Abstract:
The invention relates to a blade for a turbine comprising a blade wall, a first channel for guiding a first medium and a second channel for guiding a second medium that can be supplied to the turbine blade separately from the first medium. In order to combine both media, which are supplied separately, into one mixture, a turbine blade has least one chamber which is arranged in the interior or in the blade wall and said chamber is connected to said channels via a respective connection line. In order to provide a particularly simple component that is economical to produce, the chamber and/or the outlet conduit are a least partially delimited and/or formed by an insert accommodated in the wall.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2007/052235, filed Mar. 9, 2007 and claims the benefit thereof. The International Application claims the benefits of European application No. 06008321.9, filed Apr. 21, 2006, both of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a turbine blade for a turbine, with a blade wall and with a first passage for guiding a first medium and a second passage for guiding a second medium which can be fed to the turbine blade separately from the first medium, wherein for mixing the two separately feedable media to form a mixture the turbine blade has at least one chamber which is arranged on the inside or in the blade wall and is connected to the two passages via a connecting line in each case. 
       BACKGROUND OF THE INVENTION 
       [0003]    Such a turbine blade is known for example from WO 2005/003517 A1. The blade walls which form the blade airfoil enclose a cavity in which cooling air can flow. Furthermore, further passages for guiding a second medium, specifically fuel, are provided in the blade wall of the turbine blade. The cooling medium which flows inside the turbine blade can discharge outwards into a hot gas space through a plurality of through-holes which extend through the blade wall of the turbine blade. In order to produce a combustible mixture still in the blade wall, connecting lines are provided in this which connect the fuel-guiding passages to the through-holes. Therefore, fuel can be mixed with cooling air still inside the through-holes and can flow as a combustible mixture into the hot gas which flows around the turbine blade. With such a turbine blade, both the hot gas which flows through the turbine and the cooling air which flows out of the turbine blade can be reheated as a result of the combustion of the mixture, which in general is carried out for increasing the level of performance of the gas turbine, for reducing the pollutant emissions and for improving the efficiency of the gas turbine, and is known as a form of carnotization. This form of subsequent energy enrichment of the hot gas in the turbine is also known as “in-situ blade reheat”. 
         [0004]    Furthermore, a combustion chamber with a multiplicity of porous heat-shield elements is known from WO 99/46540 A1, by means of which a combustible mixture can be subsequently introduced into the combustion space of a gas turbine, i.e. outside burners of the gas turbine. 
         [0005]    A disadvantage in the case of the turbine blade which is known from the prior art relates to the production of the passages, of the chamber and of the outlet line if the turbine blade and its cavities are produced in the casting process. These cavities are to be produced comparatively expensively by means of mostly complex casting cores. For this purpose, a complexly structured casting core and/or casting shell corresponding to the desired cavity structure is required, which, however, are to be positioned securely and accurately in the casting device cost-intensively and only in a time-consuming manner so that when casting turbine blades with such complex structures an increased scrap rate ensues in most cases. 
         [0006]    If on the other hand the cavities which are provided in the blade wall are produced by means of different coatings, then the masking of the uncoated rough components which is required for it is an especially time-consuming working step which leads to a prolonged and expensive production. 
       SUMMARY OF THE INVENTION 
       [0007]    The object of the present invention is therefore the provision of a generic-type turbine blade which is to be produced in a particularly simple and cost-effective manner. 
         [0008]    The solution which is proposed by the invention provides that the chamber and/or the outlet line are partially delimited or formed at least by means of an insert which is seated in the wall. 
         [0009]    The invention is based on the knowledge that the turbine blade is to be produced as simply as possible if the cavities which are required inside the turbine blade, or in the wall of the turbine blade, for the guiding or for the mixing of the two media are not produced at the same time with the blade wall but in one or more working steps which can be carried out in parallel. It is proposed to assemble the turbine blade from a basic body and from at least one insert, wherein the basic body comprises the wall of the turbine blade into which the insert is inserted. The insert at least partially delimits the chamber in which the two media are mixed with each other and/or the outlet line extends through the insert. Consequently, it is possible to cost-effectively manufacture in each case by means of current production tools a simply structured basic body with a recess which is provided for the insert, and also an insert with complex hollow structures. 
         [0010]    Consequently, a particularly simple and cost-effective turbine blade is proposed by the invention, as a result of which the scrap rate which occurs during production can be reduced. In particular, the scrap rate of the preferably cast basic body can be reduced as a result. Furthermore, it is possible to cost-effectively manufacture differently operating turbine blades in many variants by the use of different inserts in identical basic bodies on their surface. 
         [0011]    An increased manufacturing accuracy is a further advantage of separately produced components of the turbine blade. Tolerances, both those of the basic body and those of the insert, can be selected closer without increasing the scrap rate at the same time as a result. If, for example, the complexly structured insert does not satisfy the constructional specifications with regard to its dimensions, only the insert itself and not the entire component is unusable as scrap. This saves on production costs. 
         [0012]    Advantageous developments of the invention are disclosed in the dependent claims. 
         [0013]    In a first development of the invention, the blade wall in its surface which faces the hot gas space has a recess with a rectangular or especially circular contour in which the insert, with a contour which corresponds to the contour of the recess, is inserted. Especially circular recesses can be particularly simply and cost-effectively produced in the blade wall, for example by means of metal-cutting methods. In the same way, an inset can be favorably produced from a cylindrical, for example solid, metal body, in which outlet lines with precise geometries can be subsequently incorporated. Recesses with essentially rectangular contours can be produced in the surface of the blade wall for example by means of milling. 
         [0014]    Instead of a recess which is produced by means of drilling or milling, the recess which accommodates the insert, as long as the blade wall or the basic body is produced by casting, can be produced directly when casting by means of a correspondingly formed casting shell or casting core. It is also conceivable to use the insert as part of a casting core in the casting device, wherein, however, the insert is cast with the turbine blade which is to be produced and remains in this after removing the remaining casting core. 
         [0015]    In a second advantageous development, a number of chambers are provided in the turbine blade or in the blade wall, in which at least one outlet line is associated with each chamber. As a result of this, the effect is achieved of the turbine blade having not only one but a multiplicity of outlet lines through which the mixture can be blown into the hot gas space. Consequently, a two-dimensional introduction of the mixture into the hot gas space is possible in this way. 
         [0016]    According to a further development, swirl elements are provided in the outlet line which bring about a further particularly efficient mixing of the two media which are brought together in the chamber. This is especially advantageous when one of the two media is a fuel and the other medium represents the oxidation medium for the fuel. The oxidation medium is preferably cooling air which is provided for cooling the turbine blade or the blade wall which delimits the hot gas space. As a result of the particularly efficient and therefore homogeneous mixing of the two media, in the present case, after entry of the mixture into the hot gas space, an automatic ignition of the mixture takes place due to the temperatures which occur there, which is used for the low-emissions reheating of the hot gas which flows through the turbine, or for the reheating of the cooling air. After self-ignition of the mixture, this combusts, forming a premix flame with low emissions and by giving off heat increases the energy content of the hot gas, which leads to an increased useful output of the turbine which is equipped with the turbine blade. 
         [0017]    In a further alternative development, it is conceivable that each chamber, and the outlet line which is associated with it in each case, is formed by means of a separate insert. This enables the use of different inserts depending upon local requirement for the outflowing mixture, or depending upon the boundary conditions which occur in the hot gas space. 
         [0018]    A group of chambers, and the outlet lines which are connected to these chambers, can advantageously be formed by means of a single separate insert. Such a development leads to a turbine blade with a low number of inserts. 
         [0019]    Furthermore, it is proposed that each insert can have a plurality of outlet lines which connect a common chamber to the hot gas space. This leads to especially simply configured inserts. 
         [0020]    It is additionally proposed by the invention that the insert is formed in a plurality of sections. A multi-section insert allows the particularly cost-effective and simple production of outlet lines as long as these are to have slightly more costly inside surfaces; if, for example, turbulators or swirl elements are provided on the inside surface of the outlet line for further improved mixing-through of the reaction partners. The insert for example can be formed from a plurality of layer elements which lie one upon the other in a stacked manner and form the chamber and/or the outlet lines in the process. An insert for example can also be assembled from a plurality of elements, of which the outermost element which faces the hot gas space is formed from a porous material or from a metal foam. The insert, however, can also be formed entirely from the porous material or foam. Porous material and metal foam are particularly suited to bringing about a uniform discharge of the mixture on its surface which faces the hot gas, in the manner of a flat effusion cooling. In particular, if the mixture is suitable as a combustible mixture for reheating the hot gas which flows through the turbine, an especially low-emissions combustion of the mixture on account of an ensuing microdiffusion flame can be achieved. 
         [0021]    It is additionally proposed that the outlet line leads to a region of the blade wall in which shock waves, which occur in the hot gas, impact. The shock waves which occur in the hot gas bring about a further improvement with regard to the mixing of the two media which are (pre-)mixed in the chamber, which in turn has an advantageous effect on the self-igniting combustion of the mixture. 
         [0022]    If the turbine blade comprises a blade airfoil which has a suction-side blade wall and a pressure-side blade wall, wherein the blade walls extend along a chord with a chord length from a leading edge to a trailing edge and in which the outlet line leads to the surface of the suction-side blade wall in the rear third of the chord length, as seen in the flow direction of the hot gas which flows around the blade airfoil, a particularly efficient mixing, which is assisted by the swirling which occurs in the hot gas, can be carried out since the shock waves impact upon the blade airfoil of the turbine blade preferably in this region. 
         [0023]    The blade wall of the turbine blade is preferably formed from a cast basic body. In this case, the insert which is inserted in the recess of the wall is welded or soldered to the cast basic body in order to ensure a particularly secure seating of the insert in the blade wall. Furthermore, an endless welding of the insert along the connecting contour to the basic body leads to a gastight sealing of the chamber which is at least partially delimited by the insert. 
         [0024]    Naturally, the proposed turbine blade can also be used for the addition of fluid media other than fuel or air inside a turbine, regardless of whether it is a gas turbine or steam turbine. 
         [0025]    The blowing out of the two media is carried out altogether in a manner which furthermore gives rise to an extremely quick mixing in the hot gas space within the shortest distance and within the shortest time. As a result, it is ensured that in the hot gas space the exceptionally homogeneous mixture of the two media automatically ignites due to the temperature which prevails in the hot gas, for reheating the hot gas which flows through the turbine. This enables an especially low-emissions combustion of the combustible mixture, which is produced in the first mixing step, by means of premix flames. 
         [0026]    As a result of the mixing within a short reaction distance and reaction time, the effect is furthermore achieved of the mixture being combusted before leaving the annular passage-shaped hot gas space, since the energy increase of the hot gas which takes place as a result of the reheating of the hot gas or of the cooling air is only for power increase and efficiency increase of the turbine when the reheated hot gas or the reheated cooling air still flows past the rotor blades of the turbine for converting the flow energy into mechanical energy. 
         [0027]    Advantageous developments are disclosed in the dependent claims and serve for the further explanation of the invention, referring to further advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    In the drawing: 
           [0029]      FIG. 1  shows a gas turbine in a longitudinal partial section, 
           [0030]      FIG. 2  shows a blade airfoil of a turbine blade as a component according to the invention in a perspective view, 
           [0031]      FIG. 3  shows a cylindrical insert for the blade airfoil of the turbine blade in a perspective view, 
           [0032]      FIG. 4  shows a section through an insert according to  FIG. 3 , 
           [0033]      FIG. 5  shows the pressure distribution along the suction-side and pressure-side blade walls of the blade airfoil of the turbine blade, 
           [0034]      FIG. 6  shows a schematic cross section through the blade airfoil of the turbine blade, 
           [0035]      FIG. 7  shows a cross section through an insert which is assembled from stacked layer elements, 
           [0036]      FIG. 8  shows an exploded view of the insert which is shown in  FIG. 7 , 
           [0037]      FIG. 9  shows a partially sectioned perspective view of the leading edge of the blade airfoil of the turbine blade, 
           [0038]      FIG. 10  shows the leading edge of the turbine blade in a sectioned perspective view, 
           [0039]      FIG. 11  shows the insert according to  FIG. 12  in a perspective exploded view, 
           [0040]      FIG. 12  shows a sectioned perspective view of the leading edge of the turbine blade with an insert which is rectangular in contour, and 
           [0041]      FIG. 13  shows a blade wall in cross section with a porous layer element as the insert. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0042]      FIG. 1  shows a gas turbine  1  in a longitudinal partial section. Inside, it has a rotor  3  which is rotatably mounted around a rotational axis  2  and which is also referred to as a turbine rotor. An intake duct  4 , a compressor  5 , a toroidal annular combustion chamber  6  with a plurality of burners  7  which are arranged rotationally symmetrically to each other, a turbine unit  8  and an exhaust gas duct  9 , follow each other along the rotor  3 . The annular combustion chamber  6  forms a combustion space  17  which communicates with an annular hot gas space  18 . Four turbine stages  10  which are connected in series form the turbine unit  8  there. Each turbine stage  10  is formed from two blade rings. In the hot gas space  18 , a row  14  which is formed from rotor blades  15  follows a stator blade row  13  in each case, as seen in the flow direction of a hot gas  11  which is produced in the annular combustion chamber  6 . The stator blades  12  are fastened on the stator, whereas the rotor blades  15  of a row  14  are attached on the rotor  3  by means of a turbine disk in each case. A generator or a driven machine (not shown) is coupled to the rotor  3 . 
         [0043]    In order to reheat the hot gas  11  which flows through the hot gas space  18  in the region of the turbine unit  8  according to the in-situ blade reheat process, the walls which delimit the hot gas space  18 , and/or the blade airfoils of turbine blades  20  which are arranged in the hot gas space  18 , are formed as components  22  in a suitable manner for it. For this purpose,  FIG. 2  shows the blade airfoil  24 , in the form of an airfoil profile, of the cast turbine blade  20  which can be formed as a rotor blade  15  or as a stator blade  12 . The blade airfoil  24  extends along a chord with a chord length from a leading edge  26  to a trailing edge  28 , as seen in the flow direction of the hot gas  11 . In this case, the blade airfoil  24  has a suction-side blade wall  30  and a pressure-side blade wall  32  which connect the leading edge  26  to the trailing edge  28  in each case. A cavity  34 , which is enclosed by the blade walls  30 ,  32 , extends over the entire height H of the blade airfoil  24  and forms a first passage  36  in which a first medium M 1 , for example cooling air, can flow. The cooling air permanently protects material which forms the blade walls  30 ,  32  against the harmful influences of the hot gas  11 , especially against its high temperatures, using an open cooling. 
         [0044]    A section  37  of the pressure-side blade wall  32  is formed slightly thicker than the remaining section of the blade wall  32 , as seen in cross section, so that in this thickened section  37  two second passages  38 , which extend in the wall, can be formed and extend essentially over the height H of the blade airfoil  24 , which height H coincides with the radial direction of the rotor  3  of the gas turbine  1 . 
         [0045]    A second medium M 2 , which is first to be mixed with the medium M 1  directly before injecting into the hot gas  11  which flows around the blade airfoil  24 , can be fed to each second passage  38 . For this purpose, a mixing chamber  40  is provided, in which the two media M 1 , M 2  which are fed separately to the turbine blade  20  are brought together for the first time. 
         [0046]    In order to feed the first medium M 1  to the chamber  40 , a first connecting line  42  extends between the first passage  36  and the chamber  40 . The first connecting line  42  is formed as a hole which penetrates the thickened section  37  of the pressure-side blade wall  32 . In this case, the connecting line  42  in the proposed development is provided between the two second passages  38  which extend in the radial direction. 
         [0047]    The feed of the second medium M 2 , for example fuel, to the chamber  40  is carried out by means of second connecting lines  44  which extend between the second passages  38  and the chamber  40 . Via an outlet line  46 , the mixture which is created in the chamber  40  can flow out of the turbine blade  20  and flow into the hot gas space  18  in order to increase, the efficiency of the turbine  8  by means of carnotization as a result of its combustion there. 
         [0048]    In order to produce the aforementioned blade airfoil  24  in a particularly simple and cost-effective manner, the represented structure of the passage system  45 , consisting of first and second passages  36 ,  38  and also first and second connecting lines  42 ,  44 , chamber  40  and outlet line  46 , is produced in a modular manner. For this purpose, the invention proposes that an insert  50  is provided in a basic body or in a blade wall  30 ,  32 , by means of which the chamber  40  is at least partially delimited and in which the outlet line  46  is formed. In the aerodynamically curved surface of the blade airfoil  24  or in the basic body, there is a recess for the insert  50 , which has no negative influence upon the strength of the component  22  or of the turbine blade  20 . This especially applies when the recess is provided in a section  37  of the blade wall  32  which is thickened in cross section. 
         [0049]    As a result of the insert  50  which is to be separately introduced, a high flexibility and accuracy for injection of the mixture into the hot gas space  18  can be combined with good producibility of the component  22 . 
         [0050]    In the turbine blade  20  which is shown in  FIG. 2 , a plurality of inserts  50  with a circular contour in each case, which are provided in the thickened section  37  of the blade wall  32 , are inserted into recesses which correspond to them and which at least partially delimit one of the chambers  40  in each case and which features the outlet line  46  in each case. The depth of each recess is selected so that it corresponds to the thickness of the associated insert  50  so that edges which project from the blade wall  32  are avoided for aerodynamic reasons. The insert  50  can be connected along its circular contour, or even any contour, to the blade wall  32  by means of an endlessly encompassing weld seam or by soldering so that this insert is seated in the blade wall  32  in a sealed manner. 
         [0051]    The segment-like insert  50  which is inserted in the wall  32  is shown in perspective view in  FIG. 3  and in sectioned view in  FIG. 4 . The insert  50  essentially comprises a cylindrical body or segment in which a concentric central hole  52  is introduced for producing the outlet line  46 . Two further holes  54 , which extend perpendicularly to the central hole  52 , lead to this and therefore form the second connecting lines  44 . Therefore, the chamber  40 , in which the two media M 1 , M 2  which flow in the turbine blade  20  are mixed for the first time, is provided inside the insert  50  and is therefore entirely delimited by the insert  50 . Consequently, the connecting lines  42 ,  44  also merge into the chamber  40  in a stepless manner. 
         [0052]    In this case, the outlet lines  46 , which are arranged in series, are evenly distributed over the height H of the blade airfoil  24  which extends along the radial direction so that the hot gas  11 , which flows perpendicularly to the row, can be evenly treated with the mixture over the entire height H of the blade airfoil  24 . 
         [0053]    With such a turbine blade  20  with the blade airfoil  24  and with a plurality of inserts  50 , it is possible to create the addition and mixing of fluids comparatively simply in a turbine blade  20  without making the production by casting technique of the basic body or of the blade walls  30 ,  32  unnecessarily difficult. 
         [0054]    According to  FIG. 6 , the inserts  50  can be provided in the region of the turbine blade  20  in which shock waves of the hot gas  11  impact upon the turbine blade  20 . This is especially advantageous when the mixture is a combustible mixture which is to be further mixed due to the shock waves and which as result of the temperature which prevails in the hot gas  11  is to be combusted as a result of self-ignition for reheating the cooling air or the hot gas  11 . A particularly good mixing-through of the mixture then leads to a particularly low-emissions combustion so that the energy which as a result is subsequently supplied to the hot gas  1 , i.e. outside the combustion chamber, can be generated with particularly low emissions. The supplied energy can be used accordingly for power increase of the gas turbine and for increasing the efficiency. 
         [0055]      FIG. 5  shows the pressure characteristic in the hot gas  11  along the chord length of the turbine blade  20 . In this case, the characteristic line which is designated PS indicates the pressure in the hot gas  11  which occurs along the pressure-side blade wall  32 , and the line which is designated SS indicates the pressure characteristic of the flow of the hot gas  11  along the suction-side blade wall  30 . The inserts  50 , and therefore the injection of the mixture into the hot gas  11 , is carried out at suitable points, which is indicated in  FIG. 6 . For example, inserts  50  are provided in the rear third of the suction-side blade wall  30 , measured on the distance between leading edge  26  and trailing edge  28  of the blade airfoil  24 , and/or in the front third of the pressure-side blade wall  32 , since in these sections vortices, for example shock waves or vortex trails, which are present in the hot gas  11  anyway, impact upon the blade walls  30 ,  32 . In each case, the mixing behavior of the mixture with the hot gas  11  can be significantly influenced by the flow field and by the pressure field of the hot gas  11  which flows around the blade airfoil  24 , depending upon positioning of the blow-in point for the mixture. 
         [0056]      FIG. 7  shows a further insert  50  in cross section and  FIG. 8  shows the insert  50  according to  FIG. 7  in an exploded view. The insert  50  according to  FIG. 7  comprises three cylindrical layer elements  60 ,  62 ,  64  which are arranged in a stacked manner in order to produce an especially complex passage system with the chamber  40  and the outlet line  46  in a particularly simple and cost-effective manner. The three layer elements  60 ,  62 ,  64  have differently configured recesses which, however, as long as the three layer elements  60 ,  62 ,  64  lie directly one upon the other, merge into each other in each case and form the flow path or the passage system which is shown in  FIG. 7 . The insert  50  for example can be inserted into the blade wall  32  or into the platform of the turbine blade  20 . The layer element  64  additionally has three openings  66 ,  68 ,  70 , wherein the first medium M 1  can be fed to the opening  66  in the installed state and the second medium M 2  can be fed to the openings  68 ,  70 . The two media M 1 , M 2  which flow into the insert  50 , flow due to the pressure drop, to a region in which they are mixed. This region is the chamber  40  which in this case is delimited both by the layer element  64  and by the layer element  62 . The mixture flows from here further along a meander-shaped passage which is delimited by the two layer elements  60 ,  62 . The meander-shaped passage represents the outlet line  46  and leads to an opening  49  which is provided in the surface  51  of the layer element  60 . The surface  51  of the layer element  60  in the installed state is exposed to the hot gas  11  so that the mixture which is produced in the chamber  40  can flow into the hot gas  11  after flowing out of the outlet line  46 . The layer elements  60 ,  62  have differently formed mixing elements  74  or swirl elements in the style of projecting teeth  72  in order to produce the meander shape of the outlet line  46 . An especially homogeneous mixing of the mixture which flows through the outlet line  46  is achieved as a result of the meander shape and as a result of the comparatively long mixing distance, i.e. the outlet line  46 , which would be almost impossible within the limits of the customary production by casting technique of the blade airfoil  24 . In the event that it concerns a combustible mixture, this can subsequently combust with low emissions in the hot gas space  18  for reheating the hot gas  11 . 
         [0057]      FIG. 9  shows a further development of the invention, in which there are essentially rectangular recesses in the suction-side blade wall  30  of the turbine blade  20 , in which the inserts  50  which correspond to them are inserted. In each of the inserts  50  a plurality of holes  78  are provided, which on the inlet side are connected to the second passage  38 , which is formed by a tube  80  inserted in the wall, and on the outlet side lead to the hot gas space  18 . The tube  80 , which is provided with further holes  82 , was part of a casting core which after the casting of the blade airfoil  24  remains in the latter. The medium M 1 , which is fed to the first passage  36 , flows via first connecting lines  42  into the chamber  40  which is arranged in the insert  50 . The second medium M 2 , which discharges from the second passage  38  through the further holes  82 , flows via the second connecting lines  44  into the chamber  40  and at this point is mixed with the first medium M 1 , which mixture which results in the process then flows through the outlet line  46  into the hot gas space  18 . 
         [0058]      FIG. 10  shows a further development of the invention, in which the one-piece insert  50  is inserted in the leading edge  26  of the turbine blade  20 . The two media M 1  and M 2  are mixed in the chamber  40  which is provided in the insert  50 , and in the manner which is shown in  FIG. 2  can be fed to this and discharged from it. 
         [0059]    As long as the mixture flows out at the leading edge  26  of the turbine blade for reheating the hot gas  11 , a greatest possible reaction distance can be achieved since the mixture is to be combusted no later than when reaching the blade row which is arranged downstream. 
         [0060]      FIG. 11  shows a further insert  50 , which is assembled from three layer elements  60 ,  62 ,  64 , in an exploded view. By means of the layer elements  60 , which are equipped with different recesses, it is possible to feed the first medium M 1  and the second medium M 2  separately to the chamber  40 , which media are mixed in this and can be blown out through an outlet line  46  into the hot gas  11 . According to  FIG. 12 , it is provided that the insert  50 , which is formed by the three layer elements  60 ,  62 ,  64  which lie one upon the other, can be provided in the leading edge  26  of the turbine blade  20 . 
         [0061]    The layer element  64  which is to be inserted first in the turbine blade  20  has a multiplicity of drilled first and second connecting lines  42 ,  44 . The drilled connecting lines  42 ,  44  can be reliably produced with increased precision compared with a cast production so that the media M 1 , M 2  which flow out as a result can consequently be metered to meet demand. The layer element which lies thereupon is provided with a plurality of rectangular openings which align with one of the first and one of the second connecting lines  42 ,  44  in each case, and which partially delimit the chamber  40  in each case. In the layer element  60  which is arranged in the turbine blade  20  on the outside, i.e. on the hot gas side, holes are provided as outlet lines  46 , on the inner walls of which, those which delimit the hole, mixing elements or swirl elements can also be provided. 
         [0062]    Other regions of the blade airfoil  24  are also suitable for accommodating such an insert  50  and for blowing out the mixture at a point other than the leading edge  26  of the turbine blade  20 . Furthermore,  FIG. 12  shows that openings  90 , which are arranged in a row and lead through at an angle to the surface of the blade walls  30 ,  32  which is exposed to the hot gas  11 , are in communication with the first passage  36 . The medium M 1 , for example cooling air, which flows out through these openings  90 , on account of the contoured diffusor-like shape of the openings  90 , form a flat film which protects the blade surface or the blade walls  30 ,  32  against the hot gas  11 , especially against its temperatures. 
         [0063]      FIG. 13  shows a modular insert  50  in the blade wall  30 ,  32  of the turbine blade  20 , which insert comprises two layer elements  60 ,  62  which are at a distance from each other, wherein the inner layer element  62  which delimits the mixing chamber  40  consists of a porous material and the layer element  60  which is exposed to the hot gas  11  is provided as a plate-like element with openings through which the mixture which is formed in the chamber  40  can discharge. 
         [0064]    Naturally, the invention is not limited to the exemplary embodiments which are shown.