Patent Publication Number: US-2015078898-A1

Title: Compound Cooling Flow Turbulator for Turbine Component

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/536,869 (attorney docket 2009P10468US) filed on 6 Aug. 2009 and incorporated by reference herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED DEVELOPMENT 
     Development for this invention was supported in part by Contract Number DE-FC26-05NT42644, awarded by the United States Department of Energy. Accordingly the United States Government may have certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to turbulators in cooling channels of turbine components, and particularly in gas turbine airfoils. 
     BACKGROUND OF THE INVENTION 
     Stationary guide vanes and rotating turbine blades in gas turbines often have internal cooling channels. Cooling effectiveness is important in order to minimize thermal stress on these airfoils. Cooling efficiency is important in order to minimize the volume of air diverted from the compressor for cooling. 
     One cooling technique uses serpentine cooling channels with turbulators. An example is shown in U.S. Pat. No. 6,533,547. The present invention provides improved turbulators with features at multiple scales in combinations that increase surface area, increase boundary layer mixing, and control boundary layer separation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in the following description in view of the drawings that show: 
         FIG. 1  is a sectional view of a prior art turbine blade with serpentine cooling channels and angled ridge turbulators. 
         FIG. 2  is a perspective view of part of a component wall, with turbulator ridges at three scales per aspects of the invention. 
         FIG. 3  is a transverse sectional view of two turbulator ridges and a valley between them, with smaller ridges. 
         FIG. 4  is a transverse sectional view of two turbulator ridges with smaller grooves, and a valley with smaller ridges. 
         FIG. 5  is a perspective view of a turbulator ridge with a boundary layer restart gap. 
         FIG. 6  is a perspective view of a turbulator ridge with bumps on the top and side surfaces. 
         FIG. 7  is a perspective view of a turbulator ridge with bumps only on the side surfaces. 
         FIG. 8  is a perspective view of a turbulator ridge with dimples on the top surface and bumps on the side surfaces. 
         FIG. 9  is a perspective view of turbulator ridges and valleys with bumps. 
         FIG. 10  is a perspective view of turbulator ridges with dimples, and valleys with bumps. 
         FIG. 11  is a partial plan view of a cooling surface with a plurality of first ridges and valleys, larger ridges perpendicular to the first ridges, and with dimples and bumps on the first ridges and valleys. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a side sectional view of a prior art turbine blade  20  with a leading edge  22 , a trailing edge  24 , cooling channels  26 , film cooling holes  28 , and coolant exit holes  30 . Cooling air  32  enters an inlet channel  34  in the blade dovetail  36 . It exits the film holes  28  and trailing edge exit holes  30 . Ridge turbulators  38 ,  40  are provided on the inner surfaces of the cooling channels. These turbulators may be oriented obliquely in the channels  26  as shown, and they may be offset on opposed surfaces of the channels  26 . The solid lines  38  represent turbulator ridges visible on the far wall in this viewpoint. The dashed lines represent offset turbulator ridges on the near wall that are not visible in this view. 
       FIG. 2  is a sectional perspective view of part of a component wall  42  having a cooling channel inner surface  44  with turbulator features at three different scales: 1) A plurality of first parallel ridges  46  separated by valleys  48 ; 2) Larger ridges  50 ; and 3) Smaller ridges  52  on each first ridge  46  and in each valley  48 . Alternately, not shown, the first ridges  46  may be separated by planar portions of the channel surface  44  rather than by concave valleys  48 . 
     Herein, the terms “larger” and “smaller” refer to relative scales such that a smaller feature has less than ⅓ of the transverse sectional area of a respective “first” feature, and a larger feature has at least 3 times the sectional area of a respective first feature. For example, if a first ridge has a transverse sectional area of 1 cm 2 , then a respective smaller ridge has a transverse sectional area of less than ⅓ cm 2 . The term “transverse sectional area” of a bump or dimple is defined as the area of a projection of the bump or dimple onto a plane normal to the channel surface  44  at the apex of the bump or at the bottom of the dimple. 
     The term “convex turbulation feature” herein includes ridges  46 ,  50 ,  51 , and  52 , and bumps  58 . For example  FIG. 9  shows a plurality of smaller convex turbulation features  58  on a plurality of first convex turbulation features  46  and on a plurality of first concave turbulation features  48 . The term “concave turbulation feature” includes valleys  48 , grooves  54 , and dimples  62 . For example  FIG. 10  shows a plurality of smaller concave turbulation features  62  on a plurality of first convex turbulation features  46 , and a plurality of smaller convex turbulation features  58  on a plurality of first concave turbulation features  48 . 
     Each additional scale of turbulation features increases the convective area of the channel inner surface  44 . For example, if a planar surface is modified with semi-cylindrical ridges separated by tangent semi-cylindrical valleys, the surface area is increased by a factor of about 1.57. If the surfaces of these ridges and valleys are then modified with smaller scale ridges, grooves, bumps, or dimples, the surface area is further increased. In the exemplary configuration of  FIG. 2 , the first ridges  46  and first valleys  48  increase the surface area by a factor of about 1.57. The smaller ridges  52  further increase it by about 1.27 for a combined factor of about 2. The ridges and valleys may use cylindrical geometries or non-cylindrical geometries such as sinusoidal, rectangular, or other shapes. 
     Smaller features may be described herein as being on a top or side surface of a first feature. A “top surface” of a turbulator is a surface distal to the cooling surface to which the turbulator is attached, and is generally parallel to or aligned with the cooling surface. On a convex turbulator with a rectangular cross section, the top surface may be a planar surface  60 , as shown in  FIGS. 6-8 . On a convex turbulator with a curved cross section, the top surface is defined as a distal portion of the surface wherein a tangent plane forms an angle “A” of less than 45° relative to a plane  45  of the cooling surface  44  as shown in  FIG. 3 , wherein plane  45  may be considered as the plane of the cooling surface prior to modification by the turbulation features. This distinction between “top” and “side” surfaces is made because there are benefits to providing different types of smaller features on the top and sides of a turbulator, and/or different types of smaller features on the top and between the first turbulators, as is later described. 
       FIG. 3  is an enlarged sectional view of the first ridges  46 , first valleys  48 , and smaller ridges  52  of  FIG. 2 .  FIG. 4  shows first ridges  46  with smaller grooves  54 , and a first valley  48  with smaller ridges  52 . The geometry of  FIG. 4  provides the same surface area increase as  FIG. 3 . However, replacing the smaller ridges  52  on the first ridges  46  with smaller grooves  54  reduces the component mass, and reduces shadowing of the first valleys  48  by the first ridges  46 , allowing coolant to more easily reach the bottoms of the first valleys  48 . 
     Alternately forming smaller grooves in the valleys  48  may create some coolant stagnation in some embodiments and is not illustrated here. However, forming smaller convex features on first convex features, and/or forming smaller concave features in first concave features, reduces crowding of the smaller features, since they extend toward the outside of the sectional curvatures of the first features. 
       FIG. 5  shows a smaller ridge  52  with a gap  56  that restarts the boundary layer of the coolant flow. Such gaps may be provided at any scale—on the first ridges  46 , the larger ridges  50 , or the smaller ridges  52 . 
       FIG. 6  shows a ridge  51  with smaller bumps  57  on the top surface  60  and sides of the ridge. The bumps add surface area and turbulence.  FIG. 7  shows a ridge  51  with smaller bumps  57  on the sides, but not on the top  60  of the ridge. This geometry provides some additional surface area with less additional turbulence than in  FIG. 6 . The ridges  51  of  FIGS. 6-8  may be any scale. For example, the larger ridges  50  of  FIG. 2  may have smaller bumps on the sides, and smaller dimples in the top surface in addition to smaller ridges  46  and valleys  48  between the large ridges  50 . 
       FIG. 8  shows a ridge  51  with smaller bumps  57  on the sides, and with smaller dimples  61  on the top surface  60  of the ridge. The smaller dimples  61  add the same amount of surface area as smaller bumps of the same size, but with less mass. Dimples  61  create a type of turbulence that causes the coolant boundary layer to follow the downstream side of the ridge  51  more closely than does a more laminar flow. Thus, smaller dimples on the top surface  60  of the ridge increase coolant contact with any smaller scale features provided between such ridges  51 . If the ridges have a tall rectangular sectional shape as shown in  FIGS. 6-8 , then providing dimples near the base of the ridge may produce some coolant stagnation in some embodiments. A configuration with bumps on the sides, especially near the base, and dimples elsewhere, avoids this. 
       FIG. 9  shows an embodiment of the invention with first ridges  46  and first valleys  48 , both of which are covered with smaller bumps  58 . The smaller bumps provide increased surface area and boundary layer mixing.  FIG. 10  shows an embodiment of the invention with first ridges  46  and first valleys  48 , with smaller dimples  62  on the ridges, and smaller bumps  58  in the valleys. This geometry provides a similar surface increase to that of  FIG. 9 . However, replacing the smaller bumps  58  on the small ridges  46  with smaller dimples  62  reduces shadowing of the first valleys  48  by the first ridges  46 . The smaller dimples add surface area while reducing mass, and they create a type of turbulence that causes the coolant boundary layer to follow the downstream side of the first ridges  46  more closely than would a more laminar flow: Thus, the smaller dimples  62  increase coolant contact with the smaller bumps  58 . Providing smaller dimples  62  near the bottom of the first valleys  48  may produce some stagnation in some embodiments, and is not illustrated here, although it may be used as an alternative in order to reduce crowding, as previously mentioned. 
       FIG. 11  shows an embodiment of the invention with first ridges  46  and first valleys  48  that are perpendicular to the larger ridges  50 . Smaller dimples  62  and smaller bumps  58  are disposed on the first ridges  46  and first valleys  48  respectively. A coolant flow  64  is illustrated. 
     Other combinations of multi-scale turbulation features are possible. For example in  FIG. 9 , the smaller bumps  58  on the first ridges  46  may be replaced with smaller ridges  52  or the smaller bumps  58  in the first valleys  48  may be replaced with smaller ridges  52 . In  FIG. 10 , the smaller dimples  62  may be replaced with smaller grooves  54 . 
     While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.