Power plants – Combustion products used as motive fluid – Process
Reexamination Certificate
2002-05-31
2004-05-11
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Process
C060S785000, C415S115000, C415S144000
Reexamination Certificate
active
06732530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas turbine compressor that can improve the efficiency of the compressor by maintaining optimal clearance between the moving blades and the rear case rings of the compressor during operation. The present invention further relates to a clearance controlling method for a gas turbine compressor.
2. Description of Related Art
In a gas turbine plant, compressed air from a gas turbine compressor is guided into a combustor, and the high-temperature gas generated when the compressed air is combusted together with a fuel is guided into the gas turbine to drive the gas turbine. A typical design is one in which a portion of the compressed air is bled and directed to the stationary and moving blades of the gas turbine side and is used to cool these blades.
FIG. 3
is a cross-sectional view showing the typical structure of the connecting member between the gas turbine compressor and the gas turbine in a conventional gas turbine plant as described above. As shown in
FIG. 3
, gas turbine compressor
1
is provided with a plurality of stationary blades
3
which are fixed in place inside case rings
2
a
in case
2
, and a plurality of moving blades
5
which are attached to the periphery of each disk
4
which are coaxially fixed on the rotor side (rotor not shown). These stationary blades
3
and moving blades
5
are disposed so as to alternate with one another along the shaft orientation of the rotor and are designed to compress and send compressed air in the direction indicated by arrow f
1
through rotation of the rotor.
The compressed air sent from gas turbine compressor
1
is directed to combustor
6
in which the compressed air is mixed with fuel and combusted to form a combustion gas. As it expands, the combustion gas hg passes through stationary blades
8
in gas turbine
7
and rotates moving blades
9
, thereby rotationally driving the rotor (not shown) in gas turbine
7
. At the same time, a portion (4~10% of the main flow, for example) of the compressed air which is flowing inside gas turbine compressor
1
becomes bleed air f
2
, and is taken up inside bleeding chamber
2
b
which is formed inside case
2
. After being expelled out from case
2
via a flange
2
c
which is provided so as to communicate with bleeding chamber
2
b
, bleed air f
2
is guided to stationary blades
8
and moving blades
9
on the gas turbine
7
side and cools these blades.
Bleeding chamber
2
b
is a ring-shaped space formed between each case ring
2
a
and case main body
2
d
which covers over the periphery of these case rings
2
a
. In the axial direction of the rotor of gas turbine
1
, bleeding chamber
2
is provided so as to be overlapped the area where the end surfaces of respective case rings
2
a
face one another. In other words, the space intervals between facing end surfaces of case rings
2
a
form bleeding holes
2
e
for bleeding air into bleeding chamber
2
b
from compressed air f
1
, which is the main flow. Bleed air f
2
is guided into bleeding chamber
2
b
toward the radial direction of the rotor with passing through bleeding holes
2
e
. Bleed air f
2
is then quickly expelled outside via flange
2
c
for cooling.
Clearance of specific dimensions is maintained between moving blades
5
and case rings
2
a
in order to avoid contact between them during operation in gas turbine compressor
1
. The clearance varies during operation depending on difference in thermal expansion between case
2
, and disks
4
and moving blades
5
. If the difference in thermal expansion between these parts becomes too large, the efficiency of the compressor in gas turbine compressor
1
may remarkably deteriorate. In view of this problem, it is necessary to adopt optimal clearance dimensions in the design after taking this factor into consideration.
In fact, however, thermal deformation of case rings
2
a
is complicated, so that it is difficult to provide a design that fits these circumstances with excellent precision. Namely, in compressor rear case ring
2
a
1
among case rings
2
a
, which is positioned at a later stage (i.e., most downstream position) in the compressor and in particular, has a great influence on the efficiency of the compressor in gas turbine compressor
1
, the temperature of the main flow (compressed air f
1
) flowing inside compressor rear case ring
2
a
1
remarkably increases, for example, from 370° C. to 460° C., due to an increase in enthalpy by the effect of compression.
As a result of such large temperature difference, the overall shape of compressor rear case ring
2
a
when undergoing thermal expansion will deform such that it becomes gradually wider toward the direction of flow of compressed air f
1
. Accordingly, the clearance formed between moving blades
5
and the inner surface of compressor rear case rings
2
a
becomes gradually wider toward downstream from upstream, and therefore, the clearance does not have uniform dimensions.
Accordingly, the clearance dimensions during operation are not uniform along the axial direction of compressor rear case rings
2
a
1
. This makes it difficult to provide a design that ensures optimal clearance dimensions, therefore, it becomes difficult to improve the efficiency of the compressor in gas turbine compressor
1
.
BRIEF SUMMARY OF THE INVENTION
The present invention was conceived in view of the above-described circumstances and has an object that is to provide a gas turbine compressor that can improve the efficiency of the compressor by maintaining optimal dimensions for the clearance formed between the ends of the moving blades and the inner surface of the rear case rings of the compressor during operation. The present invention has the other object that is to provide a clearance controlling method for a gas turbine compressor.
The present invention employs the following means to resolve the above-described problems.
A gas turbine compressor according to a first aspect of the present invention comprises a plurality of moving blades which are provided around rotor disks and rotate together with the rotor disks; compressor rear case rings surrounding the periphery of these moving blades and forming a compression flow path therein; and a bleeding chamber which is provided around the compressor rear case rings and introduces a portion of a main flow moving through the compression flow path as bleed air; and a cooling flow path which is formed between the compressor rear case rings and the bleeding chamber in which bleed air on its way to the bleeding chamber flows along the outer surface of the compressor rear case rings.
According to the above-described gas turbine compressor, the main flow moving inside the compressor rear case rings is dependent on a compressing effect such that the temperature increases as the main flow moves toward downstream. As a result, the compressor rear case rings are heated from the inside. However, the bleed air which flows through the cooling flow path cools the compressor rear case rings from their periphery, so that temperature gradient becomes small along the axial direction. As a result, when the compressor rear case rings undergo thermal expansion, the expansion in the direction of their diameters at each position along the axial direction is roughly equivalent, making it easy to predict the behavior of thermal deformation. Accordingly, a design for ensuring optimal clearance is easily provided. Thus, the dimensions of the clearance that is formed between the ends of the moving blades and the inner surface of the compressor rear case rings can be optimized, so that the efficiency of the compressor can be further improved.
Furthermore, in the above-described gas turbine compressor, the cooling flow path may comprise boundaries in the axial direction when viewed in a cross-section that includes the axis of the compressor rear case rings, in which the boundaries include at least a region extending from a position on the upstream edge of the outer surface of the compressor rear case rings to a positi
Laurello Vincent
Yuri Masanori
Freay Charles G.
Mitsubishi Heavy Industries Ltd.
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