Turbine blade

Abstract

A rotor stage of a turbine has a rotational axis, a shroud and radially inward thereof a turbine blade defined partly by a pressure side wall, a suction side wall and a tip portion. The tip portion has a pressure side tip rib and a tip cavity floor defining a tip cavity. The pressure side tip rib has a width W ps , a height H ps above the tip cavity and defines a tip gap G ps with the shroud. The pressure side tip rib has a sloping side joining the tip cavity floor and having an angle α ps to a radial line ZZ. The width W ps is in the range G ps to 5G ps , the height H ps is in the range 5G ps to 15G ps and the angle α ps is in the range 20° to 70°.

1 . A rotor stage of a turbine comprising
 a rotational axis,   a shroud and radially inward thereof   a turbine blade defined partly by a pressure side wall, a suction side wall and a tip portion,   the tip portion has a pressure side tip rib and a tip cavity floor defining a tip cavity,   the pressure side tip rib has a width W ps , a height H ps  above the tip cavity and defines a tip gap G ps  with the shroud,   the pressure side tip rib has a sloping side joining the tip cavity floor and having an angle α ps  to a radial line ZZ,   the width W ps  is in the range G ps  to 5G ps ,   the height H ps  is in the range 5G ps  to 15G ps  and   the angle α ps  is in the range 20° to 70°.   
     
     
         2 . A rotor stage of a turbine as claimed in  claim 1 , wherein
 the width W ps  is in the range 2G ps  to 3G ps ,   the height H ps  is in the range 7G ps  to 8G ps  and   the angle α ps  is in the range 40° to 60°.   
     
     
         3 . A rotor stage of a turbine as claimed in  claim 1 , wherein
 the width W ps  is approximately 2.5G ps ,   the height is approximately 7G ps  and   the angle α ps  is approximately 45°.   
     
     
         4 . A rotor stage of a turbine as claimed in  claim 1 , wherein the pressure side tip rib has a radially outer surface and the pressure side tip rib directly extends between the tip cavity floor and the radially outer surface. 
     
     
         5 . A rotor stage of a turbine as claimed in  claim 1 , wherein the tip portion has a suction side tip rib,
 the suction side tip rib has a width W ss  and defines a tip gap G ss  with the shroud,   the suction side tip rib has a sloping side joining the tip cavity floor and having an angle α ss  to a radial line ZZ,   the width W ss  is in the range G ss  to 5G ss ,   the height H ss  is in the range 5G ss  to 15G ss  and   the angle α ss  is in the range 20° to 70°.   
     
     
         6 . A rotor stage of a turbine as claimed in  claim 5 , wherein
 the width W ss  is in the range 2G ss  to 3G ss ,   the height H ss  is in the range 7G ss  to 8G ss  and   the angle α ss  is in the range 40° to 60°.   
     
     
         7 . A rotor stage of a turbine as claimed in  claim 5 , wherein
 the width W ss  is approximately 2.5G ss ,   the height H ss  is approximately 7G ss  and   the angle α ss  is approximately 45°.   
     
     
         8 . A rotor stage of a turbine as claimed in  claim 1 , wherein a cooling gallery is defined at least partly within the pressure side tip rib. 
     
     
         9 . A rotor stage of a turbine as claimed in  claim 1 , wherein a cooling gallery is located at least partly above the tip cavity floor. 
     
     
         10 . A rotor stage of a turbine as claimed in  claim 1 , wherein a major portion of the cooling gallery is situated radially outward of the tip cavity floor. 
     
     
         11 . A rotor stage of a turbine as claimed in  claim 1 , wherein a cooling gallery is located above the tip cavity floor. 
     
     
         12 . A rotor stage of a turbine as claimed in  claim 1 , wherein the blade comprises an internal cooling passage and the cooling gallery is an extension of the internal cooling passage. 
     
     
         13 . A rotor stage of a turbine as claimed in  claim 12 , wherein the tip cavity is defined by curved surfaces forming the outer surface of a wall of generally constant thickness. 
     
     
         14 . A rotor stage of a turbine as claimed in  claim 1 , wherein a cooling gallery is defined wholly within a tip rib, wherein the tip rib comprises the pressure side tip rib. 
     
     
         15 . A rotor stage of a turbine as claimed in  claim 8 , wherein at least one cooling hole extends from the cooling gallery to an external surface of the pressure side tip rib, and an inlet of the cooling hole is located radially outwardly of the tip cavity floor. 
     
     
         16 . A rotor stage of a turbine as claimed in  claim 5 , wherein the tip rib comprises the suction side rib and a cooling gallery is defined at least partly within the suction side tip rib. 
     
     
         17 . A rotor stage of a turbine as claimed in  claim 1 , comprising a tip rib, wherein the tip rib comprises the pressure side tip rib and a suction side tip rib, and wherein a cooling gallery is defined at least partly within the tip rib and the cooling gallery extends from the pressure side to the suction side. 
     
     
         18 . A rotor stage of a turbine as claimed in  claim 17 , wherein the cooling gallery is formed of an array of cooling sub-galleries. 
     
     
         19 . A rotor stage of a turbine comprising
 a rotational axis,   a shroud and radially inward thereof a turbine blade defined partly by a pressure side wall, a suction side wall and a tip portion,   the tip portion has a pressure side tip rib and a tip cavity floor defining a tip cavity,   the pressure side tip rib has a width W ps , a height H ps  above the tip cavity and defines a tip gap G ps  with the shroud,   the pressure side tip rib has a sloping side joining the tip cavity floor and having an angle α ps  to a radial line ZZ, and   a cooling gallery at least partly provided in the pressure side tip rib and arranged such that major portion of the cooling gallery is situated radially outward of the tip cavity floor.   
     
     
         20 . A rotor stage of a turbine as claimed in  claim 19 , wherein the pressure side tip rib has a radially outer surface and the pressure side tip rib directly extends between the tip cavity floor and the radially outer surface.