Abstract:
A brush seal includes a brush seal body formed of heat-resistant magnetic silicone rubber material in the form of a channel. Bristles are disposed in the channel of the brush seal body at a cant angle and project from the edges of the body terminating in bristle tips. The brush seal is formed linearly and, in use, flexed to form an annular seal between adjacent annular sealing components, with the seal carried by one component and the bristle tips engaging the opposite component. The magnetic material of the seal body enables temporary securement of the seal to one of the components, while the seal is adjusted and finally secured in place.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to brush seals for use in turbomachinery such as gas and steam turbines to minimize leakage flows and particularly to a flexible heat-resistant magnetic silicone rubber brush seal useful over a wide range of sealing dimensions. The present invention further relates to a flexible brush seal formed of a magnetic material for at least temporarily adhering the brush seal to one of the sealing components to facilitate installation, either as original equipment or as a retrofit. 
     In turbomachinery such as gas and steam turbines, compressors and turbopumps, a number of seals are used at different locations for minimizing leakage flows. For example, seals may be provided between sealing surfaces which are both movable relative to one another or between components in which one component moves relative to another component, e.g., a stationary housing and a rotating shaft. 
     Brush seals, particularly in turbomachinery, typically comprise a plurality of elongated wire bristles in contact with a movable, e.g., rotating surface. The bristles provide a tight rub-tolerant seal which experiences only slight degradation over time. The bristles of the seal are compliant in use and this minimizes damage due to transient impact between the sealing components. A typical brush seal is formed by folding bristles over a rod with an outer clamp maintaining the folded bristles, squeezing the bristles between a folded metal plate forming a clamp or sandwiching the bristles between a pair of supporting metal plates and welding the plates and bristles at their proximal ends to one another. The distal ends of the bristles typically project a certain distance from the margins of the backing plates or clamps to engage the opposing sealing component. Common to these types of brush seals is that the bristle holder or carrier is formed of metal which is usually machined with a tight tolerance and thus the brush seal is applicable to only a specific sealing dimension. For other sealing dimensions, e.g., diameters, a separately manufactured and distinct brush seal must be used in order to dimensionally fit the seal with its carrier. Consequently, the brush seals are costly in terms of tooling, manufacturing and installation and long cycle times in brush seal manufacturing and retrofitting are required. Accordingly, there is a need for an improved brush seal where one size fits many different sizes of brush seals. Additionally, there is a need to facilitate installation of a brush seal without use of ancillary jigs or fixtures typically necessary to hold or temporarily secure the brush seal to its carrier. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment of the present invention, there is provided a brush seal having a seal body formed of a flexible magnetic material such as a heat-resistant magnetic silicone rubber material. Preferably, the bristles are embedded, glued or otherwise secured to the brush seal body such that the bristles project from the body, terminating in tips for sealing engagement with the opposing sealing component. It will be appreciated that by bending the magnetic silicone rubber of the brush seal body, the brush seal can fit a wide range of sealing dimensions and complex sealing geometry. For example, where the brush seal is to be applied between a fixed annulus and a shaft rotating within the annulus, the brush seal body may be flexed to conform to the dimensions of the two components. Additionally, by changing the brush bending pattern, the brush body can be used for either outer sealing where the bristles point radially outward, inner sealing where the bristles point radially inward, or axial sealing where the bristles point parallel to the rotor axis. This type of brush seal is particularly suitable for large sealing dimensions, such as forty inches or more. It will also be appreciated that the brush seal body can be flexed or bent into virtually any irregular shape, for example, a non-linear shape other than circular, and thus may be used for sealing between irregularly-shaped components. An example of the latter is a brush seal interposed between a transition piece and a first-stage nozzle in a gas turbine. 
     Additionally, by forming the brush seal body from a magnetic silicone rubber, the seal may be readily adhered to one of the sealing components. Preferably, the adherence is temporary until the seal body can be finally adjusted and secured in its desired position. Ancillary jigs or fixtures useful to maintain the brush seal body in position while adjustments are being made prior to final securement are entirely eliminated. A magnetic silicone rubber is preferred and comprises a composite material of ferrite magnetic powder and a silicone polymer. With those characteristics, the brush seal body can be bent, twisted or coiled and thus easily configured for installation. 
     In a preferred embodiment according to the present invention, there is provided a brush seal for sealing between first and second components movable relative to one another and having non-linear opposed sealing surfaces, comprising a brush seal body carried by the first component and having a plurality of bristles secured to the body and projecting therefrom to terminate in bristle tips for engaging the second component, the brush seal body being formed of a flexible material for conformance to the non-linear opposed sealing surfaces. 
     In a further preferred embodiment according to the present invention, there is provided a brush seal for sealing between first and second components movable relative to one another and having non-linear opposed sealing surfaces, comprising a brush seal body carried by the first component and having a plurality of bristles secured to the body and projecting therefrom to terminate in bristle tips for engaging the second component, the brush seal body being formed of a magnetic material for magnetic attachment to the non-linear opposed sealing surface of one component. 
     In a still further preferred embodiment according to the present invention, there is provided a method of forming a brush seal between first and second components movable relative to one another, comprising the steps of providing a brush seal body formed of magnetic material and having a plurality of bristles projecting therefrom terminating in tips for engagement with the second component and magnetically adhering the brush seal body to the first component. 
     In a still further preferred embodiment according to the present invention, there is provided a method of forming a brush seal between first and second components movable relative to one another, comprising the steps of providing a brush seal body formed of a flexible material and having a plurality of bristles projecting therefrom terminating in tips for engagement with the second component and flexing the brush seal body for conformance to the first component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary cross-sectional view illustrating a brush seal constructed in accordance with a preferred embodiment of the present invention installed in a high pressure packing; 
     FIG. 2 is a view similar to FIG. 1 illustrating the brush seal hereof similarly as shown in FIG. 1 in a bearing; and 
     FIG. 3 is a perspective view of the brush seal in linear form prior to bending or flexing for use in a seal. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, there is illustrated a brush seal, generally designated  10 , constructed in accordance with a preferred embodiment of the present invention. Brush seal  10  includes a brush seal body  12  and a plurality of bristles  14  forming a bristle pack  16  carried by the brush seal body  12 . In a preferred embodiment, the brush seal body  12  is comprised of a heat-resistant magnetic flexible silicone rubber material in the general shape of an elongated channel having a base  18  and opposite sides  20  and  22 . The bristle pack  16  comprises a plurality of bristles  14  disposed in the groove or channel  24  of the body  12  terminating in bristle tips  17 . Typically, the bristles are elongated, formed of metal and have diameters ranging from 0.002 to 0.01 inch, depending upon the temperature, pressure and sealing pattern in which the bristles are to be used. It will be appreciated that non-metal materials such as aramid fibers, e.g., KEVLAR®, may be utilized, particularly in view of their capacity to operate at high temperature conditions, for example, up to 425° C. 
     Because turbomachinery typically operates at high temperature, the rubber material selected for the brush seal body  12  has substantial resistance to high temperatures. Silicone rubbers, for example, have high temperature resistance, up to 325° C., and also remain flexible at very low temperatures. Preferably, a magnetic silicone rubber comprised of a ferrite magnetic powder and silicone polymer is used. With those characteristics, the brush seal body  12  and bristles  14  can be bent, twisted, coiled and easily fabricated. It will also be appreciated that the body  12  need not be formed of one piece. For example, the flexible material may comprise a pair of backing pieces joined to one another at the base  18  and to the bristles. Alternatively, the proximal ends of the bristles may be secured in or to a base piece, in turn secured to a pair of side pieces. 
     The seal  10  has many applications. For example, in FIG. 1, the seal  10  is employed in a high pressure packing in a turbine. An inner barrel  30  comprising a first stationary component is generally concentrically arranged about an aft stub shaft  32  comprising a second rotating component. A brush seal  10  is mounted adjacent the end of the barrel in annular sealing relation about the stub shaft  32 , the bristle tips  17  lying in engagement with the surface of the shaft  32 . Note the labyrinth-type seals  34  disposed annularly about the grooves  35  of the stub shaft  32  for forming a labyrinth seal in combination with the brush seal  10 . Preferably, the brush seal  10  is mounted in a groove  36  formed on the end of the barrel. The brush seal  10  is secured to the barrel  30  in the groove  36  by an overlying annular or arcuately segmented end plate  38  secured to the barrel  30 , for example, by bolts  40 . The end plate  38  has a lower tapered annular edge  42  for retaining the brush seal  10  in the groove  36 . 
     It will be appreciated that the brush seal  10  is formed in a linear extending strip. For example, the silicone rubber material may be extruded in the form of a channel with the bristles planted in the base of the channel-shaped extrusion, the bristles extending at a cant angle relative to the longitudinal dimension of the linear brush seal strip. Where a pair of discrete sides are secured to one another to form the brush seal strip, the bristles may be glued between the two sides and to the base of the strip. The bristles are typically inclined relative to the longitudinal length of the strip at a cant angle of about 40 to 50° relative to a plane passing perpendicularly through the strip. Also, the strip may be installed in discrete arcuate segments or as a unitary strip extending completely between the two components being sealed. 
     To install the strip onto the inner barrel  30  of FIG. 1, the brush seal  10  can be flexed into an annular form or into arcuate segments to conform to the arcuate dimensions of the groove  36 . Once the long dimension of the brush seal strip is determined, the strip can be cut to the appropriate length and flexed for reception in the groove  36 . The magnetic material of the brush seal  10  provides a magnetic attraction with the metal of the barrel  30 . Consequently, the brush seal can be disposed in the groove  36  and temporarily held in the groove by magnetic attraction while the end plate  38  is applied to finally secure the brush seal in the groove. It will be appreciated that the brush seal may be flexed to a wide range of different diameters or radii where arcuate segments are being used as well as into irregular shapes for other seal applications. 
     Another application of the brush seal  10  hereof is illustrated in FIG.  2 . In FIG. 2, a seal carrier  50  forming part of a bearing is illustrated with the brush seal  10  installed in a groove  52  of the carrier  50 . As in the prior embodiment, the brush seal  10  is cut to length for conformance to the arcuate dimensions of the groove  52 . The brush seal can then be flexed for location in the groove  52  with the magnetic material temporarily maintaining the brush seal in the groove. The annular or segmented end plate  54  is then secured to the seal carrier  50  to finally secure the brush seal in the groove. The brush seal, as illustrated, is used in conjunction with labyrinth teeth  55  formed on the seal carrier  50 . 
     As noted previously, by changing the brush bending pattern, a rubber brush seal can be used for outer sealing where the bristles point radially outwardly, inner sealing where the bristles point radially inwardly as in the seals illustrated in FIGS. 1 and 2, or axial seals where the bristles point parallel to the rotor axis. Thus, it will be appreciated that the sealing strip can be flexed or bent both in the plane of the bristles to form an annular seal such as illustrated in FIGS. 1 and 2, or about an axis normal thereto to provide an axial projecting brush seal. In each of the illustrated embodiments of FIGS. 1 and 2, the leakage control is provided by both the brush seal and the labyrinth seal teeth. 
     It will be appreciated from the foregoing description of the brush seal hereof that the flexible nature of the brush seal enables the brush seal to be used in most sealing applications in turbomachinery and particularly without regard to the dimensions of the sealing surfaces. That is, the brush seal can be flexed to accommodate various arcuate or irregular dimensions and cut to length, thereby providing a seal where one size, for example, as illustrated in FIG. 3, fits a substantial number of different seal applications and dimensions in the turbomachinery. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.