In turbo-machines having rotating and stationary components, sealing elements of various types of construction are used for sealing off various pressure spaces. In this case, in particular, contactless seals (for example, labyrinth seals) or resilient contacting sealing elements are used between the rotating and the stationary components. The resilient contacting sealing elements include, inter alia, what are known as brush seals in which bristles are used for a sealing off between spaces having different pressures.
Whereas contactless seals are suitable for sealing off pressure differences of a few millibars up to several hundred bars, the range of use of brush seals, even in the multistage arrangement (a plurality of brush seals one behind the other), is limited in respect of the maximum pressure difference on account of the “blow-over effect” and a “farming open”.
The “blow-over effect” is made clear in FIG. 1 by a cross-sectional illustration of a brush seal 10 according to the prior art. In this brush seal 10, bristles 12 are arranged in a plurality of rows and are fastened in a basic body 14. The basic body 14 is framed on two opposite sides in each case by a guide plate 16, of which the guide plate 16 illustrated on the right in FIG. 1 extends so far to the lower end region of the bristles 12 that it supports the bristles 12 there. In the case of a correspondingly high pressure difference “p1>>p2” at the brush seal 10, however, the bristles 12 are bent at this lower end region to an extent such that medium can flow from the pressure space located on the left in FIG. 1 over into the pressure space located on the right.
FIG. 2 makes clear the “fanning open” of a brush seal 10 by means of a cross-sectional illustration corresponding to that of FIG. 1. In “fanning open”, because of an unfavorable flow against the lower end region of the bristles 12, individual bristles are bent up toward the left-hand pressure space, so that, once again, medium can pass out of this pressure space, which is under a pressure p1, into the right-hand pressure space which is under a lower pressure p2.
In order to increase the performance of known brush seals, in previous solutions the individual bristles are designed to be comparatively thick, the individual bristle bundles are held by a guide plate or a supporting ring (see FIGS. 1 and 2, the right guide plate 16) and/or the individual bristle bundle, overall, is designed to be relatively wide or thick.