Brush seal between a rotor and a stator in a turbine machine

A brush seal is provided for sealing, with minimized leakage, a circumferential gap (S), for example between a rotor (1) and a stator (2) in a gas turbine engine. The brush seal includes a bristle housing (4) rigidly mounted on the stator or the rotor, and bristles (6) having fixed ends securely and durably held in the housing (4) and free ends protruding toward and into the annular gap (S). The housing (4) includes two holder disks (5A, 5B) with an interspace (Z) therebetween, wherein the interspace includes at least one of an axially directed first clamping portion (8) and a radially directed second clamping portion (10), and a widened non-clamping portion (7A, 7B). The fixed ends of the bristles are clampingly held in the first and second clamping portions, while the free ends of the bristles extend generally toward the opposite rotor or stator while being movably supported and guided by the widened non-clamping portion of the interspace (Z). The bristles (6) may extend at a tilt angle in the circumferential direction and may be stitched, woven, or glued together at their fixed ends in order to form a single bristle packet.

FIELD OF THE INVENTION 
The invention relates to a brush seal for sealing a gap between a rotor and 
a stator in a turbine machine such as a gas turbine engine. 
BACKGROUND INFORMATION 
Brush seals of the above mentioned general type are used in turbine 
machines, and especially gas turbine engines, to provide a seal with the 
minimum possible leakage at circumferential gaps, for example between a 
machine housing and rotor or around a rotary shaft of the turbine machine, 
between two spaces having different prevailing fluid pressures within the 
turbine machine. Generally, the bristles of the brush seal are held and 
guided so as to be elastically yieldable or movable in order to compensate 
for any eccentric or oscillating motions of the rotor or shaft relative to 
the housing, which may result, for example, from rotor imbalances or the 
like. In this context, brush seals have been recognized as advantageous 
over the previously long utilized labyrinth seals, because such labyrinth 
seals can only adapt themselves to eccentric shaft movements to a very 
limited degree. Furthermore, brush seals advantageously distinguish 
themselves over prior labyrinth seals by a lower production cost and a 
lower weight. 
Brush seals are generally known having a brush housing including two 
support disks or holder disks with an interspace therebetween, and with 
the seal bristles held in the interspace. The housing is mounted on the 
rotor or stator of a turbine machine, so that the bristles are directed 
toward the opposite stator or rotor. Such a brush seal arrangement is, for 
example, disclosed in German Patent 3,720,069. 
In order to achieve a long operating life for such a brush seal, it is 
essential that the brush bristles are securely and durably mounted and 
held in the seal housing, so that the bristles cannot come loose and fall 
out during operation. Namely, such a loss of bristles would at least 
reduce the seal effectiveness, and in the worst case could damage or 
destroy the rotor or other components of the turbine machine and thus 
jeopardize the operating condition of the machine. According to German 
Patent 3,907,614, the bristles of a brush seal are looped around a core 
ring, and the bristles together with the core ring are further encircled 
and held by a clamping ring. The clamping ring is split or slotted in the 
circumferential direction so that the free ends of the bristles are 
directed radially inwardly so as to project out of the clamping ring 
toward the rotor. The bristle ring that is embodied and held together in 
such a manner is then inserted between two holding disks which form the 
brush housing and which then exert and transfer the clamping force onto 
the clamping ring. Disadvantageously, such a known brush seal arrangement 
is relatively complicated in structure, and also requires complicated and 
time consuming assembly and maintenance steps. 
SUMMARY OF THE INVENTION 
In view of the above it is an object of invention to provide a brush seal 
of the above described general type that is improved in such a manner to 
achieve a simplified mounting and holding of the bristles in the brush 
housing as compared to the state of the art, while maintaining the same or 
even improving the reliability and durability of the securing of the 
bristles. Further objects of the invention are to avoid or overcome the 
other disadvantages of the prior art, and to achieve additional 
advantages, as are apparent from the present description. 
The above objects have been achieved in a brush seal for sealing a gap 
between a rotor and a stator, according to the invention, including a 
bristle housing that comprises two holding disks mounted on the rotor or 
the stator, with an interspace between the two holding disks. The 
arrangement further includes seal bristles arranged in the interspace 
between the holding disks so as to extend toward the opposite rotor or 
stator. The interspace between the two holding disks has a special 
configuration including a clamping zone at a radially outer end of the 
interspace that clampingly holds radially outer fixed ends of the seal 
bristles. The clamping zone of the interspace includes at least one of a 
substantially axially directed first clamping portion and a substantially 
radially directed second clamping portion. Thus, the radially outer fixed 
ends of the seal bristles are clampingly held in at least either the 
axially directed first clamping portion or the radially directed second 
clamping portion of the interspace. Preferably, the interspace includes 
both the first clamping portion and the second clamping portion. 
The present brush seal provides the advantage that the bristles are 
subjected to a deflection, due to the clamping of the radially outer 
bristle ends in the axial or radially directed clamping portion of the 
interspace between the two holding disks. 
This deflection of the bristles causes an increased friction of the 
bristles relative to one another and relative to the bristle housing, 
which provides an increased frictional securing of the bristles. Moreover, 
the special interspace configuration according to the invention provides a 
certain form-locking hold or securing of the bristles due to the mating 
convoluted shape of the bristles and the clamping portion of the 
interspace. In this manner, the invention ensures a reliable and durable 
securing of the bristles in their housing, without requiring any 
additional clamping means such as a clamping ring or a core ring. 
Due to the minimal number of components, which is reduced relative to the 
prior art, the invention considerably simplifies the production, i.e. 
reduces the production effort and cost, of the brush seal. Especially, 
since the holding disks require only a moderate deformation in the axial 
direction, the holding disks can easily be produced with the required 
shape using simple bending, pressing, and drawing operations. This is 
especially true in the embodiment in which the clamping of the bristles is 
carried out in a radially extending clamping portion of the interspace. 
Once the bristles have been placed between the two holding disks, the two 
disks with the bristles held therebetween can be joined together to form a 
bristle housing by means of welding, soldering, flanging or any other 
suitable joining technique. This results in a compact ring-shaped brush 
seal which may then simply be installed by appropriately mounting it on 
the stator or on the rotor depending upon the particular application. 
In an alternative embodiment of the invention, the radially outer fixed 
ends of the bristles are secured by clamping in an axially directed first 
clamping portion of the interspace, and in a radially directed second 
clamping portion of the interspace between the two holder disks. Due to 
the plural or redundant provision of clamping in different directions, and 
due to the deflection of the bristles from the radial direction into the 
axial direction, an especially strong and durable securing of the bristles 
is achieved without significantly increasing the necessary production 
complexity or effort, which would arise by using additional complex 
components or the like. 
In order to meet increased demands or requirements on the securing strength 
of the bristles in the housing, the fixed end portions of the bristles may 
additionally be stitched or glued together with one another in the 
clamping portions of the interspace, and at further locations if necessary 
for the specific function. In this manner, the production is also 
simplified, because it is no longer necessary to handle individual 
bristles, but instead a bristle packet of all the bristles adhered 
together may be handled as a single unit. If the joining of the bristles 
by stitching or gluing or the like is only necessary for improving the 
handling of the bristles during assembly of the brush seal arrangement, 
then this stitching or gluing may be removed after the bristles have been 
secured in the bristle housing. 
The stitching or sewing or weaving of thread packages has the advantage 
that the resulting bristle packets may be produced in an expedient and 
economical manner. Furthermore, the stitching thread seams or for example 
the weft threads may be carried out to extend at a non-perpendicular angle 
relative to the bristle threads or fibers, whereby bristle packets having 
the bristles extending at an angle may easily be produced by cutting off 
the bristle thread or fiber courses parallel to and adjacent the weft 
threads or the stitching thread seams. Then, the bristle packets may be 
inserted and installed in the bristle housing in such a manner that the 
weft threads or stitching thread seams are arranged extending around the 
circumferential direction within the housing enclosure. In this manner it 
is possible to achieve a desired tilt angle of the installed bristles 
relative to the rotor radial directions, at an early stage in the 
production without requiring additional production steps. Brush seal 
arrangements having such bristle threads or fibers that are tilted or 
angled in the circumferential direction are necessary for sealing 
rotor-stator arrangements that operate at high rotational speeds. The weft 
threads or stitching thread seams may remain permanently in place so as to 
provide an additional holding and securing of the bristles to prevent them 
from falling out, in addition to the above described clamping of the 
bristles in the housing. 
According to further details of the invention, the interspace between the 
two holding disks includes a curved or circular arcshaped portion forming 
a transition between the axially directed first clamping portion and the 
radially directed second clamping portion. This arrangement provides a 
first clamping location or particularly a first clamping shoulder for 
clamping the bristles in the first clamping portion of the interspace. 
Moreover, the radially directed second clamping portion may include a 
meanderloop shaped or convolute corrugation shaped second clamping 
configuration that is formed between a ring-shaped depression in the first 
holder disk and a corresponding ring-shaped bulge or protrusion in the 
second holder disk. A radially inner end portion of the interspace may be 
widened or expanded to allow some amount of free play movement of the 
bristles at their free ends adjacent the gap that is to be sealed.

DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BEST MODE OF THE 
INVENTION 
FIG. 1 shows a portion of a rotor-stator arrangement including a rotor 1 
and a stator 2 as components of a gas turbine engine, which is not further 
shown in its entirety. Within the rotor-stator arrangement 1, 2, a first 
space R1 and a second space R2 are subjected to two different fluid 
pressures, and are to be sealed relative to one another with a minimum of 
leakage. For this purpose, a ring-shaped brush seal 3 is arranged 
substantially concentrically with the axis of the rotor-stator arrangement 
between the rotor 1 and the stator 2 in the annular space formed by the 
above-mentioned spaces R1 and R2. The brush seal 3 essentially comprises a 
bristle housing 4 including two holder disks 5A and 5B that are arranged 
coaxially to each other and joined together by a welded, soldered or 
flanged joint 4A, and a bristle bundle 6 that is secured in an interspace 
Z between the two holder disks 5A and 5B in such a manner that the free 
ends of the bristles 6 protrude radially inwardly against the outer 
circumferential surface of the rotor shaft 1 in order to seal the gap S 
between the rotor 1 and the stator 2. The bristle housing 4 is secured to 
the stator 2, for example by a securing ring 22 holding the housing 4 
against a shoulder 2A of the stator 2. 
The specific illustrated embodiment uses a two-fold clamping arrangement 
with a radially directed clamping portion and an axially directed clamping 
portion as will be discussed. It should be understood that this is also 
essentially representative of two simpler embodiments using only the 
radial clamping portion or the axial clamping portion as will be 
described. 
The bristles 6 may be arranged in the housing 4 such that their radially 
inwardly directed free ends protrude toward the rotor 1 essentially 
radially, or with a circumferential tilt angle relative to the respective 
radial direction. In order to receive and hold the bristles 6 in this 
manner, the bristle housing 4 comprises an annular disk-shaped interspace 
Z arranged concentrically about the axis of the rotor-stator arrangement. 
This interspace Z is formed by means of appropriate corresponding 
profiling of the respectively opposed end faces 7A and 7B of the two 
holder disks 5A and 5B. At the radially outer area of the bristle housing 
4, the interspace Z transitions into and ends in an axially directed, 
concentric, first clamping portion 8. A circular arc-shaped transition 9 
connects and transitions from the first clamping portion 8 radially 
inwardly to a second concentric clamping portion 10 of the interspace Z. 
The first clamping portion 8 provides a first clamping location or 
particularly a first clamping shoulder 11A on the first holder disk 5A, 
for clamping the bristles 6 especially with a radially directed clamping 
force. Namely, the first axial extending clamping portion 8 has a gap 
width S1 of a proper dimension that the radially outer ends of the 
bristles 6 are clamped therein in such a manner that the individual 
bristles 6 cannot slip out of the bristle housing 4, on the one hand due 
to the clamping, and on the other hand additionally due to the 
form-locking connection provided by the deflection of the bristles 6 from 
the radial direction into the axial direction. 
The essentially radially directed second clamping portion 10 of the 
interspace Z comprises an additional clamping location or configuration 
11B, which is embodied in the form of a meander loop shaped curve. To 
achieve this, the first holder disk 5A has a ring-shaped depression 12 
therein, and the adjacent facing surface of the holder disk 5B has a 
corresponding ring-shaped bulge or convex projection 13, so that the 
bristles 6 running through this second clamping portion 10 extend with a 
substantially .OMEGA.-shaped lengthwise sectional shape in this area. This 
configuration achieves a further improved holding of the bristles 6 in the 
bristle housing 4, because it exerts both axially and radially directed 
clamping force components and an interlocking configuration on the 
bristles 6. 
Radially inwardly from the second clamping portion 10, the end face 7A of 
the first holder disk 5A extends substantially flat or straight, so as to 
contact or guide the radially inner free end portions of the bristles 6 
from the second clamping portion 10 radially inwardly to the sealing gap 
S. However, the opposite end face 7B of the second holder disk 5B has a 
step or set-back 14 at the radially inner end of the second clamping 
portion 10, so that this face 7B is not in contact with, but rather is 
spaced from the bristles 6 in a normal resting state. Thus, the area or 
range over which the bristles 6 are clamped in the bristle housing 4 ends 
at a definite or distinct location defined by this step or set-back 14. 
With this arrangement, the radially inner free end portion of the bristles 
6 between the step 14 and the sealing gap S are elastically deflectable in 
the circumferential direction, and to a limited extent also in the axial 
direction, so that an eccentric running motion of the rotor 1 can be 
compensated for while still providing an effective seal. 
In order to simplify the assembly and installation of the brush seal 3, the 
bristles 6 are connected or held together in the area of their radially 
outer ends, or especially in the area of the first clamping portion 8, by 
means of a fixing or binding thread 15, so that the bristles 6 are more 
easily handleable while being inserted or installed in one of the two 
holder disks 5A or 5B. In other words, the individual bristles 6 are 
joined together to form a bristle bundle or packet 6. Preferably, in order 
to provide an additional holding of the bristle bundle 6 in the housing 4, 
the fixing thread or stitching 15 is carried out in a multi-ply fashion 
using warp and weft threads as shown in FIG. 2, for example. Another 
fixing thread stitching line 15 is provided in the bristle bundle 6 in the 
area of the second clamping portion 10. Moreover, alternatively, reference 
number 15 in FIG. 1 may represent a glue applied to the bristles 6 so as 
to bind them together. 
FIG. 3 shows a thread package 16 that forms an intermediate product for 
producing the brush seal 3 as shown in FIG. 5, especially for sealing from 
each other two stages in a rotor-stator arrangement of a gas turbine 
engine that is not shown in its entirety. The thread package 16 shown in 
FIG. 3 comprises a plurality of bristle threads or fibers 6 extending 
substantially parallel to one another in width and depth so as to form a 
substantially rectangular sheet or web. 
Furthermore, the thread package 16 comprises stitching threads 15 or weft 
threads 15' running generally across the bristle threads or fibers 6. The 
stitching threads 15 or weft threads 15' may be substantially 
perpendicular to the bristle threads or fibers 6, to form a general brush 
seal as described above, but especially the stitching threads 15 or weft 
threads 15' extend at an angle .alpha. relative to the extension direction 
F of the bristle threads or fibers 6 for manufacturing a brush seal with 
bristles having a tilt angle in the circumferential direction. 
In the illustrated embodiment, the stitching threads 15 or weft threads 15' 
cross the bristle threads 6 at an angle .alpha. of approximately 
65.degree., which substantially corresponds to the final tilt angle 
.alpha.' of the bristles 6 in the circumferential direction relative to a 
radial R' of the rotor which rotates in direction R as shown in FIG. 5. 
The stitching threads 15 or weft threads 15' extending at an angle, run 
entirely through the rectangular thread package 16 from edge to edge 
thereof, as shown in FIG. 3. In the illustrated embodiment, the stitching 
threads 15 or weft threads 15' are carried out double-fold respectively in 
a stitching zone N, whereby the respective stitching zones N are offset 
from one another at the repeating linear spacing distance or offset A. As 
a result, the respective portions of the thread package 16 that lie 
between the stitching seam zones N and that are thus free of weft threads 
or stitching threads, correspond to the free bristle length B that is 
determined by the spacing A and the angle a through a simple trigonometric 
angular relationship, namely A sin .alpha.. 
As the next step in processing the laid-up or woven thread package 16, 
individual bristle courses 17 are cut out of the thread package 16 by 
cutting along each respective stitching thread zone N, such that one edge 
of the bristle course 17 is formed by the stitched zone N and the opposite 
edge of the bristle course 17 is formed by the free end 18 of the bristles 
6, as shown in FIG. 4. In other words, each cut for separating respective 
bristle courses 17 is carried out parallel to and directly adjacent the 
stitching threads 15 or weft threads 15'. The individual bristle courses 
17 are then installed in a bristle housing 4 in such a manner that the 
stitching threads 15 or weft threads 15' come to rest within the bristle 
housing 4 while the free ends 18 of the bristles 6 extend toward the rotor 
1 and protrude radially inwardly from the housing 4. If the weft threads 
15' or stitching threads 15 are not necessary for achieving a secure 
seating and holding of the bristles 6 in the bristle housing 4 once it is 
in an assembled condition, then these threads may thereafter be removed 
from the housing 4. 
Two different production methods can alternatively be used for producing 
the multi-layered thread package 16. In the first method, the thread 
package 16 of bristle threads or fibers 6 is first laid up in a 
multi-layered surfacial manner, and then the multi-layers are sewed or 
stitched together along a plurality of parallel extending stitching lines 
directed at a stitching angle .alpha. as described above, using stitching 
threads 15. In this context, the material of the stitching threads is 
preferably the same as that of the bristle threads or fibers. In the 
second, alternative method, the thread package 16 is produced by a weaving 
method. In this context, the warp threads form the bristles 6 and the 
spaced or relatively offset weft threads 15' cross and interweave the 
bristles 6 at an angle of approximately 65.degree. in order to bind 
together the bristles 6. After a number of weft threads 15' have been 
picked, i.e. inserted into the warp threads forming the bristles 6, so as 
to form a woven band or margin in the stitching zone N, then the warp is 
advanced without inserting weft threads for a distance corresponding to 
the offset or spacing A before inserting the next group of weft threads 
15'. In this manner, a weft free portion forms the free bristle length B, 
in which the free ends of the bristle threads or fibers 6 are not 
connected to one another and will protrude from the bristle housing and be 
deflectable or yieldable without hindrance in the final assembled 
condition, as described above. 
Although the invention has been described with reference to specific 
example embodiments, it will be appreciated that it is intended to cover 
all modifications and equivalents within the scope of the appended claims. 
It should also be understood that the present disclosure includes all 
possible combinations of any individual features recited in any of the 
appended claims.