Patent Publication Number: US-10309652-B2

Title: Gas turbine engine combustor basket with inverted platefins

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to combustor baskets for gas turbine engine combustors. More particularly, the invention relates to combustor baskets of the type having nested inner and outer liners separated by a cooling air gap. 
     2. Description of the Prior Art 
     Some known types of gas turbine engines having annular combustor construction incorporate combustor baskets with nested inner and outer liners, separated by a cooling air gap. The cooling air gap is maintained at the distal downstream tip of the basket by radially outwardly directed dimples formed in the inner basket distal tip that abut against the outer liner. A standoff gap is preserved between the respective liners so long as the dimples maintain structural integrity. The inner liner is in direct communication with the combusted gas flow, experiencing higher temperature exposure than the outer liner. The combustion gas thermal and fluid contact erodes and/or distorts the inner basket during engine operation. In some operating environments dimples formed on the inner liner distal tip erode or collapse, facilitating collapsing of the cooling gap between the inner and outer liners. Diminished cooling flow hastens further thermal erosion of the combustion basket. In an effort to improve cooling airflow in the combustor basket gap between the inner and outer liners, some combustor basket designs have incorporated through holes in the inner liner circumference, especially proximal the basket distal tip portion, in order to induce radial airflow into the gap as well as axial airflow. 
     SUMMARY OF THE INVENTION 
     Accordingly, a suggested object of embodiments of the invention is to maintain combustor basket cooling airflow in the gap between inner and outer liners during operation of the gas turbine engine. 
     Another object of embodiments of the invention is to maintain the invention is to combustor basket cooling airflow in the gap between inner and outer liners during operation of the gas turbine engine while preserving the option of forming cooling air through holes in the inner liner. 
     Yet another object of embodiments of the invention is to enhance combustor basket service life by maintaining combustor basket cooling airflow in in the gap between inner and outer liners during operation of the gas turbine engine. 
     These and other objects are achieved in one or more embodiments of the invention by a gas turbine engine combustor basket, which has nested outer and inner liners that are separated by a gap at their respective distal downstream ends for passage of cooling air between the liners. Radially inwardly projecting platefins formed on an inner circumferential surface of the outer liner maintain the cooling air passage gap. In some embodiments effusion cooling through holes are formed in the inner liner outer circumference, oriented in the air passage gap between the fins, so that cooling air passes through the effusion holes into the cooling air passage gap. By locating the platefins on the outer liner they are less susceptible to thermal erosion and distortion than previously known liner separation constructions that were located on the inner liner. Locating the platefins on the outer liner also facilitates inclusion of cooling through holes on the inner liner between the corresponding outer liner platefins, so that additional radial cooling flow is introduced into the gap between the liners. Combustor basket service life is enhanced by maintaining cooling airflow gap between the inner and outer liners. 
     Other embodiments of the invention feature a gas turbine engine including a turbine casing, which in turn includes therein a rotatable rotor as well as compressor, combustor and turbine sections. The combustor section has a plurality of nested outer and inner liners, respectively having axial length and radially spaced downstream distal ends. The respective liners form a gap between themselves for passage of cooling air. Radially inwardly projecting platefins formed on an inner circumferential surface of each of the outer liners maintains the cooling air passage gap. 
     Additional embodiments of the invention feature method for cooling a gas turbine engine combustor basket, for passage of combustion gas there through. The method includes the steps of providing nesting outer and inner liners, respectively having axial length and radially spaced downstream distal ends; and forming radially inwardly projecting platefins on an inner circumferential surface of the outer liner. The inner liner is nested within the outer liner, so that distal tips of the platefins abut an outer circumference of the inner liner distal end, thereby forming a cooling air passage gap between the respective liners, for passage of cooling air. The combustor basket is installed within a gas turbine combustor. The engine is operated, so that cooling air passes through the cooling air passage gap. 
     The respective objects and features of the present invention may be applied jointly or severally in any combination or sub-combination by those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
         FIGS. 1 and 2  are axial cross sectional views of a gas turbine engine incorporating an embodiment of a combustor including a combustor basket of the invention; 
         FIG. 3  is a perspective end view of the combustor basket of  FIGS. 1 and 2 , including a detailed view of the distal tip gap formed between the basket&#39;s inner and outer liners; 
         FIG. 4  is a radial cross sectional view of the combustor basket outer and inner liners, taken along  4 - 4  of  FIG. 3 , showing abutment of outer liner platefins against an outer circumferential surface of the inner liner between the inner liner effusion cooling through holes; and 
         FIG. 5  is a detailed axial cross sectional view of the inner and outer liner interface at a distal tip of the combustor basket of  FIG. 2 , showing abutment of platefins against an outer circumferential surface of a corresponding inner liner. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
     DETAILED DESCRIPTION 
     After considering the following description, those skilled in the art will clearly realize that the teachings of embodiments of the invention can be readily utilized in a gas turbine engine combustor basket, which has nested outer and inner liners that are separated by a gap at their respective distal downstream ends for passage of cooling air between the liners. Radially inwardly projecting platefins formed on an inner circumferential surface of the outer liner maintain the cooling air passage gap. In some embodiments effusion cooling through holes are formed in the inner liner outer circumference, oriented in the air passage gap between the fins, so that cooling air passes through the effusion holes into the cooling air passage gap. By locating the platefins on the outer liner they are less susceptible to thermal erosion and distortion than previously known liner separation constructions that were located on the inner liner. Locating the platefins on the outer liner also facilitates inclusion of cooling through holes on the inner liner between the corresponding outer liner platefins, so that additional radial cooling flow is introduced into the gap between the liners. 
       FIGS. 1 and 2  show a gas turbine engine  20 , having a gas turbine casing  22 , a compressor section  24 , a combustor section  26 , a turbine section  28  and a rotor  30 . One of a plurality of basket-type combustors  32  is coupled to a downstream transition  34  that directs combustion gasses from the combustor to the turbine section  28 . As shown in greater detail in  FIG. 3 , the combustor  32  has a known pilot nozzle and a plurality of circumferentially arrayed main nozzles  38  within a combustor basket  40 . The combustor basket distal downstream end  42  interfaces with the transition  34 . 
     Referring to  FIGS. 3-5 , the exemplary combustor basket  40  has nested outer  44  and inner  46  liners, respectively having axial length, as well as radially spaced downstream distal ends that terminate at the combustor basket downstream end  42 . The outer  44  and inner  46  liners form a cooling gap or cavity  48  between their respective opposed surfaces. At the combustor basket distal tip  42  interface the radial cooling gap  48  is maintained by radially inwardly projecting platefins  50 , which are formed equidistantly apart from one neighboring platefins  50  on an inner circumferential surface of the outer liner  44 , for abutting contact with the inner liner  46 . The platefins  50  have a generally spline-like profile to facilitate axial cooling airflow through the radial cooling gap  48  between the outer and inner liners  44 ,  46 . Other platefins cross sectional profiles, such as triangular or trapezoidal profiles may be substituted for the generally rectangular cross sectional profile shown in  FIG. 4 . The platefins  50  optionally have distal tip  52  curved profiles that conform with an outer circumferential profile of the inner liner  46 . The exemplary embodiment platefins  50  shown in  FIGS. 4 and 5  are directly formed in the outer liner  44  by cutting or pressing metal forming operations. Alternatively, the platefins  50  can be formed in a separate component that is welded, fused or otherwise coupled to the outer liner  44 . 
     Cooling air flows axially through the gap  48  formed between the outer  44  and inner  46  liners, as shown schematically by the arrow F A  shown in  FIG. 3 . Optionally the inner liner  46  defines through-holes  54  along at least a portion of its axial length, for passage of effusion cooling air in the radial direction, as shown schematically in  FIG. 3 . At the downstream distal end  42  of the combustor basket  40  the inner liner through holes  54  are arrayed in airflow gaps  48  between the platefins  50 . Directed passage of cooling air via the through holes  50  at the downstream distal end  42  helps to reduce thermal erosion of the combustor basket  40 . Placement of the platefins  50  on the relatively cooler outer liner  44  rather than the known conventional placement of dimples on the relatively hotter inner liner  46  reduce risk of structural collapse of the platefins that might otherwise inadvertently restrict or close off cooling airflow gaps  48  near the collapsed portion. Added potential hotspots in the combustor basket distal end  42  would further increase risk of thermal damage to the combustor basket  40 . 
     Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.