Compressor blades and/or vanes

Abstract

This disclosure concerns aerofoils for an axial flow compressor. The compressor has an array of aerofoils angularly spaced about its axis of rotation. The aerofoils have leading and trailing edges extending in a direction spanning a flow region defined between a radially inner rotor component and a radially outer casing. Each aerofoil has opposing pressure and suction surfaces extending between the leading and trailing edges and terminating at a free end of the aerofoil. Each aerofoil leans towards the pressure surface by an angle of between 10° and 80 ° in the vicinity of the aerofoil tip. The aggressive negative lean towards the tip may help reduce over-tip leakage flow in use.

We claim: 
     
         1 . An axial flow machine having an axis of rotation and comprising an array of aerofoils angularly spaced about said axis, each aerofoil comprising:
 leading and trailing edges extending in a direction spanning a flow region defined between a radially inner rotor component and a radially outer casing, the leading and trailing edges terminating at a free end of the aerofoil;   opposing pressure and suction surfaces extending between the leading and trailing edges;   wherein each aerofoil leans towards the pressure surface by an angle of between 10° and 80° in the vicinity of the free end of the aerofoil.   
     
     
         2 . A machine according to  claim 1 , wherein the vicinity of the free end of the aerofoil comprises less than 15% of the aerofoil height. 
     
     
         3 . A machine according to  claim 1 , wherein the vicinity of the free end of the aerofoil comprises less than or equal to 12% of the aerofoil height. 
     
     
         4 . A machine according to  claim 1 , wherein each aerofoil leans towards the pressure surface by an angle of between 30° and 60° in the vicinity of the free end of the aerofoil. 
     
     
         5 . A machine according to  claim 1 , wherein each aerofoil leans towards the pressure surface in the vicinity of the free end of the aerofoil over the whole chord length between the leading and trailing edges. 
     
     
         6 . A machine according to  claim 1 , wherein the aerofoil cross-section profile remains substantially constant through the height of the aerofoil in the vicinity of the free end. 
     
     
         7 . A machine according to  claim 1 , wherein the free end of the aerofoil has an end face that is obliquely angled relative to the orientation of the aerofoil in the vicinity of the free end. 
     
     
         8 . A machine according to  claim 1 , wherein the free end of the aerofoil faces radially outwardly relative to the axis of rotation. 
     
     
         9 . A machine according to  claim 1 , wherein each aerofoil leans away from a radial direction (R) towards the circumferential direction in the vicinity of the free end. 
     
     
         10 . A machine according to  claim 1 , wherein each of the pressure and suction surfaces are smoothly curved towards the pressure surface in the vicinity of the free end. 
     
     
         11 . A machine according to  claim 1 , wherein each aerofoil has a negative turning point (A) defining the boundary between the vicinity of the free end of the aerofoil and a remainder of the aerofoil, wherein the lean of the aerofoil towards the pressure side increases from the turning point (A) to the free end. 
     
     
         12 . A machine according to  claim 1 , wherein the angular orientation of the aerofoil at the free end is less than or equal to 60° from a radial direction (R) with respect to the axis of rotation. 
     
     
         13 . A machine according to  claim 1 , wherein the array of aerofoils are an array of blades mounted to a rotor of the axial flow machine and the free ends of the blades face an opposing rotor casing. 
     
     
         14 . A machine according to  claim 1 , comprising a compressor of a gas turbine engine, wherein the compressor comprises the array of aerofoils. 
     
     
         15 . An aerofoil for an axial flow compressor, the aerofoil comprising leading and trailing edges extending over a height of the aerofoil from a root of the aerofoil to a tip of the aerofoil, the aerofoil comprising opposing major surfaces extending between the leading and trailing edges and terminating at the tip, wherein the aerofoil leans towards a pressure surface by an angle of between 10° and 80° over a minority of the height of the aerofoil towards the tip.