Turbine Nozzle Blade and Steam Turbine Equipment Using Same

Abstract

Disclosed is a highly efficient turbine nozzle blade that reduces the number of blades in an axial-flow turbine while reducing secondary-flow loss. In the nozzle blade, when a differential pressure between a pressure side and a suction side of each blade, at the same axial chord position of the blade, is defined as a load of the blade, and a ratio between axial chord length “Cx” of the blade and an axial distance “xp” from a leading edge of the blade at a maximum load position that maximizes the blade load is defined as a maximum load relative position, Cx is greater at a hub and tip than at an intermediate vertical portion, and simultaneously a maximum load relative position at the hub and tip is set to be nearer to a trailing edge thereof than a maximum load relative position of the intermediate vertical portion of the blade.

1 . A nozzle blade for an axial-flow turbine,
 wherein, when a differential pressure between a pressure side and a suction side of each of blades, at one same axial chord position of the blade, is defined as a load of the blade, and a ratio between axial chord length of the blade and an axial distance from a leading edge thereof at one same vertical position of the blade where the blade load becomes a maximum is defined as a maximum load relative position,   the axial chord length of the blade is greater at a hub and tip thereof than at an intermediate vertical portion thereof, and a maximum load relative position at the hub and tip of the blade is set to be nearer to a trailing edge thereof than a maximum load relative position of the intermediate vertical portion of the blade.   
     
     
         2 . A nozzle blade for an axial-flow turbine, wherein:
 when a point, except at a leading edge and trailing edge of each of blades, at which a static pressure on a suction surface of the blade becomes a minimum, is defined as a suction-side minimum pressure position,   axial chord length of the blade is greater at a hub and tip thereof than at an intermediate vertical portion thereof, and a suction-side minimum pressure position at the hub and tip of the blade is set to be nearer to a trailing-edge side than a suction-side minimum pressure position of the intermediate vertical portion of the blade.   
     
     
         3 . A nozzle blade for an axial-flow turbine, wherein:
 each of blades is formed into a concave shape on a suction surface of a trailing edge of the blade, the blade being further formed into a convex shape on a pressure surface of the blade trailing edge; and   axial chord length of the blade is greater at a hub and tip of the blade than at an intermediate vertical portion of the blade; and   circumferential chord length is smaller at the hub and tip of the blade than at the intermediate vertical portion of the blade.   
     
     
         4 . A nozzle blade for an axial-flow turbine, wherein:
 axial chord length of each of blades is greater at a hub and tip thereof than at an intermediate vertical portion of the blade;   circumferential chord length is smaller at the hub and tip of the blade than at the intermediate vertical portion of the blade; and   a stagger angle of the blade is smaller at the hub and tip of the blade than at the intermediate vertical portion thereof.   
     
     
         5 . The turbine nozzle blade according to  claim 1 , wherein:
 when an interblade pitch is expressed as “t,” the axial chord length as “Cx,” an inflow angle when measured from an axial direction, as “α,” and an outflow angle when measured from the axial direction, as “β,” and a value Ψ given by
   Ψ=2( t/Cx )cos 2  β|tan α−tan β|  (Expression 1)
 
   
       is defined as a load coefficient,
 the load coefficient at the intermediate vertical position of the blade takes any value ranging between 0.7 and 1.1 in Expression 1. 
 
     
     
         6 . The turbine nozzle blade according to  claim 5 , wherein:
 as the axial chord length heads from the blade hub towards the blade tip, the axial chord length of the blade hub decreases at a rate equivalent to or higher than a change rate of the axial chord length in the vicinity of the intermediate vertical position of the blade, and the axial chord length of the blade tip increases at a rate equivalent to or higher than the change rate of the axial chord length in the vicinity of the intermediate vertical position of the blade.   
     
     
         7 . Steam turbine equipment comprising:
 a steam generator for heating water and generating steam;   a steam turbine driven by the steam generated by the steam generator; and   a condenser for condensing the steam that has driven the steam turbine;   wherein the steam turbine includes the turbine nozzle blade according to  claim 1 .   
     
     
         8 . The turbine nozzle blade according to  2 , wherein:
 when an interblade pitch is expressed as “t,” the axial chord length as “Cx,” an inflow angle when measured from an axial direction, as “α,” and an outflow angle when measured from the axial direction, as “β,” and a value Ψ given by
   Ψ=2( t/Cx )cos 2  β|tan α−tan β|  (Expression 1)
 
   
       is defined as a load coefficient,
 the load coefficient at the intermediate vertical position of the blade takes any value ranging between 0.7 and 1.1 in Expression 1. 
 
     
     
         9 . The turbine nozzle blade according to  3 , wherein:
 when an interblade pitch is expressed as “t,” the axial chord length as “Cx,” an inflow angle when measured from an axial direction, as “α,” and an outflow angle when measured from the axial direction, as “β,” and a value Ψ given by
   Ψ=2( t/Cx )cos 2  β|tan α−tan β|  (Expression 1)
 
   
       is defined as a load coefficient,
 the load coefficient at the intermediate vertical position of the blade takes any value ranging between 0.7 and 1.1 in Expression 1. 
 
     
     
         10 . The turbine nozzle blade according to  4 , wherein:
 when an interblade pitch is expressed as “t,” the axial chord length as “Cx,” an inflow angle when measured from an axial direction, as “α,” and an outflow angle when measured from the axial direction, as “β,” and a value Ψ given by
   Ψ=2( t/Cx )cos 2  β|tan α−tan β|  (Expression 1)
 
   
       is defined as a load coefficient,
 the load coefficient at the intermediate vertical position of the blade takes any value ranging between 0.7 and 1.1 in Expression 1. 
 
     
     
         11 . Steam turbine equipment comprising:
 a steam generator for heating water and generating steam;   a steam turbine driven by the steam generated by the steam generator; and   a condenser for condensing the steam that has driven the steam turbine;   wherein the steam turbine includes the turbine nozzle blade according to  claim 2 .   
     
     
         12 . Steam turbine equipment comprising:
 a steam generator for heating water and generating steam;   a steam turbine driven by the steam generated by the steam generator; and   a condenser for condensing the steam that has driven the steam turbine;   wherein the steam turbine includes the turbine nozzle blade according to  claim 3 .   
     
     
         13 . Steam turbine equipment comprising:
 a steam generator for heating water and generating steam;   a steam turbine driven by the steam generated by the steam generator; and   a condenser for condensing the steam that has driven the steam turbine;   wherein the steam turbine includes the turbine nozzle blade according to  claim 4 .   
     
     
         14 . Steam turbine equipment comprising:
 a steam generator for heating water and generating steam;   a steam turbine driven by the steam generated by the steam generator; and   a condenser for condensing the steam that has driven the steam turbine;   wherein the steam turbine includes the turbine nozzle blade according to  claim 5 .   
     
     
         15 . Steam turbine equipment comprising:
 a steam generator for heating water and generating steam;   a steam turbine driven by the steam generated by the steam generator; and   a condenser for condensing the steam that has driven the steam turbine;   wherein the steam turbine includes the turbine nozzle blade according to  claim 6 .