U.S. patent number 3,652,177 [Application Number 05/038,679] was granted by the patent office on 1972-03-28 for installation for the support of pivotal guide blades.
This patent grant is currently assigned to Motoren-und Turbinen-Union Munchen GmbH. Invention is credited to Wolf Loebel.
United States Patent |
3,652,177 |
Loebel |
March 28, 1972 |
INSTALLATION FOR THE SUPPORT OF PIVOTAL GUIDE BLADES
Abstract
An installation for the pivotal support of guide blades of turbo
machines particularly gas turbines in which chambers or passages
are provided in the bearing support through which flows the cooling
air; the blade shaft constructed as adjusting shaft is provided
with an annular groove in its center bearing area and with another
annular groove at the blade end whereby the two annular grooves are
connected with each other by a thread; the central annular groove
is in communication with the chambers or passages while the other
annular groove is in communication with the guide blade space of
the machine.
Inventors: |
Loebel; Wolf (Munich,
DT) |
Assignee: |
Motoren-und Turbinen-Union Munchen
GmbH (DT)
|
Family
ID: |
5734972 |
Appl.
No.: |
05/038,679 |
Filed: |
May 19, 1970 |
Foreign Application Priority Data
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|
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May 23, 1969 [DT] |
|
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P 19 26 327.5 |
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Current U.S.
Class: |
415/110; 415/116;
415/147; 415/156; 415/160 |
Current CPC
Class: |
F01D
17/162 (20130101) |
Current International
Class: |
F01D
17/16 (20060101); F01D 17/00 (20060101); F01d
011/00 (); F04d 027/00 () |
Field of
Search: |
;415/109,110,111,112,116,115,149,150,156 ;416/95,96,97,156 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Raduazo; Henry F.
Claims
I claim:
1. An installation for supporting pivotal guide blades of
turbo-machines in which at least one passage is provided in a
bearing support through which flows cooling air, characterized in
that a blade shaft constructed as an adjusting shaft is provided
with annular grooves in its central bearing area and near the blade
end thereof, which are in communication with each other by way of a
thread, the central annular groove being in communication with the
passage conducting the cooling air while the annular groove near
the blade end is in communication with the guide blade space of the
machine.
2. An installation according to claim 1, characterized in that said
thread has substantially cylindrical external surfaces.
3. An installation according to claim 2, characterized in that the
blade shaft, starting from the central annular groove in the
outward direction, is provided with a labyrinth seal means
consisting of a number of annular grooves.
4. An installation according to claim 3, characterized in that the
labyrinth seal means has cylindrical outer surfaces.
5. An installation according to claim 4, characterized in that the
blade shaft is constructed as a hollow shaft.
6. An installation according to claim 5, characterized in that a
bearing bush means with good anti-friction properties is inserted
between the bearing support and the blade shaft, said bush means
being provided with inlet and discharge bores for the cooling air
corresponding to the support means.
7. An installation according to claim 6, characterized in that the
bearing bush means is provided near the blade end with a portion of
reduced diametric dimension so that an inwardly open annular space
results between the housing bore and the bearing bush means, and in
that the cooling air leaving the bearing bush means is conducted
through the inwardly open annular space into the main flow channel
of the turbo-machine.
8. An installation according to claim 7, characterized in that the
blade shaft is provided near the blade end thereof with an annular
collar that abuts at the inner end face of one of the two parts
consisting of housing and bearing bush means.
9. An installation according to claim 8, characterized in that an
axially prestressed spring means is provided which is supported, on
the one hand, on the outer side of the bearing support and, on the
other, at the blade shaft.
10. An installation according to claim 1, characterized in that a
bearing bush means with good anti-friction properties is inserted
between the bearing support and the blade shaft, said bush means
being provided with inlet and discharge bores for the cooling air
corresponding to the support means.
11. An installation according to claim 10, characterized in that
the bearing bush means is provided near the blade end with a
portion of reduced diametric dimension so that an inwardly open
annular space results between the housing bore and the bearing bush
means, and in that the cooling air leaving the bearing bush means
is conducted through the inwardly open annular space into the main
flow channel of the turbo-machine.
12. An installation according to claim 1, characterized in that the
blade shaft is provided near the blade end thereof with an annular
collar that abuts at the inner end face of one of the two parts
consisting of housing and bearing bush means.
13. An installation according to claim 12, characterized in that an
axially prestressed spring means is provided which is supported, on
the one hand, on the outer side of the bearing support and, on the
other, at the blade shaft.
14. An installation according to claim 12, characterized in that
the blade shaft, starting from the central annular groove in the
outward direction, is provided with a labyrinth seal means
consisting of a number of annular grooves.
15. An installation according to claim 1, characterized in that an
axially prestressed spring means is provided which is supported, on
the one hand, on the outer side of the bearing support and, on the
other, at the blade shaft.
16. An installation according to claim 1, characterized in that the
blade shaft, starting from the central annular groove in the
outward direction, is provided with a labyrinth seal means
consisting of a number of annular grooves.
17. An installation for supporting pivotal guide blades of
turbo-machines, comprising a blade shaft formed as an adjusting
shaft carrying a blade at one end thereof, a bearing support
surrounding said shaft and having at least one passage for
conducting cooling air, said shaft being provided with an annular
groove in its central bearing area and an annular groove near the
blade end thereof, the central annular groove being in
communication with the passage conducting the cooling air while the
annular groove near the blade end is in communication with the
guide blade space of the machine, the portion of said blade shaft
between the central and blade end grooves being provided with a
helical thread for communication therebetween.
18. An installation according to claim 17, wherein the portion of
said shaft extending from the central annular groove in the outward
direction is provided with a labyrinth seal means in the form of a
plurality of annular grooves for preventing the flow of cooling
air.
Description
The present invention relates to an installation for the support of
pivotal guide blades of turbo-machines, especially of gas turbines,
whereby chambers or passages are provided in a bearing support,
through which flows cooling air. Particular difficulties have to be
overcome in the support of pivotal guide blades of gas turbines, by
reason of the large temperature range in which a satisfactory
operation must be assured at all times, which difficulties consist
in that the bearing clearance necessary for the pivoting movement
has to be maintained notwithstanding the considerable thermal
expansions.
It is known to cool the bearing places with compressed air in order
to avoid large thermal expansions and the danger connected
therewith of a binding of the guide blades. The heretofore known
arrangements, however, provide only cooling passages or chambers in
the bearing housing whereby the cooling flow frequently cannot be
conducted sufficiently close to the hottest and therewith the most
endangered places of the bearing so that the desired cooling effect
is completely absent or is attained only unsatisfactorily.
It is therefore the object of the present invention to provide a
bearing support installation for guide blades, in which a cooling
medium is conducted directly to the hottest places of the bearing
and thus an effective cooling of the bearing is achieved.
As solution to the underlying problems, it is proposed in
accordance with the present invention that a blade shaft
constructed as adjusting or actuating shaft be provided with
annular grooves in its central bearing portion and at the blade
end, which are connected with each other by a thread with
cylindrical external surfaces, whereby the central annular groove
is in communication with the chambers or passages conducting the
cooling air and the annular groove at the blade side is in
communication with the guide blade space of the machine.
The cooling air, which can be derived, for example, from a suitable
compressor stage or from a similar air supply, flows through the
central bore into the central annular groove of the blade shaft and
from there by way of the thread to the blade end of the shaft where
it flows off into the guide blade space by way of the second bore.
The particular advantage of this arrangement resides in that the
bearing support is effectively cooled at its hottest place; namely,
at the blade shaft itself.
A further advantage resides in that the blade shaft and bearing
bore are kept by the cooling system approximately at the same
operating temperature at their contact places whereby the bearing
clearance which exists with a cold machine, remains approximately
constant over the entire operating range (temperature range) of the
machine.
Finally, an extradordinarily favorable sealing of the guide blade
space with respect to the surrounding area is achieved
simultaneously by the cooling air guide system of the present
invention since the cooling air has simultaneously the effect of a
sealing medium.
In an appropriate construction of the present invention, the blade
shaft includes, starting from its central annular groove toward the
outside, a labyrinth seal having cylindrical external surfaces and
consisting of a large number of annular grooves. The labyrinth is
advantageously formed by a number of annular grooves of rectangular
cross-section. With this type of labyrinth, the cooling air flow
from the shaft center in the outward direction is kept as small as
possible since it is only of subordinate significance for a cooling
effect within this area and the cooling medium mass flow, which
represents a loss, should be kept as small as possible.
According to a further feature of the present invention, the blade
shaft is constructed as hollow shaft which results in a relatively
slight heat flow from the blade through the shaft so that the ratio
of heat transferred to the bearing place to the heat removed by
cooling can be kept small.
According to a further favorable construction of the bearing
support installation according to the present invention, a bearing
bush with good anti-friction properties is inserted between the
bearing support and the blade shaft, which bush is provided with
inlet and outlet bores or ports for the cooling air corresponding
to the bores in the bearing support.
The use of a bearing bush between housing and adjusting shaft
offers the advantage that a material can be selected for the
bearing bush which, first of all, has good anti-friction properties
that do not change or change only slightly over a certain
temperature range, without requiring at the same time high strength
properties as are required, for example, in connection with the
housing material. The good anti-friction properties must be ensured
by a suitable material combination since a reduction of the
friction by a lubricant must be considered impractical. Thus, by
the use of anti-friction bushes, a favorable low friction clearance
conditioned on the material can be attained at the blade adjusting
shaft which results correspondingly in slight adjusting forces
(moments).
According to a further feature of the present invention, the
bearing bush is provided at its blade end with an offset of reduced
diametric dimension so that an inwardly open annular space results
between the housing bore and bearing bush, through which the
cooling air leaving the bearing bush is conducted into the main gas
stream of the turbo-machine. Returning the cooling air into the
guide blade space through such an annular space offers the
advantage that any combustion residues which are deposited in the
annular gap between the upper guide blade end and the housing bore,
are constantly blown off by the inwardly directed air stream and
are returned to the main gas stream.
According to a further development of the present invention, the
blade shaft is provided at its blade end with an annular collar
that abuts at the inner end face of the housing or of the bearing
bush. An outwardly directed pressure force results at the annular
collar from the gas pressure in the guide blade space which presses
the annular collar against the end surface of the housing or
bearing bush so that a good seal of the guide blade space with
respect to the bearing place is realized.
In an advantageous manner according to a further feature of the
present invention, a spring prestressed in the axial direction is
provided which is supported on the outer side of the bearing
support, on the one hand, and on the blade shaft, on the other.
This spring pulls the blade shaft outwardly with its prestress so
that it causes an abutment of the annular collar of the blade shaft
at the inner end face of the bearing bush or housing also with a
slight excess pressure in the guide blade space and thus assures a
good sealing effect.
These and further objects, features and advantages of the present
invention will become more obvious from the following description
when taken in connection with the accompanying drawing which shows,
for purposes of illustration only, one embodiment in accordance
with the present invention, and wherein;
The single FIGURE is a partial cross-sectional view through a guide
blade adjusting mechanism of a gas turbine with a bearing bush in
accordance with the present invention.
Referring now to the single FIGURE of the drawing, a bearing bush 3
is securely fitted into a bore 21 provided in a housing 2 forming a
bearing support. A bore or port 5 is disposed approximately in the
center of the bush 3 which is in communication by way of a further
bore or port 25 in the housing 2 with a cooling air passage 4 of
the housing. At the inner end of the housing, the bush 3 is
provided with a reduced diametric portion forming an offset 23 so
that an annular space 22 remains between the bore 21 and the bush 3
at this place. One or several radial bores 6 of the bush 3
terminate in this annular space 22. The shaft of the guide blade 9
constructed as actuating or adjusting shaft 7 is supported in the
bush 3. The guide blade shaft 7 is provided at its blade end with
an annular collar 8 and adjoining the same with an annular groove
18. The shaft 7 is provided in the central area thereof, at the
place of the bore 5 of the bush 3, with an annular groove 16. This
annular groove 16 is in communication with the annular groove 18 by
way of several threads of trapezoidal cross-section such as ACME
thread form. The support of the shaft 7 takes place at the
cylindrical outer surfaces of the thread 17 within the bearing bush
3. Extending outwardly from the annular groove 16, the shaft
surface is provided with a number of annular grooves 20 constructed
as labyrinth seal. A pivot or actuating lever 13 is clampingly
secured to the outer end 12 of the blade shaft 7. The pivoting of
this adjusting lever 13 takes place by an adjusting or actuating
ring 14 arranged at the housing 2. An axially prestressed disk or
cup spring 10 is provided between the lever 13 and the outer end
face of the bush 3, on which rests a closure disk or carrying
washer 10a; the prestress force of the spring 10 is transmitted by
way of the lever 13 to the blade shaft 7 so that the annular collar
8 of the shaft 7 is pressed against the end surface 3a of the bush
3, located at the inner side of the housing.
The compressed air supplied by an air source and flowing through
one or several passages 15 into the space 4, flows through the
bores 25 and 5 into the annular groove 16 between the bush 3 and
the blade shaft 7.
From there, the cooling air flows inwardly and outwardly, following
the pressure drop, and more particularly inwardly by way of the
thread 17 whereby it cools in an effective manner the blade shaft 7
and the bush 3. After leaving the thread 17, the cooling air
reaches the annular groove 18 from where it flows off by way of the
bore 6 into the annular space 22 and from there into the main
stream duct 1. A very small amount of compressed air flows from the
annular groove 16 in the outward direction by way of the labyrinth
seal 20 and exits into the atmosphere at the spring 10 by way of
gaps.
While I have shown and described only one embodiment in accordance
with the present invention, it is understood that the same is not
limited thereto but is susceptible of numerous changes and
modifications as known to those skilled in the art, and I therefore
do not wish to be limited to the details shown and described herein
but intend to cover all such changes and modifications as are
encompassed by the scope of the appended claims.
* * * * *