Patent Publication Number: US-2013230379-A1

Title: Rotating turbomachine component having a tip leakage flow guide

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a rotating turbomachine component having a tip leakage flow guide. 
     Many turbomachines include a compressor portion linked to a turbine portion through a common compressor/turbine shaft or rotor and a combustor assembly. The compressor portion guides a compressed air flow through a number of sequential stages toward the combustor assembly. In the combustor assembly, the compressed air flow mixes with a fuel to form a combustible mixture. The combustible mixture is combusted in the combustor assembly to form hot gases. The hot gases are guided to the turbine portion through a transition piece. The hot gases expand through the turbine rotating turbine blades to create work that is output, for example, to power a generator, a pump, or to provide power to a vehicle. In addition to providing compressed air for combustion, a portion of the compressed airflow is passed through the turbine portion for cooling purposes. 
     In some cases, the hot gases expanding through the turbine portion leak or pass over tip end portions of the turbine blades. In order to reduce leakage, manufactures maintain tight clearances between the tip end portions and stationary components of the turbomachine. Generally, seals are provided on the stationary component or turbine shroud. While effective, existing seals still allow a portion of the hot gases or leakage gases to pass over the tip end portion. The tight clearance established by the seal causes the leakage gases to exit at an angle that is generally parallel to an axis defined by a turbomachine rotor. In contrast, hot gases passing along the gas path exit the rotor blades at an angle. Interactions between the leakage gases and the hot gases flowing along the gas path create localized pressure drops that have a negative impact on turbomachine performance. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the exemplary embodiment, a rotating turbomachine component includes a base portion and an airfoil portion extending from the base portion. The airfoil portion includes a base portion and a tip end portion that is cantilevered from the base portion. A tip leakage flow guide is provided at the tip end portion of the airfoil portion. The tip leakage flow guide includes one or more turning vane members configured and disposed to guide a leakage flow from the tip end portion at a flow angle that substantially coincides with a flow angle of gases flowing downstream from the rotating turbomachine component. 
     According to another aspect of the exemplary embodiment, a method of operating a turbomachine includes passing hot gases from a combustor assembly toward a plurality of buckets, guiding the hot gases onto the plurality of buckets, directing the hot gases downstream relative to the plurality of buckets along a gas path at a first flow angle, passing a portion of the hot gases over a tip end portion of the plurality of buckets at a second flow angle that is distinct from the first flow angle, and guiding the portion of the hot gases from the tip end portion of the plurality of buckets at a third flow angle that substantially coincides with the first angle. 
     According to yet another aspect of the exemplary embodiment, a turbomachine includes a compressor portion, a combustor assembly fluidly connecting the compressor portion and a turbine portion mechanically linked to the compressor portion and fluidly connected to the combustor assembly. The turbine portion includes a rotating component having a base portion and an airfoil portion extending from the base portion. The airfoil portion includes a first end connected to the base portion and a tip end portion that is cantilevered from the base portion. A tip leakage flow guide is provided at the tip end portion of the airfoil portion. The tip leakage flow guide includes one or more turning vane members configured and disposed to guide a leakage flow from the tip end portion at a flow angle that substantially coincides with a flow angle of gases flowing downstream from the rotating turbomachine component. A turning vane support member is positioned at the tip end portion. The turning vane support member includes an upstream end and a downstream end. The one or more turning vane members project outward from the turning vane support member 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic view of a turbomachine including a tip leakage flow guide in accordance with an exemplary embodiment; 
         FIG. 2  is a partial cross-sectional view of the turbomachine of  FIG. 1 ; 
         FIG. 3  is a detail view of a rotating component of the turbomachine of  FIG. 1  including a tip leakage flow guide in accordance with an exemplary embodiment; 
         FIG. 4  is a perspective view of the tip leakage flow guide of  FIG. 3  having a plurality of turning vane members in accordance with one aspect of the exemplary embodiment; 
         FIG. 5  is a perspective view of the tip leakage flow guide of  FIG. 3  having a plurality of turning vane members in accordance with another aspect of the exemplary embodiment; and 
         FIG. 6  is a perspective view of the tip leakage flow guide of  FIG. 3  having a plurality of turning vane members in accordance with still another aspect of the exemplary embodiment. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIGS. 1 and 2 , a turbomachine constructed in accordance with an exemplary embodiment is indicated generally at  2 . Turbomachine  2  includes a compressor portion  4  operatively connected to a turbine portion  6 . A combustor assembly  8  is fluidly connected to compressor portion  4  and turbine portion  6 . Combustor assembly  8  is formed from a plurality of circumferentially spaced combustors, one of which is indicated at  10 . Of course it should be understood that combustor assembly  8  could include other arrangements of combustors. Compressor portion  4  is also linked to turbine portion  6  through a common compressor/turbine shaft  12 . With this arrangement, compressor portion  4  delivers compressed air to combustor assembly  8 . The compressed air mixes with a combustible fluid to form a combustible mixture. The combustible mixture is combusted in combustor  10  to form products of combustion that are delivered to turbine portion  6  through a transition piece (not shown). The products of combustion expand along a gas path  18  of turbine portion  6  to power, for example, a generator, a pump, or a vehicle or the like (also not shown). 
     In the exemplary embodiment shown, turbine portion  6  includes a housing  19  that encases a first, stage  20  and a second stage  21  that define gas path  18 . First stage  20  includes a plurality of first stage stators or nozzles, one of which is indicated at  30 , supported to turbine housing  19  through a nozzle platform  31 . First stage  20  also includes a plurality of first stage buckets or blades, one of which is indicated at  32 , mounted to a first stage rotor wheel  34 . Blades  32  are spaced from a stationary shroud member  35 . Blades  32  include a base portion  38  and an airfoil portion  40 . Airfoil portion  40  includes a first end  42  coupled to base portion  38  and a second end or tip end portion  44  that is spaced from stationary shroud member  35 . Second stage  21  includes a plurality of second stage stators or nozzles, one of which is indicated at  48  supported to turbine housing  19  through a nozzle platform  49 . Second stage  21  also includes a plurality of second stage buckets or blades, one of which is indicated at  50 . At this point it should be understood that the number of stages in turbine portion  6  could vary. 
     In accordance with an exemplary embodiment, turbomachine  2  includes a tip leakage flow guide  60  that conditions tip leakage flow passing over tip portions of blades  32 . As best shown in  FIG. 3 , tip leakage flow guide  60  includes a turning vane support member  64  mounted to tip end portion  44  of blade  32 . Turning vane support member  64  includes an upstream end  66  that extends to a downstream end  68  through a substantially planar surface  70 . A seal element  74  extends from substantially planar surface  70  into a pocket (not separately labeled) of stationary shroud member  35 . Seal element  74  limits flow passing from gas path  18  across tip end portion  44  of blade  36 . However, while reduced, some leakage flow does flow over tip end portion  44  despite the presence of seal element  74 . In order to reduce losses associated with the leakage flow, one or more turning vane members  80  are positioned on turning vane support member  64 . In the exemplary aspect shown, turning vane member  80  is arranged adjacent to downstream end  68 . Turning vane member  80  alters a flow path of the leakage flow. 
     Combustion gases flow along gas path  18  and pass over nozzles  30  and are guided toward blades  32 . A first or main flow  85  passes over blades  32  and a second or leakage flow  88  passes over tip end portion  44  along gas path  18 . Main flow  85  flows at a first flow angle as a result of interactions with blade  36 . Leakage flow  88  flows at a second flow angle, that is distinct from the first flow angle, and which runs generally parallel to shaft  12 . Turning vane member  80  is configured to condition or turn leakage flow  88  exiting tip end portion  44  to create a turned flow  91  that returns to gas path  18  at a third flow angle that substantially coincides with the first flow angle of main flow  85  flowing downstream from blades  32 . By matching the third flow angle with the first flow angle, undesirable interactions between turned flow  91  and main flow  85  are reduced. In this manner, turning vane member  80  reduces losses within turbine portion  6  associated with pressure variations along gas path  18  resulting from undesirable interactions between leakage flow  88  and the main flow  85 . In the event that nozzles  30  form part of a last stage (not separately labeled) of turbine portion  6 , turning vane  80  may be configured to guide the leakage flow gases at an angle that generally corresponds to the flow angle of gases flowing downstream toward and along a radial diffusion section (not shown) of turbine portion  6  so as to enhance pressure recovery. 
     In accordance with one aspect of the exemplary embodiment illustrated in  FIG. 4 , turning vane member  80  takes the form of a plurality of substantially linear vane members  97 . Each vane member  97  includes a first end  99  and a second end  100 . Second end  100  is off-set relative to first end  99  such that vane members  97  are angled relative to, for example, shaft  12 . More specifically, vane members  97  are angled so as to generally correspond to an airfoil profile  102  of airfoil portion  40 . In accordance with one aspect of the exemplary embodiment, the angle of vane members  97  is substantially equal to or ±30° of a trailing edge angle θ of airfoil profile  102 .  FIG. 5  illustrates turning vanes  106  in accordance with another aspect of the exemplary embodiment. Turing vanes  106  take the form of a plurality of curvilinear vane members  110  having first and second curvilinear surfaces  112  and  113 . In a manner similar to that described above, vane members  110  are angled so as to generally correspond to an airfoil profile  102  of airfoil portion  40 . In accordance with one aspect of the exemplary embodiment, the angle of vane members  110  is substantially equal to or ±30° of a trailing edge angle θ of airfoil profile  102 .  FIG. 6  illustrates turning vanes  117  in accordance with yet another aspect of the exemplary embodiment. Turning vanes  117  take the form of complex geometrical vane members  121 . Complex geometrical vane members  121  include a first vane member  123  and a second vane member  124 . First vane member  123  includes a first end section  126  that extends to a second end section  127 . Second vane member  124  includes a first end portion  129  that extends from second end section  127  of first vane member  123  to a second end portion  130 . Second end portion  130  is off-set relative to first end section  126  of first vane member  123  and is angled so as to generally correspond to an airfoil profile  102  of airfoil portion  40 . In accordance with one aspect of the exemplary embodiment, the angle of second end portion  130  is substantially equal to or ±30° of a trailing edge angle θ of airfoil profile  102 . Regardless of form, the turning vanes condition the leakage flow to pass back into the gas path at an angle the substantially coincides with the main flow to reduce undesirable interactions. 
     At this point it should be understood that the exemplary embodiments provide a system for redirecting tip leakage flow back into the gas path to reduce undesirable interactions with the main flow. Reducing undesirable interactions with the main flow leads to a reduction in pressure losses that may detract from turbine performance. It should also be understood that while shown in connection with a gas turbomachine, the exemplary embodiments could also be employed in a steam turbomachine. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.