Seal Structure and Control Method Therefor

Abstract

Provided are a seal structure and a control method therefor that can improve sealing performance between a rotating portion and a fixed portion, smoothly start up a steam turbine, and suppress the temperature rise of the rotating portion even if the rotating portion is continuously rotated for a long period of time. A seal structure is configured such that seal fins 62 on a seal base-plate 61 side and corresponding breathable spacers 4 b on a rotor 2 a side are opposed to each other and breathable spacers 4 a on the seal base-plate 61 side and corresponding seal fins 2 a 1 on the rotor 2 a side are opposed to each other. The seal base-plate 61 is installed shiftably in a direction coming close to or moving away from the rotor 2 a . If steam St has low pressure, the seal fins 62 and the corresponding breathable spacers 4 b are not in contact with each other and the seal fins 2 a 1 and the corresponding breathable spacers 4 a are not in contact with each other. If the steam St has high pressure, the seal fins 62 and the corresponding breathable spacers 4 b are in contact with each other and the seal fins 2 a 1 and the corresponding breathable spacers 4 a are in contact with each other.

1 . A seal structure assembled into a steam turbine including a rotating portion composed of a rotor and a member rotating integrally with the rotor, and a fixed portion composed of a casing embracing the rotating portion and a member secured to the casing, the seal structure comprising:
 a seal fin provided on both or either one of the rotating portion and the fixed portion,   wherein if the seal fin is provided on the fixed portion, a spacer made of breathable metal is provided on the rotating portion so as to oppose to the seal fin provided on the fixed portion, the seal fin provided on the fixed portion can be shifted in a direction coming close to or moving away from the rotating portion, and   if the seal fin is provided on the rotating portion, a spacer made of breathable metal is provided on the fixed portion so as to oppose to the seal fin provided on the rotating portion, the spacer provided on the fixed portion can be shifted in a direction coming close to or moving away from the rotating portion.   
     
     
         2 . The seal structure according to  claim 1 ,
 wherein the member secured to the casing is a stator blade provided on the casing,   the seal fin is provided at both or either one of a distal end of the stator blade and a portion, of the rotor, opposed to the distal end of the stator blade,   if the seal fin is provided at the distal end of the stator blade, the spacer is provided on the rotor so as to oppose to the seal fin provided at the distal end of the stator blade, the seal fin provided at the distal end of the stator blade can be shifted in a direction coming close to or moving away from the rotor, and   if the seal fin is provided on the rotor, the spacer is provided at the distal end of the stator blade so as to oppose to the seal fin provided on the rotor, the spacer provided at the distal end of the stator blade can be shifted in a direction coming close to or moving away from the rotor.   
     
     
         3 . The seal structure according to  claim 1 ,
 wherein the member rotating integrally with the rotor is a rotor blade provided on the rotor,   the seal fin is provided at both or either one of a portion, of the casing, opposed to a distal end of the rotor blade and the distal end of the rotor blade,   if the seal fin is provided on the casing, the spacer is provided at the distal end of the rotor blade so as to oppose to the seal fin provided on the casing, the seal fin provided on the casing can be shifted in a direction coming close to or moving away from the distal end of the rotor blade, and   if the seal fin is provided at the distal end of the rotor blade, the spacer is provided on the casing so as to oppose to the seal fin provided at the distal end of the rotor blade, the spacer provided on the casing can be shifted in a direction coming close to or moving away from the distal end of the rotor blade.   
     
     
         4 . The seal structure according to any one of  claims 1  to  3   wherein the fixed portion is provided with a movable portion biased by biasing means in a direction moving away from the rotating portion, and being shiftable in a direction coming close to the rotating portion by pressure of steam flowing through the steam turbine,   if the seal fin is provided on the fixed portion, the seal fin provided on the fixed portion is attached to the movable portion,   if the spacer is provided on the fixed portion, the spacer provided on the fixed portion is attached to the movable portion,   when a pressing force, resulting from the pressure of the steam, adapted to shift the movable portion in a direction coming close to the rotating portion is smaller than a biasing force, of the biasing means, adapted to bias the movable portion in a direction moving away from the rotating portion, the movable portion is shifted to a position away from the rotating portion, so that the seal fin and the spacer opposed thereto are not in contact with each other, and   when the pressing force is equal to or greater than the biasing force, the movable portion is shifted to a position close to the rotating portion, so that the seal fin and the spacer opposed thereto come into contact with each other.   
     
     
         5 . The seal structure according to any one of  claims 1  to  3 ,
 wherein the fixed portion is provided with a movable portion biased by biasing means in a direction moving away from the rotating portion, and being shiftable in a direction coming close to the rotating portion,   if the seal fin is provided on the fixed portion, the seal fin provided on the fixed portion is attached to the movable portion,   if the spacer is provided on the fixed portion, the spacer provided on the fixed portion is attached to the movable portion,   the seal structure further includes   an operating condition detecting device for detecting an operating condition of the steam turbine, and   a drive device for shifting the movable portion in a direction coming close to the rotating portion, and   on the basis of the operating condition of the steam turbine detected by the operating condition detecting device, the drive device shifts the movable portion in a direction coming close to the rotating portion to bring the seal fin and the spacer opposed thereto into contact with each other.   
     
     
         6 . The seal structure according to  claim 5 ,
 wherein the operating condition detecting device is a rotation speed detecting device for detecting rotation speed of the rotor and detects the operating condition of the steam turbine through the rotation speed of the rotor, and   the drive device shifts the movable portion in a direction coming close to the rotating portion when the rotation speed of the rotor is equal to or higher than a predetermined rotation speed.   
     
     
         7 . The seal structure according to  claim 5 ,
 wherein the operating condition detecting device is a pressure detecting device for detecting pressure of steam flowing through the steam turbine and detects the operating condition of the steam turbine through the pressure of the steam, and   the drive device shifts the movable portion in a direction coming close to the rotating portion when the pressure of the steam is equal to or greater than a predetermined pressure value.   
     
     
         8 . A control method for a seal structure assembled into a steam turbine including a rotating portion composed of a rotor and a member rotating integrally with the rotor, and a fixed portion composed of a casing embracing the rotating portion and a member secured to the casing, the seal structure including:
 a seal fin provided on both or either one of the rotating portion and the fixed portion,   wherein the fixed portion is provided with a movable portion biased by biasing means in a direction moving away from the rotating portion, and being shiftable in a direction coming close to the rotating portion by a drive device,   if the seal fin is provided on the fixed portion, a spacer made of breathable metal is provided on the rotating portion so as to oppose to the seal fin provided on the fixed portion, the seal fin provided on the fixed portion is attached to the movable portion, and   if the seal fin is provided on the rotating portion, a spacer made of breathable metal is provided on the fixed portion so as to oppose to the seal fin provided on the rotating portion, the spacer provided on the fixed portion is attached to the movable portion,   the control method comprising the steps of:   detecting rotation speed of the rotating portion; and   shifting the movable portion in a direction coming close to the rotating portion when the rotation speed of the rotating portion is equal to or higher than a predetermined rotation speed;   wherein when the rotation speed of the rotating portion is equal to or higher than the predetermined rotation speed, the seal fin and the spacer opposed thereto are brought into contact with each other.   
     
     
         9 . A control method for a seal structure assembled into a steam turbine including a rotating portion composed of a rotor and a member rotating integrally with the rotor, and a fixed portion composed of a casing embracing the rotating portion and a member secured to the casing, the seal structure including:
 a seal fin provided on both or either one of the rotating portion and the fixed portion,   wherein the fixed portion is provided with a movable portion biased by biasing means in a direction moving away from the rotating portion, and being shiftable in a direction coming close to the rotating portion by a drive device,   if the seal fin is provided on the fixed portion, a spacer made of breathable metal is provided on the rotating portion so as to oppose to the seal fin provided on the fixed portion, the seal fin provided on the fixed portion is attached to the movable portion, and   if the seal fin is provided on the rotating portion, a spacer made of breathable metal is provided on the fixed portion so as to oppose to the seal fin provided on the rotating portion, the spacer provided on the fixed portion is attached to the movable portion,   the control method comprising the steps of:   detecting pressure of steam flowing through the steam turbine, and   shifting the movable portion in a direction coming close to the rotating portion when the pressure of the steam is equal to or greater than a predetermined pressure value;   wherein when the pressure of the steam is equal to or greater than the predetermined pressure value, the seal fin and the spacer opposed thereto are brought into contact with each other.