Expander

Abstract

An expander includes a piston formed from a top portion, a skirt portion, and a land portion. A hollow heat-insulating space is formed within the piston making heat transfer difficult. It is possible to maintain the land portion, which is in contact with the high temperature, high pressure steam in an expansion chamber, at a high temperature, thereby minimizing any decrease in the temperature of the high temperature, high pressure steam to prevent any decrease in the efficiency of the expander. Any increase in the temperature of the skirt portion, which is in sliding contact with a cylinder sleeve, is suppressed to ensure the performance of the lubrication. Piston rings are provided on the land portion to separate the high temperature, high pressure steam in the expansion chamber from the oil in the skirt portion for preventing the oil and the high temperature, high pressure steam from being mixed together.

1 . A piston for use in a rotor comprising: 
 an axial piston cylinder group arranged in the rotor for surrounding an axis of the rotor, said rotor being adapted to be rotated by supplying high-temperature, high-pressure steam to an expansion chamber defined between a piston and a cylinder sleeve of the axial piston cylinder group with sliding sections of the piston and the cylinder sleeve being lubricated with oil;    a land portion formed on said piston of the axial piston cylinder group, said land portion being exposed to the high temperature, high pressure steam in the expansion chamber;    a top portion formed on said piston adapted to abut against a swash plate;    a skirt portion formed on said piston that is disposed between the land portion and the top portion for sliding against the cylinder sleeve;    a hollow heat-insulating space formed within the piston; and    a piston ring provided on the land portion, the piston ring separating high temperature, high pressure steam in the expansion chamber from oil in the skirt portion.    
   
   
       2 . The piston for use in a rotor according to  claim 1 , wherein a plurality of piston rings are provided along the longitudinal direction of the piston.  
   
   
       3 . The piston for use in a rotor according to  claim 2 , wherein a depression is provided between the plurality of piston rings.  
   
   
       4 . The piston for use in a rotor according to  claim 1 , wherein an oil channel is provided in at least one of an outer peripheral face of the skirt portion of the piston and an inner peripheral face of the cylinder sleeve.  
   
   
       5 . The piston for use in a rotor according to  claim 1 , wherein the top portion includes a spherical portion adapted to abut against the swash plate.  
   
   
       6 . The piston for use in a rotor according to  claim 1 , wherein the heat-insulating space is evacuated.  
   
   
       7 . The piston for use in a rotor according to  claim 1 , wherein the heat-insulating space includes air sealed therein.  
   
   
       8 . The piston for use in a rotor according to  claim 1 , wherein a ceramic selected from the group consisting of TiN and CrN is formed on an outer surface of said piston ring.  
   
   
       9 . The piston for use in a rotor according to  claim 1 , and further including an oil channel formed in a mid-section of the skirt portion of said piston.  
   
   
       10 . The piston for use in a rotor according to  claim 9 , wherein a plurality of spiral oil channels are formed in the mid-section of the skirt portion of said piston.  
   
   
       11 . An expander comprising: 
 a casing;    a rotor rotatably supported in the casing; and    an axial piston cylinder group arranged in the rotor so as to surround an axis of the rotor;    the rotor being rotated by supplying high-temperature, high-pressure steam to an expansion chamber defined between a piston and a cylinder sleeve of the axial piston cylinder group with sliding sections of the piston and the cylinder sleeve being lubricated with oil;    said piston of the axial piston cylinder group including a land portion that is exposed to the high temperature, high pressure steam in the expansion chamber, a top portion that abuts against a swash plate, and a skirt portion that is disposed between the land portion and the top portion and slides against the cylinder sleeve;    a hollow heat-insulating space formed within the piston; and    a piston ring provided on the land portion, the piston ring separating high temperature, high pressure steam in the expansion chamber from oil in the skirt portion.    
   
   
       12 . The expander according to  claim 11 , wherein a plurality of piston rings are provided along the longitudinal direction of the piston.  
   
   
       13 . The expander according to  claim 12 , wherein a depression is provided between the plurality of piston rings.  
   
   
       14 . The expander according to  claim 11 , wherein an oil channel is provided in at least one of an outer peripheral face of the skirt portion of the piston and an inner peripheral face of the cylinder sleeve.  
   
   
       15 . The expander according to  claim 11 , wherein the top portion includes a spherical portion for abutting against the swash plate.  
   
   
       16 . The expander according to  claim 11 , wherein the heat-insulating space is evacuated.  
   
   
       17 . The expander according to  claim 11 , wherein the heat-insulating space includes a air sealed therein.  
   
   
       18 . The expander according to  claim 11 , wherein a ceramic selected from the group consisting of TiN and CrN is formed on an outer surface of said piston ring.  
   
   
       19 . The expander according to  claim 11 , and further including an oil channel formed in a mid-section of the skirt portion of said piston.  
   
   
       20 . The expander according to  claim 19 , wherein a plurality of spiral oil channels are formed in the mid-section of the skirt portion of said piston.