Patent Publication Number: US-2016230993-A1

Title: Combustor liner effusion cooling holes

Description:
FIELD 
     The disclosure relates generally to gas turbine engines, and more particularly to effusion cooling holes in gas turbine engines. 
     BACKGROUND 
     Gas turbine engines typically comprise compressor stages which feed compressed air to a combustor. A portion of the compressed air is mixed with fuel and ignited in the combustor. A portion of the compressed air is directed through cooling holes in the combustor and protects the combustor from the high temperatures caused by the combustion. The cooling holes are typically drilled through the combustor liner, at an angle relative to the combustor liner. The holes are typically linear, as it is difficult to create complex hole shapes with known drilling techniques. The loss or pressure drop across the linear holes is generally small and fixed so that it is difficult to increase the number density of the holes without increasing the cooling flow. Therefore, the spacing and pitch distance for the linear holes are generally very large, resulting in poor film cooling effectiveness. In addition, compared to the liner backside or impingement convective cooling, the convective cooling within the linear effusion holes is generally small due to small surface area, which is related to the number, passage length, and diameter of the holes. 
     There is continuous effort to reduce the cooling flow of the combustor liner in order to improve combustor performance. In recent times, gas turbine engines have been designed with higher overall pressure ratios (“OPR”). The temperature of the cooling air in these high OPR engines is higher compared to engines with lower OPRs. The higher temperature of the cooling air results in less heat transfer from the combustor liner to the cooling air. A larger portion of the compressed air may be utilized for cooling air, which significantly impacts combustor design and combustor performance. 
     SUMMARY 
     A gas turbine engine component may comprise an outer surface of a first wall, an inner surface of the first wall, and a first cooling hole extending from the outer surface of the first wall to the inner surface of the first wall. The first cooling hole may be nonlinear. 
     In various embodiments, the gas turbine engine component may be manufactured by an additive manufacturing process. The first cooling hole may comprise a first straight passage connected to a second straight passage by a first bend. The first straight passage may be parallel to the second straight passage. The gas turbine engine component may be a combustor liner. A length of the first cooling hole may be at least twice a thickness of the combustor liner. The gas turbine engine component may comprise a second wall comprising a second cooling hole, wherein the second cooling hole is configured to direct cooling air to the first wall. The second cooling hole may be a linear cooling hole. The combustor liner may comprise a segmented wall coupling the first wall to the second wall. 
     A combustor for a gas turbine engine may comprise a first wall comprising a first cooling hole, wherein the cooling hole comprises an inlet, a first straight passage connected to the inlet by a first bend, and a second straight passage connected to the first straight passage by a second bend. 
     In various embodiments, the combustor may be manufactured by an additive manufacturing process. A length of the first cooling hole may be at least five times a thickness of the first wall. The combustor may comprise a second wall comprising an impingement hole, wherein the impingement hole is configured to direct cooling air to the first wall. The impingement hole may be a linear cooling hole. The combustor liner may be a single-wall liner comprising the first wall, a second wall, and a segmented wall between the first wall and the second wall. A combustor liner may comprise the first wall only as a single-wall liner. A combustor liner may also comprise both the first and second wall with these two walls bolted together. In addition, using additive manufacturing process or welding, a combustor liner may be built as a single-wall liner by adding a segmented wall to combine the first and second wall together. 
     A combustor liner may be manufactured by an additive manufacturing process. The combustor liner may comprise a nonlinear cooling hole. 
     In various embodiments, the nonlinear cooling hole may extend through a first wall of the combustor liner. A length of the cooling hole may be at least five times a thickness of the first wall. The combustor liner may be a single-wall liner comprising the first wall, a second wall, and a segmented wall between the first wall and the second wall. The cooling hole may comprise an inlet, a first straight passage connected to the inlet by a first bend, a second straight passage connected to the first straight passage by a second bend, a third straight passage connected to the second straight passage by a third bend, and an outlet connected to the third straight passage by a fourth bend. 
     The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures. 
         FIG. 1  illustrates a schematic cross-section view of a gas turbine engine in accordance with various embodiments; 
         FIG. 2A  illustrates a perspective view of a combustor in accordance with various embodiments; 
         FIG. 2B  illustrates a perspective view of a turbine vane in accordance with various embodiments; 
         FIG. 3A  illustrates a perspective view of a single-wall combustor liner in accordance with various embodiments; 
         FIG. 3B  illustrates a perspective view of a cooling hole in a combustor liner in accordance with various embodiments; 
         FIG. 4  illustrates a perspective view of a double-wall combustor liner in accordance with various embodiments; 
         FIG. 5  illustrates a perspective view of a single-wall combustor liner with segmented walls in accordance with various embodiments; and 
         FIG. 6  illustrates a detailed view the single-wall combustor liner of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
     Referring to  FIG. 1 , a gas turbine engine  100  (such as a turbofan gas turbine engine) is illustrated according to various embodiments. Gas turbine engine  100  is disposed about axial centerline axis  120 , which may also be referred to as axis of rotation  120 . Gas turbine engine  100  may comprise a fan  140 , compressor sections  150  and  160 , a combustion section  180  including a combustor, and turbine sections  190 ,  191 . Air compressed in the compressor sections  150 ,  160  may be mixed with fuel and burned in combustion section  180  and expanded across the turbine sections  190 ,  191 . The turbine sections  190 ,  191  may include high pressure rotors  192  and low pressure rotors  194 , which rotate in response to the expansion. The turbine sections  190 ,  191  may comprise alternating rows of rotary airfoils or blades  196  and static airfoils or vanes  198 . Cooling air may be supplied to the combustor and turbine sections  190 ,  191  from the compressor sections  150 ,  160 . A plurality of bearings  115  may support spools in the gas turbine engine  100 .  FIG. 1  provides a general understanding of the sections in a gas turbine engine, and is not intended to limit the disclosure. The present disclosure may extend to all types of turbine engines, including turbofan gas turbine engines and turbojet engines, for all types of applications. 
     The forward-aft positions of gas turbine engine  100  lie along axis of rotation  120 . For example, fan  140  may be referred to as forward of turbine section  190  and turbine section  190  may be referred to as aft of fan  140 . Typically, during operation of gas turbine engine  100 , air flows from forward to aft, for example, from fan  140  to turbine section  190 . As air flows from fan  140  to the more aft components of gas turbine engine  100 , axis of rotation  120  may also generally define the direction of the air stream flow. 
     Referring to  FIG. 2A , a perspective view of a combustor liner  200  is illustrated according to various embodiments. The combustor liner  200  may be generally annular. The combustor liner  200  may be a combustor for a high overall pressure ratio (“OPR”) engine. The overall pressure ratio is the ratio of the stagnation pressure at the front and rear of the compressor section of the gas turbine engine. In general, engines with higher OPRs will have higher efficiencies. As used herein, a high OPR engine refers to a gas turbine engine with an OPR of 15:1 or higher. However, those skilled in the art will recognize that the concepts disclosed herein are not limited to high OPR engines. 
     The combustor liner  200  may comprise cooling holes  210 . Cooling air from the last compressor stage may impinge on the outer surface  201  of the combustor liner  200 . The cooling air may flow through the cooling holes  210 . Heat may transfer from the combustor liner  200  to the cooling air as the cooling air travels through the cooling holes  210 . The cooling air may then flow along the inner surface  202  and create a film cooling layer along the inner surface  202 . 
     In high OPR engines, the temperature of the cooling air may be 1300° F. (700° C.) or greater. In combustors with conventional drilled cooling holes, the heat transfer from the combustor liner  200  to the cooling air in the cooling holes may be decreased due to the higher temperature of the cooling air. 
     Recent advances in additive manufacturing techniques allows for the construction of combustors with complex shapes. The combustor liner  200  may be manufactured by an additive manufacturing process, such as direct metal laser sintering (“DMLS”). DMLS may comprise fusing metal powder into a solid part by melting it locally using a laser. Using DMLS or other additive manufacturing techniques to manufacture the combustor liner  200  may allow the cooling holes  210  to be nonlinear. As used herein, a nonlinear cooling hole refers to a cooling hole that causes the cooling air to change direction as the cooling air flows through the nonlinear cooling hole. 
     Although described herein primarily with reference to combustor liners, those skilled in the art will appreciate that many gas turbine engine components or other components which utilize effusive cooling may be manufactured with nonlinear cooling holes using an additive manufacturing process. For example, referring to  FIG. 2B , a turbine vane  290  is illustrated with nonlinear cooling holes  295 . The turbine vane  290  may be manufactured by an additive manufacturing process. Cooling air may flow through the nonlinear cooling holes  295  from the interior to the exterior of the turbine vane  290  to cool the turbine vane. Blades, vanes, airfoils, and combustors are merely a few examples of components that may be manufactured with nonlinear cooling holes. 
     Referring to  FIGS. 3A and 3B , a perspective view of the combustor liner  200  with cooling holes  210  is illustrated in  FIG. 3A , and a perspective view of a cooling hole  210  is illustrated in  FIG. 3B  according to various embodiments. Cooling air may impinge on the outer surface  201  of the combustor liner  200 . The cooling air may enter the cooling holes  210  through the inlets  211 , travel through the cooling holes  210 , and exit the cooling holes through the outlets  212  at the inner surface  202  of the combustor liner  200 . As the cooling air travels through the cooling holes  210 , heat is transferred from the combustor liner  200  to the cooling air. After exiting the outlets  212 , the cooling air forms a film cooling layer along the inner surface  202  of the combustor liner  200 . The cooling holes  210  may be manufactured with a variety of cross-sectional shapes. Although illustrated with a circular cross-sectional shape, the cross-sectional shape may be square, square with rounded corners, ovoid, or any other suitable shape. 
     Using additive manufacturing for manufacturing the combustor liner  200  allows for the cooling holes  210  to be formed in complex shapes. Those skilled in the art will recognize that an infinite number of nonlinear hole shapes may be consistent with the present disclosure, and the shape illustrated in  FIGS. 3A and 3B  is merely one example of a nonlinear cooling hole. Nonlinear cooling holes may comprise any number of straight passages or bends, and the inlets and outlets for nonlinear cooling holes may be coupled to the straight passages or bends at any suitable angles. The cooling holes  210  may comprise an inlet  211  which is formed at an acute angle relative to the outer surface  201 . The cooling holes  210  may comprise a first bend  213  connecting the inlet  211  to a first straight passage  214 . The first straight passage  214  may be parallel to the outer surface  201  and/or the inner surface  202 . The first straight passage  214  may be connected to a second straight passage  216  by a second bend  215 . The second bend  215  may be a 180° turn, such that the second straight passage  216  is parallel to the first straight passage  214 . The direction of flow F 2  in the second straight passage  216  may be opposite to the direction of flow F 1  in the first straight passage  214 . The second straight passage  216  may be connected to a third straight passage  218  by a third bend  217 . The third bend  217  may be a 180° turn, such that the second straight passage  216  is parallel to the third straight passage  218 . The direction of flow F 2  in the second straight passage  216  may be opposite to the direction of flow F 3  in the third straight passage  218 . The third straight passage  218  may be connected to the outlet  212  via a fourth bend  219 . The outlet  212  may form an acute angle with the inner surface  202 . The cooling air may remove heat from the combustor liner  200  as the cooling air travels through the cooling holes  210 . 
     The cooling holes  210  may have a longer flow path (the path of the cooling air through the cooling holes  210 ) than straight drilled cooling holes. The cooling holes  210  may have an increased length as compared to conventional linear drilled cooling holes. In various embodiments, the length of the cooling holes  210  may be at least twice the thickness T of the combustor liner. However, in various embodiments, the length of the cooling holes may be at least 5 times, or at least 10 times the thickness T. Such ratios may not be possible with conventional drilled cooling holes. The increased length may increase the surface area of the cooling holes  210 , and increase the amount of heat transferred from the combustor liner  200  to the cooling air in the cooling holes  210 . Additionally, the increased length may increase the pressure drop across each cooling hole  210 , e.g. four times compared with linear holes, which may allow for the combustor liner  200  to be manufactured with more cooling holes  210  than a combustor with linear cooling holes. In various embodiments, the length of the flow path through the cooling holes  210  may be at least twice as long as the distance between the inlet  211  and the outlet  212 . The cooling holes  210  may also have a larger surface area as compared to straight cooling holes, which may increase the amount of heat transferred from the combustor liner  200  to the cooling air. Therefore, if keeping the same number density as straight holes, the cooling flow will be significantly reduced while still being effective. 
     Referring to  FIG. 4 , a double-walled combustor liner  400  is illustrated according to various embodiments. The double-walled combustor liner  400  may comprise an outer wall  410  and an inner wall  420 . The outer wall  410  may also be referred to as the “cold wall,” and the inner wall  420  may also be referred to as the “hot wall.” The outer wall  410  may comprise impingement holes  415 . In various embodiments, the impingement holes  415  may be linear cooling holes formed by a drilling process. The impingement holes  415  may be perpendicular to the outer surface  411 . Cooling air may impinge on the outer surface  411  of the outer wall  410 . The cooling air may flow through the impingement holes  415 . Heat may be transferred from the outer wall  410  to the cooling air in the impingement holes  415 . After travelling through the impingement holes  415 , the cooling air may impinge on the outer surface  421  of the inner wall  420 . The inner wall  420  may comprise cooling holes  425 . The cooling holes  425  may be nonlinear cooling holes, as previously described with reference to  FIGS. 3A-3B . The cooling air may travel through the cooling holes  425  and absorb heat from the inner wall  420 . The cooling air may create a film cooling layer on the inner surface  422  of the inner wall  420 . 
     Referring to  FIG. 5 , a perspective view of a single-wall combustor liner  500  with segmented walls is illustrated according to various embodiments. The single-wall combustor liner  500  may comprise an outer wall  510  and an inner wall  520 . The single-wall combustor liner  500  may comprise segmented walls  530 . The segmented walls  530  may couple the outer wall  510  to the inner wall  520 . The segmented walls  530  may be perpendicular to at least one of the outer wall  510  or the inner wall  520 . In various embodiments, the outer wall  510 , the segmented walls  530 , and the inner wall  520  may be formed together by a DMLS process. However, in various embodiments, at least one of the outer wall  510 , the segmented walls,  530 , or the inner wall  520  may be independently formed and coupled to the other components by any suitable process, such as welding. The segmented walls  530  may conduct heat from the inner wall  520  to the outer wall  510  to remove heat from the combustor liner  500 . The conduction may heat up the outer wall  510 , and the outer wall  510  may transfer heat to cooling air flowing through the cooling holes  515 . Heat may be transferred from the inner wall  520  to cooling air flowing through nonlinear cooling holes  525 . 
     Referring to  FIG. 6 , a detailed view of the single-wall combustor liner  500  with the outer wall not showing is illustrated. The segmented walls  530  may form isolated segments  560 . The segmented walls  530  may prevent airflow between adjacent isolated segments  560 . Preventing airflow between the isolated segments  560  may cause a more even distribution of cooling air to flow through the cooling holes  525 . 
     Those skilled in the art will appreciate that the present disclosure is not limited to the particular shapes and configurations of cooling holes and segmented walls described herein. Rather, the use of additive manufacturing allows for a variety of new shapes for cooling holes and segmented walls which improve the cooling effect in combustor liners. The particular shapes disclosed herein are merely examples of such configurations. 
     Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
     Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. 
     Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.