Turbine stage

Abstract

A turbine stage includes a circumferentially distributed row of adjacent airfoils between which there is a flow passage. The passage has a surface, which in its unmodified form, defines a datum plane. A channel, located in the passage, extends in the direction of an airfoil pressure face from a point towards a leading edge line to a point towards a trailing edge line. The channel includes two channel walls angled relative to the datum plane. Relative to the datum plane, the channel has a low point, two high points, and a channel height, which is measured between the low point and the highest one of the high points. The channel provides a means to reduce secondary flow losses.

1 . A turbine stage comprising:
 a circumferentially distributed row of adjacent airfoils, each of the airfoils respectively having
 a pressure face, 
 a suction face, and 
 at least one end wall from which the airfoils radially extend, respectively; and 
   a flow passage defined by a region between
 a pressure face of a first one of the airfoils, 
 a suction face of a second one of the airfoils adjacent to the first airfoil, 
 a leading edge line extending between lead edges of adjacent airfoils, and 
 a trailing edge line extending between trailing edges of adjacent airfoils, 
   wherein the flow passage has a defined datum plane extending between a base of the pressure face and a base of the suction face of adjacent airfoils, and   wherein the turbine stage further comprises a channel, in the flow passage, adjacent to the pressure face and extending in the direction of the pressure face from a point towards the leading edge line to a point towards the trailing edge line, the channel including two angled and joined channels walls that, relative to the datum plane, form a low point at the joined channel walls, two high points, and a channel height, the channel height defining the radial distance between the low point and highest one of the high points.   
     
     
         2 . The turbine stage of  claim 1 , wherein each flow passage includes at least two adjacent channels. 
     
     
         3 . The turbine stage of  claim 1 , wherein the high points of the channel do not extend above the datum plane. 
     
     
         4 . The turbine stage of  claim 1 , wherein the low point of the channel in each flow passage is substantially in the midpoint, in the pitchwise direction, between the high points of each channel. 
     
     
         5 . The turbine stage of  claim 1 , wherein in each flow passage, an angle of the channel wall closer to the pressure face is less, relative to the datum plane, than an angle of the channel wall closer to the suction face. 
     
     
         6 . The turbine stage of  claim 1 , wherein in each flow passage, the channel height in the primary flow direction increases to a maximum, at a relative channel length measured in the direction from the leading edge line to the trailing edge line, of between approximately 0.35-0.55, at which point the channel height decreases. 
     
     
         7 . The turbine stage of  claim 2 , wherein in the pitchwise direction from the pressure face to the suction face, the channel height of each successive adjacent channel one of remains the same and decreases. 
     
     
         8 . The turbine stage of  claim 7 , wherein, in each flow passage, the channel height of the channel adjacent the pressure face is at least twice that of the channel furthest, in the pitchwise direction, from the pressure face. 
     
     
         9 . The turbine stage of  claim 2 , wherein, in each flow passage, in the pitchwise direction from the pressure face to the suction face, each successive adjacent channel extends from a point that is one of the same and further from the leading edge line to form an extended region, adjacent the suction face, free of channels. 
     
     
         10 . The turbine stage of  claim 9 , wherein the extended region is a region that, in operation, encompasses a region essentially free of secondary flow vortices caused by cross flow originating from the pressure face. 
     
     
         11 . The turbine stage of  claim 2 , wherein the high points of the channel do not extend above the datum plane. 
     
     
         12 . The turbine stage of  claim 11 , wherein in the pitchwise direction from the pressure face to the suction face, the channel height of each successive adjacent channel one of remains the same and decreases. 
     
     
         13 . The turbine stage of  claim 12 , wherein, in each flow passage, the channel height of the channel adjacent the pressure face is at least twice that of the channel furthest, in the pitchwise direction, from the pressure face. 
     
     
         14 . The turbine stage of  claim 11 , wherein, in each flow passage, in the pitchwise direction from the pressure face to the suction face, each successive adjacent channel extends from a point that is one of the same and further from the leading edge line to form an extended region, adjacent the suction face, free of channels. 
     
     
         15 . The turbine stage of  claim 14 , wherein the extended region is a region that, in operation, encompasses a region essentially free of secondary flow vortices caused by cross flow originating from the pressure face. 
     
     
         16 . The turbine stage of  claim 2 , wherein the low point of the channel in each flow passage is substantially in the midpoint, in the pitchwise direction, between the high points of each channel. 
     
     
         17 . The turbine stage of  claim 2 , wherein in each flow passage, an angle of the channel wall closer to the pressure face is less, relative to the datum plane, than an angle of the channel wall closer to the suction face. 
     
     
         18 . The turbine stage of  claim 2 , wherein in each flow passage, the channel height in the primary flow direction increases to a maximum, at a relative channel length measured in the direction from the leading edge line to the trailing edge line, of between approximately 0.35-0.55, at which point the channel height decreases. 
     
     
         19 . The turbine stage of  claim 3 , wherein the low point of the channel in each flow passage is substantially in the midpoint, in the pitchwise direction, between the high points of each channel. 
     
     
         20 . The turbine stage of  claim 3 , wherein in each flow passage, an angle of the channel wall closer to the pressure face is less, relative to the datum plane, than an angle of the channel wall closer to the suction face. 
     
     
         21 . The turbine stage of  claim 3 , wherein in each flow passage, the channel height in the primary flow direction increases to a maximum, at a relative channel length measured in the direction from the leading edge line to the trailing edge line, of between approximately 0.35-0.55, at which point the channel height decreases. 
     
     
         22 . The turbine stage of  claim 4 , wherein in each flow passage, an angle of the channel wall closer to the pressure face is less, relative to the datum plane, than an angle of the channel wall closer to the suction face. 
     
     
         23 . The turbine stage of  claim 4 , wherein in each flow passage, the channel height in the primary flow direction increases to a maximum, at a relative channel length measured in the direction from the leading edge line to the trailing edge line, of between approximately 0.35-0.55, at which point the channel height decreases. 
     
     
         24 . The turbine stage of  claim 1 , wherein each airfoil respectively has two end walls between which the airfoils respectively extend.