Gas turbine split ring

Details Gas turbine split ring Gas turbine split ring

2001-12-03

2003-08-05

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

With diversely oriented inlet or additional inlet for...

C415S138000, C415S173100, C415S173200, C415S175000, C415S176000, C415S178000

Reexamination Certificate

active

06602048

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a gas turbine split ring and. More specifically, this invention relates to a split ring which appropriately secures an interval (chip clearance) with respect to a tip end of a moving blade in the operating state of a gas turbine (under high temperatures).
BACKGROUND OF THE INVENTION
FIG. 10
shows a general section view showing a front stage part in a gas passage part of a gas turbine. In the drawing, to an attachment flange
31
of a combustor
30
, an outer shroud
33
and an inner shroud
34
which fix each end of a first stage stationary blade (
1
c
)
32
are attached, and the first stage stationary blade
32
is circumferentially arranged in plural about the axis of the turbine and fixed to the cabin on the stationary side.
On the downstream side of the first stage stationary blade
32
, a first stage moving blade (
1
s
)
35
is arranged in plural, and the first stage moving blade
35
is fixed to a platform
36
, the platform
36
being fixed to the periphery of a rotor disc so that the first stage moving blade
35
rotates together with the rotor. Furthermore, in the periphery to which the tip end of the first stage moving blade
35
neighbors, a split ring
42
of circular ring shape having a plural split number is attached and fixed to the side cabin side.
On the downstream side of the first stage moving blade
35
, a second stage stationary blade (
2
c
)
37
of which each side is fixed to an outer shroud
38
and an inner shroud
39
is circumferentially attached in plural to the stationary side in the same manner as the first stage stationary blade
32
. Furthermore, on the downstream side of the second stationary stage
37
, a second stage moving blade (
2
s
)
40
is attached to the rotor disc via a platform
41
, and in the periphery to which the tip end of the second stage moving blade
40
neighbors, a split ring
43
of circular ring shape having a plural split number is attached.
The gas turbine having such a blade arrangement is configured by, for example, four stages, wherein high temperature gas
50
obtained by combustion in the combustor
30
enters from the first stage stationary blade
32
, expands while flowing between each blade of the second to fourth stages, supplies rotation power to the rotor by rotating each of the moving blades
35
,
40
or the like, and then is discharged outside.
FIG. 11
is a detailed section view of the split ring
42
to which the tip end of the first stage moving blade
35
neighbors. In this drawing, a number of cooling ports
61
are provided in an impingement plate
60
so as to penetrate through it, and this impingement plate
60
is attached to a heat shielding ring
65
.
Also the split ring
42
is attached to the heat shielding ring
65
by means of cabin attachment flanges formed on both the upstream and downstream sides of main flow gas
80
which is the high temperature gas
50
. Inside the split ring
42
, a plurality of cooling passages
64
thorough which the cooling air passes are pierced in the flow direction of the main flow gas
80
, and one opening
63
of the cooling passage
64
opens to the outer peripheral surface on the upstream side of the split ring
42
, while another opening opens to the end surface on the downstream side.
In the above-mentioned configuration, cooling air
70
extracted from a compressor or supplied from an external cooling air supply source flows into a cavity
62
via the cooling port
61
of the impingement plate
60
, and the cooling air
70
having flown into the cavity
62
comes into collision with the split ring
42
to forcefully cool the split ring
42
, and then the cooling air
70
flows into the cooling passage
64
via the opening
63
of the cavity
62
to further cool the split ring
42
from inside, and is finally discharged into the main flow gas
80
via the opening of the downstream side.
FIG. 12
is a perspective view of the above-described split ring
42
. As shown in the drawing, the split ring
42
is composed of a plurality of split structure segments divided in the circumferential direction about the axis of the turbine, and a plurality of these split structure segments are connected in the circumferential direction to form the split ring
42
having a circular ring shape as a whole. On the outside (upper side in the drawing) of the split ring
42
is provided the impingement plate
60
which forms the cavity
62
together with the recess portion of the split ring
42
.
The impingement plate
60
is formed with a number of cooling ports
61
, and the cooling air
70
flows into the cavity
62
via the cooling ports
61
, comes into collision with the outer peripheral surface of the split ring
42
, cools the split ring
42
from outer peripheral surface, flows into the cooling passage
64
via the opening
63
, flows through the cooling passage
64
, and is discharged into the main flow gas
80
from the end surface, whereby the cooling air
70
cools the split ring from inside in the course of passing through the cooling passage
64
.
As described above, the split ring of the gas turbine is cooled by the cooling air, however, in the operating state of the gas turbine, since the surface of the split ring is exposed to the main flow gas
80
of extremely high temperature, the split ring will heat expand in both the circumferential and the axial direction.
The interval between the tip end of the moving blade of the gas turbine and the inner peripheral surface of the split ring becomes small under high temperatures or under the operating state due to the influence of centrifugal force and heat expansion in comparison with the situation under low temperatures or under the unoperating state, and it is usual to determine a design value and a management value of the tip clearance in consideration of the amount of change of this interval. In practice, however, the inner peripheral surface of the split ring often deforms into a shape which is not a shape that forms apart of the cylindrical surface because of a temperature difference between the inner peripheral side and the outer peripheral side of the split ring, so that there is a possibility that the rotating moving blade and the split ring at rest interfere with each other to cause damages of both members.
In view of the above situation, the applicant of the present invention has proposed a split ring in which for the purpose of suppressing the heat deformation under high temperatures, on the outer peripheral surface between two cabin attachment flanges in the split structure segments constituting the split ring, a circumferential rib extending in the circumferential direction and an axial rib extending in the direction parallel to the axis of the circular ring shape are formed in plural lines to provide a rib in the shape of a waffle grid as a whole (Japanese Patent Application No. 2000-62492). According to this invention, the rib in the form of a waffle grid suppresses the heat deformation, making it possible to secure an appropriate tip clearance.
However, even by the above proposition of the present applicant, that is, by formation of the rib in the form of a waffle grid, it is impossible to suppress the heat deformation of the split ring satisfactorily.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a split ring which makes it possible to secure a tip clearance with respect to a tip end of a moving blade in the operating state of a gas turbine (under high temperatures).
The gas turbine split ring according to one aspect of the present invention is a gas turbine split ring which is provided on a peripheral surface in a cabin at a predetermined distance with respect to a tip end of a moving blade, the split ring being made up of a plurality of split structure segments that are connected in the circumferential direction to form the split ring of a circular ring shape, each split structure segment having cabin attachment flanges extending in the circumferential direction on both of the upstream and downstream sides of high te

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