Abstract:
A thermally loaded component has at least one cooling passage for the flow of a cooling fluid passing through it. In the region of a bend, at least one diverter device for the integral capturing of the flow of the cooling fluid is provided within the cooling passage. The diverter device comprises, over the height of the cooling passage, two diverter parts which are spaced apart from one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of the U.S. National Stage designation of co-pending International Patent Application PCT/CH02/00661 filed Dec. 4, 2002, the entire content of which is expressly incorporated herein by reference thereto.  
       FIELD OF THE INVENTION  
       [0002]     The invention is related to a thermally loaded component.  
       BACKGROUND OF THE INVENTION  
       [0003]     An increase in the efficiency of a thermal power machine, e.g. a gas turbine, is directly dependent on an increase in the working temperature of the thermally loaded components and therefore, in the case of a gas turbine, on the combustion gas temperature of the combustion chamber and the turbine which follows it. Despite improvements in materials which are able to withstand high temperatures, cooling technology also needs to be improved in order to keep the materials temperature within a safe range when thermally loaded components of this type are in operation. Cooling passages are used for this purpose and have to be fed with cooling fluid, for example from the compressor. It is attempted in this context to achieve the maximum possible cooling effect combined with the minimum possible losses in power of the overall system. For this purpose, specific improved heat-transfer techniques, such as for example fins in the cooling passages, are used.  
         [0004]     GB 2 165 315 has disclosed blades or vanes in which cooling fluid is passed from the trailing-edge region of the blade or vane to the leading-edge region via cooling passages formed by partition walls and is then blown out via openings in the head of the blade or vane. To sufficiently cool the trailing-edge region of the blade or vane, air is blown out of the trailing edge of the blade or vane. Diverter blades are provided in order to divert the cooling fluid into the cooling passages.  
         [0005]     In general terms, cooling passages which in many instances run substantially parallel and which are connected via diverter passages are used in thermally loaded components, e.g. blades or vanes of turbines. These diverter passages are configured in such a way that the pressure loss involved in the diversion is minimal and the heat transfer is as homogeneous as possible, in order to avoid local hot zones. To achieve this, in many cases diverter blades are arranged in the region of the diverter passages. However, these diverter blades are very fragile and are difficult to produce by casting, even in the case of large components, such as for example large blades or vanes of stationary gas turbines. By way of example, during cooling of the casting following the casting operation, stresses may form in the casting, since the inner parts, which are of relatively small dimensions, and the outer parts have different cooling rates. In some cases, these stresses may cause cracks to occur in the inner structures, with the result that the casting cannot be used. If the defects are not noticed, the casting may break in use and may then, for example in the case of blades or vanes, cause damage to further blades or vanes and the turbine.  
         [0006]     Cooling of turbine blades is known for example from U.S. Pat. No. 3,171,631 or from U.S. Pat. No. 5,232,343.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention is related to a thermally loaded component with at least one cooling passage of the type described in the introduction, and avoiding problems with previously known means for diverting the cooling fluid yet at the same time allowing efficient cooling to be achieved.  
         [0008]     The invention is therefore related to a diverter device that comprises two diverter parts that are spaced apart from one another over the height of the cooling passage.  
         [0009]     Advantageously, the configuration of the diverter device according to the invention means that the functioning of the diverter device is not impaired compared to previously known diverter blades. The primary function of the diverter device, that of preventing pressure losses and avoiding separation of the cooling fluid stream downstream of the diverter passage, continues to be guaranteed.  
         [0010]     Dividing the diverter device into two diverter parts that are spaced apart from one another avoids stresses and cracks that have been detected in blades and vanes that have been disclosed hitherto. Furthermore, the service life of the blades or vanes has been improved with regard to thermomechanical fatigue (TMF).  
         [0011]     It is particularly expedient if the diverter parts according to the invention are arranged in cooling passages of blades or vanes of thermal power machines. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The text which follows provides a more detailed explanation of exemplary embodiments of the invention on the basis of the drawings. All the features that are not essential to gaining a direct understanding of the invention have been omitted. Identical components are provided with identical reference numerals throughout the various figures. The direction of flow of the media is indicated by arrows. In the drawings:  
         [0013]      FIG. 1  shows a partial longitudinal section through a blade or vane of a turbine;  
         [0014]      FIGS. 2   a ,  2   b  and  2   c  show various embodiments of a diverter device;  
         [0015]      FIGS. 3   a  and  3   b  show a diverter device according to the invention;  
         [0016]      FIG. 4  shows a cross-section through a diverter device according to the invention; and  
         [0017]      FIG. 5  shows a cross-section through a further diverter device according to the invention. 
     
    
       [0018]     Only the components that are essential to gaining an understanding of the invention are shown.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]      FIG. 1  shows a blade or vane  10  of a turbomachine, comprising a main blade or vane part  1  and a blade or vane root  11 , by means of which the blade or vane  10  can be mounted on a rotor or stator (not shown). A platform  12 , which shields the blade root and therefore the rotor or stator from the fluids flowing around the main blade or vane part, is usually arranged between the main blade or vane part  1  and the blade or vane root  11 . The main blade or vane part  1  has a leading-edge region  3 , a trailing-edge region  4 , a suction-side wall  5  and a pressure-side wall  6  (cf.  FIG. 3   a ), with the suction-side wall and the pressure-side wall being connected to one another in the region of the leading edge  3  and the trailing edge  4 , so that a cavity  2  is formed. The leading-edge region  3  is in each case the region which is acted on first of all by the fluids flowing around the main blade or vane part  1 . The cavity  2  runs substantially in the radial direction through the blade or vane  10  and serves as a cooling-fluid duct for a cooling fluid  20 .  
         [0020]     To improve the cooling of the blade or vane, substantially radially running partitions  8  are arranged in the cavity  2  so as to produce cooling passages  21 . These cooling passages  21  are connected by diverter passages  22 , which are configured in such a way that the pressure loss during diversion is minimal and the heat transfer is as homogeneous as possible, in order to avoid local hot zones. To achieve this integral capturing of the flow of cooling fluid, additional diverter devices, such as for example diverter blades  9 , are arranged in the region of the diverter passages  22 .  
         [0021]     These diverter blades  9 , as shown in  FIGS. 2   a ,  2   b  and  2   c , may be of any desired configuration, e.g. with regard to thickness along the blade, radius of curvature, etc., and must in each case be matched to the conditions in the diverter passage  22 .  
         [0022]      FIGS. 3   a ,  3   b  and  4  show the diverter blade according to the invention, comprising a first diverter part  9   a  on the suction side and a second diverter part  9   b  located opposite the first diverter part  9   a  on the pressure side of the blade or vane. The diverter parts  9   a  and  9   b  are at a distance  6  from one another which may amount to up to 30% of the height  23  of the cooling passage  21  at the location of the diverter parts. The configuration of the diverter parts  9   a  and  9   b  in accordance with the invention has no adverse effect on the functioning of the diverter device compared to diverter blades which have been disclosed hitherto. The primary function of the diverter blade is to prevent pressure losses and to avoid separation of the cooling fluid stream  20  downstream of the diverter passage  22 .  
         [0023]     Furthermore, tests carried out on blades or vanes according to the invention have established that dividing the previously known diverter devices into two diverter parts prevents stresses and cracks that have been detected in blades that have been disclosed hitherto. Furthermore, it has been found that the service life of the blades with regard to thermomechanical fatigue (TMF) was improved.  
         [0024]     The diverter parts may be of any desired configuration, as shown in  FIGS. 2   a ,  2   b  and  2   c  and described above in connection with the diverter blade. Furthermore, the configuration of the distance  6  between the two diverter parts in the direction of flow of the cooling fluid is variable and the configuration arbitrary, although it must be ensured that the function of the diverter parts, namely that of preventing pressure losses and avoiding separation of the cooling fluid stream  20  downstream of the diverter passage  22 , is maintained.  
         [0025]      FIG. 5  shows a further configuration according to the invention of two diverter parts  9   a  and  9   b . In this case, the distance δ was obtained by arranging a weak point in the diverter blade by means of a narrowing or notch  24  being present in the casting mold. This notch  24  causes the diverter blade to break into two parts during the cooling and resulting shrinkage which occur after the casting process, thereby producing the two diverter parts  9   a  and  9   b  with the distance δ between them. The configuration of the notch  24  makes it possible to adjust the distance δ and its shape.  
         [0026]     Of course, the invention is not restricted to the exemplary embodiment which has been shown and described. Diverter parts of this type may in general terms be arranged in bends in cooling passages of thermally loaded components in order to avoid the problems described above.  
       LIST OF REFERENCE NUMERALS  
       [0027]    
       
         
           
               1  main blade or vane part  
               2  cavity  
               3  leading-edge region  
               4  trailing-edge region  
               5  suction-side wall  
               6  pressure-side wall  
               8  partition  
               9  diverter device/diverter blade  
               9   a  first diverter part, suction side  
               9   b  second diverter part, pressure side  
               10  blade or vane  
               11  blade or vane root  
               12  platform  
               20  cooling fluid  
               21  cooling passage  
               22  diverter passage  
               23  height of cooling passage  
               24  notch  
              δ distance