U.S. patent number 3,801,220 [Application Number 05/207,897] was granted by the patent office on 1974-04-02 for sealing element for a turbo-machine.
This patent grant is currently assigned to Brown Boveri-Sulzer Turbomaschinen AG. Invention is credited to Wolfgang Beckershoff.
United States Patent |
3,801,220 |
Beckershoff |
April 2, 1974 |
SEALING ELEMENT FOR A TURBO-MACHINE
Abstract
An arrangement for packing expansion joints on turbo-machines
and particularly packing the axially extending gaps provided
between adjacent blading of a blade row and circumferentially
extending gaps provided between each blade row and an adjacent row
of blade segments which serve to provide axial spacing between
adjacent rows of blading on the rotor of the machine includes two
sets of packing strips inserted respectively in grooves provided
along the confronting sides of the blading which establish the
axially and circumferentially extending gaps that form
intersections with each other. Each packing strip of each set is
constituted by two layers which are shifted in a longitudinal
direction relative to each other such that one layer of each strip
of each set continues across each intersection while an end of the
other layer of each strip of one set terminates at an intersection
at the side of and is joined to the layer of the other set which
continues across that intersection, thus providing a complete
sealing not only along the axially and circumferentially extending
gaps but also at their intersections.
Inventors: |
Beckershoff; Wolfgang
(Fislisbach, CH) |
Assignee: |
Brown Boveri-Sulzer Turbomaschinen
AG (Zurich, CH)
|
Family
ID: |
4435259 |
Appl.
No.: |
05/207,897 |
Filed: |
December 14, 1971 |
Foreign Application Priority Data
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|
|
|
|
Dec 18, 1970 [CH] |
|
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18783/70 |
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Current U.S.
Class: |
416/198R;
415/134; 415/139; 416/95; 416/193A; 416/198A; 416/193R;
416/215 |
Current CPC
Class: |
F01D
5/3038 (20130101); F01D 5/06 (20130101); F01D
11/006 (20130101); F16J 15/00 (20130101) |
Current International
Class: |
F16J
15/00 (20060101); F01D 11/00 (20060101); F01D
5/06 (20060101); F01D 5/00 (20060101); F01D
5/02 (20060101); F01D 5/30 (20060101); F01d
005/06 () |
Field of
Search: |
;416/219-221,198,193,215,90,92,95-97 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Powell, Jr.; Everette A.
Attorney, Agent or Firm: Pierce, Scheffler & Parker
Claims
I claim:
1. In an arrangement for packing expansion joints on turbo-machines
and more particularly packing the axially extending gaps provided
between adjacent blading of a blade row and circumferentially
extending gaps provided between each blade row and an adjacent row
of blade segments which serve to provide axial spacing between
adjacent rows of blading on the rotor of the machine, the
combination comprising a first set of packing strips inserted in
grooves provided along those confronting sides of the blading which
establish the axially extending gaps, a second set of packing
strips inserted in grooves provided along those confronting sides
of the blading which establish the circumferentially extending gaps
that intersect said axially extending gaps, each of said packing
strips of each set being constituted by two layers which are
shifted in a longitudinal direction relative to each other such
that one layer of each strip of each set continues across each
intersection of said axial and circumferentially extending gaps
while an end of the other layer of each strip of one set terminates
at an intersection at the side of the layer of the other set which
continues across said intersection, and means for interconnecting
the strips of said first and second sets in the axial and
circumferential directions at said intersections by interconnecting
the ends of the layers of the strips of one set at their junctions
with the sides of the layers of the strips of the other set.
2. A packing arrangement for turbo-machines as defined in claim 1
wherein said means for interconnecting the layers of the strips of
said first and second sets in axial and circumferential directions
are constituted by inter-engaging lobes and cutouts provided on the
layers.
3. A packing arrangement for turbo-machines as defined in claim 1
wherein the layers of each said packing strip includes elastically
deformable edge zones facing the bottom of the groove in which it
is inserted.
4. A packing arrangement for turbo-machines as defined in claim 1
and which further includes plastically deformable inserts located
at the bottom of each groove.
Description
This invention relates to an improvement for a packing element for
expansion joints on turbo-machines of the type which consists of
packing strips inserted into grooves of the parts to be sealed from
each other, the individual packing strips having cutouts or lobes
which are fitted one into the other at least partially at mutually
crossing points.
In the case of uncooled multi-stage turbo-machines there is danger,
due to the pressure gradient from stage to stage, that the hot
operating gases will leave the flow channel through the heat
expansion joints between the parts forming the channel walls and
will sweep these parts outside the flow channel. This causes, for
example, rotor bodies, guide vane supports or housings to be heated
up unnecessarily, owing to which they lose in strength and length
of life or must be made of expensive, highly heat resistant
material.
In the case of cooled turbo-machines there results a considerable
loss of cooling gases through the pervious heat expansion joints,
as the cooling gas admitted at higher pressure flows into the gas
duct. To compensate the lost quantity of cooling gas in gas
turbines, removal of a still greater proportion of cooling gas from
the circulation is necessary, which in the case of gas turbines
would immediately result in a perceptible loss of efficiency.
Unsealed heat expansion joints usually have within the same machine
somewhat different sizes, whereby the heating in uncooled machines
as well as the cooling effect in cooled machines may turn out to be
different. This sometimes brings about warping at stationary or
rotating parts, which later leads to damage to the machines.
For the partial elimination of these disadvantages, several
different packing modes have been applied, as for example staggered
arrangements of the parts or a tongue-and-groove type construction
of the parts. It is also known practice in gas turbines of the
axial flow type to insert between the rims of rotor and guide vanes
packing elements formed of packing strips which are intended to
prevent axial and radial passage of the operating medium, for which
purpose packing strips are provided which are arranged one after
the other in axial packing grooves. Between the individual parts
packing strips extending in radial direction are also inserted
which cross with the packing strips arranged in the axial
direction, the packing strips being provided with tongues and
cutouts at the intersections so that the parts interengage.
The disadvantages of these packing constructions are to be seen in
that, although a reduction of the leakage is achieved, it is not
possible to suppress free passage completely. In particular, on
turbo-machine systems with a distribution of heat expansion joints
over the rotor and the guide vane support like a grid, residual
gaps remain at the intersections and at the butt joints of the
packing strips which in accordance with the radial-axial packing of
the above described type are not controllable from a sealing point
of view. This again leads to the previously mentioned general
disadvantages.
The principal object of the present invention is to avoid the above
disadvantages and to exclude, almost completely, any leakages
between the parts forming the flow channel of a turbo-machine.
The problem is solved according to the invention in that the
packing strip is formed with at least two layers, the first of
which is shifted relatively to the second layer in the longitudinal
direction of the packing strip by at least the amount of the butt
joint between the contiguous packing strips, and that the packing
strips are fitted together in the circumferential direction and the
axial direction, the lobes of the first layer slidingly inserted in
the cutouts being covered at the intersections by the relatively
offset second layer of the packing strip.
Another form of construction is characterized by an approximately
elastically deformable edge zone of the individual layers of the
packing strips on the sides toward the bottom of the groove.
A special embodiment of the invention provides that plastically
deformable packing inserts are inserted in the groove, on the
groove bottom.
An advantageous form of construction is characterized according to
the invention by the length of the packing strips, which in the
axial direction and in the circumferential direction corresponds
approximately to the length of the parts to be sealed from each
other, minus one strip width.
The advantages of the invention reside, on the one hand, in that a
separate securing of the packing strips against shifting becomes
unnecessary, since the packing strips are mutually anchored by the
intersecting layers of the packing strips, and on the other hand,
in that even the radial gaps or passageways at the intersections
are sealed almost completely.
In the special form of construction with lobes and cutouts at the
individual layers of the packing strips, it has been found to be
advantageous that the layers have a reinforcement of the
cross-section area at the intersection where the greatest radial
loads and expansion forces engage.
The cooling effect is improved in cooled turbo-machines, the heat
damming effect being influenced much more favorably at the
intermediate sections or segments provided for this purpose,
because the transfer of heat occurs now only be conduction, and not
by radiation acting directly on the housing or rotor.
Another advantage of the invention is to be seen in that the
packing strips are mutually strutted during every operational state
by the narrow slideways of the lobes and cutouts, whereby the wear
tendency is reduced.
Further it is advantageous to dimension the individual layers of
the packing strips so that the edge zones of the layers are pressed
one against the other during temperature rise, whereby there is
formed at the packing strips an uninterrupted band of a blocking
zone, which precludes the issuance of a cooling medium, for
example, helium.
A major advance is achieved by the opening up of a new field of
application, since such turbo-machines packed according to the
invention can, for example, be installed in the direct circuit of a
gas-cooled atomic reactor. Also for the transport or poisonous or
corrosion-favoring substances an advantage becomes attainable,
since on the one hand a loss of the cooling gas or an admixture
thereof into the operating gas is practically avoided, and on the
other hand the need for corrosion-proof material is considerably
reduced since the parts made of corrosion-resistant material are
limited to the parts coming into direct contact with the aggressive
operating gas.
The invention will now be described in detail and is illustrated in
the accompanying drawings with reference to a preferred mode of
construction, all parts not necessary for an understanding of the
invention having been omitted for greater clarity. In the
drawings:
FIG. 1 is an axial section through a turbo-rotor according to prior
art;
FIG. 2 is a radial section along line A--A in FIG. 1;
FIG. 3 is a top view in direction B according to FIG. 1;
FIG. 4 is a detail of the packing constructed according to the
present invention;
FIG. 5 is a section along line D-D in FIG. 4;
FIG. 6 is an oblique elevation of an intersection packed according
to the invention;
FIG. 7 shows a further example of construction according to the
invention, in the cold state; and
FIG. 8 shows the construction according to FIG. 7 at the operating
temperature of the turbo-machine.
In FIG. 1 there is marked by the reference symbol 1 the rotor of a
turbo-machine, where in annular grooves 2 the blades 3 are inserted
and anchored by means of their T-shaped feet 4. Between the
individual blade rows 5 and 5', intermediate sections 7 are
inserted in annular grooves 6; between the blade feet 4 and the
intermediate sections 7 there is thus formed a gap 8, which in
uncooled machines permits penetration of the operating medium into
the interstice 10. Thereby the rotor 1 is heated directly by the
operating medium, which is undesirable because of the disadvantages
mentioned in the introduction.
In cooled machines there is supplied through the interstice 10 a
medium which carries the heat away from the rotor 1 and from the
blade feet 4 and intermediate sections 7. If packing arrangements
are not provided, cooling gas must be supplied in large quantities
and at a higher pressure than that at the point in the flow channel
11 corresponding to the respective gap 8, to suppress the
unhindered entrance of hot or operating gas into the interstice
10.
To keep these gases away from the rotor 1, it has been proposed to
arrange grooves 12 at the cheeks of the intermediate sections 7 and
of the blade feet 4 and to insert packing strips 9 therein. At
first glance it would appear that it is thus possible to seal the
interstice 10 from the flow channel 11 and to improve conditions.
However, it was found that with such arrangements great leakage
gaps still occur, which it is not possible to provide for by the
known elements, and which lead to the initially mentioned
disadvantages.
FIG. 2 shows a radial section through the turbo-rotor 1 along line
A--A in FIG. 1, similar parts having been marked by corresponding
reference symbols. It can be seen that for the packing according to
the known proposal also packing strips 9' have been provided, which
are inserted in the axial direction at the circumference between
the blade feet 4 and the intermediate sections not shown. For this,
corresponding grooves 12' have been provided, which now extend in
the axial direction instead of in circumferential direction like
the grooves 12 (see FIG. 1).
If the rotor is viewed in direction B and its surface developed,
there results the representation as shown in FIG. 3. The section
along line C--C in FIG. 1 shows the viewer a lattice-work or grid
formed by the packing strips 9 and 9'. From this it is visible that
there are still passageways 15 between the butt joints 13 of the
packing strips 9 and 9' and also at the intersections 14.
FIG. 4 shows a detail of a radial section through a rotor 1 on a
larger scale, a packing strip 16 of the form according to the
invention being inserted in the groove 12 along the circumference.
The blade feet 4 are separated by the gap 8, which is blocked in
radial direction by the first layer 17 of the packing strip 16. The
second layer 18 thereof is displaced in the example shown by
approximately one blade division in the circumferential direction.
The length of the individual packing strips 16 is equal to double
the division of the blade row less the strip width and double the
width of gap 8. In combining blade groups into segments, the
segment length is analogously taken as division. The packing strip
length in the axial direction is determined in the same manner as
above, except that instead of the division measured at the blade
row the distance between the blade rows 5 and 5' is considered.
When arranging intermediate sections 7, it is necessary to consider
the dimension of the length of the packing strip by replacement of
double the division by the axial length sum resulting from blade
feet 4 and intermediate section 7.
Between the layers 17 and 18 of the packing strip 16 staggered in
circumferential direction, the individual layers 19 and 20 of the
packing strips 16' are inserted in axial direction, and this so
that between the butt joints of the individual layers of the
packing strips 16 a corresponding layer of the packing strip 16' is
inserted crosswise.
FIG. 5 shows a transverse section of the packing strip 16 along
line D--D of FIG. 4, forces which in the operating state act on the
layers 17 and 18 being indicated by the arrows. By suitable design
of the groove 12 or respectively of the groove bottom 21 in the
blade foot 4 or respectively the intermediate section 7 it can be
achieved that the layers 17 and 18 of the packing strips are
pressed firmly against one another at the mutual contact areas of
the edge zones 22 as soon as the edges of the packing strips get
into the zone of the groove base radius. The packing strips 16 and
16' are provided at the edge zones 22, but not at the mutual
contact areas of the layers 17 and 18, with a slightly rounded
45.degree. bevel. It is thereby achieved that material displaced by
plastic deformation finds sufficient space to give way and that
besides the gripping forces act on the edge zone 22 in an evenly
distributed manner.
For better comprehension of the subject matter of the invention,
there is shown in FIG. 6 a parallel perspective representation of
an intersection 14. The packing strips 16 and 16' again are
composed of the individual layers 17, 18 and 19, 20, which are
arranged in a staggered manner relative to each other. To achieve a
perfect packing, it is necessary to pack, or to avoid, also the
butt joints 23 which are necessary because of the heat expansion of
the material when starting a turbo-machine.
The mere staggering of the individual layers 17 to 20 of the
packing strips does not, however, achieve perfect tightness between
flow channel 11 and interstice 10, which in the present FIG. 6 must
be conceived above or respectively below the intersection 14. The
gap or joint 8 is defined by the blade feet 4 and intermediate
sections 7, the thin solid lines 24 and the broken lines 25
indicating the contours of the expansion joint 8.
At the front sides of the individual layers 17 to 20 of the packing
strips 16 and 16' cutouts 26 are provided, the visible
representation being limited to the upper layer 17 of the packing
strip 16 and to the upper layer 19 of the packing strip 16'.
At the longitudinal sides of the packing strips 16 and 16' with the
layers 18 and 19 there are arranged lobes 27 corresponding to the
cutouts 26. These cutouts 26 and lobes 27 are arranged in like
manner with respect to all packing strip layers 17 to 20, so that
expediently they can be simply exchanged for one another. This can
be the case also when the axial lengths of the rotor blades are
different than those of the intermediate sections 7.
Since strong gripping forces must be expected because of the heat
expansion during the starting or stopping of the turbo-machine, the
cutouts 26 in the individual layers of the packing strips 16 and
16' are provided with large curvatures, the radii of which
preferably correspond to half the width of the cutout 26, so as to
avoid as much as possible an additional notch effect at the
individual layers 17 to 20 of the packing strips 16 and 16'. The
lobes 27 are likewise rounded, their form being adapted to that of
the cutouts 26 and the width of the lobes being chosen so that the
lobes 27 are guided for lateral sliding in the cutouts 26. The
width of the lobes 27 must, however, be greater in every state than
the maximum width of the expansion joints 8 between parts to be
packed. The length of the lobes 27 is at least as great as the butt
joints 23, so that a close guiding of the lobes 27 in the cutouts
26 during every operating state is ensured.
The arrows indicate the possible path of the cooling gas or
operating medium which remains open by the minimum gaps necessary
for the adaptation of the gripping forces during operation. It can
be seen that now any radial and axial passage of the medium is
blocked in all directions.
By the almost perfect sealing of the flow channel, it is possible
to admix the cooling gas at a suitable point under control, whereby
the losses of efficiency resulting from the removal of cooling air
are approximately compensated by the removal of cooling air. At
sufficient cooling output, on the other hand, an increase of the
total efficiency of the installation can be achieved by the
reduction of the quantity of cooling gas.
FIG. 7 shows another embodiment of the invention, as used, for
example, in gas turbine rotor packings. For packing strips 16, made
of highly heat resistant materials, it is proposed to insert in
groove 12 an insert 30 which simply absorbs the gripping forces by
deformation and yet insures sealing.
FIG. 8 shows the same construction as FIG. 7, the difference being
that the packing strips 16 and the gap 8 have been changed by the
temperature rise in the materials and the insert 30 is deformed in
order to improve the tightness. This is achieved because the gas no
longer flows along the longitudinal gap in the bottom of the groove
to the next butt joint 23 between the packing strips 16, since the
packing strips 16 form a tight strip offering gapless packing at
the edge zones 22 clamped in the groove bottom.
The subject matter of the invention is, of course, not limited to
what is represented in the drawings. Thus, instead of the lobes and
cutouts, there may be used a fitting together of the front sides of
the individual layers of the packing strips in corresponding
cutouts on the longitudinal side of the packing strip layers, the
individual layers having toward the front areas offsets insertable
one into the other.
* * * * *