EP1717419A1 - Method and device for adjustement of a radial clearance in an axial turbomachine and compressor - Google Patents

Abstract

Coolant (51) such as air or water is circulated into a guide ring (21), facing the rubbing edge (35) of a rotor blade (15), prior to starting the axial flow fluid machine. The coolant circulation is halted once the machine is started, during which steam or hot air is circulated into the guide ring. Independent claims are included for the following: (1) a compressor; and (2) a device for adjusting radial clearance in an axial flow fluid machine.

Description

The invention relates to a method for adjusting a radial gap formed between a squealer edge of a blade profile and an opposing guide surface of an axial flow-through turbomachine, wherein a guide ring forming the guide surface is acted upon by a coolant. Furthermore, the invention relates to a compressor.

For this purpose is from the published patent application DE 199 38 274 A1 a method and apparatus for targeted radial gap adjustment between stator and rotor assemblies of a gas turbine known. The design-related radial gaps are formed between the rotatable blades of the rotor of the turbomachine and the non-rotatably on the stator opposite guide surfaces. The guide surfaces serve to guide the working medium and are formed by circumferentially divided ring segments, which extend coaxially as a guide ring about the axis of rotation of the rotor in the axial direction. During operation of the gas turbine, the blades of the rotor move at a distance from the guide surfaces. Conversely, freestanding guide vanes may also form a radial gap with respect to a rotating conical or cylindrical guide surface arranged on the rotor. In order to further optimize the efficiency of the gas turbine, the radial gaps are to be made as small as possible. It is known from the aforementioned Offenlegungsschrift to fasten guide rings to a stator by obliquely arranged holding partners to the radial direction and to displace them during operation of the gas turbine due to the thermal material expansion of the guide ring in the direction of the blade ends towards the reduction of the radial gap.

The similar discloses the EP 1 163 430 B1 , A guide member opposite a tip of a turbine blade deflects in the direction of the blade tip during operation of the gas turbine due to the thermal expansions, decreasing the radial gap. At the same time, the guide element can be acted upon from the back with cooling air so that it can withstand the temperatures prevailing in the flow channel.

Moreover, it is off GB 2 397 102 A known to isolate the guide ring of a turbine relative to the support structure.

It is also known that the gap dimension determining design parameters for the warm start of a gas turbine are designed to be as small as possible operating gap, i. Radial gap to meet. After the shutdown of the gas turbine, the housing cools comparatively quickly with respect to the rotor of the gas turbine. The housing or the guide rings shrink due to their cooling back to their original design size, the initially warm rotor remains initially extended due to the heat stored in it and retarded cools and shrinks. The result is the so-called constricting effect. This situation can cause the radial gap to decrease and the blades of the rotor to touch or even streak the housing or guide ring, which can permanently increase the radial gap or even damage blades. An increased radial gap leads to increased fuel consumption, damaged blades may require early maintenance with corresponding additional costs.

During start-up, ie start-up of the gas turbine, the centrifugal forces acting on the blades bring about a further elongation of these, which close the radial gap still present before the start of the gas turbine and can cause the harmful and undesired brushing of the blades.

Object of the present invention is to provide a method of the type mentioned, which improves the warm start behavior of the turbomachine to increase the availability and at the same time to increase the efficiency. In addition, it is an object of the invention to provide a compressor.

The object of the method is solved by the features of claim 1 and the object directed to the compressor by the features of claim 7.

The solution suggests that coolant is applied to the guide ring before starting the turbomachine. The invention is based on the recognition that the hot start conditions of the turbomachine are improved by influencing the radial gap by the gap size of the radial gaps is increased by the proposed method in a still warm or heated, but not in operation turbomachine, compared with the Gap of the radial gap of a gas turbine known from the prior art in the identical state. The hammer-shaped in cross-section guide ring is formed over the circumference by adjacent ring segments. Since the guide ring facing the blades (or vanes) is radially further outward (or inboard), its application of coolant will result in a displacement of the guide surfaces directed away from the opposite squealer edges of the vanes. The increase of the radial gap achieved in this way results in a reduction of the described constricting effect and the risk of being scuffed, which significantly improves the warm start behavior of the turbomachine, ie the turbomachine could be started earlier, relative to its previous departure time.

In addition, the radial gaps no longer need to be dimensioned after the warm start as unfavorable start of operation.

The cooling of the warm guide rings increases the radial gap of the non-operating turbomachine. The radial gap increase obtained for this condition can also be partially utilized, rather than improving the warm start, to reduce the radial gaps of one in an idle and cold condition, i. a smaller lying at ambient temperature fluid flow machine, based on a known from the prior art turbomachine.

This has an advantageous effect on the operation, in particular on the stationary operation of the turbomachine, in particular in a compressor and in a turbine unit. In this operating state, the inventive method is no longer used, so that the radial gaps shrink again. The reduction of the design-related radial gaps reduce efficiency-enhancing losses in the working fluid during operation, caused by the unused leakage flow through the radial gap away, especially at higher pressure ratios of the working fluid in the flow channel.

Advantageous embodiments are specified in the dependent claims.

After the (warm) start of the turbomachine, both the rotor and the housing of the continuous-duty turbomachine warm up to a maximum operating temperature. Both housing and rotor expand, so that the risk of constriction no longer exists. Accordingly, the method is particularly advantageous if the admission of the guide ring with coolant is set during the start of the turbomachine. After reaching the maximum operating temperature, the temperature-induced strains of the turbomachine, ie the stator and the Rotor, completed. Consequently, the guide ring also heats up so that it expands and shifts its guide surface in the direction of the scrape edges of the blades, which leads to an efficiency-increasing reduction of the radial gaps. In particular, when the turbomachine is designed as a compressor of a gas turbine, in which the guide rings are usually uncooled during operation, this can be used advantageously.

It is particularly advantageous if the coolant is taken from an external coolant source. In the case of a turbomachine designed as a turbomachine, coolant in the form of cooling air is usually taken from the compressor. Since the method is used before the start of the gas turbine, this is not possible. Thus, an external coolant source, such as a separately driven auxiliary compressor or external fan, must be used to provide the coolant for cooling the guide rings prior to the warm start of the gas turbine.

Preferred dimensions can be acted upon by the start of the turbomachine of the guide ring with a heating medium. This is particularly advantageous when the turbomachine is, for example, a compressor or a turbine of a gas turbine and the methods known from the prior art, in which material expansions of the guide ring are used for adjusting the radial gap, is applied to the guide ring of a compressor. Preferably, air or steam can be used as the heating means. By heating the guide ring whose guide surface grows against the squealer edge of the blades and thus reduces the radial gap enclosed by them.

The invention will be explained with reference to a drawing.

FIG 1

einen Längsteilschnitt durch eine als Gasturbine ausgebildete Strömungsmaschine mit einem Verdichter und einer Turbineneinheit und

FIG 2

das Detail X der FIG 1, ein Führungsring im Querschnitt mit einer gegenüberliegenden Schaufelspitze.

It shows:

FIG. 1

a partial longitudinal section through a gas turbine designed as turbomachine with a compressor and a turbine unit and

FIG. 2

the detail X of FIG 1, a guide ring in cross-section with an opposite blade tip.

FIG. 1 shows, by way of example for a turbomachine, a gas turbine 1 in a longitudinal partial section. It has inside a rotatably mounted about a rotation axis 2 rotor 3, which is also referred to as a turbine runner. Along the rotor 3 follow one another a suction housing 4, a compressor 5, a toroidal annular combustion chamber 6 with a plurality of coaxially arranged burners 7, a turbine unit 8 and the exhaust housing 9. The annular combustion chamber 6 forms a combustion chamber 17 which communicates with an annular flow channel 18. There four successive turbine stages 10 form the turbine unit 8. Each turbine stage 10 and each compressor stage is formed of two blade rings.

In the turbine unit 8 seen in the flow direction of a hot gas 11, follows in the flow channel 18 of a row of vanes 13 formed by a blade 15 row 14. The vanes 12 are attached to the stator, whereas the blades 15 of a row 14 are mounted by a turbine disk on the rotor 3 , On the rotor 3, a generator or a working machine is coupled (not shown).

In contrast, in compressor 5, a compressor stage is formed by a blade row 13 with a ring of guide blade 12 following in the flow direction of the air to be compressed.

The blade 15 is radially outside a guide ring 21 and the guide vane 12 radially inward of a guide ring 23 against. The guide rings 21, 23 delimit the flow channel 18 extending in the axial direction of the rotor 3 in the radial direction. The guide rings 21, 23 may be formed from over the circumference adjacent ring segments.

After the start of the gas turbine 1 and through the working medium flowing in the flow channel 18, all components of the gas turbine 1 heat up. Due to the temperature rise, these components, including the rotor 3, the rotor blade 15, the guide vanes 12 and the inner housing 27 extend from their cold state.

If the gas turbine 1 is completely heated and has set a no-changing temperature distribution, all temperature-induced strains are completed. The gas turbine 1 is then in a stationary state.

FIG. 2 shows the detail II from FIG. 1, a cross-section through a guide ring 21 with an opposite blade, after all temperature-induced strains have been completed. In this case, the device shown in FIG. 2 can be provided both in the turbine unit 8 and / or in the compressor 5 of the gas turbine 1.

The blades each have a blade profile 19, which is drop-shaped in cross-section, and has a front edge 20, which can be flowed on by a working medium, and a rear edge 22.

A cylindrical or conically extending to the axis of rotation 2 of the gas turbine rotor 3 wall 25 forms part of a rotationally fixed inner housing 27. The wall 25 encloses the annular flow channel 18. In the inner housing 27 and in the Wall 25 is a running in the circumferential direction and in cross-section hammer-shaped groove 29 incorporated, in which the guide ring 21 is arranged. Thus, the guide ring 21 surrounds the flow channel 18 coaxial with the axis of rotation 2 of the rotor. 3

Between the wall 25 and the guide ring 21, an insulating layer 26 may be formed, which shields the guide ring 21 thermally against the wall 25 and insulated so that the wall 25 and the inner housing 27 does not shrink also in the direction of the blade.

The guide ring 21 is made of a material which under the action of heat, i. a temperature increase, expands, preferably expands more than the wall 25 and the inner housing 27, i. the guide ring 21 has a greater coefficient of thermal expansion than the wall 25 and the inner housing 27th

The guide ring 21 is formed substantially corresponding to the hammer-shaped groove 29 and is directly on the back, or as shown, on the insulating layer 26 on the groove bottom of the groove 29 and the front to a contact surface 50 of the undercut 31, so that the guide ring 21 is fixed. The contact surface 50 determines the radial position of the guide ring 21 and is radially further out (or inside) arranged as the tips of the blades 15 (and vanes 12) opposite guide surface 33rd

The flow channel 18 facing the guide surface 33 of the guide ring 21 is the blade 15, in particular their squeal edge 35 opposite. Between the squeal edge 35 of each blade 15 and the guide surface 33, a radial gap 36 is formed. During operation of the gas turbine, the blade rotates 15 under the surface 33 away, this is to illustrate the axis of rotation 2 - not true to scale - indicated.

On the back surface 37 of the guide ring 21 with respect to the guide surface 33, there is incorporated a groove 39 provided with the wall 25 or, if present, the insulating layer 26 extending in the circumferential direction, i. form annular supply channel 41.

Furthermore, in the circumferential direction, i. coaxial with the axis of rotation 2, a plurality, preferably three, cooling channels 43, which communicate with the supply channel 41 via radial connection channels 45.

From the flow channel 18 facing away from side 47 of the wall 25 extends through this a supply channel 49, which opens into the supply channel 41.

After switching off the gas turbine 1, the housing cools faster than the rotor 3, so that the expansions of the housing decrease faster or go back and constrict the still warm and thus more extended rotor 3. This reduces the gap of the radial gap 36.

In the case of an early start of the still warm gas turbine 1, i. During the warm start, the forces acting on the rotor 3 and the blades 15 and centrifugal forces cause an additional radial growth, which can reduce the radial gap 36 such that the squashing edges 35 can rub against the guide surface 33 defective.

This is where the invention starts. Before restarting the operation of the still-warm gas turbine coolant 51 is supplied through the supply channel 49 to the supply channel 41, which passes from there via the connection channels 45 in the cooling channels 43 and the guide ring 21 cools. The coolant 51 absorbs the heat still stored in the guide ring 21 and is then blown through openings, not shown, either in the flow channel 18 or returned to the outside via the return channels also not shown from the inside of the machine. By removing the heat, in particular close to the guide surface, from the guide ring 21, the temperature-induced material expansions of the guide ring 21 go back. In conjunction with its local location defined radially outside in the groove 29, the guide surface 33 delimiting the flow channel 16 shifts radially outward into the position 33 '. As a result, the radial gap 36 increases by the distance X to 36 ', thereby reducing the risk of rubbing the blades 15 on the guide surface 33 or 33' in the case of warm start. This effect can be used to reduce the time between shutdown and warm start of the gas turbine.

The method is particularly effective when the guide ring 21 is insulated from the wall 25. In this embodiment, only the guide ring 21 is cooled, and not beyond the wall 25. This leads to a particularly efficient cooling of the guide ring 21 and prevents the wall 25 also moves along the same way. This ensures that only the guide ring 21 takes back its heat-related strains.

After or during the start, ie during the starting process of the gas turbine 1, the housing heats up and expands. The housing and the inner housing 27 move radially outward. The risk of rubbing the blades 15 with their squeal edge 35 on the guide surface 33 of the guide rings 21 is reduced, so that after a predetermined period of operation, the cooling of the guide rings 21 can be adjusted.

At the same time, the gas turbine 1 continues to heat up until a temperature distribution that is no longer changing has set in it.

If the material of the guide ring 21 allows a further increase in temperature, even in place of the coolant 51 during operation of the gas turbine 1, a heating medium through the channels 49, 41, 45 are passed. A further increase in temperature of the guide ring 21 causes an additional expansion in the radial direction, with which the radial gap 36 is further reduced. This leads to an increase in efficiency, since less working fluid - in the compressor 5, the gas to be compressed and in the turbine unit 8, the expanding hot gas 11 - can escape unused by the reduced radial gap 36.

The radial gap 36 may not only be formed between a radially outer guide surface 33 and a blade 15, but it may also be between the non-rotating guide vane 12 and arranged on the rotor 3 guide surface 23. Accordingly, wall 25 would be part of the rotor 3, so that the guide ring 23 is opposite a guide vane 12. In this case, the directions of displacement also change from outside to inside.

The inventive method for changing the radial gaps 36 is particularly suitable for compressor 5. However, it can also be used in the turbine unit 8.

Claims (11)

Method for changing a radial gap (36) formed between a squealer edge (35) of a blade and an opposing guide surface (33) of an axial flow-through turbomachine,
in which a guide ring (21, 23) forming the guide surface (33) can be acted upon with a coolant (51),
characterized in that
before the start of the turbomachine, the guide ring (21, 23) with coolant (51) is acted upon. Method according to claim 1,
in which during the start of the gas turbine, the admission of the guide ring (21, 23) with coolant (51) is adjusted. Method according to claim 1 or 2,
in which the coolant (51) is taken from an external coolant source. Method according to one of the preceding claims,
in which air or water is used as the coolant (51). Method according to claim 2,
in which after the start of the turbomachine the guide ring (21, 23) is acted upon by a heating medium. Method according to claim 5,
in which air or steam is used as the heating medium. Compressor (5) with a device for changing a radial gap (36) of the axially flow-through compressor (5) between a squealer edge (35) of a blade and a guide surface (33) opposite thereto,
in which a guide ring (21, 23) forming the guide surface (33) is fastened to a support structure,
characterized in that
the guide ring (21, 23) with a coolant (51) can be acted upon. Device according to claim 7,
in which the guide ring (21, 23) is thermally insulated from the support structure. Device according to claim 7 or 8,
in which the guide ring (21, 23) has a larger thermal expansion coefficient than the support structure. Apparatus according to claim 7, 8 or 9,
wherein the support structure has a contact surface (50) on which a guide ring (21, 23) rests and
the abutment surface (50) is arranged radially further outward (or inside) than the guide surface (33) opposite the abutting edges (35) of the moving blades (15) (or guide vanes (12)). Apparatus for carrying out the method according to one of claims 1 to 6.

Images