Patent Publication Number: US-9840917-B2

Title: Stator vane shroud having an offset

Description:
BACKGROUND 
     This disclosure relates generally to a stator vane assembly and, more particularly, to a stator vane shroud that limits movement of the stator vane assembly. 
     Turbomachines typically include arrays of stator vanes distributed circumferentially about an axis. The stator vanes guide fluid through the turbomachine. The fluid moving through the turbomachine loads the stator vanes. 
     When loaded, circumferentially adjacent stator vanes may undesirably shift axially (or rack) relative to each other. Circumferentially adjacent stator vanes that have circumferentially overlapping portions experience especially high loads, which can increase the likelihood of a shift. A component of the load may be opposite the general direction of flow though the turbomachine. 
     Some turbomachine compressor cases include an added feature that limits axial movement of the stator vanes to limit undesirable shifts. The feature adds complexity to the turbomachine. 
     SUMMARY 
     A stator vane assembly of a turbomachine according to an exemplary embodiment of the present disclosure includes, among other possible things, a shroud having a leading edge, a trailing edge, and at least one circumferential edge. The leading edge is circumferentially offset relative to the trailing edge when installed within the turbomachine. 
     In a further embodiment of the foregoing stator vane assembly embodiment, the circumferential edge includes a portion that is aligned with an axis of the turbomachine. 
     In a further embodiment of either of the foregoing stator vane embodiments, a vane extends radially from the shroud. 
     In a further embodiment of any of the foregoing stator vane embodiments, the vane is a cantilevered vane. 
     In a further embodiment of any of the foregoing stator vane embodiments, the circumferential edge extends from the leading edge to the trailing edge, and a first portion of the circumferential edge is aligned with, and circumferentially offset from, a second portion of the circumferential edge. 
     In a further embodiment of any of the foregoing stator vane embodiments, the circumferential edge comprises an angled edge portion extending between the first portion and the second portion. 
     In a further embodiment of any of the foregoing stator vane embodiments, the angled edge portion has an angle that is offset from the first portion and the second portion, the angled edge portion configured to be spaced from an angled edge portion of a circumferentially adjacent vane. 
     In a further embodiment of any of the foregoing stator vane embodiments, the shroud is configured to contact a circumferentially adjacent shroud exclusively through portions of the circumferential edge other than the angled edge portion when loaded during operation of the turbomachine. 
     In a further embodiment of any of the foregoing stator vane embodiments, the circumferential edge has a step area. 
     In a further embodiment of any of the foregoing stator vane embodiments, the circumferential edge includes a first and a second circumferential edge of the shroud, the first circumferential edge mimicking a profile of the second circumferential edge. 
     In a further embodiment of any of the foregoing stator vane embodiments, the shroud is an outer diameter shroud. 
     A turbine engine according to another exemplary embodiment of the present disclosure includes, among other possible things, a stator vane array including a plurality of stator vanes distributed circumferentially about an axis. Each of the stator vanes including a shroud and a vane extending from the shroud toward the axis. Each of the stator vanes is circumferentially loaded against a circumferentially adjacent stator blade during operation. At least one of the shrouds has a leading edge, a trailing edge, and at least one circumferential edge. The leading edge is circumferentially offset relative to the trailing edge. 
     In a further embodiment of the foregoing turbine engine embodiment, the stator vanes are cantilevered stator vanes. 
     In a further embodiment of either of the foregoing turbine engine embodiments, the shroud is a radially outer shroud. 
     In a further embodiment of any of the foregoing turbine engine embodiments, the shroud interfaces with a circumferentially adjacent shroud along a circumferential edge that includes a step area. 
     In a further embodiment of any of the foregoing turbine engine embodiments, each of the plurality of stator vanes includes a single shroud and a single vane. 
     In a further embodiment of any of the foregoing turbine engine embodiments, the stator vane array is a nonrotating array. 
     In a further embodiment of any of the foregoing turbine engine embodiments, a fan or a compressor contains the stator vane array. 
     In a further embodiment of any of the foregoing turbine engine embodiments, a bypass ratio of the volume of air that passes through the fan and that does not pass through the compressor to the volume of air that passes through the fan and through the compressor is greater than 10. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
         FIG. 1  shows a section view of an example turbomachine. 
         FIG. 2  shows a perspective view of an example stator vane assembly of the  FIG. 1  turbomachine. 
         FIG. 3  shows a perspective view of the  FIG. 2  stator vane assembly interfacing with a circumferentially adjacent stator vane assembly. 
         FIG. 4  shows the radially outward facing surfaces of the  FIG. 3  stator vane assemblies. 
         FIG. 5  shows the radially inward facing surfaces of the  FIG. 3  stator vane assemblies. 
         FIG. 6  shows a perspective view of the  FIG. 2  stator vane assembly interfacing with two circumferentially adjacent stator vane assemblies within a sectioned portion of the  FIG. 1  turbomachine. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an example turbomachine, such as a gas turbine engine  10 , is circumferentially disposed about an axis A. The gas turbine engine  10  includes a fan  14 , a low-pressure compressor section  16 , a high-pressure compressor section  18 , a combustion section  20 , a high-pressure turbine section  22 , and a low-pressure turbine section  24 . Other example turbomachines may include more or fewer sections. 
     The engine  10  in the disclosed embodiment is a high-bypass geared architecture aircraft engine. In one disclosed embodiment, the engine  10  bypass ratio is greater than ten (10:1), the diameter of the turbofan  14  is significantly larger than that of the low pressure compressor  16 , and the low pressure turbine  24  has a pressure ratio that is greater than 5:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present application is applicable to other gas turbine engines including direct drive turbofans. 
     During operation, air is compressed in the low-pressure compressor section  16  and the high-pressure compressor section  18 . The compressed air is then mixed with fuel and burned in the combustion section  20 . The products of combustion are expanded across the high-pressure turbine section  22  and the low-pressure turbine section  24 . Flow of air moves through the gas turbine engine  10  generally in a direction F. 
     The low-pressure compressor section  16  and the high-pressure compressor section  18  each include rotors  28  and  30 , respectively. The high-pressure turbine section  22  and the low-pressure turbine section  24  each include rotors  36  and  38 , respectively. The rotors  36  and  38  rotate in response to the expansion to rotatably drive rotors  28  and  30 . The rotor  36  is coupled to the rotor  28  with a spool  40 , and the rotor  38  is coupled to the rotor  30  with a spool  42 . 
     Arrays  44  of guide vanes are used to guide flow through the various stages of the low-pressure compressor section  16  and the high-pressure compressor section  18 . Other arrays  48  of guide vanes are used to guide flow through the various stages of the low-pressure turbine section  22  and the high-pressure turbine section  24 . 
     The examples described in this disclosure are not limited to the two-spool gas turbine architecture described, however, and may be used in other architectures, such as the single-spool axial design, a three-spool axial design, and still other architectures. That is, there are various types of gas turbine engines, and other turbomachines, that can benefit from the examples disclosed herein. 
     Referring to  FIG. 2  with continuing reference to  FIG. 1 , a stator vane assembly  50  of the gas turbine engine  10  includes a shroud  54  and a vane  58 . The example stator vane assembly  50  is one of several stator vane assemblies within one of the arrays  44  of stator vane assemblies in the high-pressure compressor section  18  of the gas turbine engine  10 . 
     The example vane  58  extends radially from the shroud  54  toward the axis A. The shroud  54  is thus considered an outer shroud. The example stator vane assembly  50  includes a single shroud, and is thus considered a cantilevered stator vane assembly. 
     Only one vane  58  extends from the example shroud  54 . In other examples, more than one vane  58  may extend from the shroud  54 . 
     The shroud  54  includes an axially leading edge  66  and an axially trailing edge  70 . The designations as leading and trailing are relative a general direction of flow through the gas turbine engine  10 . Notably, the axially leading edge  66  is circumferentially offset relative to the axially trailing edge  70 . That is, the axially leading edge  66  is not in circumferential alignment with the axially trailing edge  70 . 
     Circumferential edges  74  and  78  of the shroud  54  extend from the leading edge  66  to the trailing edge  70 . The circumferential edges  74  and  78  include a step area  82 . The step area  82  transitions the circumferential edges  74  and  78  from a circumferential position aligned with the leading edge  66  to a circumferential position aligned with the trailing edge  70 . 
     The circumferential edge  74  includes a first axially extending portion  86 , a second axially extending portion  90 , and an angled edge portion  94 . The angled edge portion  94  extends between the first axially extending portion  86  and the second axially extended portion  90 . In this example, the first and second axially extending portions  86  and  90  are parallel to the axis A. 
     An outer radius  96  transitions the angled edge portion  94  into the first axially extending portion  86 . An inner radius  98  transitions the angled edge portion  94  into the second axially extending portion  90 . 
     In this example, the axially extending portions  86  and  90  are both aligned with the axis A. The angled edge portion  94  is about 45° offset from the axially extending portions  86  and  90 . 
     In this example, the profile of the circumferential edge  78  mimics the profile of the circumferential edge  74 . The circumferential edges of circumferentially adjacent stator vanes also mimic the profiles of the circumferential edge  74 . The circumferentially adjacent stator vanes are thus able to nest with the stator vane assembly  50  when in installed positions within the gas turbine engine  10 . 
     Although the profiles of the circumferential edges generally mimic each other, the example circumferentially edges are not exact replicas of each other. For example, the step area  82  is designed to be spaced slightly from a step area of a circumferentially adjacent stator vane. The first and second axially extending portions  86  and  90 , by contrast, are designed to directly contact the axially extending portions of the circumferentially adjacent stator vane. 
     Referring now to  FIGS. 3-6  with continuing reference to  FIGS. 1-2 , during operation of the gas turbine engine  10 , flow of a working fluid moves in the direction D past the stator vane assembly  50 , a circumferentially adjacent stator vane assembly  50   a , and a circumferentially adjacent stator vane assembly  50   b . The fluid moving through the gas turbine engine  10  loads the stator vane assemblies  50 ,  50   a , and  50   b , as is known. The load L on these stator vane assemblies  50 ,  50   a , and  50   b  has at least an axial component L a  and a circumferential component L c . Notably, the axial component L a  is opposite the direction D. 
     In this example, the step area  82  of the stator vane assembly  50  and a step area  82   a  of the stator vane assembly  50   a  are spaced slightly from each other. Thus, there is a gap g between the step area  82  and the step area  82   a . Because of the gap g, none of the load L is transferred from the stator vane assembly  50  to the stator vane assembly  50   a  through the step area  82  and the step area  82   a . Instead, the axial component L a  is directed through surface  100 , and perhaps surface  104 , at the leading edge  66 . 
     In other examples, the step area  82  may contact the step area  82   a ; however, there is still no significant load transfer through the step area  82  and the step area  82   a.    
     Directing the axial component L a  through the surfaces  100  and  104 , and the circumferential component L c  though the axially extending portions  86  and  90 , does not encourage the stator vane assembly  50  to shift or rack relative to the stator vane assembly  50   a . Limiting shifting and raking limits axial misalignment between the stator vane assembly  50  and the stator vane assembly  50   a.    
     Because of the step area  82 , the shroud  54  may be considered to have a chevron shape or profile. Because of the step area  82 , surfaces of the shroud  54  that face axially contact the adjacent surfaces of the stator vane assembly  50   a  adjacent thereto, when the vane assemblies  50  and  50   a  are loaded. 
     Features of the disclosed examples include a stator vane shroud having a step area that limits relative movement between the stator vane shroud and a circumferentially adjacent shroud. Incorporating the limiting feature into the shroud eliminates the need for features in the case to prevent such racking movements. The disclosed examples limit racking geometrically. 
     Although the different examples have the specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.