Geothermal turbine

Abstract

A geothermal turbine comprises a turbine casing, a turbine rotor shaft, a plurality of nozzle diaphragm outer rings fixed to the turbine casing, a plurality of nozzle diaphragm inner rings located radially inside the nozzle diaphragm outer rings, a plurality of nozzles placed between the nozzle diaphragm outer rings and the nozzle diaphragm inner rings, which form a steam passage, a plurality of rotor blades mounted on the turbine rotor shaft, which face the nozzles and form a blade cascade in a circumferential direction, a shroud arranged on tip of the rotor blade, an overhang attached to the nozzle diaphragm outer ring, which extends downstream of the nozzles and has an inner surface facing radially outside the shroud, and a plurality of sealing fins which protrude radially outward from the shroud and face the overhang.

1 . A geothermal turbine, comprising: 
 a turbine casing;    a turbine rotor shaft;    a plurality of nozzle diaphragm outer rings fixed to the turbine casing;    a plurality of nozzle diaphragm inner rings located radially inside the nozzle diaphragm outer rings;    a plurality of nozzles placed between the nozzle diaphragm outer ring and the nozzle diaphragm inner ring, which form a steam passage; and    a plurality of rotor blades mounted on the turbine rotor shaft, which face the nozzles and form a blade cascade in a circumferential direction;    wherein the nozzle diaphragm inner ring includes high-and-low sealing fins protruding from an inner surface of the nozzle diaphragm inner ring toward the turbine rotor shaft radially inward; and    the turbine rotor shaft includes a high-and-low groove corresponding to the high-and-low arrangement of the sealing fins.    
     
     
         2 . The geothermal turbine as in  claim 1 , wherein at least a part of a surface of the high-and-low groove of the turbine rotor shaft is coated with a protective material.  
     
     
         3 . The geothermal turbine as in  claim 2 , wherein the protective material comprises at least one of titanium, an alloy of cobalt, an alloy of titanium, an alloy of chromium, an alloy of chromium and iron, and an alloy of chromium, iron and nickel.  
     
     
         4 . The geothermal turbine as in  claim 2 , wherein the protective material includes a cermet made by mixing carbide or boride and at least one of titanium, an alloy of cobalt, an alloy of titanium, an alloy of chromium, an alloy of chromium and iron, and an alloy of chromium, iron and nickel.  
     
     
         5 . The geothermal turbine as in  claim 1 , wherein the sealing fins are arranged on a cylindrical member detachably attached to the nozzle diaphragm inner ring, the cylindrical member being composed of a protective material.  
     
     
         6 . A geothermal turbine, comprising: 
 a turbine casing;    a turbine rotor shaft;    a plurality of nozzle diaphragm outer rings fixed to the turbine casing;    a plurality of nozzle diaphragm inner rings located radially inside the nozzle diaphragm outer rings;    a plurality of nozzles placed between the nozzle diaphragm outer rings and the nozzle diaphragm inner rings, which form a steam passage;    a plurality of rotor blades mounted on the turbine rotor shaft, which face the nozzles and form a blade cascade in a circumferential direction; and    a strainer installed at an inlet of the turbine;    wherein a throat is formed between adjacent nozzles, having a width larger than a mesh size of the strainer; and    at least a part of a surface of the nozzle is coated or overlay welded with a protective material.    
     
     
         7 . The geothermal turbine as in  claim 6 , wherein at least a part of surfaces of the nozzles is coated or overlay welded with a protective material having a durability greater than the material of the nozzle.