Abstract:
The invention relates to a blade ( 13; 14 ) for a turbine ( 10 ), comprising at least one channel ( 22 ) which is delimited by walls ( 19, 20, 21 ). An insert ( 25 ) which can be subjected to the action of a liquid coolant is inserted into at least one channel ( 22 ). According to the invention, at least one of the walls ( 19; 20 ) is provided with a number of horizontal ribs ( 24 ) which are located between the insert ( 25 ) and the wall ( 19; 20 ). Said insert ( 25 ) is provided with openings ( 27 ) through which the liquid coolant passes out of the insert ( 25 ) and between the horizontal ribs ( 24 ). The liquid coolant is therefore conducted along the wall ( 19, 20 ) and guided by the horizontal ribs ( 24 ) in order to provide improved convection cooling.

Description:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP01/02755 which has an International filing date of Mar. 12, 2001, which designated the United States of America and which claims priority on European Patent Application number EP 00106245.4 filed Mar. 22, 2000, the entire contents of which are hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention generally relates to a blade/vane. In particular, it relates to a turbine blade/vane, having at least one duct which is bounded by walls, a cooling fluid being admitted to an insert which is introduced into at least one duct. 
     BACKGROUND OF THE INVENTION 
     A blade/vane is known from U.S. Pat. No. 5,419,039. Chambers, which extend in the direction of a longitudinal center line of the blade/vane, are formed between the insert and the walls of the blade/vane. The cooling fluid emerges from the insert into these chambers and impinges on the walls of the blade/vane. The cooling fluid subsequently flows along the walls and emerges through outlet openings into specially shaped chambers on the outside of the walls and from there into the surroundings. In the known blade/vane, the effect of the convection cooling, when the cooling fluid is flowing along the walls, is only slight because the flow length is greatly limited. In addition, mixing of the cooling fluid in the chambers occurs along the longitudinal center line of the blade/vane, so that no targeted cooling is possible. 
     Another blade/vane is known from WO 98/25009, which originates from the same assignee. This publication describes a blade/vane with walls which have a locally hollow configuration and through which a cooling fluid flows. A high level of cooling efficiency is achieved because of the reduction of the wall thickness in the region of the hollow chambers. Blades/vanes with such hollow walls, however, require a complicated casting procedure with high scrap rates and they are therefore very expensive. 
     SUMMARY OF THE INVENTION 
     An object of an embodiment of the present invention is, therefore, to make available a blade/vane which, using a simple manufacturing process, achieves an improvement in the cooling effect. According to an embodiment of the invention, an object may be achieved, in the case of a blade/vane, by at least one of the walls being provided with a number of horizontal ribs. These ribs may be arranged between the insert and the wall. Further, the insert may be provided with openings, through which the cooling fluid from the insert can enter between the horizontal ribs. 
     The horizontal ribs conduct the coolant along the wall of the blade/vane and prevent a flow of the coolant in the direction of the longitudinal center line of the blade/vane. Good convection cooling of the wall is, therefore, achieved. In addition, the horizontal ribs reinforce the blade/vane so that the wall thickness can be reduced. A reduction in the wall thickness leads to an increased cooling efficiency. The manufacture of the blade/vane can take place without complex cross section, using known methods. Hollow walls are not necessary. The scrap quota is therefore substantially reduced. 
     In an advantageous embodiment, the insert touches the horizontal ribs. The insert is supported and aligned in the desired position. 
     According to an advantageous development of one embodiment, the horizontal ribs, the insert and the wall may form chambers through which the cooling fluid flows. A flow of the cooling fluid in the direction of the longitudinal center line of the blade/vane may be reliably prevented by the chambers. In addition, the cooling effect can be varied, in a targeted manner, along the longitudinal center line of the blade/vane by differentially admitting cooling fluid to the chambers. 
     In an advantageous embodiment, the openings of the insert are arranged at a first end of the chambers and outlet openings for the cooling fluid are arranged in the wall at a second end of the chambers. The cooling fluid therefore flows along the wall to be cooled over the complete length of the chamber, so that the convection cooling is further improved. 
     The horizontal ribs can be arranged substantially at right angles to the longitudinal center line of the blade/vane. As an alternative, an angular position can be provided. In the case of an arrangement at right angles with respect to the longitudinal center line, the length of the horizontal ribs, and therefore of the chambers, is minimized. The angular position permits an increase in the length of the chambers and, therefore, further improved convection cooling. 
     The insert is advantageously closed at one end. In this case, the cooling fluid is only supplied from the other end of the insert. Emergence of the cooling fluid through the end facing away from the supply end is prevented, so that the cooling efficiency is increased. As an alternative, the cooling fluid can be supplied from both ends. 
     According to an advantageous embodiment, turbulators are used to reinforce the wall and merge into one another and into the horizontal ribs. By this, a substantial increase in the stiffness is achieved without additional material. For the same strength of the blade/vane, the wall thickness can be further reduced. Good heat exchange between the walls and the cooling fluid is achieved at the same time. The result is, therefore, a high cooling efficiency and a high overall efficiency. 
     The reinforcement of the wall does not only occur in the region of an individual turbulator. A large-area reinforcement is, in fact, provided by the connection of the turbulators to one another. The turbulators have, advantageously, a straight configuration. The use of straight turbulators permits a high level of reinforcement, in conjunction with simple manufacture. 
     According to an advantageous embodiment, the turbulators are arranged in such a way that, together with the horizontal ribs, they form recesses adjacent to one another in the form of polygons, in particular triangles or rhombuses. The inside of the wall is provided with a honeycomb structure. The individual polygons or honeycombs respectively form a closed cross section with high load-bearing capability and mutually support one another. A substantial increase in the stiffness can be achieved. 
     In an advantageous development, the wall thickness of the wall is reduced, at least in the region between the turbulators. This reduction in the wall thickness is made possible because the turbulators effect a reinforcement of the wall. Due to the reduction in the wall thickness, the cooling efficiency is further increased. In this arrangement, the turbulators can be advantageously used as metal feed ducts during the casting of the blade/vane. The honeycomb structure can therefore be conveniently manufactured. 
     The blade/vane according to an embodiment of the invention can be configured as guide vanes or as rotor blades of a turbomachine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in more detail below using embodiment examples, which are diagrammatically represented in the drawing. The same designations are used for similar or functionally identical components throughout. In the drawings: 
     FIG. 1 shows a longitudinal section through a turbomachine; 
     FIG. 2 shows a perspective, exploded representation of a blade/vane; 
     FIG. 3 shows an end view onto the inside of a wall of the blade/vane; 
     FIG. 4 shows a section along the line IV—IV in FIG. 3; 
     FIG. 5 shows a section along the line V—V in FIG. 3; 
     FIG. 6 shows a view similar to FIG. 3 in a second embodiment; 
     FIG. 7 shows a diagrammatic representation of an insert in a first embodiment; and 
     FIG. 8 shows a view similar to FIG. 7 in a second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a longitudinal section through a turbomachine in the form of a turbine  10  with a casing  11  and a rotor  12 . The casing  11  is provided with guide vanes  13  and the rotor  12  is provided with rotor blades  14 . In operation, fluid flows through the turbine  10  in the arrow direction  15 , this fluid flowing along the guide vanes  13  and rotor blades  14  and setting the rotor  12  into rotation about a center line  16 . 
     In many applications, the temperature of the fluid is relatively high, particularly in the region of the first blading row (shown on the left in FIG.  1 ). For this reason, a cooling system is provided for the guide vanes  13  and rotor blades  14 . The flow of the cooling fluid is diagrammatically indicated by the arrows  17 ,  18 . 
     FIG. 2 shows, diagrammatically, an exploded representation of a guide vane  13 . The guide vane  13  has curved outer walls,  19 ,  20 . The internal space located between the outer walls  19 ,  20  is subdivided into a total of three ducts  22  by means of two separating walls  21 . An insert  25  is inserted into each of the ducts  22 . For better representation, the insert of the central duct  22  is not shown. 
     The two outer walls  19 ,  20  are provided with a number of horizontal ribs  24  in each of the ducts  22 . The horizontal ribs  24  extend along the walls  19 ,  20  and extend as far as the separating walls  21 . Turbulators  23  are arranged between the horizontal ribs  24 . The inserts  25  touch the horizontal ribs  24 . 
     The cooling fluid, in particular cooling air, is supplied to an internal space  26  of the inserts  25 . The inserts  25  are provided with a number of openings  27  through which the cooling fluid emerges into the intermediate space between the outer walls  19 ,  20  and the insert  25 . The cooling fluid subsequently flows along the outer walls  19 ,  20  as far as outlet openings  28  in the walls  19 ,  20 . This flow is diagrammatically indicated by the arrow  30 . In this arrangement, the openings  27  of the inserts  25  are arranged at a distance from the outlet openings  28  of the outer walls  19 ,  20 . In the exemplary embodiment represented, the outlet openings  28  form substantially straight rows  29 . 
     The cooling fluid emerging from the inserts  25  first impinges on the outer walls  19 ,  20 , causing impingement cooling there. It subsequently flows along the outer walls  19 ,  20  as far as the outlet openings  28 , so that a convection cooling is achieved. After emerging from the outlet openings  28 , a film of the cooling fluid forms on the outside of the outer walls  19 ,  20 , so that film cooling is likewise made available. This provides a substantially improved cooling. 
     The leading edge of the guide vane  13  represented to the left in FIG. 2 is additionally provided with direct impingement cooling. For this impingement cooling, the insert  25  has further openings  36 , which are arranged directly behind the leading edge of the guide vane  13 . The cooling medium emerges directly via these openings  36  and provides specific cooling of the leading edge of the guide vane  13 . 
     The associated insert  25  is also provided with a further opening  37  in the region of the trailing edge of the guide vane  13 . Through this opening  37 , cooling fluid emerges directly into a narrow gap  38  between the outer walls  19 ,  20  and effects film cooling there. FIGS. 3 to  5  show more precise details of the inside of the outer wall  19 . The horizontal ribs  24  extend substantially at right angles to the longitudinal center line  31  of the guide vane  13 . They are arranged parallel to one another. Straight turbulators  23  are arranged between the horizontal ribs  24  and these turbulators  23  merge into one another and into the horizontal ribs  24 . 
     The leading edge  33  of the horizontal ribs  24  merges into the separating wall  21  in the case of the central duct  22 . In the case of the left-hand duct  22  in FIG. 2, the leading edge  33  is arranged at a distance relative to the outlet openings  28  which are furthest forward. 
     Each two horizontal ribs  24 , together with the outer wall  19  and the insert  25 , bound a chamber  32 . The cooling fluid emerges through the openings  27  of the insert  25  into this chamber  32 . It subsequently flows, as shown by the arrow direction  30 , to the outlet openings  28 . In this arrangement, the openings  27  are arranged at one end of the chamber  32  and the outlet openings  28  are arranged at the other end. This maximizes the distance which the cooling fluid passes over when flowing along the outer wall  19 . There is, therefore, a maximum convection cooling. The effect of the convection cooling is further strengthened by the turbulators  23  because the latter improve the heat exchange between the outer wall  19  and the cooling fluid. 
     The cooling fluid can be differentially admitted to the chambers  32 . This is achieved by a variation of the number and/or size of the openings  27  of the insert  25 . In this way, individual chambers  32  can, in a targeted manner, be more strongly or less strongly cooled than others. The cooling can therefore be adjusted in a targeted manner along the longitudinal center line  31  of the guide vane  13  and matched to the boundary conditions present. 
     The turbulators  23  are additionally used for reinforcing the outer wall  19 . In this arrangement, the straight turbulators  23  are arranged in such a way that they form polygons. In FIG. 3, triangles are presented as an example and in FIG. 6, rhombuses are presented as examples. The reinforcement achieved by means of the turbulators  23  permits a reduction in the wall thickness d of the outer wall  19  in the region between the turbulators  23 . Because of this reduction in the wall thickness d, the cooling efficiency is further increased. 
     FIG. 6 shows an end view onto the inside of the outer wall  19  in a second embodiment. In this embodiment, the turbulators  24  are inclined relative to the longitudinal center line  31  of the guide vane  13 . Because of this inclination, the length of the chambers  32  is increased and, therefore, the efficiency of the convection cooling is increased. In this embodiment also, straight turbulators  23  are provided and four of these are combined to form a rhombus in each case. The reduction in the wall thickness is diagrammatically indicated in these rhombuses by means of visible edges. 
     The second outer wall  20  is also, of course, provided with corresponding turbulators  23  and horizontal ribs  24 . The horizontal ribs  24  and the turbulators  23  can also be provided, alternatively or additionally, in the case of a rotor blade  14 . 
     FIGS. 7 and 8 show two embodiments of the insert  25 . In the embodiment of FIG. 7, the cooling fluid is supplied from both ends  34 ,  35  of the insert and emerges through the openings  27 . Such an insert  25  can, for example, be used in the first blading row. 
     As an alternative, an insert  25 , which is closed at the end  34 , can—as shown in FIG.  8 —be provided. The cooling fluid is then only supplied via the end  35 . This insert  25  is used in the further blading rows, in which only one end of the guide vane  13  or of the rotor blade  14  can have cooling fluid admitted to it via the casing  11  or the rotor  12 . Because of the horizontal ribs  24  provided according to an embodiment of the invention, there is a directed flow of the cooling fluid along the outer walls  19 ,  20 . The cooling effect is therefore substantially improved. At the same time, simple manufacture is possible because it is possible to dispense with blades/vanes with hollow walls. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.