROUND 
   Rotary machines, for example turbo or compressor stages of gas or steam turbine plants, for the specific expansion or compression of gases or gas mixtures, generally have fixed guide blades and moving blades rotating about a rotation axis. The blades can be exposed to high process temperatures and therefore may have to withstand high thermal loads. In addition to the thermal load, the moving blades in particular, rotating about the rotation axis, may additionally be subjected to high mechanical loads caused by the centrifugal forces. 
   In the attempt to improve the efficiency of such heat engines, measures can be taken which result in the rotating components being subjected to ever increasing thermal and mechanical loads on account of increasing process temperatures and increased rotary speeds. However, these attempts can be subject to physical load limits on account of the materials used, from which in particular the rotating plant components can be produced. To optimize the efficiency even further, ways of effectively cooling the plant components exposed to heat and subjected to centrifugal force are looked for. To this end, a number of proposals with which cooling air is admitted to moving blades in rotary machines are already known. Typically, a moving blade of such a design, in order to fasten it to the rotor, has a moving blade root which is structured like a fir tree stem, and the moving blade airfoil radially adjoins this moving blade root. For cooling purposes, a multiplicity of radially oriented cooling passages can pass through the moving blade root, these cooling passages, for the effective cooling of the moving blade, extending along the inner walls through the entire moving blade airfoil. Cooling-air feed passages provided on the rotor serve to feed cooling air, which is fed into the cooling passages passing radially through the moving blade root. Such a cooling-air supply system therefore includes a rotor which has a multiplicity of radially oriented cooling-air passages and whose individual cooling passages, by appropriate positioning of the individual moving blades, can be brought exactly into alignment with the radial cooling passages provided in the moving blade root. Even the slightest maladjustments between moving blade root and rotor unit may permanently impair effective cooling of the moving blade, thereby considerably reducing the service life of the moving blade. 
   As an alternative to radially supplying a moving blade with cooling air via a rotor-side cooling-air supply system, it has been proposed to effect the cooling-air supply via a cooling-air supply passage passed axially through the moving blade root. In this case, the cooling-air feed flow passes into the axially oriented cooling-air supply passage inside the moving blade root, branching off from which are individual cooling-air passages projecting radially into the moving blade root. Since moving blades are generally produced by a casting process, the “core technique” is used for forming such cavities inside a cast part, this core technique in particular enabling the cooling-air supply passage passing axially through the moving blade root and the individual cooling passages passing radially at least partly through the inside of the moving blade airfoil to be produced. However, it has been found that flow baffles have to be provided inside the axially oriented cooling-air supply passage for optimized distribution of the cooling-air feed flow, these flow baffles being intended to deflect the axially directed cooling-air feed flow into the radially extending cooling passages inside the moving blade root. However, for production reasons, the flow baffles which are to be provided for this purpose and which both change the direction of and distribute the cooling-air feed flow axially directed into the blade root can be subject to production-related structural shape tolerances, which reduce the accuracy with which the cooling-air flow can be directed and distributed to the individual cooling passages extending radially along the moving blade airfoil. 
   SUMMARY 
   Exemplary embodiments disclosed herein optimize the cooling-air distribution to the individual radially oriented cooling passages inside a moving blade. The measures to be taken for this purpose can avoid costly production or assembly steps and can have robust properties which are able to cope with the high demands with regard to thermal and also mechanical loads within such components rotating about a rotation axis. 
   An arrangement is disclosed for the admission of cooling air to the internal walls of a component rotating about a rotation axis, in particular a moving blade in a rotary machine, such as a gas turbine plant for example, having a component root which can be fastened to a rotor unit in a rotationally fixed manner and adjoining which in one piece in a radially extending manner is a component airfoil in which at least one radially extending cooling passage region is provided which, in the region of the component root, opens out via a respective opening into a cooling-air supply passage passing at least partly through the component root longitudinally relative to the rotation axis, is developed in such a way that a distribution plate is provided in the region of the cooling-air supply passage in such a way that the distribution plate forms a fluid-tight connection with an opening margin, surrounding the opening of the cooling passage region, at least during the rotation of the component about the rotation axis. Furthermore, the distribution plate provides at least one through-opening in the region of the opening of the at least one cooling passage region, through which through-opening cooling air passes from the axial cooling-air supply passage into the radial cooling passage region. 
   In order to depict and describe exemplary embodiments in a simpler manner, the further explanations relate to the case of a moving blade which is fitted along a rotor unit of a gas or steam turbine plant and can be inserted into a turbo stage or compressor stage. Of course, this reference is not to restrict the general ideas described herein, which also relate to alternative plant components which are subjected to comparable loads. 
   The distribution plate, which can be produced from a temperature-resistant flat material, provides through-openings along its extent in each case in such a way as to correspond to the radially extending cooling passage regions, the through-openings each having opening diameters which can predetermine the volumetric flow of cooling air which passes into the individual cooling passage regions. The distribution plate therefore enables volumetric proportions of cooling air, which are calculated beforehand and are adapted to the respective rotating moving blade, to be distributed to the individual radially extending cooling passage regions. On account of the production tolerances unavoidably associated with the casting process, such an exact distribution of the cooling-air flow is not possible solely by using flow baffles produced by casting. 
   In order to keep the assembly cost for incorporating the distribution plate along the cooling supply passage extending axially through the component root as low as possible, and in order to exactly position the distribution plate relative to the at least one radially extending cooling passage region, at least two axially spaced-apart shoulder elements are provided inside the cooling-air supply passage, and these shoulder elements are located radially opposite the opening margin of the opening of the at least one cooling passage region and at a slight distance from this opening margin and define together with the latter a push-in slot, in which the distribution plate preferably fits snugly in a flush manner by being pushed axially into the cooling-air supply passage. At this point, it may be noted that a plurality of cooling passage regions passing radially through the moving blade root can be provided, these cooling passage regions being arranged in such a way as to be separated from one another by intermediate walls. Via a respective opening margin which is oriented so as to face the cooling-air supply passage extending in the moving blade root and encloses the opening of the respective radially extending cooling passage region, the intermediate walls open out in the region of said cooling-air supply passage. According to an exemplary embodiment, with this opening margin, a fluid-tight connection can be provided relative to the distribution plate, at least in the rotation state, in order to completely rule out possible leakage flows between distribution plate and opening margin. 
   To this end, the distribution plate can advantageously rest loosely between the shoulder elements and the at least one opening margin, so that the distribution plate is pressed radially outward against the opening margin by the centrifugal forces produced by the rotation and forms the desired fluid-tight connection with said opening margin, as a result of which any axially directed leakage flows between distribution plate and the opening margin are effectively prevented. 
   Due to the fluid-tight connection, produced automatically by the rotation, between the distribution plate and the opening margin of the opening of the at least one radially extending cooling passage region, it is not necessary to provide tolerance-free gap sizes for the push-in slot which is defined between the shoulder elements and the at least one opening margin, a requirement which cannot be met anyway by conventional casting processes. 
   In order to provide for ensuring a fluid-tight connection between the distribution plate and the corresponding opening margins, at least during rotation, the distribution plate can be produced from such a material and with such a material thickness that the bending moment of the distribution plate is exceeded due to the centrifugal forces produced by the rotation and acting on the distribution plate, and the distribution plate is able to correctly conform to the casting geometry of the opening margins. In addition, in a further exemplary embodiment, this conformity action is assisted by the distribution plate having locally limited material weak points, for example in the form of mechanical notches or cracks. Such material weak points can also be produced by specifically changing the structure in the distribution plate. Such points of reduced strength are arranged in a distributed manner along the distribution plate, for example, in regions close to the opening margins where it may be desired to produce a fluid-tight connection. 
   It may also be advantageous in some cases to fixedly join the distribution plate to the inner structure of the moving blade root in the region of the cooling-air supply passage at least at the ends—at one end or at both ends—by a brazed or welded joint. The joint locations required for this are easily accessible axially through the cooling-air supply passage for assembly purposes, so that the assembly cost necessary for this is not substantially increased. 
   Since the cooling-air supply extending axially completely through the moving blade root is designed to be open on both sides with regard to the moving blade root, as will be explained in more detail below with reference to an exemplary embodiment, it is necessary to close the axial opening in a fluid-tight manner. 
   A very simple embodiment provides for an end closure of the cooling-air supply passage to be created by appropriately bending over an end region of the distribution plate, and to weld or braze the distribution plate to the inner wall of the cooling-air supply passage at least in the region of its plate section bent over at the end. However, fixing in this respect could have an adverse effect on the required fluid-tight connection, produced at least in the rotation state, between the distribution plate and the at least one opening margin, so that a further preferred embodiment, instead of fixedly joining the distribution plate in the region of the bent-over distribution plate section, provides a separate closing plate which axially closes off the cooling-air supply passage in a fluid-tight manner on one side. It is suitable for this purpose for the closing plate, adapted to the cross-sectional contour of the cooling-air supply passage, to be joined to the moving blade root in a fluid-tight manner via brazed or welded joints. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments are explained below, without restricting the general idea, with reference to the drawings, in which: 
       FIG. 1  shows a cross section through an exemplary moving blade of a gas turbine plant, 
       FIG. 2  shows a detailed cross-sectional illustration through the root region of an exemplary moving blade, 
       FIG. 3  shows a detailed illustration of an exemplary closing plate which axially closes off the cooling-air supply passage in a gas-tight manner, 
       FIGS. 4   a - d  show views of exemplary distribution plates of alternative design, and 
       FIG. 5  shows an alternative exemplary distribution plate inside a moving blade root. 
   

   DETAILED DESCRIPTION 
   Shown in  FIG. 1  is the cross section through an exemplary moving blade  1 , which is rotatable about a rotation axis  2  of a rotor unit integrated in a gas turbine arrangement. The moving blade  1  has a moving blade root  3 , which can be frictionally connected to the rotor unit (not shown in any more detail) via an appropriately designed joining contour (fir-tree structure—not shown). Radially adjoining the moving blade root  3  is the moving blade airfoil  4 , in the interior of which cooling passage regions K 1  to K 4  are provided. Extending in the region of the moving blade root  3  is a cooling-air supply passage  5  which is oriented axially, i.e. parallel to the rotation axis  2 , and passes first of all through the entire axial width of the blade root  3 . Provided in the interior of the cooling-air supply passage  5  are “shoulder elements”  6  which, by the casting process with which the entire moving blade  1  can be produced, are fashioned from the casting material from which the rest of the moving blade is made. The shoulder elements  6  have top surface sections  61 , which are radially opposite and at a slight distance from “opening margins”  71 . The opening margins  71  surround openings  7  facing the cooling-air supply passage  5 , and radially adjoining these openings  7  are the cooling passage regions K 1  and K 2 , which are each defined by cooling passage wall regions  72 . Like the cooling-air supply passage  5 , the cooling passage regions K 1  to K 4  provided in the interior of the moving blade airfoil can also be produced by the casting process by providing a suitably modeled displacement core, which serves as a spacer for the respective cavities and is inserted in the casting mold during the casting process. 
   A distribution plate  8  in which appropriately positioned and dimensioned through-openings  81  are incorporated is provided in order to direct, but in particular in order to proportion, the cooling-air flow passing through the cooling passage regions K 1 , K 2 , K 3  and K 4 . The through-openings  81  are correspondingly provided in the orifice region of the openings  7 . 
   In the exemplary embodiment shown according to  FIG. 1 , the cooling-air feed flow is supplied axially via the cooling-air supply passage  5  to be fed specifically into the cooling passage regions K 1  and K 2 . The through-openings  81  provided in the orifice region of the cooling passage region K 1  permit a cooling-air flow radially through the cooling passage K 1 , which provides an outlet opening A at the top flank of the moving blade airfoil  4 , through which outlet opening A the cooling air escapes into the hot-gas passage H. In contrast, the cooling air entering the cooling passage region K 2  via the through-openings  81  is for the most part diverted by appropriate flow baffles  9  into the cooling passage region K 3 , adjoining which in the direction of flow (see flow arrows) is the cooling passage region K 4 . In the connecting region between the cooling passage regions K 3  and K 4 , the distribution plate  8  provides for the cooling-air flow flowing downward in the cooling passage region K 3  to be deflected entirely into the cooling passage region K 4  extending radially upward. For this purpose, the distribution plate  8  conforms to the corresponding opening margins  71  and the marginal contour  10  in a gas- or fluid-tight manner. At the same time, no leakage flows occur between the distribution plate  8  and the opening margins  71 . In order to ensure this, dimensions of the distribution plate  8  and its material are selected in such a way that it is pressed firmly against the corresponding opening margins  71  and the marginal contour  10  in a fluid-tight and flush manner by the centrifugal forces caused by the rotation about the rotation axis  2 . In this case, the distribution plate  8  lies loosely in the inlet slot  11  defined between the surface sections  61  of the shoulder elements  6  and the opening margins  71  and the marginal contour  10  (see  FIG. 2 ). 
   A closing plate  12  which is fixedly joined to the moving blade root  3  by a welded or brazed joint provides for an axial, gas-tight closure of the cooling-air supply passage  5  on one side. 
     FIG. 2  shows a detailed illustration of the exemplary distribution plate  8  inserted into the axially extending cooling-air supply passage  5 . As already mentioned, the shoulder elements  6  present in the interior of the cooling-air supply passage  5  and also the individual cooling passage regions K 1  to K 4 , i.e. the cooling passage wall regions  72  with the corresponding opening margins  71 , are jointly produced by the casting process. The opening margins  71  enclose with the surface sections  61  of the shoulder elements  6  a push-in slot  11 , along which the distribution plate  8 , which is formed with a plane surface in the initial state, can be pushed in axially. After the distribution plate  8  in the form shown in  figure 2  has been pushed into position inside the cooling-air supply passage  5 , the end regions of the distribution plate  8  are bent over in the manner indicated in  figure 2  in order to largely fix the distribution plate  8  axially and radially inside the push-in slot  11 . Otherwise, the distribution plate  8  still rests loosely on the surface sections  61  of the shoulder elements  6 . In order to axially close off the cooling-air supply passage  5  on one side in a fluid-tight manner, a closing plate  12  is inserted into the cooling-air supply passage  5  at the left-hand inlet opening in  figure 2  and is welded or brazed to the moving blade root  3  in marginal regions. Due to the gas-tight closure of the cooling-air supply passage  5  on one side, the cooling-air feed flow S entering the cooling-air supply passage  5  from the right-hand side is subjected to a baffle effect forming inside the cooling-air supply passage  5 , as a result of which the cooling-air feed flow S is driven through the through-openings  81  provided in the distribution plate  8 . The size and arrangement of the individual through-openings  81  define the volumetric flow of the cooling-air flow entering the respective cooling passage regions K 1  and K 2 . Due to the intimate fluid-tight connection, forming during the rotation, between the distribution plate  8  and the opening margins  71  which surround the respective openings  7  of the cooling passage regions K 1  and K 2 , any leakage flows which could form between the distribution plate  8  and the opening margins  71  can be prevented. This ensures that the cooling-air flow is directed free of losses solely along the cooling passage regions K 1  to K 4  provided in the interior of the moving blade airfoil. 
     FIG. 3  shows a further detailed illustration of the exemplary closing plate  12  welded to the axial end region of the cooling-air supply passage  5  in a fluid-tight manner. The closing plate  12  sits in a recess  13  of corresponding matching contour inside the moving blade root  3  and is welded to the latter in a fluid-tight manner. It can also be seen from  FIG. 3  that the distribution plate  8  rests loosely on the shoulder element  6  inside the push-in slot  11 . It is only by means of the rotation and the resulting centrifugal forces that the distribution plate  8  is lifted radially and thus comes into contact with the marginal contour  10 , with which it forms a correspondingly fluid-tight connection. This avoids a situation where cooling air can pass back into the cooling-air supply passage  5  from the cooling passage region K 4  at this point. 
     FIGS. 4   a - d  show two different respective embodiments for a distribution plate  8 .  FIGS. 4   a  and  b  show a plan view and side view of a first distribution plate  8 , the geometrical dimensions of which are adapted to the push-in slot  11  described above. The distribution plate  8  is produced from a heat-resistant flat material and, for fitting purposes, is first of all of plane design on one side (see  FIG. 4   a ). Furthermore, the distribution plate  8  has through-openings  81 , the arrangement, shape and size of which determines the cooling-air volume which is delivered through the cooling passage regions K 1  to K 4 . 
   For fitting purposes, the distribution plate  8  of plane design on one side can be pushed in axially between the opening margins  71  and the surface sections  61  of the shoulder elements  6  and can be appropriately bent over in the manner described above at an end section  82  or  83  after it has been completely inserted into the cooling-air supply passage  5 . In this respect, see the side view in  FIG. 4   b . As already mentioned at the beginning, the dimensions of the distribution plate  8  and the material are selected in such a way that at least local deflections can occur on the distribution plate  8  in the region of the opening margins  71 , so that the distribution plate  8  can form a fluid-tight connection with the opening margins  71 . In order to improve the bendability of the distribution plate  8 , in particular in regions which are opposite the opening margins  71 , local material weak points in the form of notches  14  are provided along the distribution plate  8  according to the exemplary embodiment in  FIGS. 4   c  and  d . Due to the deliberate provision of the locally limited notches  14 , the bending stiffness of the distribution plate  8  can be reduced at least locally, in order to optimize local conformity of the distribution plate  8  to the opening margins  71 . Likewise, the exemplary embodiment in  FIGS. 4   c  and  4   d  provides through-openings  81  of different dimensions in each case for the cooling-air feed into the cooling passage sections K 1  and K 2 . Thus substantially less cooling air is admitted to the cooling passage region K 1  than to the cooling passage region K 2 . 
   The measures described above serve the loose mounting of the distribution plate  8  inside the cooling-air supply passage  5 , the distribution plate  8  being spatially fixed merely inside the push-in slot  11  on the one hand by the shoulder elements  6  and on the other hand by the opening margins  71  or respectively the marginal contour  10 . In this way, welding operations which are complicated in terms of assembly can be completely avoided, but may be locally provided if required. 
     FIG. 5  shows a partial cross section through the root region  3  of a moving blade  1  which is designed in accordance with the above explanations. Provided along the cooling-air supply passage  5  is a single cooling passage region K 1 , into which cooling air is to be specifically branched off from the cooling-air supply passage  5 . This is effected via appropriately provided through-openings in the axially inserted distribution plate  8 , which has notches  14 , improving the bendability, at suitable points along the distribution plate  8 . 
   It will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein. 
   LIST OF DESIGNATIONS 
   
       
         1  Moving blade 
         2  Rotation axis 
         3  Moving blade root 
         4  Blade airfoil 
         5  Cooling-air supply passage 
         6  Shoulder elements 
         61  Surface section 
         7  Opening 
         71  Opening margin 
         72  Cooling passage intermediate wall 
         8  Distribution plate 
         81  Through-opening 
         82 ,  83  End sections 
         9  Deflection elements 
         10  Marginal contour 
         11  Push-in slot 
         12  Closing plate 
         13  Recess 
         14  Notches