U.S. patent application number 13/238645 was filed with the patent office on 2012-08-23 for self-adjusting seal for rotating turbomachinery.
Invention is credited to Takashi Nakano, Shin NISHIMOTO, Hidekazu Uehara.
Application Number | 20120211944 13/238645 |
Document ID | / |
Family ID | 45873872 |
Filed Date | 2012-08-23 |
United States Patent
Application |
20120211944 |
Kind Code |
A1 |
NISHIMOTO; Shin ; et
al. |
August 23, 2012 |
SELF-ADJUSTING SEAL FOR ROTATING TURBOMACHINERY
Abstract
A self-adjusting seal has a movable seal member fitted in a
groove of a dummy ring along a rotor. The movable seal member is
biased outwardly in a radial direction by a disc spring, and a gap
between the movable seal member and the rotor is large during the
start-up or shutdown of rotating turbomachinery. On the other hand,
during a rated operation of the rotating turbomachinery, by a fluid
having flown into the internal portion of the groove via a gap
between a high pressure side end surface of the movable seal member
and the groove, the movable seal member is pressed toward the rotor
against a biasing force of the disc spring.
Inventors: |
NISHIMOTO; Shin; (Tokyo,
JP) ; Nakano; Takashi; (Tokyo, JP) ; Uehara;
Hidekazu; (Tokyo, JP) |
Family ID: |
45873872 |
Appl. No.: |
13/238645 |
Filed: |
September 21, 2011 |
Current U.S.
Class: |
277/422 |
Current CPC
Class: |
F16J 15/442 20130101;
F01D 11/16 20130101 |
Class at
Publication: |
277/422 |
International
Class: |
F01D 11/04 20060101
F01D011/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 2010 |
JP |
2010-214414 |
Claims
1. A self-adjusting seal for rotating turbomachinery in which a
rotational member rotates while confronting a stationary member and
energy transfer between the rotational member and a fluid is
performed, comprising: a movable seal member fitted in a groove
provided in the stationary member along the rotational member; and
a biasing member biasing the movable seal member so as to increase
a gap between the rotational member and the movable seal member,
wherein at least during a rated operation of the rotating
turbomachinery, the movable seal member is pressed toward the
rotational member against a biasing force of the biasing member by
the fluid having flown into an internal portion of the groove via a
gap between a high pressure side end surface of the movable seal
member and the groove, and at least one of a low pressure side end
surface of the movable seal member and a wall surface of the groove
opposing the low pressure side end surface is subjected to a
process for facilitating relative sliding between the low pressure
side end surface of the movable seal member and the wall surface of
the groove.
2. The self-adjusting seal for rotating turbomachinery according to
claim 1, wherein, as the process for facilitating the relative
sliding, a lubricating coating is formed on at least one of the low
pressure side end surface of the movable seal member and the wall
surface of the groove opposing the low pressure side end
surface.
3. The self-adjusting seal for rotating turbomachinery according to
claim 2, wherein the lubricating coating is formed by application,
thermal spraying, or plating.
4. The self-adjusting seal for rotating turbomachinery according to
claim 2, wherein the lubricating coating contains a solid lubricant
made of at least one of molybdenum disulfide, graphite, tungsten
disulfide, graphite fluoride, boron nitride, copper, nickel, lead,
tin, silver, tetrafluoroethylene, polyimide, and high density
polyethylene.
5. The self-adjusting seal for rotating turbomachinery according to
claim 4, wherein a dimple for fixing the solid lubricant is formed
on at least one of the low pressure side end surface of the movable
seal member and the wall surface of the groove opposing the low
pressure side end surface.
6. The self-adjusting seal for rotating turbomachinery according to
claim 1, wherein, as the process for facilitating the relative
sliding, a corner of the wall surface of the groove opposing the
low pressure side end surface of the movable seal member is
chamfered.
7. The self-adjusting seal for rotating turbomachinery according to
claim 1, wherein, as the process for facilitating the relative
sliding, a surface roughness Ra of at least one of the low pressure
side end surface of the movable seal member and the wall surface of
the groove opposing the low pressure side end surface is set to not
more than 6.3 .mu.m.
8. The self-adjusting seal for rotating turbomachinery according to
claim 1, wherein a coating made of an abradable material is formed
on a surface of the movable seal member opposing the rotational
member.
9. The self-adjusting seal for rotating turbomachinery according to
claim 2, wherein, as the process for facilitating the relative
sliding, a corner of the wall surface of the groove opposing the
low pressure side end surface of the movable seal member is
chamfered.
10. The self-adjusting seal for rotating turbomachinery according
to claim 3, wherein, as the process for facilitating the relative
sliding, a corner of the wall surface of the groove opposing the
low pressure side end surface of the movable seal member is
chamfered.
11. The self-adjusting seal for rotating turbomachinery according
to claim 4, wherein, as the process for facilitating the relative
sliding, a corner of the wall surface of the groove opposing the
low pressure side end surface of the movable seal member is
chamfered.
12. The self-adjusting seal for rotating turbomachinery according
to claim 5, wherein, as the process for facilitating the relative
sliding, a corner of the wall surface of the groove opposing the
low pressure side end surface of the movable seal member is
chamfered.
Description
TECHNICAL FIELD
[0001] The present invention relates to a self-adjusting seal used
in rotating turbomachinery such as, for example, a steam turbine, a
gas turbine and a compressor. Herein, the self-adjusting seal
denotes a seal in which a seal gap is automatically adjusted in
accordance with the operational state of the rotating
turbomachinery.
BACKGROUND ART
[0002] In rotating turbomachinery such as a steam turbine, a gas
turbine and a compressor, in terms of an improvement in operation
efficiency, a seal for preventing the leakage of a working fluid
via a gap between a rotational member (a rotor or a blade) and a
stationary member (a casing or a vane) is provided at various
positions.
[0003] Examples of the seal include a dummy ring seal provided
between a high pressure portion and an intermediate pressure
portion of a high/intermediate pressure integrated type steam
turbine, a ground seal provided at a portion where a rotor extends
through a casing, a blade tip seal provided between the tip of a
blade and the casing, and a vane tip seal provided between the tip
of a vane and the rotor.
[0004] As the seal of this type, conventionally, a labyrinth seal
composed of a labyrinth block having a plurality of fins and a
plate spring for elastically supporting the labyrinth block from
its back surface side has been typically used. In this case, the
labyrinth block is held from the back surface side by the plate
spring in a state where the labyrinth block is fitted in a groove
formed in a stationary member, and the gap between the fins and a
rotational member is kept constant. With this, when passing through
the minute gap between the fins and the rotational member, a fluid
sharply expands and the pressure is reduced so that the leakage of
the fluid is prevented.
[0005] However, in the labyrinth seal having the above-described
configuration, when the gap between the fins and the rotational
member is extremely small, depending on the operational state of
the rotating turbomachinery (particularly during the start-up or
shutdown), there have been cases where the fins comes in contact
with the rotational member due to the influence resulting from a
difference in thermal expansion between the rotational member and
the stationary member, and the abrasion of the fins and a shaft
vibration are generated. On the other hand, when the gap between
the fins and the rotational member is increased, there has been a
problem that the leakage of the fluid cannot be sufficiently
prevented so that the operation efficiency of the rotating
turbomachinery is reduced.
[0006] To cope with this, as a seal replacing the conventional
labyrinth seal, Patent Document 1 describes a self-adjusting seal
in which the seal gap is automatically adjusted in accordance with
the operational state of the rotating turbomachinery.
[0007] The seal is composed of a stationary seal ring disposed
close to a horizontal dividing plane of a rotational member (a
rotor) and a movable seal ring disposed close to the center. Of the
members, the movable seal ring is biased outwardly in a radial
direction by an elastic body (a corrugated plate spring, disc
spring, metal bellows, and the like) so that the seal gap during
the start-up or shutdown of the rotating turbomachinery is
sufficiently secured. On the other hand, during a rated operation
of the rotating turbomachinery, the movable seal ring is pressed
inwardly in the radial direction against a biasing force of the
elastic body by the pressure of a fluid in the rotating
turbomachinery so that the seal gap can be minimized. [0008]
[Patent Document 1] Japanese Patent Application Laid-open No.
2000-97352
[0009] In consideration of a frictional force (f) of a relative
sliding portion between the movable seal ring and a stationary
member to which the movable seal ring is fixed, the self-adjusting
seal described in Patent Document 1 is designed such that a fluid
pressure (P) applied to the back surface of the movable seal ring
is sufficiently larger than the biasing force (F) by the elastic
body.
[0010] That is, the shape (an effective area) of the movable seal
ring and the material and shape of the elastic body are determined
such that the following inequality (1) is satisfied during the
rated operation of the rotating turbomachinery:
back surface pressure (P).times.seal ring effective area
(A)>biasing force (F)+frictional force (f) (1).
[0011] However, in reality, the self-adjusting seal designed by
such method does not necessarily work properly, and there is a
possibility that the seal gap during the rated operation of the
rotating turbomachinery becomes excessively large so that the
leakage of the fluid cannot be sufficiently prevented, or that, by
contrast, the movable seal ring operates before the rotating
turbomachinery passes a critical point during an unsteady operation
of the rotating turbomachinery, and the movable seal ring comes in
contact with the rotational member. In particular, when the latter
situation occurs in an ACC abradable seal which has been actively
developed in recent years, damage beyond expectation is caused to
an abradable material provided on the surface of the movable seal
ring, and a desired seal gap cannot be formed thereafter. Note that
the ACC abradable seal mentioned herein denotes a self-adjusting
seal in which the abradable material, which can be easily cut, is
provided on the surface of the movable seal ring such that heat
generation resulting in a bending deformation of the rotational
member is suppressed even when the movable seal ring is brought
into contact with the rotational member from any cause.
[0012] In addition, when a plurality of self-adjusting seals are
arranged as a dummy ring seal, there are cases where timing at
which the movable seal ring operates varies.
[0013] To cope with this, as the result of elaborate studies on a
factor which influences the operation of the self-adjusting seal by
the present inventors, there has been obtained knowledge that the
frictional force (f) of the relative sliding portion between the
movable seal ring and the stationary member greatly varies due to
the individual difference of the self-adjusting seal, and
significantly influences the operation of the self-adjusting
seal.
SUMMARY OF INVENTION
[0014] The present invention has been achieved in view of the
above-described circumstances, and an object thereof is to provide
a self-adjusting seal which operates at desired timing in
accordance with the operational state of the rotating
turbomachinery, and is capable of properly adjusting the seal
gap.
[0015] The self-adjusting seal for rotating turbomachinery
according to the present invention is a self-adjusting seal for
rotating turbomachinery in which a rotational member rotates while
confronting a stationary member and energy transfer between the
rotational member and a fluid is performed, including a movable
seal member fitted in a groove provided in the stationary member
along the rotational member, and a biasing member biasing the
movable seal member so as to increase a gap between the rotational
member and the movable seal member, wherein at least during a rated
operation of the rotating turbomachinery, the movable seal member
is pressed toward the rotational member against a biasing force of
the biasing member by the fluid having flown into an internal
portion of the groove via a gap between a high pressure side end
surface of the movable seal member and the groove, and at least one
of a low pressure side end surface of the movable seal member and a
wall surface of the groove opposing the low pressure side end
surface is subjected to a process for facilitating relative sliding
between the low pressure side end surface of the movable seal
member and the wall surface of the groove.
[0016] In the present specification, the process for facilitating
relative sliding denotes any process for reducing a friction
coefficient in a relative sliding portion. Note that, although the
friction coefficient in the relative sliding portion differs
depending on materials for the movable seal member and the
stationary member and the like, when a special process is not
performed, the friction coefficient is normally more than 0.5.
Therefore, the process for facilitating relative sliding can be
defined as a process for setting the friction coefficient in the
relative sliding portion to not more than 0.5, and means a process
for setting the friction coefficient in the relative sliding
portion to, e.g., 0.1 to 0.5.
[0017] In the above-described self-adjusting seal, at least one of
the low pressure side end surface of the movable seal member and
the wall surface of the groove of the stationary member opposing
the low pressure side end surface (i.e., the relative sliding
portion between the movable seal member and the stationary member)
is subjected to the process for facilitating the relative sliding
therebetween. As a result, frictional force (f) of the second term
on the right side of the above-described inequality (1) is reduced,
and the operation timing of the self-adjusting seal is determined
mainly by the magnitude relation between back surface pressure
(P).times.seal ring effective area (A) on the left side and biasing
force (F) of the first term on the right side. With this, the
frictional force of the relative sliding portion which tends to
vary due to the individual difference of the self-adjusting seal
does not significantly influence the operation of the
self-adjusting seal, and hence it is possible to cause the
self-adjusting seal to operate at desired timing in accordance with
the operational state of the rotating turbomachinery.
[0018] In addition, the relative sliding portion between the
movable seal member and the stationary member is subjected to the
process for facilitating the relative sliding, whereby variations
in the frictional force of the relative sliding portion themselves
are reduced, and hence it is possible to cause the self-adjusting
seal to operate at desired timing in accordance with the
operational state of the rotating turbomachinery.
[0019] In the above-described self-adjusting seal for rotating
turbomachinery, as the process for facilitating the relative
sliding, a lubricating coating may be formed on at least one of the
low pressure side end surface of the movable seal member and the
wall surface of the groove opposing the low pressure side end
surface.
[0020] In this case, the lubricating coating can be formed by,
e.g., application, thermal spraying, or plating.
[0021] In addition, the lubricating coating may contain a solid
lubricant made of at least one of molybdenum disulfide, graphite,
tungsten disulfide, graphite fluoride, boron nitride, copper,
nickel, lead, tin, silver, tetrafluoroethylene, polyimide, and high
density polyethylene.
[0022] When the lubricating coating containing the solid lubricant
is used, a dimple for fixing the solid lubricant is preferably
formed on at least one of the low pressure side end surface of the
movable seal member and the wall surface of the groove opposing the
low pressure side end surface.
[0023] With this, it is possible to prevent the loss of the effect
of facilitating the relative sliding between the movable seal
member and the groove wall surface of the stationary member, and
maintain the normal operation of the self-adjusting seal for a long
period of time.
[0024] In the above-described self-adjusting seal for rotating
turbomachinery, as the process for facilitating the relative
sliding, a corner of the wall surface of the groove opposing the
low pressure side end surface of the movable seal member may be
chamfered.
[0025] Alternatively, in the above-described self-adjusting seal
for rotating turbomachinery, as the process for facilitating the
relative sliding, a surface roughness Ra of at least one of the low
pressure side end surface of the movable seal member and the wall
surface of the groove opposing the low pressure side end surface
may be set to not more than 6.3 .mu.m.
[0026] In the above-described self-adjusting seal for rotating
turbomachinery, a coating made of an abradable material is
preferably formed on a surface of the movable seal member opposing
the rotational member.
[0027] In the self-adjusting seal having the abradable material
provided on the surface of the movable seal member in this manner
(what is called an ACC abradable seal), even when the movable seal
member is brought into contact with the rotational member from any
cause during the operation of the rotating turbomachinery, the
abradable material is easily cut so that it is possible to suppress
heat generation and prevent a bending deformation of the rotational
member resulting from the heat generation. Consequently, the
commercialization thereof is in strong demand. However, in the case
of the ACC abradable seal, when the movable seal member operates
before desired timing so that the seal gap is reduced before the
rotating turbomachinery reaches the rated operation (particularly
before passing a critical point during an unsteady operation) and
the movable seal member comes in contact with the rotational
member, damage beyond expectation is caused to the abradable
material, and a desired seal gap cannot be formed thereafter.
[0028] In this regard, since the above-described self-adjusting
seal can operate at desired timing in accordance with the
operational state of the rotating turbomachinery, when the
self-adjusting seal is applied to the ACC abradable seal, it is
possible to prevent the damage beyond expectation to the abradable
material.
[0029] According to the present invention, since the relative
sliding portion between the movable seal member and the stationary
member is subjected to the process for facilitating the relative
sliding therebetween, the operation timing of the self-adjusting
seal is determined mainly by the relation between the biasing force
by the biasing member and the pressure of the fluid pressing the
movable seal member toward the rotational member against the
biasing force. Consequently, the frictional force of the relative
sliding portion which tends to vary due to the individual
difference of the self-adjusting seal does not significantly
influence the operation of the self-adjusting seal, and hence it is
possible to cause the self-adjusting seal to operate at desired
timing in accordance with the operational state of the rotating
turbomachinery.
[0030] In addition, the relative sliding portion between the
movable seal member and the stationary member is subjected to the
process for facilitating the relative sliding, whereby variations
in the frictional force of the relative sliding portion themselves
are reduced, and hence it is possible to cause the self-adjusting
seal to operate at desired timing in accordance with the
operational state of the rotating turbomachinery.
BRIEF DESCRIPTION OF DRAWINGS
[0031] FIG. 1 is a front view showing an example of an entire
configuration of a self-adjusting seal;
[0032] FIG. 2 is a cross-sectional view showing an example of a
configuration of a movable seal member;
[0033] FIG. 3 is a view schematically showing the movement of the
movable seal member in accordance with an operational state of
rotating turbomachinery in which FIG. 3(a) shows the state of the
movable seal member during the start-up or shutdown, while FIG.
3(b) shows the state of the movable seal member during a rated
operation;
[0034] FIG. 4 is a cross-sectional view showing an example of a
configuration of a movable seal member in a self-adjusting seal of
a first embodiment;
[0035] FIG. 5 is a cross-sectional view showing an example of a
configuration of a movable seal member in a self-adjusting seal of
a second embodiment;
[0036] FIG. 6 is a cross-sectional view showing an example of a
configuration of a movable seal member in a self-adjusting seal of
a third embodiment; and
[0037] FIG. 7 is a cross-sectional view showing an example of
another configuration of the movable seal member.
DESCRIPTION OF EMBODIMENTS
[0038] A description is given hereinbelow of embodiments of the
present invention with reference to the accompanying drawings. Note
that the scope of the present invention is not limited to
dimensions, materials, shapes, and relative arrangements of
constituent parts described in the embodiments unless specifically
described, and they are only explanatory examples.
First Embodiment
[0039] FIG. 1 is a front view showing an example of an entire
configuration of a self-adjusting seal for rotating turbomachinery.
As shown in the drawing, a self-adjusting seal 1 is composed of a
stationary seal member 10 and a movable seal member 20 which are
annularly provided along a rotor 2 of rotating turbomachinery.
[0040] The self-adjusting seal 1 is fitted in a groove formed in a
dummy ring 4 (see FIG. 2) attached to a casing (not shown) of the
rotating turbomachinery so as to seal a gap between the rotor 2 and
the dummy ring 4. Although a description is given hereinbelow of an
example in which the self-adjusting seal 1 is used as a dummy ring
seal provided between the dummy ring 4 serving as a stationary
member of the rotating turbomachinery and the rotor 2 serving as a
rotational member, the self-adjusting seal according to the present
invention can be used as various seals for the rotating
turbomachinery including a ground seal, blade and vane tip seals,
and the like.
[0041] The stationary seal member 10 has a pair of an upper member
10A and a lower member 10B provided on left and right sides of the
rotor 2, and the upper and lower members 10A and 10B making the
pair are joined to each other at joint surfaces 12. An inner
periphery of the stationary seal member 10 is provided with seal
fins, and the seal fins and an uneven groove formed along a
circumferential direction of the rotor 2 create a labyrinth effect
to prevent the leakage of a fluid (steam when the rotating
turbomachinery is a steam turbine) via the gap between the
stationary seal member 10 and the rotor 2.
[0042] The stationary seal member 10 is elastically supported from
its back surface side by a plate spring or the like, and can move
outwardly in a radial direction when the stationary seal member 10
comes in contact with the rotor 2. However, the stationary seal
member 10 is basically immovable, and does not move in accordance
with the operational state of the rotating turbomachinery.
[0043] On the other hand, as described later, the movable seal
member 20 has a large seal gap between itself and the rotor 2
during the start-up or shutdown of the rotating turbomachinery,
and, during a rated operation of the rotating turbomachinery, the
movable seal member 20 moves in directions of arrows in the drawing
so as to abut on the stationary seal member 10 at joint surfaces
14, whereby the seal gap is reduced.
[0044] FIG. 2 is a cross-sectional view showing an example of a
configuration of the movable seal member 20. As shown in the
drawing, the movable seal member 20 is fitted in a groove 6 formed
in the dummy ring 4 attached to the casing.
[0045] An inner periphery of the movable seal member 20 is provided
with seal fins 22, and an uneven groove 8 formed along the
circumferential direction of the rotor 2 and the seal fins 22
create the labyrinth effect to prevent the leakage of the fluid via
the gap between the movable seal member 20 and the rotor 2.
[0046] In addition, inside the groove 6 of the dummy ring 4, there
are provided a disc spring 30 for biasing an upper holding plate 24
of the movable seal member 20 outwardly in the radial direction,
and a support plate 32 for supporting the disc spring 30 from
below. With this, the movable seal member 20 is biased by the disc
spring 30 such that the gap between the seal fins 22 and the rotor
2 is increased. Note that any biasing member such as a plate spring
or metal bellows may also be used instead of the disc spring
30.
[0047] FIG. 3 is a view schematically showing the movement of the
movable seal member 20 in accordance with the operational state of
the rotating turbomachinery in which FIG. 3(a) shows the state of
the movable seal member 20 during the start-up or shutdown of the
rotating turbomachinery, while FIG. 3(b) shows the state of the
movable seal member 20 during the rated operation of the rotating
turbomachinery.
[0048] As shown in FIG. 3(a), during the start-up or shutdown of
the rotating turbomachinery, the movable seal member 20 is pushed
up outwardly in the radial direction by a biasing force F of the
disc spring 30, and the gap between the seal fins 22 and the rotor
2 is increased.
[0049] On the other hand, during the rated operation of the
rotating turbomachinery, as shown in FIG. 3(b), a difference in the
pressure of the fluid is generated between both sides of the
movable seal member 20, the movable seal member 20 receives a
thrust force (a force resulting from the pressure difference)
F.sub.0 to move toward a low pressure side (the right side of the
movable seal member 20 in the example shown in the drawing), and a
low pressure side end surface 26 of the movable seal member 20
comes in contact with a groove wall surface (a wall surface 9 of
the groove 6 opposing the low pressure side end surface 26) of the
dummy ring 4. At this point, the fluid on the high pressure side
passes through the gap between a high pressure side end surface 28
of the movable seal member 20 and the groove 6 of the dummy ring 4,
and flows into an internal space 7 of the groove 6 so that the
pressure in the internal space 7 of the groove 6 rises (note that,
though not shown, there are provided bypass grooves for guiding the
fluid on the high pressure side to the internal space 7 of the
groove 6 at several positions along the circumferential direction
of the stationary seal member 20 in FIG. 1). As a result, the
movable seal member 20 is pressed inwardly in the radial direction
by the high pressure fluid having flown into the internal space 7
of the groove 6.
[0050] At this point, in order to actually cause the movable seal
member 20 to move inwardly in the radial direction, the following
inequality needs to be satisfied:
back surface pressure (P).times.seal ring effective area
(A)>biasing force (F)+frictional force (f) (1).
[0051] Herein, the frictional force (f) is obtained by multiplying
a friction coefficient .mu..sub.0 in a relative sliding portion 29
between the low pressure side end surface 26 of the movable seal
member 20 and the wall surface 9 of the groove 6 by the thrust
force F.sub.0.
[0052] As the result of elaborate studies, the present inventors
have understood that the frictional force (f) of the relative
sliding portion 29 tends to vary, and the frictional force (f) of
the relative sliding portion 29 significantly influences the
operation of the self-adjusting seal 1.
[0053] Consequently, in the present embodiment, a process for
facilitating the relative sliding in the relative sliding portion
29 is performed by providing a lubricating coating on at least one
of the low pressure side end surface 26 of the movable seal member
20 and the wall surface 9 of the groove 6 opposing the low pressure
side end surface 26.
[0054] FIG. 4 is a cross-sectional view showing an example of a
configuration of the movable seal member 20 having the lubricating
coating provided in the relative sliding portion 29. In the example
shown in the drawing, although a rubricating coating 40 is provided
on both of the low pressure side end surface 26 of the movable seal
member 20 and the wall surface 9 of the groove 6 opposing the low
pressure side end surface 26, the lubricating coating 40 may also
be provided only on one of them. Note that the thickness of the
lubricating coating 40 is preferably in a range of 2 to 7 .mu.m in
terms of sufficient facilitation of the relative sliding in the
relative sliding portion 29.
[0055] With regard to a method for forming the lubricating coating
40, an appropriate method is preferably selected in accordance with
the material forming the lubricating coating 40, and application,
thermal spraying, or plating may be selected as the method. For
example, by applying a grease or paste in which a powdery or scaly
solid lubricant having antifriction properties is dispersed, the
lubricating coating 40 may be formed.
[0056] The solid lubricant used in the lubricating coating 40 is
preferably made of at least one of molybdenum disulfide, graphite,
tungsten disulfide, graphite fluoride, boron nitride, copper,
nickel, lead, tin, silver, tetrafluoroethylene, polyimide, and high
density polyethylene. Among them, molybdenum disulfide excellent in
lubricating and heat resistance properties can be suitably used as
the material for the lubricating coating 40.
[0057] When the lubricating coating 40 contains the solid
lubricant, it is preferable to provide a dimple 42 on one of the
low pressure side end surface 26 of the movable seal member 20 and
the wall surface 9 of the groove 6 opposing the low pressure side
end surface 26 to fix the solid lubricant. Note that FIG. 4 shows
an example in which the dimple 42 is provided on the wall surface 9
of the groove 6 opposing the low pressure side end surface 26.
[0058] With this, it is possible to prevent the loss of the effect
of facilitating the relative sliding between the movable seal
member 20 and the wall surface of the groove 6, and maintain the
normal operation of the self-adjusting seal 1 for a long period of
time.
[0059] The dimple 42 may also be formed as a concave portion having
a depth of about 10 .mu.m by, e.g., shot peening.
Second Embodiment
[0060] Next, a description is given of a self-adjusting seal of a
second embodiment.
[0061] The self-adjusting seal of the present embodiment is the
same as the self-adjusting seal of the first embodiment except for
the specific implementation of the process for facilitating the
relative sliding in the relative sliding portion 29 between the low
pressure side end surface 26 of the movable seal member 20 and the
wall surface 9 of the groove 6 opposing the low pressure side end
surface 26. Accordingly, a description is given herein only of the
process for facilitating the relative sliding in the relative
sliding portion 29.
[0062] FIG. 5 is a cross-sectional view showing an example of a
configuration of the portion in the vicinity of the low pressure
side end surface 26 of the movable seal member 20 in the
self-adjusting seal of the present embodiment. As shown in the
drawing, as the process for facilitating the relative sliding in
the relative sliding portion 29, corners 44 of the wall surface 9
of the groove 6 opposing the low pressure side end surface 26 of
the movable seal member 20 are chamfered (preferably chamfering of
not less than 1 mm). By chamfering each corner 44, it is possible
to prevent the corner 44 from being caught on the low pressure side
end surface 26 of the movable seal member 20, and facilitate the
relative sliding in the relative sliding portion 29.
[0063] Note that, although the shape of the corner 44 after the
chamfering is not particularly limited, as shown in FIG. 5, by
forming the corner 44 into an R shape (a curved shape), it is
possible to reliably prevent the corner 44 from being caught on the
low pressure side end surface 26 of the movable seal member 20.
Third Embodiment
[0064] Subsequently, a description is given of a self-adjusting
seal of a third embodiment.
[0065] The self-adjusting seal of the present embodiment is the
same as the self-adjusting seal of the first embodiment except for
the specific implementation of the process for facilitating the
relative sliding in the relative sliding portion 29 between the low
pressure side end surface 26 of the movable seal member 20 and the
wall surface 9 of the groove 6 opposing the low pressure side end
surface 26. Accordingly, a description is given herein only of the
process for facilitating the relative sliding in the relative
sliding portion 29.
[0066] FIG. 6 is a cross-sectional view showing an example of a
configuration of the portion in the vicinity of the low pressure
side end surface 26 of the movable seal member 20 in the
self-adjusting seal of the present embodiment. In the present
embodiment, a surface roughness Ra of at least one of the low
pressure side end surface 26 of the movable seal member 20 and the
wall surface 9 of the groove 6 opposing the low pressure side end
surface 26 is set to not more than 6.3 .mu.m. With this, it is
possible to reduce the friction coefficient .mu..sub.0 in the
relative sliding portion 29, and facilitate the relative sliding in
the relative sliding portion 29.
[0067] As has been described above, in each of the first to third
embodiments, at least one of the low pressure side end surface 26
of the movable seal member 20 and the wall surface 9 of the groove
6 opposing the low pressure side end surface 26 is subjected to
some process for facilitating the relative sliding therebetween. As
a result, frictional force (f) of the second term on the right side
of the above-described inequality (1) is reduced, and the operation
timing of the self-adjusting seal 1 is determined mainly by the
magnitude relation between back surface pressure (P).times.seal
ring effective area (A) on the left side and biasing force (F) of
the first term on the right side. With this, the frictional force
of the relative sliding portion 29 which tends to vary due to the
individual difference of the self-adjusting seal 1 does not
significantly influence the operation of the self-adjusting seal 1,
and hence it is possible to cause the self-adjusting seal 1 to
operate at desired timing in accordance with the operational state
of the rotating turbomachinery.
[0068] In addition, at least one of the low pressure side end
surface 26 of the movable seal member 20 and the wall surface 9 of
the groove 6 opposing the low pressure side end surface 26 is
subjected to the process for facilitating the relative sliding
therebetween, whereby variations in the frictional force of the
relative sliding portion 29 themselves are reduced, and hence it is
possible to cause the self-adjusting seal 1 to operate at desired
timing in accordance with the operational state of the rotating
turbomachinery.
[0069] Although the embodiments of the present invention have been
described in detail thus far, the present invention is not limited
thereto, and it will be evident that various modifications and
changes may be made without departing from the gist of the present
invention.
[0070] For example, in each of the embodiments described above,
although the description has been given of the example in which the
relative sliding in the relative sliding portion 29 is facilitated
by the single process, the processes for facilitating the relative
sliding in the relative sliding portion 29 in the first to third
embodiments may be appropriately combined and used.
[0071] In addition, in each of the embodiments described above,
although the description has been given of the self-adjusting seal
1 in which the stationary seal member 10 and the movable seal
member 20 are provided, the seal fins are provided on the inner
peripheries of the stationary seal member 10 and the movable seal
member 20, and the seal fins and the uneven groove formed along the
circumferential direction of the rotor 2 prevent the leakage of the
fluid, the self-adjusting seal according to the present invention
is not limited to the example. For example, the uneven groove may
be provided in the stationary seal member 10 and the movable seal
member 20, and the seal fins may be provided on the rotational
member (the rotor 2).
[0072] FIG. 7 is a cross-sectional view showing an example in which
the uneven groove is provided in the movable seal member 20 and the
seal fins are provided on the rotor 2. As shown in the drawing, an
uneven groove 50 is formed in the inner peripheral surface of the
movable seal member 20 opposing the rotor 2 along the
circumferential direction, and seal fins 52 are formed on the rotor
2 along the circumferential direction.
[0073] Further, as shown in FIG. 7, on the surface of the movable
seal member 20 opposing the rotor 2, a coating 54 made of an
abradable material is preferably formed by thermal spraying.
[0074] With this, even when the movable seal member 20 is brought
into contact with the rotor 2 from any cause during the operation
of the rotating turbomachinery, the coating 54 is easily cut, and
hence it is possible to suppress heat generation, and prevent a
bending deformation of the rotational member resulting from the
heat generation. On the other hand, the self-adjusting seal 1
having the above-described configuration can operate at desired
timing in accordance with the operational state of the rotating
turbomachinery, and the seal gap is not reduced before the rotating
turbomachinery reaches the rated operation (particularly before
passing the critical point during the unsteady operation) in the
self-adjusting seal 1, and hence it is possible to prevent the
damage beyond expectation resulting from the contact between the
coating 54 made of the abradable material and the rotor 2.
* * * * *