Note: Descriptions are shown in the official language in which they were submitted.
CA 02421600 2003-03-06
Docket # 70646
DEVICE FOIL SE~L~NG TUItBOM.A,CHINES
FIELD OF THE INVENTION
The present invention pertains to a device for sealing between the guide vanes
and the
rotor of turbomachines, especially gas turbines.
s BACKGROUND OF THE INVENTION
In a seal in turbomachiries, which has been known from practice, the inner
ring suspended
on the guide vanes with the soldered honeycomb seal is uncooled. To reliably
avoid a metallic
contact between the rotor and the stator of the turbomachine, the distance
between the
honeycomb seal and the tips of the labyrinth must be dimensioned to the
largest possible amount
of the thermal expansion. The relatively great distance leads to a large
leakage flow.
A cooled honeycomb seal, which is arranged at the outer limitation of the flow
channel
within a gas turbine, has been known from DE-A 19 8~1 365. Part of the cooling
air, which is
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available to the guide vane located upstream at the outer shrouding, is fed
for cooling to the
honeycomb seal through holes in the ring carrying the honeycomb seal.
Gas turbines with internally cooled guide vanes have been known from US-A 5
749 701
and US-A 5 157 914. Sealing segments, which contain a honeycomb seal, are
rigidly connected
to the guide vanes. The sealing segments are fixed radially and are not
suspended in a thermally
elastic manner. Cooling air is fed to the sealing segments from the cooled
guide vanes. This
cooling air is used above all to block the sealing gap between the sealing
segments and labyrinth
tips and less to cool the honeycomb seal. The width of the sealing gap is not
affected by the
cooling air because of the non-thermally elastic suspension of the sealing
segments.
1o SUM:1~AR'Y OF THIJ INVENTI~I~t
The basic object of the present invention is to design the seal of this type
such that the
distance between the honeycomb seal and the labyrinth tips can be reduced to
reduce the leakage
flows while increasing the efficiency of the turbomachine at the same time.
According to the present invention a device for sealing between the guide
vanes and the
rotor of turbomachines, especially gas turbines with an inner ring suspended
on the vane footing
of the guide vanes in a thermally elastic manner with a soldered honeycomb
seal and labyrinth
tips arranged on the rotor. Each guide vane has a cavity through which cooling
air flows. First
flow channels are connected to the cavities of the guide vanes. The first flow
channels are led
through the vane footings of the guide vanes and the flow channels are
connected to at least one
of second flow channels. The second flow channels are led to the vicinity of
the honeycomb seal
and to which at least one connection leading to the outside of the inner ring
is connected.
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The second flow channels may open into at least one of axial Third flow
channel, which
are open at the rear edge of the inner ring and form connections of the second
flow channels,
which connections lead to the outside of the inner ring. The second flow
channels may be led to
an annular groove open toward the honeycomb seal on the underside of the inner
ring, which
forms the connection of the second flow channels, which connection leads to
the outside of the
inner ring.
Fourth flow channels, which may be led to another annular groove open toward
the
honeycomb seal on the underside of the inner ring, may be branched off from
the second flow
channels.
The first flow channels may be designed as a hole each passing through the
vane footing
of the guide vanes. The first flow channels may be designed as an inner hole
led through a
hollow centering pin and as a hole connecting the inner hole to the cavity of
the guide vane.
The second flow channels may be designed as holes led radially through the
inner ring or
as holes led three-dimensionally diagonally. The third flow channels may be
designed as holes
led axially through the inner ring. The fourth flow channels may be designed
as holes led
obliquely through the inner ring.
The inner ring may comprise two parts, which are provided with grooves and
protections
on sides facing each other. The grooves and projections may engage one another
such that a
serpentine-like, fifth flow channel is formed, to which at least one
connection leading to the
outside of the inner ring is connected.
'The honeycomb seal may be protected by the cooling air discharged from the
honeycomb
seal and/or the inner ring against the break-in of hot gas.
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The amount of the cooling air fed to the inner ring can be regulated and
depending on the
amount of the cooling air, the leakage flows flowing through the gap between
the honeycomb
seal and the labyrinth tips can flow only forward or both forward and
backward. The amount of
the cooling air fed to the inner ring can be regulated by the pressure of the
cooling air in the
guide vane, the diameter of the holes or by selecting the shape of the inlet
and outlet of the holes.
The annular gap between the honeycomb seal and the labyrinth tips, which gap
acts as a
sealing gap, is determined decisively by the temperature of the inner ring
suspended in a
thermally elastic manner. The cooling air led through the inner ring cools
this ring and thus
lowers its component temperature. As a result, a smaller internal diameter of
the honeycomb seal
and consequently also a smaller annular gap become established because of flue
lower thermal
expansion. Due to the inner ring being supplied with cooling air, the width of
the sealing gap can
thus be affected. The sealing gap can be dimensioned to be narrower from the
very beginning.
Furthermore, the break-in of hot gas from the flow channel of the guide vanes
into the
honeycomb seal is avoided and the leakage flow will also decrease
correspondingly as a result.
This is associated with an increase in the efficiency of the turbomachine. The
Life-limiting
material temperature is reduced, the temperature resistance and the corrosion
resistance of the
components affected are improved, and the service life of the part of the
turbomachine exposed
to hot gas is prolonged due to the cooling of the inner ring and of the
honeycomb seal. A
metallic contact between the rotor and the stator in transient states of the
turbomachine can be
avoided by regulating the cooling. Because of the advantageous properties
indicated, the present
invention is especially suitable for the hub sealing between the rotor and the
stator of gas
turbines.
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The various features of novelty which characterize the invention are pointed
out with
particularity in the claims annexed to and forming a part of this disclosure.
For a better
understanding of the invention, its operating advantages and specific objects
attained by its uses;
reference is made to the accompanying drawings and descriptive matter in which
preferred
embodiments of the invention axe illustrated.
BRIEF DESCRIhTION OF THE DRAWINGS
In the drawings: .
Figure 1 is a detail X of a gas turbine according to Figure 7 according to an
embodiment of
the invention;
Figure 2 is a detail X of a gas turbine according to Figure '7 according to
another
embodiment of the invention;
Figure 3 is a detail X of a gas turbine according to Figure 7 according to
another
embodiment of the invention;
Figure 4 is a detail X of a gas turbine according to Figure 7 according to
another
embodiment of the invention;
Figure 5 is a detail X of a gas turbine according to Figure ? according to
another
embodiment of the invention;
Figure f> is a detail Z according to Figure 3;
Figure 7 is a schematic view showing the longitudinal section through a gas
turbine;
Figure 8 is a detail Z according to Figure 3 of another embodiment of the
invention; and
Figure 9 is a schematic view showing an embodiment of the cooling air flow
distributions;
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Figure 10 is a schematic view showing another embodiment of the cooling aix
flow
distributions; and
Figure 11 is a schematic view showing another embodiment of the cooling air
flow
distributions.
DESCRIPTION OF THE PREFERRED EIVIBODIMENTS
Referring to the drawings in particular, the design of turbomachines as a gas
turbine
comprises, according to Figure 7, a housing I6, in which a rotor 17 is mounted
rotatably. The
rotor 17 carries a plurality of rows of guide vanes 18, between which
stationary guide vanes 1
fastened to the housing 1 & are arranged.
Part of the rotor I7 with two guide vanes 18 and with the lower part of a
guide vane 1 are
shown in Figures 1 through 5 and 9 through 11.
The guide vane 1 is provided with a guide vane footing 14 at its end facing
the rotor 17.
An inner ring 3 is suspended at the guide vane footing 14 in a thermally
elastic manner. The
guide vane footing 14 is provided for this purpose with an attachment l~,
which engages an
adapted recess 20 in the inner ring 3, a gap 13 absorbing the thermal
expansion being left
between the front surface of the attachment 19 of the guide vane footing 14
and the bottom of the
recess 20 of the inner ring 3. centering pins 2, which are inserted into the
attachment 19 of the
guide vane footing 14 and into the bottom of the recess 20 of the inner ring
3, ensure the
centering of the inner ring 3 at the guide vane footing 14.
A honeycomb seal 4 is soldered on the surface of the inner ring 3 facing the
rotor 17. The
honeycomb seal 4 contains an open honeycomb structure, which is formed by
webs. The webs
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are connected to the inner ring 3 and limit the inwardly open honeycombs.
Labyrinth tips 5 of a
one-part labyrinth ring acting as a seal, which ring is arranged on the rotor
17, are located
opposite the honeycomb seal 4. There is a sealing gap of a radial height,
which is to be kept
small, between the labyrinth tips S rotating with the rotor 17 and the
stationary honeycomb seal
4.
The guide vanes 1 are cooled and have a cavity 21, through which cooling air
flows. The
cooling air leaves at the rear edge 6 of the guide vane.
To keep the sealing gap between the stationary honeycomb seal 4 and the
rotating
labyrinth tips 5 small and to reduce the leakage flows passing through the
sealing gap, the inner
ring 3 and the honeycomb seal 4 are cooled as well. The cooling is brought
about by a small
partial flaw of the cooling air used to cool the guide vane l, whose main flow
escapes at the rear
edge 6 of the guide vane.
The cooling air is taken from the guide vane I . A first flow channel, which
is designed as
a hole 15 and opens into the gap I3 between the guide vane footing I~. and the
inner ring 3, is led
through the guide vane footing 14 for this puzpose. Second flow channels 13,
which axe led
through the inner ring 3 as radial holes 7 or as three-dimensionally diagonal
holes 1 l, originate
from the gap 13. The holes 7, 11 open into third flow channels, which are Ied
as axial holes 8
through the inner ring 3. The axial holes 8 are open at the rear edge of the
inner ring 3 and form
the outlet 25. The partial cooling air flow, which is taken from the guide
vane 1 through the hole
15, is distributed in the gap 13 between the guide vane footing I4 and the
inner ring 3, enters the
radial and three-dimensionally diagonal holes 7, I 1, and escapes via the
axial holes 8 through the
outlets 25. The cooling air taken from the guide vane 1 lowers the temperature
of the inner ring
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3 and the honeycomb seal 4 while this passes over the holes 7, 1 l, 8 (Figures
l, 3, 6).
According to Figure 8, the first flow channel may also be designed as an inner
hole 23 of
a hollow centering pin 2, the inner hole 23 being in connection with the
cavity 21 of the guide
vane 1 via a hole 24 extending radially through the guide vane footing 14. At
least one of the
radial holes 7, which are likewise designed as a second flow channel, is
connected to the inner
hole 23 of the hollow centering pin 2. One of the radial holes 7 each opens
into one of the axial
holes 8 each.
According to Figure 4, the radial holes 7 end in an open annular groove 10,
which is cut
into the surface of the inner ring 3 facing the rotor 17. The cooling air
taken from the guide vane
1 is discharged through the honeycomb seal 4 and cools same directly in the
process.
As is shown in Figure 2, fourth flow channels, which are led as oblique holes
9 through
the inner ring 3 and end in another annular groove 22, may branch off from at
least one of the
radial holes 7, which act as second flow channels. The honeycomb seal 4 is
thus cooled over a
large area.
According to Figure 5, the inner ring 3 comprises two parts, which are
provided with
grooves and projections on the sides facing one another. The two parts of the
inner ring 3 are
fitted together such that the grooves and projections engage one another and
form serpentines 12
as a result, which represent a fifth flow channel led through the inner ring
3. The serpentines 12
are in connection with the axial holes 8. Due to this serpentine-like guiding
of the cooling air,
the residence time of the cooling air in the inner ring 3 is longer than in
the other embodiments
described. In addition, the surface available for heat transfer (cooling) is
increased by the
serpentines 12 and so is the effectiveness of the cooling.
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Figures 9 through 11 show the cooling air flows a through 1 in the area of the
inner ring 3
for different variants; these cooling air flows are composed as follows:
a) Cooling air flowing from the guide wanes 18 of the moving blade ring,
which is arranged in front of the guide vane 1 shown,
b) as a), but on a radius closer to the rotor axis,
c) indifferent distribution flow between the rotor 17 and the inner ring ~,
d) cooling air that escapes into the flow channel in front of the guide vanes
l,
e) hot gas,
fj leakage flow (flowing forward in Figure 10 and backward in Figure 11),
g) cooling air that flows from the guide vanes 18 of the moving blade ring
that is arranged behind the guide vane 1 shown,
h) as d), but behind the guide vanes l,
k) cooling air that is fed from the cavity 21 of the guide vane 1 to the inner
ring 3,
1) leakage flow.
Figure 9 shows the cooling air flows a through h for the uncooled variant of
the inner ring
3 according to the state of the art. As is apparent from Figure 9, a hot gas
flow a is drawn from
the flow channel of the guide vane 1 into the annular gap between the
honeycomb seal 4 and the
labyrinth tips 5 and it leads to an increase in the leakage flow f there. This
leads, furthermore, to
an increase in the temperature of the inner ring 3 with a further thermal
elastic expansion of the
inner ring 3.
Figures 10 and 11 sho~.v the cooling air flows a through 1 for the cooled
variant of the
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inner ring 3, where the cooling air flow k is small in Figure I4 and large in
Figure i 1. The
amount of the cooling air flow k can be changed by a higher pressure of the
cooling air in the
guide vane 1, a larger diameter of the hole 7 or by changing the flow
resistance by selecting the
shape of the inlet and outlet (rounded, sharp-edged of the hole 7.
Figure 10 shows a variant with cooling of the inner ring 3, where the cooling
air flow k is
a cooling air flow of a small volume. It can be seen that the break-in of hot
gas a is avoided and
a substantially smaller leakage flow f flours through the annular gap between
the honeycomb seal
4 and the labyrinth tips S. The Leakage flow f flows through the annular gap
between the
honeycomb seal 4 and the labyrinth tips 5 in one direction.
LO If the cooling air flow k is increased, as is shown in Figure 1 I, it is
split into the two
leakage flows f and l, which leave the annular gap between the honeycomb seal
4 and the
labyrinth tips 5 on both sides of the inner ring 3. The break-in of hot gas a
and the pumping
action are avoided in this case as well. The inner ring 3 assumes a lower
temperature, and
thermal elastic expansion is avoided in both Figure 10 and Figure 11.
While specific embodiments ~f the invention have been shown and described in
detail to
illustrate the application of the principles of the invention, it will be
understood that the invention
may be embodied otherwise without departing from such principles.
