Abstract:
The invention relates to a brush seal for sealing a gap between a rotor and a stator, with at least one brush ring, comprising a number of sealing brushes and at least two annular brush ring carriers, running in the circumferential direction of the rotor. Each brush ring is fixed between a first front face of a first brush ring carrier and a second front face of a second brush ring carrier, whereby the second brush ring carrier is directly axially and radially fixed to the first brush ring carrier.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is the US National Stage of International Application No. PCT/EP2003/013437, filed Nov. 28, 2003 and claims the benefit thereof. The International Application claims the benefits of German Patent application No. 10258096.0 DE filed Dec. 11, 2002, both of the applications are incorporated by reference herein in their entirety. 
   FIELD OF THE INVENTION 
   This invention relates to the field of brush seals and in particular, brush seals used in turbomachinery. 
   BACKGROUND OF THE INVENTION 
   Brush seals are successfully used, for example, in turbomachines, in order to reduce the leakage flow between a rotor and a stator. Many brush seals have the disadvantage that the brush ring carriers are often not produced in one piece. This results, during operation, in out-of-roundnesses of the brush seals and of the secondary seal with respect to the housing, which have an adverse effect on the sealing action of the overall arrangement and consequently on the efficiency of the turbomachine. 
   DE 199 38 268 A1 discloses a brush seal, in which the brush ring is welded in between two annular one-piece brush ring carriers. This entire unit, consisting of two brush ring carriers and of a brush ring located between them, is inserted into a corresponding slot of the stator. That is to say, each brush ring requires two brush ring carriers and a slot in the stator for receiving the brush ring carriers. 
   DE 197 20 648 C2 discloses a brush seal, in which a brush ring is held between two brush ring carriers and the brush ring carriers are connected to one another by flanging. In this brush seal, too, each brush ring requires two brush ring carriers and a slot in the stator. 
   SUMMARY OF THE INVENTION 
   The object on which the invention is based is to provide a brush seal arrangement which is further improved with regard to the sealing action and to the outlay in terms of production and of assembly. 
   In a brush seal according to the invention for sealing a gap between a rotor and a stator, in particular of a turbomachine, with at least one brush ring having a multiplicity of sealing bristles, and with two annular brush carriers extending in the circumferential direction of the rotor, each brush ring being fixed between a first end face of a first brush ring carrier and a second end face of a second brush ring carrier, this object is achieved, according to the invention, in that the second brush ring carrier is directly fixed axially and radially to the first brush ring carrier. This may take place, for example, by means of an annular clamping connection. 
   By virtue of this measure, the outlay in terms of production and of assembly can be markedly reduced, since, merely by plugging the second brush ring carrier and the first brush ring carrier one into the other, an axial and radial fixing of the second brush ring carrier takes place, said fixing preventing complicated and cost-intensive adjusting and fixing work. Moreover, the brush ring carrier has a rotationally symmetrical construction, so that roundness is maintained, even under changing operating conditions. 
   Of course, a plurality of brush rings may also be arranged one behind the other in this way, only one further brush ring carrier being required for each additional brush ring. This, too, results in a considerable cost saving, without disadvantages with regard to the functionality and sealing action of the brush seal according to the invention. 
   Finally, the necessary construction space is also very small. 
   In connection with the invention, reference is made below to a first brush ring carrier and a second brush ring carrier. This is intended to make a distinction between two components which are identical per se. The first brush ring carrier is arranged downstream of the second brush ring carrier in the direction of flow of the fluid flowing through the sealing gap. 
   In an advantageous variant of the invention, there is provision for a slot to be formed between a first brush ring carrier, in the direction of flow of the fluid to be sealed, and a second brush ring carrier, in the direction of flow of the fluid to be sealed, and for the slot to serve for receiving the brush ring. By means of this slot, the brush ring is axially and radially fixed, likewise without any additional outlay for centering and fixing the latter, in the brush ring carriers when the second brush ring carrier is pushed onto the first brush ring carrier. According to the invention, the slot for receiving the brush ring may be present either completely in the first brush ring carrier or in the second brush ring carrier or partially in both. 
   The brush ring is the actual sealing element which consists of a multiplicity of sealing bristles. The sealing bristles are arranged, where a radial seal is concerned, in such a way that, in the installed state, the sealing bristles just touch the rotor. 
   It has proved particularly advantageous if the second brush ring carrier is fixed to the first brush ring carrier by means of a snap connection, in particular an unreleasable snap connection. In this embodiment, the connection between the first brush ring carrier and second brush ring carrier can be made very simply and cost-effectively. 
   In a further advantageous embodiment of the invention, there is provision for at least one first brush ring carrier to have on its first end face a shoulder with a circumferential slot, for at least one second brush ring carrier to have on its second end face a continuous projection, and for the projection of the second brush ring carrier to cooperate with the shoulder and with the circumferential slot of an adjacently arranged first brush ring carrier, in such a way that an axial and radial fixing of the second brush ring carrier in relation to the first brush ring carrier takes place. This connection between the first brush ring carrier and the second brush ring carrier may also be designed as a snap connection, in particular as an unreleasable snap connection. In any event, however, this connection affords a good axial and radial fixing of the second brush ring carrier, at the same time with low production costs, since the shoulder and circumferential slot and also the projection can be produced simply on a lathe in one chucking operation. 
   In a further embodiment according to the invention, there is provision for at least one brush ring carrier to have on its first end face a shoulder with a circumferential slot, for at least one brush ring carrier to have on its second end face a continuous projection, and for the projection of the first end face of the at least one brush ring carrier to cooperate with the shoulder and with the circumferential slot of an adjacently arranged further brush ring carrier. It is thereby possible to arrange any number of brush ring carriers and brush rings one behind the other, in which case completely identical components may be used, with the exception of an initial piece and an end piece. The production costs are thereby further reduced. The number of brush rings arranged in a row will be defined, as a rule, as a function of the existing construction space and the desired sealing action. In examples implemented in practice, it has proved possible for a brush ring carrier to have a thickness of about 12 mm, so that a brush ring can be arranged every 12 mm. As a result of this, too, the brush seal according to the invention is highly space-saving and therefore, with the construction space remaining the same, more brush rings than has been conventional hitherto can be provided. 
   In order to fix the brush seal securely in relation to the stator, there is provision for a brush ring carrier to be held at least indirectly on the stator. This may take place by means of a slot in the stator, screws or other means known from the prior art. 
   It has proved advantageous if the circumferential slot is arranged in the part mounted first and the latching nose is located in the newly pushed-on part. To be precise, if the latching connection is unreleasable (irreversible), as may be provided according to the invention, the advantage of this is that, in the event of a manufacturing error, only the brush ring carrier mounted last has to be demounted in a destructive way by the projection being twisted off. 
   In order to improve the sealing action of the brush seal according to the invention, there is provision for the brush ring carrier or brush ring carriers to have a support plate and/or a protective ring which extend from the brush ring carrier in the direction of the rotor and against which the brush seal bears, supported axially, on at least one axial side. Such support plates and protective rings are known per se from the prior art; however, in the brush seal according to the invention, a support plate and a protective ring may be lathe-turned directly out of the brush ring carrier, so that, either using the supporting means, the brush ring carrier remains in one piece and the number of components required and consequently also the outlay in production terms further remain minimal. 
   In a further advantageous embodiment of the invention, the support plate and the protective ring are designed to be radially elastic, so that, in the event of the rotor running up against the supporting means, these can shift aside in the radial direction, without causing damage or being damaged themselves. As soon as the rotor returns to its original centric position again, the axial supporting means resume their original shape and position. 
   The action of the brush seal according to the invention may be further improved if the rotor to be sealed off has at least one continuous bead, and the at least one bead is arranged so as to be offset with respect to the brush ring or brush rings. This bead, which may, for example, have a height of 0.7 mm, deflects the fluid flow emerging through the sealing gap in such a way that the brush rings lying downstream of the bead cannot be damaged by the fluid jet arriving upstream. Of course, in the dimensioning of the height of the bead, care must be taken to ensure that the brush seal and the axial supporting means can be pushed over the bead and are not damaged during the mounting of the brush seal according to the invention. 
   Further advantages and advantageous embodiments may be gathered from the following drawing, its description and the patent claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawing: 
       FIG. 1  shows a first exemplary embodiment of a brush seal according to the invention in section, 
       FIG. 2  shows a second exemplary embodiment of a brush seal according to the invention on a balancing piston of a steam turbine, and 
       FIG. 3  shows a third exemplary embodiment of a brush seal according to the invention for axial sealing off. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a first exemplary embodiment of a seal according to the invention which is arranged between a stator  1  and a rotor  3  of a turbomachine. The brush seal, of multistage design in the first exemplary embodiment, is designated as a whole in  FIG. 1  by  5 . The brush seal  5  consists essentially of brush rings  7  which are fixed axially and radially in brush ring carriers  9 ,  11  and  13 . Brush seals according to the invention may also be of single-stage design, that is to say with only one brush ring. 
   An individual brush ring carrier  9  has been illustrated, enlarged, in  FIG. 1 . Referring to this individual brush ring carrier  9 , the shape and functioning of the latter are explained below. The other brush ring carriers  9  are constructed identically. The other brush ring carriers  11  and  13  are constructed partially identically. 
   So as not to be detrimental to clarity in  FIG. 1 , not all the brush ring carriers  9 ,  11  and  13  have been given reference symbols. 
   The brush ring carrier  9  has a first end face  15 . On this first end face  15 , a slot  17  is cut out, into which a brush ring  7  can be inserted. A shoulder  19  with a circumferential slot  21  is formed in the first end face  15  on the outside diameter of the brush ring carrier  9 . 
   On a second end face  23 , there is a continuous projection  25  which is dimensioned such that it can be pushed onto a shoulder  19  of an adjacently arranged brush ring carrier  9 . This results in an axial and radial fixing of two adjacently arranged brush ring carriers  9  in relation to one another. The projection  25  has provided on it a latching nose  27  which can latch into the circumferential slot  21  on a first end face  17  of an adjacently arranged brush ring carrier  9 . In the exemplary embodiment illustrated in  FIG. 1 , the circumferential slot  21  and the latching nose  27  form a snap connection. 
   As may be gathered from the overall view of the brush seal  5  according to the invention in  FIG. 1 , a plurality of brush ring carriers  9  are connected to one another, in that the projection  25  on the second end face  23  of a brush ring carrier  9  is pushed onto a shoulder  19  of a first end face  15  of an adjacently arranged brush ring carrier  9 . A releasable or unreleasable snap connection can be made by means of the circumferential slot  21  and the latching nose  27 . The slot  17  on the first end face  15  is designed in terms of diameter and depth in such a way that a brush ring  7  is clamped between two brush ring carriers  9  and fixed axially and radially when these brush ring carriers  9  are latched together with one another. 
   The arrangement of this latching together expediently takes place such that, as illustrated, the circumferential slot  21  is located in the part mounted first and the latching nose  27  is located in the newly pushed-on part. 
   If, as may be provided according to the invention, the latching connection is unreleasable (irreversible), the advantage of this is that, in the event of a manufacturing error, only the ring  9  mounted last has to be demounted in a destructive way by the projection  25  being twisted off. 
   In order to support the brush rings  7  axially, a support plate  29  is provided on the first end face  15  of the brush ring carrier  9 . The first end face  15  is arranged on the brush ring carrier  9  at the front, as seen in the direction of flow of the fluid flowing through the sealing gap. The direction of flow is illustrated by an arrow  30  in  FIG. 1 . The support plates  29  are arranged after a brush ring  7  and are designed to be radially elastic, since a cavity  31  is cut out in the brush ring carrier  9 . If the rotor  3  were to be brushed against, the gap C 2  between the rotor  3  and support plate  29  would disappear and the support plate  29  would spring back radially. 
   On the second end face  23 , a protective ring  33  is provided, which is less elastic in the axial direction than the support plate  29 , since it is normally provided with a larger gap C, with respect to the rotor  3 . The second end face  23  is arranged in front of a brush ring  7 , as seen in the direction of flow  30  of the fluid flowing through the sealing gap. Depending on demand and requirements, the radial elasticity of the support plate  29  or of the protective ring  33  between the two versions, illustrated in the enlargement in  FIG. 1 , on the first end face  15  and on the second end face  23  may be varied. 
   The gap c 1  between the protective ring  33  and rotor  3  is, as a rule, somewhat larger than a gap c 2  between the support plate  29  and rotor  3 , whilst preventing the latter from brushing against the protective ring  33 . To be precise, before the brushing against the protective ring  33 , the brush seal  5  shifts away from the rotor  3  in the axial direction (see the double arrow S). 
   The brush ring carrier  13 , which is arranged on the far right in  FIG. 1  as a closing-off piece, differs from the brush ring carriers  9  in that, according to the invention, only a second end face  23  is designed with a projection  25  and with a latching nose  27 . In this bush ring carrier  13 , the first end face  15  is designed as a plane face. 
   The brush ring carrier  11  differs from the brush ring carriers  9  described in detail in that only a first end face  15  is designed with a slot  17 , shoulder  19 , circumferential slot  21  and support plate  29 . The second end face  23  is designed as a plane face. A brush ring carrier  9  can be fastened to the first end face  15  in the way described above. 
   In parallel with this second end face  23 , a further plane face  38 , which runs parallel to the second end face  23 , is formed on the brush ring carrier  11 . The stator  1  has made in it a second slot  36  into which the brush ring carrier  11  is introduced. The brush seal  5  according to the invention is thereby connected to the stator  1 , specifically in such a way that some radial displacement and adjustment, which is indicated in  FIG. 1  by the double arrow S, is possible. This radial displacement may be utilized, during assembly, in order to orient the brush seal  5  in relation to the rotor  3 . 
   Sealing between the brush ring carrier  11  and stator  1  takes place via the second end face  23  and the corresponding plane face  35  of the second slot  36 , since, as a result of the pressure difference in front of and behind the brush seal  5 , the brush seal  5  is pressed against said plane face of the stator  1 . Should this pressing force not be sufficient, additional prestressing elements (not illustrated) may be provided, which press the brush ring carrier  11  with its second end face  23  against the stator  1 . 
   The brush ring carriers  11 ,  9  and  13  may be additionally connected to one another and secured by means of screws (not illustrated). 
   On the rotor  3 , between the brush rings  7 , continuous beads  37  are provided which deflect the fluid escaping through the sealing gap in such a way that the brush ring  7  located downstream of a bead  37  is not damaged by the outflowing fluid and the sealing action of the brush seal  5  according to the invention is improved. 
   In practice, a height of 0.7 mm has proved expedient for beads  37 . Care must be taken, in any event, to ensure that the beads are not so high that it becomes impossible to mount the brush rings  7  and the brush ring carriers  11  and  13 . 
     FIG. 2  illustrates a second exemplary embodiment of a brush seal  5  according to the invention. In the application according to  FIG. 2 , the brush seal  5  according to the invention seals off a rotor  3 , in particular a turbine rotor. The basic construction is the same in this exemplary embodiment as in the exemplary embodiment according to  FIG. 1 . A detailed description is therefore dispensed with. Also, for the sake of clarity, not all the reference symbols are entered. 
   An essential difference of the second exemplary embodiment from the exemplary embodiment according to  FIG. 1  is that brush rings  7  are fastened in the brush ring carrier  11  by means of brush ring carriers  43 . The brush ring carriers  43  are constructed in a similar way to the brush ring carriers  9  described above. In the exemplary embodiment illustrated in  FIG. 2 , after the third brush ring  7 , one of the brush ring carriers  9  described in detail above with reference to  FIG. 1  adjoins the brush ring carrier  11 . However, the invention is not restricted to two brush ring carriers  43 . Instead, the number of brush rings  7  depends on the intended use of the brush seal arrangement according to the invention. By virtue of this type of construction, the space requirement for the brush seal  5  according to the invention can be reduced and the outlay in terms of production reduced. 
   The brush ring carrier  11  and/or the brush rings  9  and  13  may additionally be connected to one another by means of screws, not illustrated. 
     FIG. 3  illustrates a third exemplary embodiment of a brush seal  5  according to the invention by the example of a balancing piston  39  of a rotor  3 . In this case, the brush seal  5  is designed as an axial seal. In this exemplary embodiment, the sealing bristles of the brush rings  7  are arranged cylindrically. The diameters of the brush ring carriers  11 ,  9  and  13  are coordinated with one another in such a way that they can be connected to one another in the axial direction by means of the snap connection described above.