Abstract:
The present technology relates to the problem that during diverse machining steps of application to the production or reconditioning of internally cooled gas turbine blades, an undesired effect may be had on sections of the gas turbine blades and proposes, as an improvement, to inject the cavity of the gas turbine blades before the machining steps with a plastic material which can be removed without trace, such as polystyrene, which can be subsequently removed again, in particular by heat.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/DE2007/000361 (International Publication Number WO/2007/101423), having an International filing date of Feb. 27, 2007 entitled “Gasturbinenbauteil Sowie Verfahren Zur Bearbeitung Von Gasturbinenbauteilen Im Rahmen Der Herstellung Oder Instandsetzung Dieser Gasturbinenbauteile” (“Gas Turbine Component And Method For Machining Gas Turbine Components During Production Or Reconditioning Of Said Gas Turbine Components”). International Application No. PCT/DE/2007/000361 claimed priority benefits, in turn, from German Patent Application No. 10 2006 010 927.9, filed Mar. 9, 2006. International Application No. PCT/DE/2007/000361 and German Application No. 10 2006 010 927.9 are hereby incorporated by reference herein in their entireties. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    [Not Applicable] 
       MICROFICHE/COPYRIGHT REFERENCE 
       [0003]    [Not Applicable] 
       BACKGROUND OF THE INVENTION 
       [0004]    The present technology relates to gas turbine components and a method for machining gas turbine components. More specifically, the present technology relates to systems and methods for machining of gas turbine components during production and repair or reconditioning of these gas turbine components. 
         [0005]    Gas turbine components haveing an internal cavity—subsequently referred to as first inner cavity—are already known. An example of such a configuration is a blade, like a guide vane or turbine blade of a gas turbine or of an aircraft engine, which is provided with a first inner cavity for cooling purposes. Such a first inner cavity, which can also be designed as a channel, an arrangement of several cooperating channels, a chamber and/or a chamber system, can have one or more undercuts and can then be connected to holes or slits, so that the entire arrangement of inner cavity and holes or slits permits air flow through the blade. Such blades are also referred to as internally cooled or internally air-cooled blades. 
         [0006]    In the production and repair of such blades, a number of machining steps is typically carried out. For example, it can be prescribed that one of the machining steps conducted in the context of production is “casting” in the blade, in which the first inner cavity is formed in the context of this casting process. The first inner cavity, however, can also be formed in a different way. Holes or cooling holes or slits or cooling slits are generally introduced after formation of the mentioned first cavity. This can be so that by means of a mechanical machining method, like drilling, cooling holes are introduced that extend from the outer surface of the blade to the first cavity. Another possibility is to introduce such holes or slits by means of a laser. While it can be relatively easily ensured that the limitation section of the first cavity opposite the hole being formed will not be adversely affected or damaged during the mechanical drilling of a cooling opening, it is much more difficult to ensure during laser drilling. During mechanical drilling, an adverse effect on the mentioned opposite wall section can be simply avoided by controlling the drilling depth, however, during laser drilling, there is a not insignificant hazard that the laser radiation will produce undesired changes on the opposite wall section of the cavity limitation. 
         [0007]    The effect area, or the area upon which the laser drilling is intended to have a drilling effect, is not only in the area in which the laser drilling influences, as laser drilling also affects the wall section of the first cavity opposite the laser drilling. It is desirable, however, to avoid or reduce the adverse effects or changes that occur in the opposite wall section as a result of laser drilling. 
         [0008]    This problem of having effects occur in areas of the component, or the gas turbine component in which effects are undesired during the production or repair of gas turbine components by machining steps or by a machining tool, however, does not only exist during the mentioned laser drilling. 
         [0009]    This problem can also occur, for example, during coating of gas turbine components—be it in the context of the manufacturing process or in the process of repair. If, for example, an internally air-cooled blade is at least partially de-coated in the context of repair work and then re-coated, there is a hazard that during this coating, the cooling air holes will be clogged or their cross-sectional areas at least reduced. 
         [0010]    Here again, during a machining step, namely coating, an effect occurs on an area of the component or blade in which the corresponding effect is undesired. 
         [0011]    The underlying task of the presently described technology is to devise a method for machining especially internally cooled or internally air-cooled gas turbine components, where the machining occurs during production or repair of these gas turbine components, in which the hazard of undesired or damaging effects is reduced or even avoided during the machining steps on the gas turbine component. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    According to the presently described technology, various embodiments of methods are proposed for machining a gas turbine component or components. The present technology also describes various embodiments of gas turbine components. 
         [0013]    According to the present technology, a method is proposed for machining gas turbine components during the production or repair (reconditioning) of these gas turbine components, particularly internally cooled or internally air-cooled gas turbine components. A component is provided having at least a first internal cavity and is initially prepared. Then at least one first machining step is conducted on this component. To limit the area on which an effect occurs in the first machining step, before performing the at least first machining step, plastic material is introduced to the first cavity. This plastic material is removed again after the machining steps or the first machining step from the first cavity. As stated, a method for machining of gas turbine components is proposed; in this context, the gas turbine component being machined may be a finished gas turbine component or a partially finished or repaired gas turbine component. In certain embodiments, the gas turbine component is a gas turbine blade. 
         [0014]    In certain embodiments, the gas turbine component is an internally cooled or internally air-cooled gas turbine blade. The gas turbine blade can be configured as a guide vane or blade of a turbine or of a compressor of an aircraft engine. 
         [0015]    In certain embodiments, the plastic material is injected or applied in the liquid or viscous state. In certain embodiments, the plastic material is injected into the component, or alternatively, the first cavity can be sprayed with the plastic material. 
         [0016]    The first cavity can be an opening or an opening extending into the interior of the gas turbine component, a channel or several cooperating channels in an arrangement, a chamber or a chamber system or be formed from them. In certain embodiments, the first cavity can also be a hole, in particularly a laser hole or a cooling (air) hole. In certain advantageous embodiments, it is proposed that the first cavity forms a type of channel, from which, in the finished state of the gas turbine blade, laser holes or cooling holes extend to the outer surface of these gas turbine blades. Such a first cavity, designed as a channel, can extend lengthwise; it can be curved or meander or run in some other way. The first cavity can have one or more undercuts. In an advantageous embodiment, the first cavity is produced in the context of a casting process. 
         [0017]    The first cavity or first channel, in certain advantageous embodiments, has on its end an opening that is opened outward or main opening and is essentially closed on its other end. 
         [0018]    Certain embodiments propose that the machining step or first machining step be conducted by means of a laser. This first machining step can be laser drilling. Through holes or cooling holes are introduced to the gas turbine component or blade with such laser drilling. Such cooling holes can be introduced, so that they connect the mentioned first cavity or first channel to the outside surface of the blade. 
         [0019]    The mentioned plastic material can therefore be introduced into the first cavity or channel beforehand. The plastic material can be positioned in the first cavity along an imaginary extension of the generated laser holes or cooling holes, such that the plastic shields the opposite wall section of the channel or first cavity. 
         [0020]    The plastic material, in a certain embodiments, is a plastic material that can be removed essentially free of residue. In certain advantageous embodiments the plastic material is polystyrene. 
         [0021]    In a modification of the method according to the present technology, in which the already mentioned cooling holes are produced by laser drilling, it can be proposed that after laser drilling, the blade foot is tightened in a holding device with good heat conductivity or in copper jaws. This holding device or these copper jaws can be configured, for example, so that they have an oxygen or compressed air feed. The blade can then be configured, so that the first channel or the first cavity in the area of the blade foot is formed open outward or forms a main opening, in which the oxygen or compressed air feed is connected, so that oxygen or compressed air can be introduced, and specifically in order to carry out quality control, for example, in combination with a flow measurement or the like. A measurement device can be provided for such quality control in the context of which it is checked, in particular, whether laser or cooling openings are dimensioned in the desired manner. 
         [0022]    It can be proposed, for elimination or removal of the plastic material or polystyrene from the component, that an induction coil or induction mat be placed around the component or blade, and that the coil heats the blade, the cavity or the blade channels. In certain embodiments, the blade, the cavity or the blade channels are flooded with oxygen or atmospheric oxygen at the same time as the heating. Heating can occur at a temperature in the range between 400° C. and 800° C., preferably in the range from 400° C. to 600° C., and especially at about 500° C. The aforementioned temperature values are particularly suitable, if the plastic material is polystyrene. Polystyrene then burns up or evaporates essentially free of residue. 
         [0023]    It can also be prescribed that the blade then be cooled or rapidly cooled. This rapid cooling can occur via the copper jaws or the holding device, whose material preferably has good heat conductivity. Rapid cooling can occur, for example, with additional air or additional water, and specifically air or water that is guided to the copper jaws or holding device, whose material preferably has good heat conductivity. This can permit the blades to then be cooled relatively quickly, so that they can be grasped by hand, so that the process times in the production process for gas turbine blades can be reduced. 
         [0024]    In certain embodiments, before filling of the first cavity with the plastic material, one or some holes or openings are introduced, so that they connect the outer surface of the blade to the mentioned cavity. Such holes or openings can be arranged, for example, on the end of the cavity facing away from the mentioned main opening. The introduced holes or openings, which can be generated by laser drilling, can help ensure that a closed, or essentially closed air-filled space is not formed, which can create an air cushion thereby preventing penetration of plastic into the corresponding section. Thus, during the filling of the component with plastic, the air can therefore escape through the aforementioned holes or openings. 
         [0025]    It should be mentioned that the terms “first” and “second” machining step were chosen, in particular, to identify or for distinguish the machining steps, in which, in an advantageous embodiment, the second machining step occurs after the first machining step, if preferred modifications have both of these machining steps. However, before the first or between the first and the second machining step, one or more additional machining steps can also be conducted. 
         [0026]    The gas turbine component or the blade is preferably made from a metallic or metal-containing material and/or from material containing cobalt and/or nickel (especially as base material or as matrix material) and is optionally coated or provided with a coating and/or alitized. Other materials, and especially materials that are used in the current state of the art for gas turbine components, particularly gas turbine blades, can be used as material for the gas turbine component or blade. 
         [0027]    To perform the method or for machining, especially in the context of production or repair of the gas turbine component or components, particularly blades, a device can be used that is configured as follows, in combined or integrated form, and for which the applicant reserves protection: a laser; a holding device to hold the gas turbine component, which is configured in the aforementioned manner; an injection device to inject the plastic material, particularly for the injection of polystyrene; and a heating device to eliminate or remove the plastic material, configured, in particular, as an induction coil or induction mat or a device having such a coil or mat. In certain embodiments, the device can potentially having one or more of the following optional devices: an electronic control device to control the process for machining of the gas turbine component; a device for de-coating of the gas turbine component, which can be a laser; and a measurement device to measure or check the machining results produced by the method or to measure one or more characteristics of the gas turbine component. It can also be prescribed that an oxygen or compressed air feed device be provided, which is optionally combined in the aforementioned manner with the holding device. 
         [0028]    Without limiting the present technology thereto, practical examples of the present technology will be further explained with reference to figures, which are identified below. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0029]      FIG. 1  depicts a gas turbine blade in accordance with an embodiment of the present technology. 
           [0030]      FIG. 2  depicts a flow profile schematic diagram of the blade depicted in  FIG. 1 . 
       
    
    
       [0031]    The components, systems and methods of present technology will be explained in accordance with the figures. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    A blade  1  of a gas turbine or aircraft engine is shown in  FIGS. 1 and 2 . This blade  1  is configured as a turbine blade. In other embodiments of the present technology, to which the following description can also apply, such a blade can also be configured as a guide vane of a gas turbine or aircraft engine or as a guide vane or blade of a compressor of a gas turbine or aircraft engine. 
         [0033]    The blade  1  has a blade body  10  and a blade foot  12 . The blade  1  also has a first inner cavity  14  or a first inner chamber or a first inner channel  14 , whose wall or limitation is bounded in  FIGS. 1 and 2  by the (dashed) lines  14   a . This first inner cavity  14  can be provided with undercuts or have undercuts. The first inner cavity  14  discharges outward in the area of blade foot  12 . The corresponding (main) opening  20  provided there in the region of the blade foot  12  is positioned, so that, in a blade  1  mounted in an aircraft engine, it is situated radially inward or in the radially inward arranged area of blade  1 , referred to the turbine axis of rotation. According to a gas turbine part according to the present technology, which is a blade  1 , in particular, it is prescribed that the first inner channel  14  or first cavity  14  be filled with a plastic material that can be removed free of residue, which, in certain embodiments can be polystyrene. This can be such that the first cavity  14  is filled essentially fully with the mentioned polystyrene. 
         [0034]    The blade  1  depicted in  FIGS. 1 and 2  also has a number of first openings  16 , as well as a number of second openings  18 . The openings  16 ,  18  extend from the outer surface  21  of blade  1  to the first inner cavity  14 , and specifically in the area of blade body  10 . The first openings  16  are configured here as holes, and specifically laser holes, and can also be referred to as cooling holes. The second openings  18  are configured here slit-like, but, as an alternative, can also be (laser) holes or the like. 
         [0035]    The first inner cavity  14  is connected to the blade exterior via a main opening  20  of the first inner cavity  14 , which, as already mentioned, is arranged here in the area of blade foot  12 . The first inner cavity  14  is therefore connected to the exterior of the blade  1  only via the main opening  12 , as well as (with respect to its cross section) relatively smaller openings  16 ,  18  arranged in the area of the blade body. The channel arrangement or cavity arrangement formed in this case serves for cooling or air-cooling. The blade  1  can receive relatively cold air into blade  1  in relation to the ambient temperature via the main opening  20 , which then emerges via openings  16 ,  18 . The “relatively” cold air can lie in the range of 700° C., which is relatively low in comparison with the temperatures that are produced by the combustion gases of an aircraft engine in the area connected to the combustion chamber. 
         [0036]    It should be noted that the mentioned polystyrene is shown symbolically in cutouts by the cross-hatched areas  22 . 
         [0037]    A method in accordance with the present technology can occur as follows in a practical example. 
         [0038]    A blade  1  provided with a first inner cavity  14  is initially produced. The blade  1  can be configured as shown in  FIGS. 1 and 2  or explained with reference to these figures, in which, however, the openings  16 ,  18  are initially not present. 
         [0039]    Second openings  18 , which connect the outside of blade  1  to the first inner cavity  14 , as is readily apparent in  FIG. 2 , where the flow profile or a section through the blade body  10  is shown, are then produced, for example, by means of a laser. The openings  18  can be positioned, as shown in  FIGS. 1 and 2 , in the area of the trailing edge  24  of blade  1 , and specifically on the pressure side  26  there. As mentioned, the openings  18  can also have a shape different from that prescribed here. 
         [0040]    Polystyrene  22  is then injected into hollow chamber  14  or the hollow chamber  14  is sprayed with polystyrene  22 , which can occur through the second openings  18  and/or the main opening  20 . Depending on whether it occurs via the main opening  20  or the second openings  18 , it is ensured by the other openings  20  and  18  that no compressed air cushion builds up, which might prevent complete filing of the chamber  14  with polystyrene  22 . 
         [0041]    The first holes or cooling holes  16  are now produced by means of a laser. The holes  16  can therefore also be referred to as laser holes. These cooling holes  16  are arranged in the configuration according to  FIGS. 1 and 2  in the area of the leading edge  28  of blade  1 . The adverse and/or undesired effects of laser radiation on the wall section of the component, particularly the wall  14   a  bordering the first cavity  14  and opposite the forming holes  16 , is prevented during laser drilling as a result of the first inner cavity  14  being filled with polystyrene  22  or a plastic material. This is schematically shown in  FIG. 2  for one of the holes  16 , in which a laser head is denoted with reference number  30 , laser radiation is denoted with reference number  32  and an opposite wall section is denoted with reference number  34 . As shown, the opposite wall section  34  is shielded by the polystyrene  22 , therefore preventing an undesired effect of the laser radiation  2  on the opposite wall section  34 , or a change, especially a permanent change, in the surface or material properties of this wall section  34 . 
         [0042]    In certain embodiments, the laser radiation  32 , or its intensity, may be adjusted or set, so that, the polystyrene  22 , sufficiently prevents the laser radiation  32  from having an effect on the (opposite) wall section  34  during laser drilling. It can then be stipulated that the act of laser radiation  32  can have an effect may evaporate, or partially evaporate the polystyrene  22 . 
         [0043]    When the laser has formed the holes  16  in the aforementioned manner, the polystyrene  22  is then removed again. This can occur by heating the polystyrene  22  and burning it or evaporating it. The corresponding heating of the polystyrene  22  can occur, for example, as schematically shown in  FIG. 1 , by means of an induction coil  36 . In certain embodiments, copper jaws  38  are provided, in which the blade foot  12  can b e tightened. Such copper jaws  38 , as schematically shown in  FIG. 1 , can have an oxygen or air feed or feed device  40 , which can be connected to the main opening  20 . It should be mentioned that, instead of the induction coil  36 , an induction mat or another appropriate heating device can be provided. The coil  36  or mat is placed around the blade body and optionally the blade foot  12 . The heating device or induction coil  36  heats the blade channels or their interior to 500° C. while the blade channels or their interior are flooded with oxygen or atmospheric oxygen via the oxygen or air pressure feed device  40 . The polystyrene burns or evaporates essentially free of residue. Only water (H 2 O), as well as carbon dioxide (CO 2 ) are then formed. It can also be prescribed that rapid additional cooling can occur with air or water via the copper jaws  38 . 
         [0044]    In certain embodiments, after removal of the polystyrene  22 , the polystyrene  22  is injected again, such that that the openings  16 ,  18  are injected with the polystyrene  22  in addition to, or alternatively from the first cavity  14 . In certain embodiments, a subsequent coating process, which can also be referred to as a second machining step, is performed, making it possible to coat the surface of blade  1  with a coating material, without the coating material penetrating into openings  16 ,  18 , thereby changing their cross-sectional surface or even clogging them in the area of these openings  16 ,  18 . After the corresponding coating process, through which a hot temperature-resistant layer of a corrosion-temperature-resistant layer or the like can be applied, the polystyrene  22  can be removed again in the aforementioned manner. It should be mentioned that the previously discussed second introduction of polystyrene  22  can occur via openings  16  and/or  18  and/or the main opening  20 . It should also be noted that elimination or removal of the polystyrene  22  occurs in the practical example just described by heating, and specifically inductively. In certain embodiments, however, other removal methods can also be provided, for example, chemical removal methods. 
         [0045]    As shown in the practical example, this permits the area of effect of tools or the area of effect that is present in the context of machining steps to be limited in simple fashion by use of polystyrene  22  or a corresponding plastic. It should be mentioned that the injection molding of polystyrene can be carried out quickly, cleanly and cost-effectively. Burning or evaporation of polystyrene is also free of residue, rapid, cost-effective and environmentally safe. 
         [0046]    The present technology has now been described in such full, clear, concise and exact terms as to enable a person familiar in the art to which it pertains, to practice the same. It is to be understood that the foregoing describes preferred embodiments and examples of the present technology and that modifications may be made therein without departing from the spirit or scope of the present technology as set forth in the claims. Moreover, while particular elements, embodiments and applications of the present technology have been shown and described, it will be understood, of course, that the present technology is not limited thereto since modifications can be made by those familiar in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings and appended claims. Moreover, it is also understood that the embodiments shown in the drawings, if any, and as described above are merely for illustrative purposes and not intended to limit the scope of the present technology, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents. Further, all references cited herein are incorporated in their entirety.