Gas turbine segmental ring

Details Gas turbine segmental ring Gas turbine segmental ring

2001-10-22

2003-01-21

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Bearing, seal, or liner between runner portion and static part

Between blade edge and static part

C415S115000, C415S116000, C415S139000, C415S173200, C415S178000

Reexamination Certificate

active

06508623

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a gas turbine segmental ring made in such a structure that a cooling air leakage from connecting portions of segment structures is reduced as well as a thermal deformation in each of the segment structures and a restraining force caused by the thermal deformation are reduced.
BACKGROUND ART
FIG. 4
is a cross sectional view generally showing a front stage gas path portion of a gas turbine. In
FIG. 4
, immediately downstream of a fitting flange
31
of a combustor
30
in a flow direction of combustion gas
50
, a first stage stationary blade (
1
c
)
32
has both its ends fixed to an outer shroud
33
and inner shroud
34
and a plurality of the first stage stationary blades
32
are arranged in a turbine circumferential direction being fixed to an inner side of a turbine casing on a stationary side of the gas turbine. Downstream of the first stage stationary blade
32
, a plurality of first stage moving blades (
1
s
)
35
are arranged in the turbine circumferential direction being fixed to a platform
36
. The platform
36
is fitted around a rotor disc and thus the moving blade
35
rotates together with a rotor (not shown). Along the turbine circumferential direction close to a tip of the moving blade
35
, a segmental ring
42
of an annular shape formed of a plurality of segment structures is arranged being fixed to the turbine casing side.
Downstream of the first stage moving blade
35
, a second stage stationary blade (
2
c
)
37
has both its ends fixed to an outer shroud
38
and inner shroud
39
and likewise a plurality of the second stage stationary blades
37
are arranged in the turbine circumferential direction being fixed to the stationary side. Also, downstream thereof, a plurality of second stage moving blades (
2
s
)
40
are arranged in the turbine circumferential direction being fixed to a rotor disc (not shown) via a platform
41
. Along the turbine circumferential direction close to the tip of the moving blade
40
, likewise a segmental ring
43
formed of a plurality of segment structures is arranged. The gas turbine having such a blade arrangement is usually constructed of four blade stages and the combustion gas
50
of a high temperature generated at the combustor
30
flows in the first stage stationary blade (
1
c
)
32
. While the combustion gas
50
passes through the respective blades of the second to the fourth stages, it expands to rotate the moving blades
35
,
40
, etc. and thus to rotate the rotor and is then discharged.
FIG. 5
is a cross sectional view showing a detail of the segmental ring
42
that is arranged close to the tip of the first stage moving blade
35
, as described above. In
FIG. 5
, numeral
60
designates an impingement plate, that is fitted to a heat insulating ring
65
on the turbine casing side and comprises a plurality of through holes as cooling holes
61
. The segmental ring
42
also is fitted to the heat insulating ring.
65
and comprises a plurality of cooling passages
64
bored in the respective segment structures along a turbine axial direction or along a direction of main flow gas
80
. Each of the cooling passages
64
has at one end an opening
63
that opens in an upper surface of the segmental ring
42
on the upstream side and has at the other end an opening that opens in a circumferential side end surface of the segmental ring
42
on the downstream side, as shown in FIG.
5
.
In the construction described above, cooling air
70
bled from a compressor or supplied from an outside cooling air supply source flows through the cooling holes
61
of the impingement plate
60
to enter a cavity
62
below the impingement plate
60
and to impinge on the segmental ring
42
for effecting a forced cooling or impingement cooling of the segmental ring
42
. Then, the cooling air
70
in the cavity
62
flows into the cooling passages
64
from the openings
63
for cooling an interior of the segmental ring
42
and is discharged into the main flow gas
80
from the openings of the rear end of the segmental ring
42
.
FIG. 6
is a partial perspective view of the segmental ring
42
described above. As shown there, the segmental ring
42
is formed in the annular shape of the plurality of segment structures arranged and connected to one another in the turbine circumferential direction. The impingement plate
60
is arranged above, or on the outer side of, the segmental ring
42
and the cavity
62
is formed between the impingement plate
60
and a recessed portion of the upper side of the segmental ring
42
. Thus, as mentioned above, the cooling air
70
entering the cavity
62
through the cooling holes
61
impinges on an upper wall surface of the segmental ring
42
to forcibly cool the segmental ring
42
and then flows through the cooling passages
64
to cool the interior of the segmental ring
42
and is discharged into the main flow gas
80
.
In the gas turbine segmental ring, in order to prevent a reverse flow of the main flow gas
80
, pressure of the cooling air
70
in the cavity
62
is made higher relative to that of the main flow gas
80
. Hence, in addition to the amount of the cooling air flown through the segmental ring
42
and effectively used for the cooling thereof, there is some amount of the air leaking from connecting portions of the segment structures of the segmental ring
42
. Thus, as the number of the segment structures becomes larger, the number of the connecting portions thereof becomes larger and the amount of the leaking air becomes also larger, which results in the reduction of the cooling efficiency. Moreover, as the surface of the segmental ring
42
is directly exposed to the high temperature main flow gas
80
, unusual force due to thermal deformation of the segment structures may arise so that a roundness of the segmental ring
42
may be hardly maintained, which results in causing an increase of the air amount leaking from the connecting portions and in giving an unfavorable influence on the clearance between the tip of the moving blade
35
and the segmental ring
42
.
DISCLOSURE OF THE INVENTION
In view of the problems in the prior art, it is an object of the present invention to provide a gas turbine segmental ring made in such a structure that the number of segment structures forming the segmental ring is lessened so as to reduce a cooling air leakage amount and each of the segment structures is formed so as to reduce a thermal deformation thereof as well as to absorb a distortion caused by the thermal deformation.
In order to achieve the mentioned object, the present invention provides the means of the following inventions (1) and (2):
(1) A gas turbine segmental ring formed in an annular shape of a plurality of segment structures connected to one another in a turbine circumferential direction and arranged to be fitted to an inner circumferential surface of a turbine casing with a predetermined clearance being maintained between itself and a tip of a moving blade, each of the segment structures having at its turbine axial directional front and rear end portions flanges extending in the turbine circumferential direction to be fitted to the turbine casing, characterized in that each of the segment structures is constructed such that the flanges have their flange portions cut in so that a plurality of slits may be formed along the turbine axial direction and a plurality of ribs arranged to form a lattice shape are provided to project from an upper surface existing between the flanges of the segment structure.
(2) A gas turbine segmental ring as mentioned in the invention (1) above, characterized in being formed in the annular shape of 15 pieces of the segment structures.
In the invention (1) above, as the plurality of slits are formed in the flanges to be fitted to the turbine casing, even if the thermal deformation may arise, it can be absorbed by the deformation of these slits. Also, as the waffle pattern of the ribs is formed on the upper bottom surface of the segment structure to increase the rigidity, the therma

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