Rotary kinetic fluid motors or pumps – Bearing – seal – or liner between runner portion and static part – Between axial flow runner and vane or vane diaphragm structure
Reexamination Certificate
2001-12-26
2004-02-17
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Bearing, seal, or liner between runner portion and static part
Between axial flow runner and vane or vane diaphragm structure
Reexamination Certificate
active
06692227
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a stationary blade shroud of a gas turbine. More particularly, this invention relates to a stationary blade shroud improved in the sealing performance in the gaps between adjacent stationary blade inside shrouds.
BACKGROUND OF THE INVENTION
The turbine section of a gas turbine used in a generator or the like comprises moving blades which rotate together with the rotor, and stationary blades which are fixed in the casing. The moving blade is composed of a platform coupled to the rotor and a moving blade. The stationary blade is composed of a stationary blade and inside shroud and outside shroud fixed at both ends of this stationary blade.
The blade surface, and inside and outside shrouds of the stationary blade form a passage wall of high temperature gas flowing in the turbine section, and the blade surface and platform of the moving blade also form a passage wall of high temperature gas. In the casing, split rings for forming the passage wall of high temperature gas together with the blade surface and platform of the moving blade are fixed across a specific gap to the leading end of the moving blade. A plurality of split rings are coupled in the arraying direction of the moving blades, and a wall of an annular section is formed on the whole.
On the other hand, the moving blades and stationary blades are divided into a plurality of sections in the peripheral direction of the rotor and formed in units for the convenience of performance for absorbing thermal deformation, manufacture or maintenance, and the shrouds and platforms, like the split rings, are coupled in a plurality in the blade arraying direction, forming a wall of an annular section on the whole, and each is formed in an arc section.
When coupling the divided inside shrouds in the peripheral direction of the rotor, a gap must be held preliminarily between the coupled inside shrouds. This is because the shrouds are thermally expanded in the peripheral direction as being exposed to high temperature gas sent from the combustor of the gas turbine, and it is preferred to design so that this gap is completely eliminated in the thermally expanded state.
That is, when the high temperature gas flows in the passage formed by the blade surface, shroud, platform or split ring, the high temperature gas escapes outside through the gap formed between the coupled shrouds, and the turbine efficiency declines, or contamination may deposit in other area than the passage due to combustion gas which is high temperature gas, possibly leading to unexpected accident.
Actually, however, considering the manufacturing error and others, it is impossible to eliminate such gaps completely in high temperature condition. Accordingly, hitherto, it has been attempted to prevent escape of high temperature gas V1 from the gap
43
g
to outside by installing a seal member
44
between the coupled inside shrouds
43
as shown, for example, in the inside shroud
43
in FIG.
6
.
More specifically, as shown in
FIG. 7A
that shows a section along line I—I in FIG.
6
and
FIG. 7B
that shows a section along line II—II, the seal member
44
is disposed in the groove extending in the downstream direction from the vicinity of the upstream side end
43
b
of flow direction of high temperature gas V1 formed in the side end
43
a
of the inside shroud
43
.
Near the upstream side end
43
b
of the inside shroud
43
, and along the inner circumference of the inside shroud
43
, honeycomb members
43
d
of arc shape (shown in linear shape in
FIG. 6
for the sake of simplicity) are disposed, and are provided on the inner circumference of the inside shroud
43
through a base plate
43
c,
and are disposed across a slight gap to seal fins
47
a
formed on the platform
47
of the moving blade
46
rotating as shown in FIG.
8
.
The honeycomb members
43
d
are provided to prevent heavy contact between the rotary parts (including the platform
47
) of the moving blade
46
and the stationary part including the stationary blade
42
due to rotary shaft runout of the rotating moving blades
46
, and as far as the shaft runout is small, that is, in a stage of light contact before coming into heavy contact, the seal fin
47
a
and honeycomb member
43
d
contact with each other, and the honeycomb member
43
d
is broken. On the other hand, the seal fin
47
a
is higher in hardness than the honeycomb member
43
d,
and is not broken, and only by replacing the honeycomb member
43
d,
the original state is restored, and therefore the honeycomb member
43
d
may be called light contact detecting step for preventing heavy contact with the rotary part of the moving blade
46
.
In the example shown in FIG.
6
and
FIG. 7
, the seal member
44
is disposed nearly along the overall length in the flow direction of high temperature gas V1 at the side end
43
a
of the inside shroud
43
, and leak of high temperature gas V1 is nearly prevented, but in other structure of inside shroud
43
, the seal member
44
cannot be disposed in the overall length of the side end
43
a.
That is, in such structure, the seal member
44
cannot be disposed because the thickness is insufficient near the upstream side end
43
b
of the inside shroud
43
. Such structure is explained in FIG.
8
and FIG.
9
.
FIG. 8
shows a stage composed of the moving blade
46
and the stationary blade
42
in the turbine section. Purge air V3 is first supplied into an outside shroud
45
to cool the outside shroud
45
as cooling air for cooling the outside shroud
45
, and part of the cooling air passes through the cooling air passage formed in the stationary blade
42
to cool the stationary blade
42
, and is supplied into the inside shroud
43
as cooling air, and is partly used as purge air V3.
Further, part of the purge air V3 is blown out from the gap between the moving blade
46
of the front stage and the platform
47
as shown in
FIG. 8
as seal air V4, thereby preventing high temperature gas V1 from escaping from the gap between the platform
47
and inside shroud
43
, but it is not desired if the blown-out seal air V4 disturbs the flow of the high temperature gas V1 too much, and it is desired to guide the seal air V4 smoothly into the flow direction of high temperature gas V1.
In order to guide the flow of the seal air V4 smoothly, as shown in
FIG. 9A
, the upper end corner of the inside shroud
43
is rounded, so that the seal air V4 may flow along the upper side
43
b
(passage side of the high temperature gas V1) of the inside shroud
43
.
The cooling air passage
43
e
for passing the cooling air may be formed inside of the inside shroud
43
. This cooling air passage
43
e
is formed at a deep position near the top of the inside shroud
43
so as to cool the inside shroud
43
itself and also cool the junction between the stationary blade
42
and the inside shroud
43
, but when this cooling air passage
43
e
is formed up to the upstream side end
43
b,
as shown in
FIG. 9A
, it interferes with the cooling air passage
43
e,
and hence the seal member
44
cannot be disposed near the upstream side end
43
b.
As a result, as shown in
FIG. 9B
, near the upstream side end
43
b,
there is a missing range of seal member
44
, and the purge air V3 may massively escape from the mixing range, and the gas turbine efficiency may be lowered.
Thus, in addition to the case of forming the upstream side end
43
b
of the inside shroud
43
by rounding, missing range of seal member
44
may occur due to various causes in design and structure, and anyway if missing range of seal member
44
occurs, regardless of the cause, the efficiency of the gas turbine may be lowered due to massive leak of purge air V3.
SUMMARY OF THE INVENTION
It is an object of this invention to present a stationary blade shroud capable of suppressing leak of purge air, without increasing the cost, even if a seal missing range occurs in the seal member in the gap of the inside shroud.
The stationary blade shroud according to the present invention comprises circular honeyco
Kuwabara Masamitsu
Tomita Yasuoki
Torii Shunsuke
Mitsubishi Heavy Industries Ltd.
White Dwayne J.
LandOfFree
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