Patent Publication Number: US-10781707-B2

Title: Integral half vane, ringcase, and id shroud

Description:
STATEMENT OF GOVERNMENT INTEREST 
     This invention was made with Government support awarded by the United States. The Government has certain rights in this invention. 
    
    
     BACKGROUND 
     The present disclosure relates to variable area vanes in gas turbine engines. 
     Gas turbine engines typically include a compressor section, a combustor section, and a turbine section. During operation, air is pressurized in the compressor section, and is mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases are communicated through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and other gas turbine engine loads. 
     Typically, both the compressor and turbine sections include alternating arrays of vanes and rotating blades that extend into a core airflow path of the gas turbine engine. For example, in the compressor section, compressor blades rotate to pull air into the compressor section for compression. The compressor vanes guide the airflow between different arrays (also called stages) of rotating blades and prepare the airflow for a downstream array of blades. Some compressor sections include variable area vanes, which include vanes that are moveable to vary the area or direction of the flow of the core airflow path between two stages of rotating blades. Movement of the variable area vanes is controlled to optimize the performance of the gas turbine engine during various operating conditions. 
     SUMMARY 
     In one aspect of the invention, a vane stage includes a ringcase extending circumferentially about a center axis of the vane stage. The ringcase extends completely about the center axis to form a first ring. An inner shroud extends circumferentially about the center axis of the vane stage. The inner shroud extends completely about the center axis to form a second ring positioned radially within the ringcase relative the center axis. A plurality of stationary half vanes extend radially between the ringcase and the inner shroud, and are circumferentially spaced about the center axis. The plurality of stationary half vanes are integral with the ringcase and the inner shroud. 
     In another aspect of the invention, a vane stage includes a ringcase extending circumferentially about a center axis of the vane stage. The ringcase extends completely about the center axis to form a first non-segmented ring. An inner shroud extends circumferentially about the center axis of the vane stage. The inner shroud extends completely about the center axis to form a second non-segmented ring radially within the ringcase relative the center axis. A plurality of stationary half vanes extend radially between the ringcase and the inner shroud. The plurality of stationary half vanes are circumferentially spaced about the center axis and are integrally connected to the ringcase and the inner shroud. Each of the plurality of stationary half vanes includes both a leading edge extending radially from the inner shroud to the ringcase, and a groove extending radially from the inner shroud to the ringcase aft of the leading edge. A partial suction surface extends radially from the inner shroud to the ringcase and extends axially from the leading edge to the groove. A partial pressure surface extends radially from the inner shroud to the ringcase and extends axially from the leading edge to the groove opposite the partial suction surface. The groove is positioned between the partial suction surface and the partial pressure surface. 
     In another aspect of the invention, a vane stage includes a ringcase extending circumferentially about a center axis of the vane stage. The ringcase extends completely about the center axis to form a first non-segmented ring. An inner shroud extends circumferentially about the center axis of the vane stage. The inner shroud extends completely about the center axis to form a second non-segmented ring positioned radially within the ringcase relative the center axis. A plurality of stationary half vanes extend radially between the ringcase and the inner shroud, and are circumferentially spaced about the center axis. The plurality of stationary half vanes are integral with the ringcase and the inner shroud. A plurality of trunnion holes are formed in the ringcase aft of the plurality of stationary half vanes. Each trunnion hole of the plurality of trunnion holes is circumferentially aligned with one of the plurality of stationary half vanes and extends radially through the ringcase. 
     Persons of ordinary skill in the art will recognize that other aspects and embodiments of the present invention are possible in view of the entirety of the present disclosure, including the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view of a gas turbine engine. 
         FIG. 2  is a perspective view of an integral half vane structure with an outer ringcase, and inner shroud, and a plurality of stationary half vanes. 
         FIG. 3  is a perspective cross-sectional view of the integral half vane structure from  FIG. 2  with the cross section taken in the axial-radial plane. 
         FIG. 4  is a perspective cross-sectional view of the integral half vane structure of  FIGS. 2 and 3  with the cross section taken in the axial-circumferential plane. 
         FIG. 5  is a cross-sectional view in the axial-radial plane of the integral half vane structure assembled with a plurality of rotating variable half vanes. 
         FIG. 6  is a cross-sectional view of one of the stationary half vanes and one of variable half vanes from  FIG. 5 . 
         FIG. 7  is a perspective view of ribs on the outer surface of the ringcase of the integral half vane structure of  FIGS. 1 and 5 . 
     
    
    
     While the above-identified drawing figures set forth one or more embodiments of the invention, other embodiments are also contemplated. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features and components not specifically shown in the drawings. Like reference numerals identify similar structural elements. 
     DETAILED DESCRIPTION 
     The present disclosure provides a vane stage with an integral half vane structure with an outer ringcase, and inner shroud, and a plurality of stationary half vanes. Rotating variable half vanes are assembled onto the integral half vane structure aft of the stationary half vanes. Together, the stationary half vanes and the variable half vanes form an array of vanes where each vane has a fixed leading edge and an adjustable trailing edge that can be controlled to optimize the performance of a gas turbine engine during various operating conditions. Because the plurality of stationary half vanes, the outer ringcase and the inner shroud are integral, the position of stationary half vanes within integral half vane structure can be tightly controlled, which leads to tighter tolerances between the stationary half vanes and the variable half vanes. Tighter tolerances between the stationary half vanes and the variable vanes reduce flow irregularities across the vane stage. Making the ringcase, the inner shroud, and the plurality of stationary half vanes integral also reduces the number of parts and the weight of the vane stage when compared to traditional vane stages where vanes and shroud segments are fastened together into a vane pack. 
       FIG. 1  is a quarter-sectional view that schematically illustrates example gas turbine engine  20  that includes fan section  22 , compressor section  24 , combustor section  26  and turbine section  28 . Fan section  22  drives air along bypass flow path B in bypass duct D while compressor section  24  draws air in along core flow path C where air is compressed and communicated to combustor section  26 . In combustor section  26 , air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through turbine section  28  where energy is extracted and utilized to drive fan section  22  and compressor section  24 . Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
     The example gas turbine engine  20  generally includes low speed spool  30  and high speed spool  32  mounted for rotation about center axis CA of gas turbine engine  20  relative to engine static structure  36  via several bearing assemblies  38 . It should be understood that various bearing assemblies  38  at various locations may alternatively or additionally be provided. 
     Low speed spool  30  generally includes inner shaft  40  that connects fan  42  and low pressure (or first) compressor  44  to low pressure (or first) turbine  46 . Inner shaft  40  drives fan  42  through a speed change device, such as geared architecture  48 , to drive fan  42  at a lower speed than low speed spool  30 . High-speed spool  32  includes outer shaft  50  that interconnects high pressure (or second) compressor  52  and high pressure (or second) turbine  54 . Inner shaft  40  and outer shaft  50  are concentric and rotate via bearing assemblies  38  about center axis CA. 
     Combustor  56  is arranged between high pressure compressor  52  and high pressure turbine  54 . Mid-turbine frame  57  of engine static structure  36  can be arranged generally between high pressure turbine  54  and low pressure turbine  46 . Mid-turbine frame  57  further supports bearing assemblies  38  in turbine section  28  as well as setting airflow entering the low pressure turbine  46 . Mid-turbine frame  57  includes airfoils  59  which are in core flow path C. The air in core flow path C is compressed first by low pressure compressor  44  and then by high pressure compressor  52 . Next, the air is mixed with fuel and ignited in combustor  56  to produce high speed exhaust gases that are then expanded through high pressure turbine  54 , mid-turbine frame  58 , and low pressure turbine  46 . As discussed below with reference to  FIGS. 2-4 , compressor section  24  can include an integral half vane structure  60  that is used in a variable vane stage. 
       FIGS. 2-4  will be discussed concurrently.  FIG. 2  is a perspective view of integral half vane structure  60 .  FIG. 3  is a perspective cross-sectional view of integral half vane structure  60  with the cross section taken in the axial-radial plane.  FIG. 4  is a perspective cross-sectional view of integral half vane structure  60  with the cross section taken in the axial-circumferential plane. As shown in  FIGS. 2-4 , integral half vane structure  60  includes ringcase  62 , inner shroud  64 , and a plurality of stationary half vanes  66 . As shown best in  FIG. 2 , integral half vane structure  60  also includes forward flange  68  and aft flange  70  on ring case  62 , and mounting tabs  72  on inner shroud  64 . As shown best in  FIGS. 3 and 4 , each stationary half vane  66  in the plurality of half vanes  66  includes leading edge  74 , groove  76 , partial suction surface  78 , and partial pressure surface  80 . Inner shroud includes forward edge  82 , aft edge  84 , and a plurality of sockets  86 . Ringcase  62  includes forward edge  88 , aft edge  90  (shown in  FIG. 2 ), and a plurality of outer trunnion holes  92 . As shown best in  FIG. 4 , each stationary half vane  66  can also include undercut  94 . Aft ring  96  and inner trunnion holes  98  are also shown in  FIG. 4 . 
     Ringcase  62  extends circumferentially about center axis CA. Ringcase  62  extends completely about center axis CA to form a first complete and non-segmented ring. Ringcase  62  extends axially from forward edge  88  to aft edge  90 . Forward flange  68  is formed on forward edge  88  of ringcase  62  and extends radially outward from ringcase  62 . Aft flange  70  is formed on aft edge  90  of ringcase  62  and extends radially outward from ringcase  62 . Forward flange  68  and aft flange  70  are configured to allow ringcase  62  to be mounted between two axially-adjacent structures (not shown) in gas turbine engine  20 . Inner shroud  64  also extends circumferentially about center axis CA. Similar to ringcase  62 , inner shroud  64  extends completely about center axis CA to form a second complete and non-segmented ring. Inner shroud  64  is smaller in diameter than ringcase  62  and is positioned radially within ringcase  62  such that ringcase  62  and inner shroud  64  are concentric on central axis CA. Inner shroud  64  extends axially from forward edge  82  to aft edge  84 . Mounting tabs  72  are formed on a radially inner surface of inner shroud  64  between forward edge  82  and aft edge  84 . Mounting tabs  72  are circumferentially spaced from one another and extend radially inward from inner shroud  64 . Mounting tabs  72  are provided to connect inner shroud  64  to forward and aft adjacent structures (such as aft ring  96  shown in  FIG. 5 ) in gas turbine engine  20 . 
     The plurality of stationary half vanes  66  extend radially between ringcase  62  and inner shroud  64  and connect ringcase  62  and inner shroud  64  together. Stationary half vanes  66  are spaced circumferentially about center axis CA. Stationary half vanes  66  are integral with ring case  62  and inner shroud  64 . Integral half vane structure  60  can be formed by machining ringcase  62 , inner shroud  64  and stationary half vanes  66  from a single piece of metal. Integral half vane structure  60  can also be made by first forming ringcase  62 , welding a cylindrical plate (not shown) inside ringcase  62 , and machining the cylindrical plate to form inner shroud  64  and stationary half vanes  66 . Integral half vane structure  60  can also be made by separately forming ringcase  62 , inner shroud  64 , and stationary half vanes  66 , and welding ringcase  62 , inner shroud  64 , and stationary half vanes  66  together. Integral half vane structure  60  can also be formed through additive manufacturing. 
     As shown best in  FIGS. 3 and 4 , leading edge  74  of each stationary half vane  66  extends radially from inner shroud  64  to ringcase  62 . The body of stationary half vane  66  extends axially aft from leading edge  74 . Groove  76  is formed on an aft end of stationary half vane  66  and is thus axially aft of leading edge  74 . Groove  76  extends on stationary half vane  66  from inner shroud  64  to ringcase  62 . In the embodiments of  FIGS. 3 and 4 , groove  76  has a concave cross-sectional profile such that groove  76  has a surface that curves axially forward into stationary half vane  66 . Partial suction surface  78  of stationary half vane  66  extends radially from inner shroud  64  to ringcase  62  and extends axially from leading edge  74  to groove  76 . Partial pressure surface  80  of stationary half vane  66  also extends radially from inner shroud  64  to ringcase  62  and extends axially from leading edge  74  to groove  76  opposite partial suction surface  78 . Groove  76  is positioned between partial suction surface  78  and partial pressure surface  80  at the aft end of stationary half vane  66 . As shown in  FIG. 4 , an undercut  94  can be formed between the aft end of each stationary half vane  66  and inner shroud  64  to reduce bending stress concentrations between half vane  66  and inner shroud  64  during operation of gas turbine engine  20  (shown in  FIG. 1 ). Another undercut (not shown) can be formed between the aft end of each stationary half vane  66  and ringcase  62  to reduce bending stress concentrations between half vane  66  and ringcase  62  during operation of gas turbine engine  20 . 
     The plurality of outer trunnion holes  92  are formed in ringcase  62  aft of the plurality of stationary half vanes  66 . Each of the outer trunnion holes  92  is circumferentially aligned with one of the plurality of stationary half vanes  66  and extends radially through ringcase  62  just aft of groove  76 . A boss can be formed around each of the outer trunnion holes  92  to reinforce the circumference of the outer trunnion holes  92 . The plurality of sockets  86  are formed on aft edge  84  of inner shroud  64 . Each socket  86  of the plurality of sockets  86  is circumferentially aligned with one of the plurality of stationary half vanes  66 . As shown best in  FIG. 4 , inner trunnion holes  98  are formed by inner shroud  64  and aft ring  96 . Aft ring  96  abuts aft edge  84  of inner shroud  64  and is fastened to mounting tabs  72  of inner shroud  64 . Half of each inner trunnion hole  98  is formed on aft edge  84  over one of the plurality of sockets  86 , and the other half of each inner trunnion hole  98  is formed on aft ring  96 . As discussed below with reference to  FIGS. 5 and 6 , groove  76  on each of stationary half vanes  66 , the plurality of outer trunnion holes  92 , the plurality of sockets  86 , and the inner trunnion holes  98  are features that accommodate the assembly of a plurality of variable half vanes  100  onto integral half vane structure  60 . 
       FIGS. 5 and 6  will be discussed concurrently.  FIG. 5  is a cross-sectional view in the axial-radial plane of integral half vane structure  60  assembled with a plurality of rotating variable half vanes  100 .  FIG. 6  is a cross-sectional view of one of the stationary half vanes  66  and one of the variable half vanes  100 . Each one of the variable half vanes  100  in  FIGS. 5 and 6  include trailing edge  102 , joining edge  104 , first trunnion  106 , second trunnion  108 , button  110 , partial pressure surface  120 , and partial suction surface  122 . Trunnion nuts  112  and outer surface  114  and ribs  116  of ringcase  62  are shown in the embodiment of  FIG. 5 . 
     Each variable half vane  100  is assembled onto integral half vane structure  60  immediately aft of one of stationary half vanes  66 . On each of variable half vanes  100 , trailing edge  102  extends radially between inner shroud  64  and ringcase  62 . Joining edge  104  is forward of trailing edge  102  and aft of groove  76 . Joining edge  104  extends radially from inner shroud  64  to ringcase  62 . As shown best in  FIG. 6 , joining edge  104  of each variable half vane  100  is configured to mate with groove  76  on the adjacent stationary half vane  66 . In the embodiment of  FIG. 6 , joining edge  104  is rounded with a convex cross-sectional profile, so as to correspond with the concave profile of groove  76 . Partial suction surface  122  of variable half vane  100  extends from joining edge  104  to trailing edge  102 . Partial pressure surface  120  of variable half vane  100  extends from joining edge  104  to trailing edge  102  opposite partial suction surface  122 . Partial suction surface  122  and partial pressure surface  120  of variable half vane  100  cooperate with partial suction surface  78  and partial pressure surface  80  of stationary half vane  66  respectively to create a complete airfoil profile that extends axially from leading edge  74  to trailing edge  102 . The portion of the airfoil profile formed by stationary half vane  66  does not move or change position during operation of gas turbine engine  20  (shown in  FIG. 1 ), whereas the portion of the airfoil profile formed by variable half vane  100  is able to pivot and move on axis R relative stationary half vane  66 . 
     On each of variable half vanes  100 , first trunnion  106  extends radially outward proximate joining edge  104  and into one of outer trunnion holes  92  on ringcase  62 . Trunnion nut  112  is fastened to first trunnion  106  to fasten variable half vane  100  to ringcase  62 . Second trunnion  108  extends radially inward proximate joining edge  104  and is positioned aft of aft edge  84  (shown in  FIG. 3 ) of inner shroud  64 . Second trunnion  108  extends through one of inner trunnion holes  98  (shown in  FIG. 4 ). Button  110  is formed on second trunnion  108 , and a portion of button  110  is received by one of the plurality of sockets  86  on inner shroud  64 . The other portion of button  110  is housed within a pocket on aft ring  96 . Button  110 , socket  86 , and the pocket on aft ring  96  work together to connect variable half vane  100  to inner shroud  64 . 
     Aft ring  96  forms an inner diameter flow surface aft and downstream of stationary half vanes  66 . Aft ring  96  also forms the inner diameter flow surface under at least a portion of variable half vanes  100 . As shown in  FIG. 5 , ringcase  62  is axially longer than inner shroud  64  and extends aft of variable half vanes  100 . In the embodiment of  FIG. 5 , ringcase  62  can be axially long enough such that aft end  90  of ringcase  62  can extend around a stage of rotor blades (not shown). Ringcase  62  can also increase in diameter from aft of stationary half vanes  66 . Due to the longer axial length of ringcase  62 , ribs  116  are formed on outer surface  114  of ringcase  62  to stiffen ringcase  62  against bending and other forces integral half vane structure  60  may encounter during operation of gas turbine engine  20  (shown in  FIG. 1 ). The configuration of ribs  116  is discussed below with reference to  FIG. 7 . 
       FIG. 7  is a perspective view of ribs  116  on outer surface  114  of ringcase  62 . As shown in  FIG. 7 , ribs  116  include axial ribs  116 A, first angled ribs  116 B, and second angled ribs  116 C. Ribs  116  also include nodes  124 . Axial ribs  116 A, first angled ribs  116 B, and second angled ribs  116 C are all formed on outer surface  114  of ringcase  62  aft of stationary half vanes  66  (shown in  FIGS. 2-6 ). Axial ribs  116 A extend on outer surface  114  parallel to center axis CA and are circumferentially spaced apart from one another on outer surface  114 . First angled ribs  116 B extend on outer surface  114  non parallel to center axis CA and intersect axial ribs  116 A at nodes  124 . 
     In the embodiment of  FIG. 7 , each of first angled ribs  116 B intersect two axial ribs  116 A. Second angled ribs  116 C extend on outer surface  114  non parallel to center axis CA and intersect axial ribs  116 A and first angled ribs  116 B at nodes  124 . In the embodiment of  FIG. 7 , each of second angled ribs  116 C intersects two axial ribs  116 A and two first angled ribs  116 B. First angled ribs  116 B can intersect second angled ribs  116 C at a forty-five degree angle. As shown in  FIG. 7 , nodes  24  are not centered on axial ribs  116 A, but alternate such that nodes  24  are on a forward portion of every other axial rib  116 A and on an aft portion of the remaining axial ribs  116 A. Alternating the position of nodes  24  on axial ribs  116 A distributes ribs  116  on outer surface  114  of ringcase  62  such that ribs  116  evenly reinforce ringcase  62 . Axial ribs  116 A, first angled ribs  116 B, and second angled ribs  116 C all increase in radial thickness in the axially aft direction to accommodate the increasing diameter of ringcase  62 , as discussed above with reference to  FIG. 5 . 
     In view of the foregoing description, it will be recognized that the present disclosure provides numerous advantages and benefits. For example, the present disclosure provides integral half vane structure  60  with ringcase  62 , inner shroud  64 , and a plurality of stationary half vanes  66 . Stationary half vanes  66  are integral with ring case  62  and inner shroud  64 . Because stationary half vanes  66  are integral with ring case  62  and inner shroud  64 , the position of each stationary half vane  66  can be tightly controlled during manufacturing and does not shift or vary like prior art vane assemblies. Furthermore, by making stationary half vanes  66  integral with ringcase  62  and inner shroud  64 , fewer parts, fasteners, and overall mass are required to assemble a vane stage that incorporates integral half vane structure  60  than prior art vane assemblies. 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     In one embodiment, a vane stage includes a ringcase extending circumferentially about a center axis of the vane stage. The ringcase extends completely about the center axis to form a first ring. An inner shroud extends circumferentially about the center axis of the vane stage. The inner shroud extends completely about the center axis to form a second ring positioned radially within the ringcase relative the center axis. A plurality of stationary half vanes extend radially between the ringcase and the inner shroud, and are circumferentially spaced about the center axis. The plurality of stationary half vanes are integral with the ringcase and the inner shroud. 
     The vane stage of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     each of the plurality of stationary half vanes comprises: a leading edge extending radially from the inner shroud to the ringcase; a concave groove extending radially from the inner shroud to the ringcase and aft of the leading edge; a partial suction surface extending radially from the inner shroud to the ringcase and extending axially from the leading edge to the concave groove; and a partial pressure surface extending radially from the inner shroud to the ringcase and extending axially from the leading edge to the concave groove opposite the partial suction surface, and wherein the concave groove is positioned between the partial suction surface and the partial pressure surface; 
     each of the plurality of stationary half vanes further comprises: a first undercut formed between the concave groove and the inner shroud; and a second undercut formed between the concave groove and the ringcase; 
     a plurality of trunnion holes formed in the ringcase, wherein each trunnion hole of the plurality of trunnion holes is circumferentially aligned with one of the plurality of stationary half vanes and extends radially through the ringcase aft of the concave groove; 
     a plurality of sockets formed on an aft edge of the inner shroud, wherein each socket of the plurality of sockets is circumferentially aligned with one of the plurality of stationary half vanes; 
     a plurality of variable half vanes, wherein each of the plurality of variable half vanes comprises: a trailing edge extending radially between the inner shroud and the ringcase; a convex edge extending radially from the inner shroud to the ringcase, wherein the convex edge is forward of the trailing edge and configured to mate with the concave groove of one of the plurality of stationary half vanes; a first trunnion extending radially from the convex edge into one of the plurality of trunnion holes; a second trunnion extending radially from the convex edge opposite the first trunnion, wherein the second trunnion is aft of the aft edge of the inner shroud; and a button formed on the second trunnion, wherein a portion of the button is received by one of the plurality of sockets; 
     the ringcase is axially longer than the inner shroud and increases in diameter aft of the plurality of stationary half vanes; 
     the ringcase comprises a plurality of ribs formed on an outer surface of the ringcase aft of the plurality of stationary half vanes; 
     each of the plurality of ribs increases in radial thickness in an aft direction; 
     the plurality of ribs comprises: an axial rib extending parallel to the center axis; a first angled rib intersecting the axial rib at a node; and a second angled rib intersecting the axial rib and the first angled rib at the node; and/or 
     the node is not centered on the axial rib. 
     In another embodiment, a vane stage includes a ringcase extending circumferentially about a center axis of the vane stage. The ringcase extends completely about the center axis to form a first non-segmented ring. An inner shroud extends circumferentially about the center axis of the vane stage. The inner shroud extends completely about the center axis to form a second non-segmented ring radially within the ringcase relative the center axis. A plurality of stationary half vanes extend radially between the ringcase and the inner shroud. The plurality of stationary half vanes are circumferentially spaced about the center axis and are integrally connected to the ringcase and the inner shroud. Each of the plurality of stationary half vanes includes both a leading edge extending radially from the inner shroud to the ringcase, and a groove extending radially from the inner shroud to the ringcase aft of the leading edge. A partial suction surface extends radially from the inner shroud to the ringcase and extends axially from the leading edge to the groove. A partial pressure surface extends radially from the inner shroud to the ringcase and extends axially from the leading edge to the groove opposite the partial suction surface. The groove is positioned between the partial suction surface and the partial pressure surface. 
     The vane stage of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     the groove of each of the plurality of stationary half vanes is a concave groove with a surface that curves axially forward into the respective stationary half vane; 
     a plurality of trunnion holes formed in the ringcase, wherein each trunnion hole of the plurality of trunnion holes is circumferentially aligned with one of the plurality of stationary half vanes and extends radially through the ringcase aft of the groove; 
     a plurality of sockets formed on an aft edge of the inner shroud, wherein each socket of the plurality of sockets is circumferentially aligned with one of the plurality of stationary half vanes; 
     a plurality of variable half vanes, wherein each of the plurality of variable half vanes comprises: a trailing edge extending radially between the inner shroud and the ringcase; a joining edge extending radially from the inner shroud to the ringcase, wherein the joining edge is forward of the trailing edge and configured to mate with the groove of one of the plurality of stationary half vanes; a first trunnion extending radially from the joining edge into one of the plurality of trunnion holes; a second trunnion extending radially from the joining edge opposite the first trunnion, wherein the second trunnion is aft of the aft edge of the inner shroud; and a button formed on the second trunnion, wherein a portion of the button is received by one of the plurality of sockets; and/or 
     the ringcase is axially longer than the inner shroud. 
     In another embodiment, a vane stage includes a ringcase extending circumferentially about a center axis of the vane stage. The ringcase extends completely about the center axis to form a first non-segmented ring. An inner shroud extends circumferentially about the center axis of the vane stage. The inner shroud extends completely about the center axis to form a second non-segmented ring positioned radially within the ringcase relative the center axis. A plurality of stationary half vanes extend radially between the ringcase and the inner shroud, and are circumferentially spaced about the center axis. The plurality of stationary half vanes are integral with the ringcase and the inner shroud. A plurality of trunnion holes are formed in the ringcase aft of the plurality of stationary half vanes. Each trunnion hole of the plurality of trunnion holes is circumferentially aligned with one of the plurality of stationary half vanes and extends radially through the ringcase. 
     The vane stage of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components: 
     each of the plurality of stationary half vanes comprises: a leading edge extending radially from the inner shroud to the ringcase; a groove extending radially from the inner shroud to the ringcase and aft of the leading edge, wherein the groove has a concave cross-sectional profile; a partial suction surface extending radially from the inner shroud to the ringcase and extending axially from the leading edge to the groove; and a partial pressure surface extending radially from the inner shroud to the ringcase and extending axially from the leading edge to the groove opposite the partial suction surface, and wherein the groove is positioned between the partial suction surface and the partial pressure surface; and/or 
     a plurality of variable half vanes, wherein each of the plurality of variable half vanes comprises: a trailing edge extending radially between the inner shroud and the ringcase; a joining edge extending radially from the inner shroud to the ringcase, wherein the joining edge is forward of the trailing edge and configured to mate with the groove of one of the plurality of stationary half vanes; a first trunnion extending radially from the joining edge into one of the plurality of trunnion holes; a second trunnion extending radially from the convex edge opposite the first trunnion, wherein the second trunnion is aft of an aft edge of the inner shroud. 
     Any relative terms or terms of degree used herein, such as “substantially”, “essentially”, “generally”, “approximately”, and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, transitory vibrations and sway movements, temporary alignment or shape variations induced by operational conditions, and the like. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. For example, while  FIGS. 1-7  disclose integral half vane structure  60  being used in compressor section  24 , integral half vane structure  60  can be adapted for use in turbine section  28 . Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.