Abstract:
A method for controlling combustor liner carbon formation on repaired combustors includes making modular effusion panel subassemblies remote from the combustor liner; removing a non-effusion or damaged panel from the combustor liner; and replacing the non-effusion or damaged panel with the modular effusion panel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. application Ser. No. 10/755,560, filed Jan. 9, 2004 now U.S. Pat. No. 6,868,675. 

   BACKGROUND OF THE INVENTION 
   This invention generally relates to combustor liners, such as those used on Honeywell TPE331-10, TPE331-11, and TPE331-12 series turbine aircraft engines and, more particularly, to methods for controlling carbon formation within such repaired combustor liners and constructing such combustor liners. 
   A turbine engine typically includes a compressor section, combustion section, and a turbine section. Within the combustion section is the combustor liner wherein fuel is burned producing a hot gas usually at an intensely high temperature. To prevent this high temperature heat from damaging the combustor liner before it exits to the turbine section, the interior of the combustor liner is provided with effusion holes and film cooling, and may include thermal barrier coating. This combustor liner can be created by securing a series of panels together in series with one panel being secured to a dome assembly. The effusion holes and film cooling, and thermal barrier coating, of the combustor liner prevents the intense combustion heat from damaging the combustor liner as well as the rest of the engine. The combustor liner, however, becomes very hot in the process. 
   A negative effect of the intense heat in the combustion process is the build-up of carbon on the combustion liner near the dome assembly. Over time, the carbon build-up can break off the combustion liner and pass through the turbine section. When this occurs, the carbon build-up may strike the turbine blades located therein, causing damage to those blades. This reduces the life span of the turbine blades and requires more frequent repairs to the engine. 
   U.S. Pat. Nos. 6,581,285 and 6,568,079 describe a method of replacing combustor liner panels. The inner and outer liners include a series of panels and between which are nuggets. The inner and outer liners are attached to a dome assembly by respective bolt bands that enable fasteners to be removed and re-attached to the liners and dome assembly. In the event of a damaged panel, a cut is made through at least one panel or nugget to remove the damaged panel and replace it with new panel. However, some of the disadvantages of this method include distortion and blockage of the cooling air metering holes if the cut and subsequent weld is in the nugget adjacent to such holes. Loss of thermal barrier coating can result if the cut and subsequent weld is in the area of the thermal barrier coated panel. The use of fasteners for assembling combustor liners can affect the combustion process and engine performance, due to leakage of air around such fasteners, and the loss of heat transfer through this joining method. 
   A combustor liner developed by the applicants herein is shown in partial cross-section in  FIG. 1 . In this combustor liner  100 , a generally cylindrical outer liner subassembly  102  encloses a generally cylindrical inner liner subassembly  103 , both of which are integrated (i.e., non-modular) with a dome subassembly  110 . The inner liner subassembly  103  includes a plurality of inner panels  103   a  of decreasing diameter  113  with one of the panels  103   a  integrated with the dome subassembly  110 . The inner panel integrated with the dome assembly  110  includes four rows of  181  effusion holes  104 , while the panel that is second closest to the dome assembly includes five rows of  206  effusion holes  104 . 
   Likewise, and as better shown in  FIG. 2 , the outer liner subassembly  102  is made up of plurality of outer panels  102   a , of which one is integrated (i.e., non-modular) with the dome assembly  110 . Each panel  102   a  has a decreasing diameter  112 , ( FIG. 1 ) to accommodate the attachment of the panels to one another. Eleven rows  106  of effusions holes  108  are in the outer panel  102   a  closest to the dome assembly  110 . A first group  105   a  of seven rows  106 , which are the closest rows to the dome assembly  110 , has 239 effusion holes in each row. A second group  105   b  of four rows  106 , which are the farthest rows to the dome assembly, has 281 effusion holes in each row. The effusion hole configuration, however, can stress the panel closest to the dome assembly  110 , resulting in a shorter lifespan of the outer liner subassembly  102  and consequently the entire combustor liner  100  since the inner and outer liner subassemblies are integrated with the dome assembly. 
   As can be seen, there is a need to improve the ease of replacement of either the inner and/or outer liner subassemblies to eliminate the need to replace the entire combustor liner. 
   SUMMARY OF THE INVENTION 
   In one aspect of the present invention, a method of converting a non-effusion combustor liner to an effusion combustor liner comprises making a modular inner effusion panel subassembly and a modular outer effusion panel subassembly remote from the non-effusion combustor liner removing the non-effusion inner panel and the non-effusion outer panel from the non-effusion combustor liner and replacing the non-effusion panels with the modular effusion panels. 
   In another aspect of the present invention, a method of converting a non-effusion combustor liner to an effusion combustor liner comprises making a first modular effusion liner panel subassembly remote from the non-effusion combustor liner; removing a first non-effusion liner panel subassembly from the non-effusion combustor liner; replacing the first non-effusion liner panel subassembly with the first modular effusion liner panel subassembly; wherein the first modular effusion liner panel subassembly includes six rows of first effusion holes proximate to one end of the first modular effusion liner panel subassembly and wherein at least one of the six rows includes 239 first effusion holes; and five rows of second effusion holes distal from the one end of the first modular effusion liner panel subassembly and wherein at least one of the five rows includes 281 second effusion holes. 
   In another aspect of the present invention, a method of converting a non-effusion combustor liner to an effusion combustor liner comprises making a second modular effusion liner panel subassembly remote from the non-effusion combustor liner; removing a second non-effusion liner panel subassembly from the non-effusion combustor liner; replacing the second non-effusion liner panel subassembly with the second modular effusion liner panel subassembly; wherein the second modular effusion liner panel subassembly includes four rows of third effusion holes proximate to one end of the modular second effusion liner panel subassembly and wherein at least one of the four rows includes 181 third effusion holes; and five rows of forth effusion holes distal from the one end of the second modular effusion liner panel subassembly and wherein at least one of the five rows includes 206 second effusion holes. 
   In yet another aspect of the present invention, a method of repairing a combustor liner comprises making a first modular effusion panel of a first liner panel subassembly remote from the combustor liner; removing a first damaged panel from the combustor liner; replacing the first damaged panel with the first modular effusion panel; wherein the first modular effusion panel includes six rows of first effusion holes proximate to one end of the first modular effusion panel and wherein at least one of the six rows includes 239 first effusion holes; and five rows of second effusion holes distal from the one end of the first modular effusion panel and wherein at least one of the five rows includes 281 second effusion holes. 
   In yet another aspect of the present invention, a method of repairing a combustor liner comprises making a second modular effusion panel of a second liner panel subassembly remote from the combustor liner; removing a second damaged panel from the combustor liner; replacing the second damaged panel with the second modular effusion panel; wherein the second modular effusion panel includes four rows of third effusion holes proximate to one end of the second modular effusion panel and wherein at least one of the four rows includes 181 third effusion holes; and five rows of forth effusion holes distal from the one end of the second modular effusion panel and wherein at least one of the five rows includes 206 forth effusion holes. 
   In yet a further aspect of the present invention, a method of repairing a combustor liner comprises making a modular effusion panel of a liner panel subassembly remote from the combustor liner; removing a damaged panel from the combustor liner; replacing the damaged panel with the modular effusion panel; wherein the effusion panel comprises one of a first modular effusion panel and a second modular effusion panel; the first modular effusion panel including six rows of first effusion holes proximate to one end of the first modular effusion panel and wherein at least one of the six rows includes 239 first effusion holes; and five rows of second effusion holes distal from the one end of the first modular effusion panel and wherein at least one of the five rows includes 281 second effusion holes; the second modular effusion panel including one of four rows of third effusion holes and wherein at least one of the four rows includes 181 third effusion holes; and five rows of fourth effusion holes and wherein at least one of the five rows includes 206 fourth effusion holes. 
   These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial, cross-sectional side view of a prior art combustor liner; 
       FIG. 2  is an enlarged, partial view of the outer panel subassembly shown in  FIG. 1 ; 
       FIG. 3  is a perspective view of a combustor liner according to an embodiment of the present invention; 
       FIG. 4  is a partial, cross-sectional side view of a combustor liner according to an embodiment of the present invention; 
       FIG. 5  is an enlarged, partial view of the outer panel shown in  FIG. 4 ; 
       FIG. 6  is a partial side view of a modular outer panel subassembly and the dome subassembly of the present invention showing effusion holes configured in an equilateral triangle according to an embodiment of the present invention; 
       FIG. 7  is a cross-sectional view of the modular outer panel subassembly depicting the angles of the individual panels according to an embodiment of the present invention; 
       FIG. 8  is a cross-sectional view of the modular inner panel subassembly depicting the angles of the individual panels according to an embodiment of the present invention. 
       FIG. 9A  is a flowchart depicting a method of converting a non-effusion combustor liner to an effusion combustor liner according to an embodiment of the present invention; 
       FIG. 9B  is a flowchart depicting a method of repairing an effusion combustor liner according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
   Broadly, the present invention provides a combustor liner repair method that can be used on Honeywell TPE331-10, TPE331-11, and TPE331-12 series turbine aircraft engines, and could apply to other turbine aircraft engines. More particularly, the present invention provides a method for providing effusion characteristics to an in-service combustor liner, but is lacking in effusion characteristics. Also provided by the present invention is a method of repairing an in-service combustor liner that already has effusion characteristics but may have been damaged. 
   From either of the foregoing methods, the end-result is a combustor liner that is modular in design and prevents the formation of carbon-build up on the inner surfaces of the inner and outer panel subassemblies by introducing sweeping air through a series of effusion holes located proximate to a dome assembly. These effusion holes are positioned in a configuration that minimizes stress to the panel. Also, the individual panels are configured with an angle that improves carbon removal and manufacturability. The modular design permits the shipment of completely finished inner and outer panel subassemblies, including drilling of effusion holes and thermal barrier coating to facilitate repair of existing combustor liners. 
   The foregoing characteristics of the present invention, among others, are in contrast to past combustor liners that were integral in design and, thus, more difficult to repair. Also, the past effusion row/hole configuration tended to increase stress at a panel area that transitioned from flat to angled. 
   As shown in  FIG. 3 , an embodiment of the combustor liner  10  of the present invention may comprise a generally cylindrical, modular inner panel subassembly  13  encircled by a modular outer panel subassembly  14 , both of which are removeably affixed to a dome subassembly  12 . Thereby, fuel and air may enter inlets  12   c ; combust between the panel subassemblies  13 ,  14 ; and exit from an outlet (not shown) at an end of the combustor liner  10  opposite the inlets  12   c  and into a turbine section (not shown). 
   In  FIG. 4 , a view of a combustor liner  10  shows a modular inner panel subassembly  13  with a plurality of serially connected inner panels  13   a , which in this example includes four inner panels  13   a . The inner panel  13   a  closest to the dome subassembly  12  may be removeably affixed, such as by welding and/or brazing, at a point  12   a  to the dome subassembly. The inner panel  13   a  that is most distal from the dome subassembly  12  may be removeably affixed, such as by welding and/or brazing, to a support  21  which mates with the turbine section. 
   The modular outer panel subassembly  14  may include a plurality of serially connected outer panels  14   a , which in this example includes three outer panels  14   a . The panel  14   a  closest to the dome subassembly  12  may be removeably affixed, such as by welding and/or brazing, at a point  12   b  to the dome subassembly. The panel  14   a  that is most distal from the dome subassembly  12  is left un-affixed and channels gas flow to the turbine section, by way of an outer transition liner (not shown). Each outer panel  14   a  and inner panel  13   a  may be affixed to one another, such as by welding and/or brazing. The braze alloys used for brazing any of the above may have differing melting points to facilitate brazing at one point without melting the braze at another point. The same may apply when welding. 
   As shown in  FIG. 4 , one or more of the inner panels  13   a  may include one or more of rows of dilution hole  17 , as well as one or more rows  11  each having one or more effusion holes  19 . The dilution holes  17  and/or effusion holes  19  may cover all or a portion of the entire circumference of the modular inner panel subassembly  13 . For one embodiment each dilution hole may have a diameter between 187/1000 and about 229/1000 inches. In the example shown in  FIG. 4 , the inner panel  13   a  closest to the dome subassembly  12  may include four rows  11 , with each row  11  having the same or different number of effusion holes  19 . In one embodiment, the four rows  11  may each have 181 effusion holes  19 . The example of  FIG. 4  also depicts the inner panel  13   a  that is the second closest to the dome subassembly  12  with five rows  11 , with each row  11  having the same or different number of effusion holes  19 . In an embodiment, the five rows  11  may each have 206 effusion holes  19 . 
   As an example, the effusion holes  19  may have a diameter between about 17/1000 to 23/1000 inches, and be at an angle to a horizontal reference line between about 26 to 28 degrees. 
   Similar to the inner panels  13   a , and in referring to  FIGS. 4 and 5 , one or more of the outer panels  14   a  may include one or more of rows of dilution holes (not shown), as well as one or more of the outer panels  14   a  may include one or more of rows  16  each having one or a plurality of effusion holes  15 . The dilution holes and/or effusion holes  15  may cover all or a portion of the entire circumference of the modular outer panel subassembly  14 . For one embodiment, each dilution hole may have a diameter of about 230/1000 inches. In the example shown in  FIG. 4 , the rows  16  may be divided into groups, such as a first group and a second group. In an embodiment, the outer panel  14   a  closest to the dome subassembly  12  may include a first group  15   a , and as better shown in  FIG. 5 , of six rows  16 , with each row  16  having the same or different number of effusion holes  15 . In one embodiment, the six rows  16  may each have 239 effusion holes  15 . The example of  FIG. 4 , and as better shown in  FIG. 5 , also depicts the outer panel  14   a  that is the closest to the dome subassembly  12  with a second group  15   b  of five rows  16  that are distal (in comparison to the first group  15   a ) from the dome subassembly  12 , with each row  16  having the same or different number of effusion holes  15 . In an embodiment, the five rows  16  may each have 281 effusion holes  15 . 
   It should be understood that the number of dilution holes and rows of dilution holes, and number of effusion holes and rows of effusion holes is illustrative and not meant to be limiting. The number of effusion holes and number of rows can be dependent upon the specific dimensions of the combustor liner  10 . Nevertheless, the number of possible combinations of numbers of rows of dilution and effusion and the number of dilution and effusion holes at any point along the outer panel  14   a  is extremely large. Therefore, adding/subtracting a row(s) and/or adding/subtracting a hole(s) in any row(s) is not necessarily obvious in terms of achieving a reduction in carbon build-up. 
   Referring to  FIG. 5 , it can be seen in the exemplary embodiment that the first group  15   a  of rows  16  can be on a relatively flat portion  14   b  of the outer panel  14   a , while the second group  15   b  of rows  16  can be on a relatively angled portion  14   c  of the modular outer panel subassembly  14   a . Between the flat portion  14   b  and angled portion  14   c  can be a transition area  14   d  of the modular outer panel subassembly  14   a . In the past liner design shown in  FIG. 2 , a similar transition area  102   d  between a flat portion  102   b  and angled portion  102   c  exists. 
   However, it can also be seen in  FIG. 2  that the fifth and sixth rows of holes (starting from the left of the figure) straddle the transition area  102   d , but do so in a configuration such that the holes from the fifth and sixth rows do not maintain the uniform separation seen between other adjacent rows, thereby causing stress in the transition area  102 . In the embodiment shown in  FIG. 5 , the fifth and sixth rows likewise straddle the transition area  14   d . But in contrast to the past design, the fifth and sixth rows of the present invention maintain the uniform spacing among adjacent rows. 
   In an exemplary embodiment, one or more of the effusion holes  15  can be at an angle  26  that is between about 15 and 25 degrees from a surface  20  of the outer panel  14   a . About a 20 degree effusion hole angle  26  can be in another exemplary embodiment. It is understood by those skilled in the art that this range of angles for the effusion holes is illustrative, and not meant to be limiting. Also, there is no requirement that the angles  26  for each effusion hole be identical, but merely have a sufficient angle to create a film of sweeping air on the inner surface of the panel  14   a.    
   Further, in this embodiment, one or more of the effusion holes  19 ,  15  of the modular inner and outer subassemblies can be generally circular in cross-section. Additionally, a diameter of the effusion hole  19 ,  15  can be between about 17/1000to 23/1000 of an inch in size, and can be approximately 200/1000 of an inch apart from a center of one effusion hole  19 ,  15  to another. However, there is no requirement that the diameters for each of the effusion holes  19 ,  15  be the same or different. 
   Additionally, as shown in  FIG. 6 , one or more of the rows  16  of effusion holes  15  in the modular outer panel subassemblies  13 , can be offset from one another such that the holes  15  in adjacent rows  16  are positioned on apexes of an imaginary equilateral triangle  70 . This equilateral triangular configuration  70  among adjacent rows of effusion holes maintains a uniform distance (although changing with the changing diameter of the modular outer panel  14   a  among the holes  15 . Likewise, as shown in  FIG. 4 , one or more of the rows of effusion holes  19  in the modular inner panel subassemblies  13 , can be offset from one another such that the holes  19  in adjacent rows are positioned on apexes of an imaginary equilateral triangle. This equilateral triangular configuration among adjacent rows of effusion holes maintains a uniform distance (although changing with the changing diameter of the modular inner panel  13   a  among the holes  19 . In turn, the uniform configuration increases the durability of the modular inner and/or modular outer panels  13   a ,  14   a.    
   As mentioned above, the modular outer panel subassembly  14   a  may include a flat portion  14   b  and an angled portion  14   c . In the exemplary embodiment of  FIG. 7 , the angled portion  14   c  may be characterized by an angle  14   e  measured from a surface  18 . In this embodiment, each angle  14   e  is different from one another. More specifically, in this example, the angle  14   e  for the panel closest to the dome subassembly  12  (not shown) is about 6.99 degrees, the angle  14   e  for the panel furthest from the dome subassembly  12  is about 11.54 degrees, and the angle  14   e  for the intermediate panel is about 7.64 degrees. 
   Similarly, as shown in  FIG. 8 , each inner panel  13   a  may include an angled portion  13   c  that can be characterized by an angle  13   e  as measured from a horizontal reference line  28 . In this embodiment, and starting from the inner panel  13   a  that is most distal from the dome subassembly  12  (not shown), the angles may be 9.41, 5.48. 7.06, and 4.85 degrees. While the angles  13   e , as well as the angles  14   e  may vary depending upon the application, such angles are important in that they can increase the efficiency of the combustor liner  10 , in addition to its ease of manufacturability. 
   From the above, it can be appreciated that the present invention also provides a method for minimizing carbon-build up in a combustor liner. As an example, the method may include creating a film of air along an interior surface of the modular inner panel subassembly and/or the modular outer panel subassembly. For the inner panel subassembly, the air film may be created by a plurality of rows of effusion holes in one or more inner panels. For the outer panel subassembly, the air film may be created by a plurality of rows of effusion holes in one or more outer panels. The plurality of holes in the outer panel(s) may be divided into a first group and a second group. The first group may have six rows, each with 239 effusion holes, while the second group may have five rows, each with 281 effusion holes. 
   Furthermore, it can be appreciated that the combustor liner  10  is provided with a modular design in that the components are removeably affixed to one another. In other words, and as an example, the dome subassembly may be removed from the outer panel and/or inner panel subassemblies  13 ,  14  by removing the welded and/or brazed areas at points  12   a  and/or  12   b . Once the dome subassembly  12  is removed, one or more of the outer panels  14   a  can be removed from the remaining outer panels  14   a . The same can occur for the inner panels  13   a . Since the outer panel subassembly  14  is un-affixed to the transition liner, and the inner panel subassembly  13  is un-affixed to the turbine section, the entire outer panel subassembly  14  and/or inner panel subassembly  13  may be removed from the combustor liner without removing a fixation means. The modular inner and/or outer panel subassemblies can then be efficiently replaced by welding and/or brazing completely manufactured modular subassemblies, including effusion cooling holes and thermal barrier coating, to the dome subassembly. By using completely manufactured modular subassemblies, to repair existing combustor liners, the quality of the repaired combustor liners is better controlled resulting in improved functionality and reliability. 
   Furthermore, it can be appreciated that the combustor liner  10  is provided with a modular design in that the components are removeably affixed to one another. In another example, the dome subassembly may be removed from the outer panel and/or inner panel subassemblies  13 ,  14  by cutting off the majority of the inner and outer panel below points  12   a  and/or  12   b , but above the rows of effusion holes, leaving the dome assembly welded and/or brazed to the remaining inner and outer panel remnants. Once the dome subassembly  12  is removed, one or more of the outer panels  14   a  can be removed from the remaining outer panels  14   a . The same can occur for the inner panels  13   a . Since the outer panel subassembly  14  is un-affixed to the transition liner, and the inner panel subassembly  13  is un-affixed to the turbine section, the entire outer panel subassembly  14  and/or inner panel subassembly  13  may be removed from the combustor liner without removing a fixation means. The modular inner and/or outer panel subassemblies can then be efficiently replaced by welding and/or brazing completely manufactured modular subassemblies, including effusion cooling holes and thermal barrier coating, to the dome subassembly. By using completely manufactured modular subassemblies, to repair existing combustor liners, the quality of the repaired combustor liners is better controlled resulting in improved functionality and reliability. 
   Accordingly, and in reference to  FIGS. 9A and 9B , the present invention additionally provides a method  900  of retrofitting non-effusion combustor liners with modular effusion panel subassemblies, in addition to a method  950  of repairing effusion panel subassemblies of a combustor liner, such as those described in connection with  FIGS. 3–8 . What is meant by “non-effusion” combustor liners and “non-effusion” panel subassemblies are combustor liners and panel subassemblies that have no effusion capability. In contrast, the term “effusion” combustor liners and “effusion” panel subassemblies refer to combustor liners and panel assemblies that have desired effusion capabilities, such as that described in connection with  FIGS. 3–8 . 
   In the exemplary method  900  shown in  FIG. 9A , a step  910  may include the off-site manufacture of a modular effusion panel subassembly, such as the inner panel subassembly  13  or outer panel subassembly  14 . In other words, a non-effusion combustor liner may be in-service at a given location and the modular effusion panel subassemblies can be made at a different location. In a step  912 , the manufactured panel subassembly can be brought on-site to the non-effusion combustor liner. In a step  914 , either or both of the in-service inner and outer panel subassemblies that do not have desired effusion characteristics can be removed, such as by cutting the panel subassembly away from the dome assembly. In a step  916 , the manufactured panel subassembly can be installed in place of the removed panel subassembly. 
   Similarly, in the exemplary method  950  shown in  FIG. 9B , a step  960  may include the off-site manufacture of a modular effusion panel subassembly or single effusion panel of such subassembly, such as the inner panel subassembly  13  or outer panel subassembly  14 , as in the above step  910 . In a step  962 , the manufactured modular panel subassembly or panel can be brought on-site to a damaged combustor liner, as in step  912 . In a step  964 , either or both of the inner and outer panel subassemblies that may have been damaged can be removed. And in a step  966 , the manufactured modular effusion panel subassembly is installed in place of the damaged subassembly. 
   In the event the damaged combustor liner is one made in accordance with the present invention as described above, at step  964 , the weld and/or braze at point  12   a  can be removed in order to remove the inner panel subassembly, while the weld and/or braze at point  12   b  can be removed for the outer panel subassembly. Next, at step  966 , a manufactured subassembly can replace the damaged subassembly. 
   In another embodiment where less than the entire panel subassembly is to be replaced, for example one damaged panel  14   a  of the outer panel subassembly  14 , the weld and/or braze is removed that otherwise connects the damaged panel from at least one un-damaged panel. The replacement panel may then be welded and/or brazed to the un-damaged portion of the panel subassembly. Since the braze alloy used to braze the panels together may have a different melting point temperature than that used to braze the panel subassembly to the dome assembly, replacement of a panel may not affect the braze melting point at the dome assembly. 
   It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.