Fluid Flow Machine

Abstract

A fluid flow machine has a stator, a rotor which is supported so as to be rotatable relative to the stator, and a brush seal which seals a gap formed between the stator and rotor in a radial direction to prevent the passage of fluid. The brush seal has a brush holder and a plurality of sealing bristles, each of which has a first end that is fastened to the brush holder and a second end that contacts a sealing surface. The sealing surface is rotationally displaceable relative to the second ends of the respective sealing bristles. The sealing surface is formed by a circumferential surface of an intermediate sleeve which is arranged between the stator and rotor and which radially divides the gap.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a fluid flow machine with a stator, a rotor which is supported so as to be rotatable relative to the stator and a brush seal which seals the gap between the stator and the rotor in the radial direction to prevent the passage of fluid.

2. Description of the Related Art

A fluid flow machine of the type mentioned above is known, e.g., from EP 0 834 688 A1. An adjustable brush seal is known from U.S. Pat. No. 6,435,514, the entire content of which is incorporated herein by reference.

Fluid flow machines include, for example, propellers and repellers, centrifugal pumps and turbo machinery of any kind such as gas turbines, steam turbines and rotary compressors such as, e.g., radial compressors and axial compressors.

The rotor in fluid flow machines such as turbo machines can be sealed by means of labyrinth tip seals, mechanical seals or brush seals to prevent the leakage of fluid. In brush seals, sealing bristles (also known as brush wires) of the brush seal make direct contact with the rotor of the turbo machine, this rotor being constructed, e.g., as a shaft. The brush seal limits the amount of work fluid, e.g., the amount of compressor air, flowing out of a flow part of the turbo machine into a bearing periphery of the turbo machine, for example.

FIGS. 1 and 2 show a prior art fluid flow machine 1 which is constructed as a gas turbine. As can be seen from FIG. 1 and FIG. 2, the fluid flow machine 1 has a stator 10 which is constructed in this instance as a gas turbine housing, a rotor 20 which is supported so as to be rotatable relative to the stator 10 and which is constructed in this instance as a shaft, rotational bearings 30, 40 which carry out the rotatable bearing support of the rotor 20 in the stator 10, and two brush seals 50 which seal a gap S formed in radial direction RR between the stator 10 and rotor 20 to prevent the passage of fluid.

As can be seen particularly from FIG. 2, every brush seal 50 has a brush holder 51 and a plurality of sealing bristles 5, each of which has a first end which is fastened to the brush holder 51 and a second end which contacts a sealing surface D which is formed in this case by an outer circumferential surface 21 of the rotor 20, so that a sealing bristle-on-sealing surface contact zone is formed. The sealing surface D is rotationally displaceable, particularly rotatable in this case, relative to the second ends of the respective sealing bristles 52.

During operation of the fluid flow machine 1, the relative movement between the rotating rotor 20 and the brush seal 50, which is static in this case, leads to heating of the sealing surface D of the rotor 20 and sealing bristles 52 due to the friction between the sealing bristles 52 and the outer circumferential surface 21 of the rotor 20.

However, problems arise in this conventional seal in that an uneven heating of the sealing surface D is brought about in the absence of a state of true in the contact zone of the sealing surface D and sealing bristles 52. This uneven heating can exacerbate the out-of-true state and lead to a deformation of the rotor 20 (manifesting itself in this case as sagging between the rotational bearings 30 and 40 of the shaft) which impairs continued operation of the fluid flow machine 1 owing to impermissibly strong rotor vibrations.

It is an object of the invention to provide a fluid flow machine in which the sealing bristle-on-sealing surface contact zone is thermally decoupled in order to prevent a deformation in the fluid flow machine which is brought about by introduced heat and which impairs the operation of the fluid flow machine.

SUMMARY OF THE INVENTION

According to the present invention, a fluid flow machine has a stator, a rotor which is supported so as to be rotatable relative to the stator, and a brush seal which seals a gap formed between the stator and rotor in a radial direction of the rotor to prevent the passage of fluid. The brush seal has a brush holder and a plurality of sealing bristles, each of which has a first end that is fastened to the brush holder and a second end that contacts a sealing surface so that a sealing bristle-on-sealing surface contact zone is formed. The sealing surface is rotationally displaceable relative to the second ends of the respective sealing bristles.

The fluid flow machine according to the present invention is characterized in that the sealing surface is formed by a circumferential surface of an intermediate sleeve or intermediate bushing which is arranged between the stator and rotor and which radially divides the gap.

By moving the sealing surface to an intermediate sleeve, the sealing bristle-on-sealing surface contact zone is thermally decoupled so as to prevent a deformation in the fluid flow machine which is brought about by introduced heat and which impairs the operation of the fluid flow machine.

According to the present invention, the intermediate sleeve is fastened either to a rotating part or to a stationary part of the brush seal. This fastening is advantageously carried out in such a way that, on the one hand, sufficient stability is achieved and, on the other hand, a heat transfer between the intermediate sleeve and the part to which the intermediate sleeve is fastened is as small as possible. The small heat transfer can be achieved, e.g., by means of the smallest possible contact surfaces and/or by providing an insulating layer between the contact surfaces of the intermediate sleeve and the part fastening the latter.

According to the present invention, the brush holder can be arranged at the stator and the intermediate sleeve can be arranged at the rotor so as to rotate along with the latter. In this case, the circumferential surface of the intermediate sleeve forming the sealing surface would be an outer circumferential surface. However, it is also possible according to the invention that the brush holder is arranged at the rotor and the intermediate sleeve is arranged in a stationary manner at the stator so that the circumferential surface of the intermediate sleeve forming the sealing surface would be an inner circumferential surface in this case. The respective solution can be determined depending on the desired operating characteristics and design factors.

Further, according to the present invention, the rotor can be formed, e.g., by a shaft rotating in a stator (e.g., in a housing) and, e.g., by a housing rotating around a stator (e.g., around an axle). The respective solution can be determined depending on the desired operating characteristics and the design factors.

According to an embodiment of the invention, the intermediate sleeve divides the gap radially into a first gap portion adjoining the sealing surface and a second gap portion adjoining a circumferential surface of the intermediate sleeve remote of the sealing surface, wherein a radial extension of the second gap portion is greater than zero.

In other words, there is an air gap between the intermediate sleeve and the part (e.g., the rotor or the stator) fastening this intermediate sleeve. This air gap advantageously ensures additional thermal insulation between the intermediate sleeve and the part fastening the same. This makes it even more difficult for heat to transfer from the sealing surface and the part fastening the intermediate sleeve so that a deformation of the part fastening the intermediate sleeve that is brought about by introduced heat is prevented in an even more reliable manner.

According to another embodiment of the invention, the intermediate sleeve has a flange by means of which the intermediate sleeve is mounted at a flange mounting portion of the stator or rotor so as to be fixed with respect to rotation relative to it.

This construction of the invention is advantageous particularly with respect to ensuring the smallest possible contact surfaces between the intermediate sleeve and the part (in this case, particularly the stator or the rotor) fastening this intermediate sleeve, while at the same time ensuring that the fastening is sufficiently stable.

According to yet another embodiment of the present invention, the flange is mounted at the flange mounting portion by detachable fastening means. Such fastening means can be, for example, screw connections, rivet connections, clamping connections, etc. In particular, the detachable connection facilitates the changing of worn intermediate sleeves, for example.

Further, the flange connection makes it possible to introduce a thermal insulation layer between the flange and the flange mounting portion in a simple manner.

According to another embodiment of the invention, the flange is arranged at an axial end of the intermediate sleeve so that the flange has, at the axial end, an annular flange surface which contacts a mounting surface of the flange mounting portion so as to be tight against fluid.

This construction of the invention reliably ensures a seal between the intermediate sleeve and the part fastening this intermediate sleeve to prevent the passage of fluid.

According to another embodiment of the invention, the rotor is formed by a shaft and the intermediate sleeve is mounted on the rotor so as to be fixed with respect to rotation relative to it so that the sealing surface is formed by an outer circumferential surface of the intermediate sleeve, wherein the brush holder is arranged at the stator so as to be fixed with respect to rotation relative to it.

An embodiment of the invention of the kind mentioned above can be produced in a particularly simple and dependably operating manner.

According to yet another embodiment of the invention, an inner diameter of the intermediate sleeve is greater than an outer diameter of the shaft so that an annular gap is formed between an inner circumferential surface of the intermediate sleeve and an outer circumferential surface of the shaft.

This construction of the invention achieves a thermally insulating air gap between the intermediate sleeve and the part fastening this intermediate sleeve in a simple and robust manner, this part being formed in this case by the rotor which is constructed as a shaft.

According to embodiment forms of the present invention, the fluid flow machine is a turbo machine, particularly a gas turbine or a turbo compressor.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following with reference to preferred embodiments and the accompanying drawings in which:

FIG. 1 is a schematic sectional view of the basic construction of a fluid flow machine constructed as a gas turbine according to the prior art;

FIG. 2 is an enlarged section A from FIG. 1 showing a brush seal of a fluid flow machine according to the prior art; and

FIG. 3 an enlarged section A′ from FIG. 1 showing a brush seal of a fluid flow machine according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

As is shown in FIGS. 1 and 3, a fluid flow machine 1 which is constructed in this instance as a gas turbine has a stator 10 which is constructed in this instance as a gas turbine housing, a rotor 20 which is constructed in this instance as a shaft which is mounted so as to be rotatable relative to the stator 10, two rotational bearings 30, 40 which form the rotatable bearing support of the rotor 20 in the stator 10, and two brush seals 50′ which seal a gap S which is formed in a radial direction RR between the stator 10 and rotor 20 so as to be prevent the passage of fluid.

As can be seen particularly from FIG. 3, every brush seal 50′ has a brush holder 51 and a plurality of sealing bristles 52 each of which has a first end fastened to the brush holder 51 and a second end contacting a sealing surface D′ so as to form a sealing bristle-on-sealing surface contact zone, the sealing surface D′ being displaceable with respect to rotation, particularly rotatable in this instance, relative to the second ends of the respective sealing bristles 52.

As can be seen from FIG. 3, the sealing surface D′ is formed by an outer circumferential surface 61 of an intermediate sleeve 60 which is arranged between the stator 10 and rotor 20 and which is mounted on the rotor 20 so as to be fixed with respect to rotation relative to it and so as to divide the gap S radially. The brush holder 51 is arranged at the stator 10 so as to be fixed with respect to rotation relative to it.

The intermediate sleeve 60 divides the gap S radially into a first gap portion adjoining the sealing surface D′ and a second gap portion adjoining an inner circumferential surface D″ of the intermediate sleeve 60 remote of the sealing surface D′. A radial extension of the second gap portion is greater than zero.

This means that an inner diameter of the intermediate sleeve 60 is greater than an outer diameter of the rotor (shaft) 20 so that an annular gap LS is formed between the inner circumferential surface of the intermediate sleeve 60 and an outer circumferential surface 21 of the rotor 20.

In other words, an air gap (annular gap) LS is provided between the intermediate sleeve 60 and the rotor 20 fastening the latter, which air gap advantageously ensures a thermal insulation between the intermediate sleeve 60 and the rotor 20. This makes it more difficult for heat to be transferred from the sealing surface D′ to the rotor 20, which prevents a deformation of the rotor 20 fastening the intermediate sleeve 60 due to introduced heat.

Further, as can be seen from FIG. 3, the intermediate sleeve 60 has a flange 62 by means of which the intermediate sleeve 60 is mounted at the flange mounting portion 22 of the rotor 20 so as to be fixed with respect to rotation relative to it. The flange 62 is arranged at an axial end of the intermediate sleeve 60 so that the flange 62 has, at the axial end, an annular flange surface 62′ which contacts a recessed mounting surface (not designated separately) of the flange mounting portion 22 in a fluid-tight manner. Although not shown in FIG. 3, a flat seal can be provided for achieving the fluid tightness and a thermal insulation between the annular flange surface of the flange 62 and the recessed mounting surface of the flange mounting portion 22.

As is shown in FIG. 3, the flange 62 is mounted at the flange mounting portion 22 of the rotor 20 by detachable fastening means which are realized in this instance in the form of a screw connection.

In conclusion, the rotor 20 which is constructed in this instance as a shaft is provided with an intermediate sleeve or intermediate bushing 60 according to an embodiment of the invention. The intermediate sleeve 60 is connected to the rotor 20 by means of an axial flange 62 and detachable fastening means. There is an annular gap LS between the intermediate sleeve 60 and the rotor 20. The sealing bristles or brush wires 52 of the brush seal 50′ contact the sealing surface D′ formed by the outer circumferential surface 61 of the intermediate sleeve 60.

Accordingly, in the event of an out-of-true state of the intermediate sleeve 60, an uneven deformation of the intermediate sleeve 60 may only aggravate the out-of-true state of the intermediate sleeve 60 because the rotor 20 is only connected to the intermediate sleeve 60 by the connection of its flange mounting portion 22 to the flange 62 so that a direct heating of the rotor 20 caused by heat entering the area of the brush seal 50′ is prevented.

The solution according to the invention can be applied wherever a fluid flow machine, e.g., a gas turbine, is to be sealed with brush seals. The invention can be applied, e.g., in disk rotor units, full rotor units and welded rotor units.

The solution according to the invention can be used to seal a bearing periphery of a fluid flow machine and to seal between individual stages of the fluid flow machine, e.g., compressor stages or turbine stages.

Apart from the flange connection described above, fastening of the intermediate sleeve to the part which fastens or holds it can also be carried out by means of shrinking or welding or by means of other fastening elements.

The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.

Claims

1. A fluid flow machine comprising a stator (10),a rotor (20) supported so as to be rotatable relative to the stator (10), said stator and rotor defining a gap (S) therebetween in a radial direction (RR);a brush seal (50′) for sealing said gap (S) between said stator and said rotor to prevent a leakage of fluid, said the brush seal comprising a brush holder (51) and a plurality of sealing bristles (52);a sealing surface (D′) in contact with said sealing bristles; each sealing bristle having a first end fastened to said brush holder (51) and a second end contacting said sealing surface (D′);said sealing surface (D′) being rotationally displaceable relative to said second ends of said respective sealing bristles (52); said sealing surface (D′) being formed by a circumferential surface of an intermediate sleeve arranged between said stator (10) and said rotor (20) for radially dividing said gap (S).

2. The fluid flow machine according to claim 1, wherein said intermediate sleeve (60) divides said gap (S) radially into a first gap portion adjoining said sealing surface (D′) and a second gap portion adjoining a circumferential surface of said intermediate sleeve (60) remote of said sealing surface (D′), and wherein a radial extension of said second gap portion is greater than zero.

3. The fluid flow machine according to claim 1, additionally comprising a flange mounting portion (62) at one of said stator and said rotor and wherein said intermediate sleeve (60) comprises a flange (62) for mounting said sleeve (60) at said flange mounting portion (22) of one of said stator (10) and said rotor (20) so as to be fixed with respect to rotation relative thereto.

4. The fluid flow machine according to claim 3, wherein said flange (62) is detachably mounted at said flange mounting portion (22).

5. The fluid flow machine according to claim 3, wherein said flange (62) comprises an annular flange surface at an axial end thereof and said flange mounting portion (22) comprises a mounting surface; and wherein said flange (62) is arranged at an axial end of said intermediate sleeve (60) so that said annular flange surface is contacting said mounting surface of said flange mounting portion (22) so as to be tight against fluid.

6. The fluid flow machine according to claim 1, wherein said intermediate sleeve (60) comprises an outer circumferential surface (61) and wherein said rotor (20) is formed by a shaft, and said intermediate sleeve (60) is mounted on said rotor (20) so as to be fixed with respect to rotation relative thereto so that said sealing surface (D′) is formed by an outer circumferential surface (61) of said intermediate sleeve (60), and wherein said brush holder (51) is arranged at said stator (10) so as to be fixed with respect to rotation relative thereto.

7. The fluid flow machine according to claim 6, wherein said intermediate sleeve (60) comprises an inner diameter and an inner circumferential surface; and said shaft comprises an outer diameter and an outer circumferential surface (21) and wherein said inner diameter of said intermediate sleeve (60) is greater than said outer diameter of said shaft so that an annular gap is formed between said inner circumferential surface of said intermediate sleeve (60) and said outer circumferential surface (21) of said shaft.

8. The fluid flow machine according to claim 1, wherein said fluid flow machine is a turbo machine.

9. The fluid flow machine according to claim 8, wherein said turbo machine is one of a gas turbine and a turbo compressor.