Turbine and turbine blade

Abstract

In order to provide a turbine in which fir tree root or similar types of turbine blades can be inserted into the turbine shaft at an angle close to the axial direction without frictional blocking of shroud sections, each blade comprising a root for insertion into the shaft, along an insertion axis which is at an angle of not more than 30° the axial direction, an aerofoil section and a shroud section, each shroud having lateral surface sections comprising a contact surface section and a free surface section, the contact surface sections of adjacent shroud sections contacting one another, the free surface sections of adjacent shroud sections being spaced from one another. Each contact surface section lies at an angle of from 20° to 50° to the axial direction and each free surface section lies at an angle of not more than 30° to the axial direction, each contact surface section lies at a greater angle to the axial direction of the shaft than the corresponding free surface section. The contact surface sections suitably lie at an angle of about 30° to the axial direction of the shaft.

1 . A turbine blade, comprising: 
 a root for insertion along an insertion axis into the shaft of a turbine, which turbine has an axial direction, the insertion axis being at an angle of not more than 30° to the axial direction of the shaft, the turbine blade further comprising an aerofoil section, and a shroud section, each shroud section having lateral surfaces each comprising a contact surface section and a free surface section, the contact surface section being for contacting adjacent contact surface sections of adjacent shroud sections when assembled into the turbine and the free surface sections being spaced from adjacent free surface sections of adjacent shroud sections when assembled into the turbine, each contact surface section lying at an angle of from 20° to 50° to the axial direction, each free surface section lying at an angle of not more than 30° to the axial direction, each contact surface section lying at a greater angle to the axial direction than the corresponding free surface section.    
   
   
       2 . The turbine blade according to  claim 1 , wherein the root comprises a fir tree root.  
   
   
       3 . The turbine blade according to  claim 1 , wherein the bottom surface of the shroud section is inclined with respect to the axial direction.  
   
   
       4 . The turbine blade according to  claim 1 , wherein the top surface of the shroud section comprises a first surface which is inclined with respect to the axial direction and a second surface which is substantially parallel to the axial direction.  
   
   
       5 . The turbine blade according to  claim 4 , wherein the contact surface section of the lateral surface is located in the first surface.  
   
   
       6 . The turbine blade according to  claim 1 , wherein the lateral surface comprises a first, free surface section, followed by a second, contact surface section, followed by a third, free surface section.  
   
   
       7 . The turbine blade according to  claim 1 , wherein the contact surface section is 50% or less in length compared to the free surface section, preferably 40% or less, more preferably 25% or less.  
   
   
       8 . A turbine, having a turbine shaft defining an axial direction and a plurality of turbine blades according to  claim 1 , inserted in the turbine shaft.  
   
   
       9 . A turbine, having: 
 a turbine shaft defining an axial direction,    a plurality of turbine blades mounted in the shaft, each blade comprising:    a root for insertion into the shaft along an insertion axis which is at an angle of the less than 30° to the axial direction,    an aerofoil section, and    a shroud section, each shroud section having lateral surfaces each comprising a contact surface section and a free surface section, the contact surface sections of adjacent shroud sections contacting one another and the free surface sections of adjacent shroud sections being spaced from one another,    each contact surface section lying at an angle of from 20° to 50° to the axial direction, each free surface section lying at an angle of not more than 30° to the axial direction,    each contact surface lying at a greater angle to the axial direction of the shaft than the corresponding free surface section.    
   
   
       10 . A turbine according to  claim 6 , wherein the free surface sections of adjacent turbine blades are spaced apart from one another by a distance in the range 0.5-5.0 mm.  
   
   
       11 . A turbine according to  claim 8 , wherein the turbine blades are provided with a pre-twist.  
   
   
       12 . A method of assembling a turbine comprising the steps of inserting a plurality of turbine blades into a turbine shaft, the turbine shaft defining an axial direction, the blades being inserted along an insertion axis which is at an angle of less than 30° to the axial direction, each blade comprising a root which is inserted into the shaft, an aerofoil section and a shroud section, each shroud section having lateral surfaces each comprising a contact surface section and a free surface section, the contact surface sections lying at an angle of from 20° to 50° to the axial direction when assembled and the free surface sections lying at an angle of not more than 30° to the axial direction when assembled, the contact surface section lying at a greater angle to the axial direction than the corresponding free surface section, adjacent turbine blades being inserted so that their respective contact sections contact one another and so that their respective free surface sections are spaced from one another.  
   
   
       13 . A method according to  claim 12 , further comprising the steps of inserting all but one of the turbine blades into the turbine shaft, forcing apart the turbine blades adjacent the position of the final turbine blade, inserting the final turbine blade into the turbine shaft between the two forced apart turbine blades and removing the force on the two forced apart turbine blades.