Airfoil insert

Abstract

An airfoil insert comprises an insert wall, a contact element and a flow director. The insert wall defines an interior extending inside the insert wall from a first end to second end, and an exterior extending outside the insert wall from the first end to the second end. The contact element is formed on the exterior of the insert wall. The flow director is formed on the insert wall at a boundary between the interior and the exterior. The flow director increases a heat transfer coefficient of convective flow along the insert wall by directing the convective flow to the exterior of the insert wall.

1 . An airfoil insert comprising:
 an insert wall defining an interior extending inside the insert wall from a first end to a second end, and an exterior extending outside the insert wall from the first end to the second end;   a contact element formed on the exterior of the insert wall; and   a flow director formed on the insert wall at a boundary between the interior and the exterior, wherein the flow director increases a heat transfer coefficient of convective flow along the insert wall by directing the convective flow to the exterior of the insert wall.   
   
   
       2 . The insert of  claim 1 , wherein the contact element comprises a collar for spacing the insert wall from an internal cooling passage of an airfoil. 
   
   
       3 . The insert of  claim 1 , wherein the flow director comprises convection flow apertures for directing the convective flow to the exterior of the insert wall. 
   
   
       4 . The insert of  claim 3 , wherein the contact element comprises tabs for spacing the insert wall from an internal cooling passage of an airfoil. 
   
   
       5 . The insert of  claim 4 , wherein the tabs define the convection flow apertures therebetween. 
   
   
       6 . The insert of  claim 3 , wherein the flow director comprises an inlet for conducting flow to the interior of the insert wall. 
   
   
       7 . The insert of  claim 6 , wherein the convection flow apertures are formed in the insert wall. 
   
   
       8 . The insert of  claim 6 , further comprising an outlet formed in the second end of the insert wall, for conducting flow from the interior of the insert wall to a downstream cooling load. 
   
   
       9 . The insert of  claim 1 , wherein the flow director comprise a stop for stopping flow through the interior of the insert wall. 
   
   
       10 . The insert of  claim 1 , further comprising a flame spray coating on the insert wall for attaching the insert along an internal cooling passage of an airfoil. 
   
   
       11 . The insert of  claim 1 , wherein the insert wall has a closed cross-sectional geometry. 
   
   
       12 . The insert of  claim 1 , wherein the insert wall has an open cross-sectional geometry formed by a unitary U-shaped or C-shaped structure. 
   
   
       13 . The insert of  claim 1 , wherein the insert wall has an open cross-sectional geometry formed by two panels. 
   
   
       14 . An airfoil comprising:
 an airfoil section comprising a leading edge, a trailing edge, pressure and suction surfaces defined between the leading edge and the trailing edge, and an inner surface defining an internal cooling passage; and   an insert comprising an insert wall and a flow director for restricting convective flow to a region between the insert wall and the inner surface of the airfoil section.   
   
   
       15 . The airfoil of  claim 14 , wherein the flow director increases a Reynolds number of the convective flow. 
   
   
       16 . The airfoil of  claim 14 , wherein the flow director increases a Mach number of the convective flow. 
   
   
       17 . The airfoil of  claim 14 , further comprising augmentors formed along the internal cooling passage to augment convective heat transfer along the inner surface of the airfoil section. 
   
   
       18 . The airfoil of  claim 17 , wherein the augmentors comprise at least one of trip strips, turbulators, pins, dimples, warts and pedestals. 
   
   
       19 . The airfoil of  claim 14 , further comprising a plurality of ribs, pin-fins or other stand-off features of various cross section, formed along the internal cooling passage for spacing the insert wall from the inner surface of the airfoil section. 
   
   
       20 . The airfoil of  claim 14 , further comprising a contact element formed on an exterior of the insert wall for spacing the insert wall from the inner surface of the airfoil section. 
   
   
       21 . The airfoil of  claim 14 , wherein the flow director comprises a convection flow aperture for directing convective flow to the region between the insert wall and the inner surface of the airfoil. 
   
   
       22 . The airfoil of  claim 21 , wherein the flow director further comprises an inlet for conducting flow into an interior of the insert wall. 
   
   
       23 . The airfoil of  claim 22 , wherein the convection flow aperture is formed in the insert wall. 
   
   
       24 . The airfoil of  claim 22 , further comprising an outlet for conducting flow from the interior of the insert wall to a downstream cooling load. 
   
   
       25 . The airfoil of  claim 14 , wherein the flow director further comprises a flow stop for stopping flow through an interior of the insert wall. 
   
   
       26 . The airfoil of  claim 14 , wherein the insert wall has a substantially closed cross-sectional geometry. 
   
   
       27 . The airfoil of  claim 14 , wherein the insert wall has a substantially open cross-sectional geometry and forms a seal against the internal cooling passage. 
   
   
       28 . The airfoil of  claim 14 , further comprising a platform for attaching the airfoil to a stationary component of a turbine. 
   
   
       29 . The airfoil of  claim 14 , further comprising a root for attaching the airfoil to a rotating component of a turbine. 
   
   
       30 . A method for cooling an airfoil, the method comprising:
 positioning an insert along an internal surface of the airfoil;   spacing the insert from the internal surface; and   restricting convective flow along the insert to a region between the insert and the internal surface, such that a Reynolds number of the convective flow is increased.   
   
   
       31 . The method of  claim 30 , further comprising directing non-convective flow into an interior of the insert. 
   
   
       32 . The method of  claim 31 , further comprising converting the non-convective flow to the convective flow. 
   
   
       33 . The method of  claim 31 , further comprising conducting the non-convective flow to a downstream cooling load. 
   
   
       34 . The method of  claim 30 , further comprising forming augmentors on the internal surface of the airfoil to augment the convective cooling. 
   
   
       35 . The method of  claim 30 , further comprising attaching the insert to the airfoil such that the insert functions as a cast-in wall.