Turbine blades

Abstract

In turbine blades used as nozzle guide vanes 2, 12, 22, 31 for turbine stages of an engine there is a problem with respect to high lift vanes in that there may be significant stagnation point migration about the pressure surface 13, 21, 32 of that vane. In such circumstances, appropriate positioning of coolant flow apertures 11, 24, 34 for coolant film cooling of the vane is difficult. The present invention provides on the leading edge a bulge ridge 37 which limits the range of potential movement for the stagnation point 30 whilst retaining improved lift for higher engine performance. The present invention has particular applicability with flows directed to the turbine NGV which have a significantly variable swirl angle and therefore presentation to the vane 31.

1 . A guide vane for an engine comprising a pressure surface towards which an air flow is directed in use, the surface being curved with a leading edge bulge ridge to limit the proportion of pressure surface in a flat presentation aspect to the air flow in use and so limit in use possible stagnation point position for that flow upon the vane.  
   
   
       2 . A vane as claimed in  claim 1  wherein the bulge ridge is located substantially centrally upon the surface of the vane.  
   
   
       3 . A vane as claimed in  claim 1  wherein the bulge ridge is positioned off-centre upon the surface of the vane.  
   
   
       4 . A vane as claimed in  claim 1  wherein slopes extend either side of the bulge ridge and the slopes either side of the bulge ridge are one of differently shaped and symmetrical.  
   
   
       5 . A vane as claimed in  claim 4  wherein one slope is substantially flat whilst the other slope is trailingly curved.  
   
   
       6 . A vane as claimed in  claim 1  wherein a portion of the surface develops into an early suction side for the vane due to one of its shape and position of that portion of the surface relative to the bulge ridge.  
   
   
       7 . A nozzle guide vane arrangement for a turbine engine incorporating a plurality of vanes as claimed in  claim 1 .  
   
   
       8 . An engine incorporating a nozzle guide vane arrangement as claimed in  claim 8.