Patent Publication Number: US-9840919-B2

Title: Method for producing a run-in coating, a run-in system, a turbomachine, as well as a guide vane

Description:
The present invention relates to a method for producing a run-in coating for a turbomachine for braking a rotor in response to a shaft breakage, a run-in system having a run-in coating of this type, a turbomachine having such a run-in system, as well as to a guide vane having a run-in coating of this type. 
     BACKGROUND 
     If a turbine component in a turbomachine, such as an aircraft engine, experiences a shaft breakage, the rotor must be prevented from moving uncontrollably out of the position thereof and from radially, respectively axially penetrating the housing surrounding it. For that reason, aircraft engines are generally provided with a run-in system that is supposed to brake the kinetic energy of the rotor by selectively, axially running in the shaft fragments to the point where no fragments can be hurled through the housing to the external environment. Known run-in systems are configured in the turbine, for example, between an outer shroud of a rotor blade row and the blades of a following guide vane row. 
     The U.S. Patent Application 2008/0289315 A1 describes an alternative run-in system where the downstream hub region of a rotor blade row has a circumferential toothed rim configured therein that engages into a guide vane-side run-in coating in response to a shaft breakage. This run-in system does, in fact, relieve the guide vane blades, however, the toothed rim also creates a plurality of point contacts between the toothed profile and the run-in coating. This run-in system can be produced in a mechanical machining process. Alternatively, a subsequent mounting of the toothed rim and a subsequent application of the run-in coating are possible. Moreover, both the mechanical machining, as well as the subsequent binding process constitute time-consuming manufacturing variants. 
     The U.S. Patent Application 2009/0126336 A1 describes a run-in system where a radially inner, guide vane-side, ring-shaped run-in coating is produced from a granular material by sintering under the action of temperature and pressure, respectively is subsequently bound. However, the sintering and, in particular, the subsequent binding of the run-in coating are relatively expensive. In particular, a faulty binding can lead to an abrasion, respectively breaking-away of the run-in coating, and, consequently, to an uncontrolled braking of the broken shaft pieces. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method for producing a run-in coating for a turbomachine for braking a rotor in the event of a shaft breakage that overcomes the aforementioned disadvantages and is readily implemented. Moreover, it is an object of the present invention to provide a run-in system having a run-in coating that will make possible a selective braking of a broken shaft, and to provide a turbomachine, whose rotor is able to be braked in a controlled fashion in response to a shaft breakage, as well as a guide vane having a run-in coating. 
     It is an object of the present invention to provide a method according to the present invention for producing a run-in coating for a turbomachine for braking a rotor in the event of a shaft breakage, the run-in coating is formed as an integral, generative blade portion during a generative manufacture of the blades. 
     Due to the integral generative formation thereof, the run-in coating is produced in one step along with the blade, thereby eliminating a subsequent binding, respectively formation of the run-in coating. Moreover, the generative production of the run-in coating makes possible a flexible form and, in particular, a form and a positioning that render possible an optimal braking and optimal guidance of the rotor. 
     Moreover, by employing a generative production, individual process parameters may be adjusted to produce the run-in coating. The run-in coating may be hereby provided with a different internal structure, respectively material structure than the actual blade and thus be provided with its own specific properties. Thus, even in the case of a homogeneous material, the material structure and, thus, the structural stability of the run-in coating and of the blade may be optimally adapted to the specific technical requirements to be met. 
     A generative auxiliary structure may be constructed during manufacture of the blades to create a reference plane and/or a supporting structure that supports the blades during the manufacture thereof and is then removed following the manufacture of the blades. For example, the auxiliary structure is constructed along with the blades as pins that stabilize the same. 
     A run-in system according to the present invention has a plurality of integral, preferably generatively produced run-in coatings that form a closed or open abradable ring that extends over a blade row and has a chamber-type material structure. In this context, “chamber-type” signifies a porous, cellular, honeycomb-shaped, skeleton-type, latticework-type and similar material structure. In particular, “chamber-type” signifies a structurally weaker internal structure than a bearing structure accommodating the run-in coating and an abrasive element, such as an abrasive ring that runs into the run-in coatings, abrading the same. In accordance with the wording of the present invention, “closed” signifies a circumferentially closed formation of the abradable ring; the planes of separation, respectively the circumferential gaps of the adjacent run-in coatings being so small that they may be disregarded or closed by adapters suited for that purpose. The closed, respectively circumferential formation creates a circumferential braking surface and guide surface which make possible a reliable and rapid braking and thus at least greatly reduce damage to the rotor and housing structure. In this context, the chamber-type material structure prevents, inter alia, cracks from being introduced into a blade portion that accommodates the run-in coating. In addition, the chamber structure reduces the introduction of heat into the blade row when grazing contact is made. In accordance with the wording of the present invention, “open” signifies that the run-in coatings are circumferentially spaced apart. 
     To further minimize damage to the rotor structure during the run-in process, it is advantageous when the abradable ring is formed on the outer shroud side. This results, on the one hand, in an outer radial, stable support and, on the other hand, in an especially rapid kinetic energy absorption since the ring surface of the radially outer run-in coating is enlarged relative to a radially inner run-in coating. Moreover, the risk of damage to the rotor in essential regions is minimized as is, therefore, any endangerment of the rotor integrity. 
     It is possible to prevent the abradable ring from influencing the rotating mass of the rotor by configuring it on a guide vane row. One exemplary embodiment of a closed abradable ring provides for it to be configured on the leading sides of outer shrouds of the guide vanes. 
     One exemplary embodiment of an open abradable ring provides for it to be configured on the leading edges of guide vanes. 
     In addition, the chamber-type material structure of the abradable ring allows the trailing sides of outer shrouds of a rotor blade row to act as an abrasive ring that presses against the abradable ring in response to a shaft breakage. There is no need for a special formation, respectively hardening of the trailing sides or for special abrasive elements. Since the trailing sides have a planar form, a largest possible contact area is created when the abrasive ring runs onto the abradable ring, which, in particular, accelerates the braking. 
     To further optimize and guide the broken rotor, the abradable ring may feature different local material structures. For example, the abradable ring may be subdivided into layers that are optimally adapted in terms of structural engineering to individual braking phases. Thus, for example, a front layer may be used as a damping layer for shock absorption in response to the abrasive ring running onto the abradable ring, and may feature an appropriately soft material structure. On the other hand, a rear layer may have a solid material structure for optimizing the braking. 
     In the same way, the abradable ring may have different cross sections and thus be adapted alternatively or in combination with the local material structure to the particular technical requirement. For example, a ring region of the abradable ring may be in the form of a predetermined breaking point to achieve a fastest possible braking of the rotor in the case of a potential destruction of intact rotor structure portions in response to unexpectedly high forces. 
     A turbomachine according to the present invention has a run-in system having an integral, preferably generatively produced abradable ring and an abrasive ring for running onto the abradable ring in response to a shaft breakage, the abradable ring being disposed in the leading region of a guide vane row and having a chamber-type material structure, and the abrasive ring being formed of a rotor blade row facing opposite the abradable ring. A turbomachine of this type is distinguished by an optimal guidance and braking of a rotor in response to a shaft breakage. Any danger of fragments penetrating the housing of the turbomachine is prevented, respectively at least greatly reduced. 
     In a leading region, a guide vane according to the present invention has an integral run-in coating that features a chamber-type material structure and, thus, at least an optimal kinetic energy dissipation. 
     In one exemplary embodiment, the run-in coating is disposed on a leading side of an outer shroud and is circumferentially closed, thereby forming a largest possible friction surface between the run-in coating and the abradable ring. 
     In one alternative exemplary embodiment, the run-in coating is disposed radially outwardly on a leading edge of a blade and thus has an open form. 
     To additionally impede fragmentation of the rotor blades and guide vanes in the event of a shaft breakage, it is advantageous for the run-in coating to be disposed quasi in front of the blade. In one exemplary embodiment, this is achieved in that the run-in coating is displaced upstream, respectively forms an edge portion of the leading edge that is displaced upstream relative to a radially inner edge portion. Thus, the leading edge has a stepped form, the blade having a greater axial extent radially outwardly than radially inwardly due to the run-in coating. In addition, an axial distance is hereby reduced between the rotor blades and the guide vanes, whereby a frictional contact is rapidly produced, and a rapid braking is initiated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred exemplary embodiments of the present invention are described in greater detail in the following with reference to greatly simplified schematic representations, in which: 
         FIG. 1  shows a part section through a turbomachine including a first exemplary embodiment of a run-in system according to the present invention; 
         FIG. 2  shows an axial plan view of a leading region of a guide vane row; 
         FIG. 3  is a lateral detailed representation of the leading region; 
         FIG. 4  shows a plan view of a rotor blade row in the region of the outer trailing edges thereof; 
         FIGS. 5 and 6  illustrate methods of functioning of the run-in system in the event of a shaft breakage; 
         FIG. 7  illustrates a method for producing a run-in coating according to the present invention; and 
         FIG. 8  shows a part section through a turbomachine having a second exemplary embodiment of the run-in system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The part-sectional view in  FIG. 1  shows a lateral view of a rotor blade  2  and of an adjacent downstream guide vane, respectively of a guide vane segment  4  of a rotor in the compressor of an aircraft engine. 
     Together with a multitude of other rotor blades, rotor blade  2  forms a rotor blade rim, respectively a rotor blade row that is configured via a hub  6  on the blade root side and a disk accommodating the same on a shaft  10  rotating about an axis of rotation  8 . Rotor blades  2  each have a blade root  12  that is configured in an annular space between an inner shroud  14  and an outer shroud  16  of rotor blades  2 . Shrouds  14 ,  16  each define the annular space traversed by a main flow and each have a leading side  18  oriented oppositely to the flow direction, as well as a trailing side  20  oriented in the flow direction. 
     In this exemplary embodiment, guide vanes  4  are each fixed in position by root portions  24   a ,  24   b  thereof in a housing-side recess. In alternative exemplary embodiments, guide vanes  4  are integrally included on or bolted to the housing. In correspondence with rotor blades  2 , they each have a blade leaf  22  that is configured in an annular space between an inner shroud  26  and an outer shroud  28  of rotor blades  4  and that each feature an upstream oriented leading side  30  and a downstream oriented trailing side  32 . However, when guide vanes  4  are combined into guide vane segments, a plurality of blades  22  are configured in each case between an inner shroud  26  and an outer shroud  28 . 
     In accordance with the representation in  FIG. 1 , a run-in system  34  (marked by a dashed-line circle) for guiding and braking the rotor in response to a shaft breakage is configured between outer shrouds  16  of the rotor blade row and outer shrouds  28  of guide vane row. Run-in system  34  has an abradable ring  36  configured in the leading region of the guide vane row and an opposite abrasive ring  38  configured in the trailing region of the upstream rotor blade row that are mutually axially spaced apart in the case of an undamaged rotor. In this first exemplary embodiment, abradable ring  36  and abrasive ring  38  are circumferentially closed. 
     As shown in  FIG. 2 , abradable ring  36  is formed by a multitude of preferably generatively produced run-in coatings  40  that are configured on the leading sides  30  of outer shrouds  28  as integral blade portions and are mutually laterally spaced apart across a narrow circumferential gap  42   a ,  42   b . For the sake of clarity, merely two circumferential gaps  42   a ,  42   b  are shown that may be closed using adapters suited for that purpose. Thus, each run-in coating  40  forms a ring segment of abradable ring  36  and covers only a radially inner region of leading sides  30 . 
     As shown by the detail view in  FIG. 3 , run-in coatings  40  have a chamber-type material structure. In this context, “chamber-type” signifies a porous, cellular, honeycomb-shaped, skeleton-type, latticework-type and similar material structure. In particular, “chamber-type” signifies a structurally weaker internal structure than a bearing structure accommodating run-in coating  40  and an abrasive element, such as abrasive ring  38 , that runs into run-in coatings  40 , abrading the same. They merge transitionally by a peripheral surface  44  facing the annular space into a cylindrical or conical shroud surface  46  facing the annular space. They have a maximum radial extent that corresponds to a radial extent, respectively thickness of outer shrouds  16  of rotor blades  2  in the region of trailing edges  20  thereof (see  FIGS. 5 and 6 ). 
     Abrasive ring  38  indicated in  FIG. 4  is formed by outer trailing sides  20  of rotor blades  2 . Rotor blades  2  are likewise mutually spaced apart, in each case across a small circumferential gap  42   a ,  42   b  that may be closed using adapters suited for that purpose. Abrasive ring  38  is made of a harder material than abradable ring  36  and thus leads to an ablation of abradable ring  36  in response to a shaft breakage. 
     As shown in  FIG. 5 , in response to a shaft breakage, rotor blades  2  run onto abradable ring  36  of guide vanes  4  via abrasive ring  38  thereof and thus directly via trailing sides  20  thereof forming abrasive ring  38 , in the direction of flow in accordance with the arrow. Abrasive ring  38  rubs into run-in coating  36 , whereby the rotor is braked, and abradable ring  36  is abraded, respectively worn down, at least in portions thereof, as shown in  FIG. 6 . In this context, abradable ring  36  has such a chamber-type material structure and such an axial extent that outer shrouds  16  of rotor blades  2  are prevented from running directly by trailing sides  20  thereof onto leading sides  30  of outer shrouds  28  of guide vanes  4 . Any fragmentation of rotor blades  2  and/or of guide vanes  4  is thereby effectively prevented. 
     As shown in  FIG. 7 , run-in coatings  40  are integrally produced with particular guide vane  4  in a generative process. To this end, a suitable metal powder is deposited in layers onto a base plate  48 , and an auxiliary structure  50  marked by hatched shading is produced by a high-energy beam, such as an electron beam or a laser beam. The high-energy beam is guided in tracks over the top powder layer, whereby it is melted thereon and bonded to the preceding powder layer. Auxiliary structure  50  makes it possible to compensate for unevenness of base plate  48 , for example, and permits a step-by-step construction of overlying structures and, thus, the creation of a defined reference plane for particular guide vane  4 . In addition, auxiliary structure  50  acts as a support for stabilizing guide vanes  4  during the generative production. 
     By modifying the process parameters, guide vanes  4  in question are constructed generatively in layers, horizontally from leading side  30  to trailing side  32 , together with integrated run-in coating  40 , during production of auxiliary structure  50 . Once particular guide vane  4  is completely constructed, it is separated from auxiliary structure  50 . 
     The chamber-type material structure of run-in coatings  38  is produced by varying the manufacturing parameters and thus by employing process parameters that are individualized relative to the other blade portions, such as root portions  24   a ,  24   b , shrouds  26 ,  28 , as well blade  22 , respectively blades  22  in the case of rotor blade segments. 
     A second exemplary embodiment of run-in system  34  according to the present invention is shown in  FIG. 8 . In contrast to the first exemplary embodiment, an abradable ring  36  is configured at leading edges  52  of blades  22  or guide vanes  4  and thus has an open form over the circumference of the guide vane row. Run-in coatings  40  forming abradable ring  36  are provided with the greatest axial extent thereof radially outwardly and thus in the region of an opposing abrasive ring  38 . They have a chamber-type, respectively cellular, porous, honeycomb-shaped and similar material structure, as described above, and are generatively formed together with guide vanes  4 . The material structure of the other blade region  54  is of the conventional type and is thus provided with a structurally harder internal structure than run-in coating  40 . Run-in coatings  40  are disposed quasi in front of the particular blade  22 , whereby leading edges  52  each have a radially outer, respectively outer shroud-proximate edge portion  56  that is displaced upstream in relation to a radially inner edge portion  58 . Thus, leading edge  52  has a stepped form. 
     Abrasive ring  38  of the upstream rotor blade row is identical to abrasive ring  38  in accordance with the first exemplary embodiment. Thus, abrasive ring  38  is likewise formed of outer shroud-side trailing sides  20  of the upstream rotor blade row and is made of a harder material than abradable ring  36 . 
     The method of functioning is identical to that of the first exemplary embodiment. In response to a shaft breakage, rotor blades  2  run onto open abradable ring  36  of guide vanes  4  via abrasive ring  38  thereof and thus directly via trailing sides  20  thereof forming abrasive ring  38 . Abrasive ring  38  rubs into run-in coating  36 , respectively partially abrades the same, whereby the rotor is braked. The chamber-type material structure and the axial extent of abradable ring  36  prevent outer shrouds  16  from running directly onto blade region  54 . Thus, any fragmentation of the rotor blades and/or of the guide vanes is effectively prevented. 
     Blade-side run-in coatings  50  are generatively, integrally produced during manufacture of guide vanes  4 , so that reference is made to the above explanations pertaining to  FIG. 7 . 
     A method is described for producing a run-in coating for a turbomachine for braking a rotor in the event of a shaft breakage; the run-in coating being formed as an integral blade portion in the context of a blade manufacture; a run-in system having an abradable ring having a chamber-type material structure configured circumferentially on a blade row, a turbomachine having such a run-in system, as well as a guide vane having a run-in coating of this type. 
     LIST OF REFERENCE NUMERALS 
     
         
           2  rotor blade 
           4  guide vane 
           6  hub 
           8  axis of rotation 
           10  shaft 
           12  blade root 
           14  inner shroud 
           16  outer shroud 
           18  leading side 
           20  trailing side 
           22  blade leaf 
           24   a, b  root portion 
           26  inner shroud 
           28  outer shroud 
           30  leading side 
           32  trailing side 
           34  run-in system 
           36  abradable ring 
           38  abrasive ring 
           40  run-in coating 
           42   a, b  circumferential gap 
           44  peripheral surface 
           46  shroud surface 
           48  base plate 
           50  auxiliary structure 
           52  leading edge 
           54  blade region 
           56  outer edge portion 
           58  inner edge portion