EP2474744A1 - Annular flow channel for an axial compressor - Google Patents

Abstract

The blades (36,44) fixed to two consecutive rings (32,42) are arranged on outer boundary wall (22) of flow channel. The inner ring (40) is held by blades (36) of one ring, such that blades (44) of other ring (42) are arranged opposite to each other under a radial gap formation between inner ring and blades. An independent claim is included for axial flow compressor.

Description

The invention relates to an annular flow channel for an axial compressor, in which attached to an outer boundary wall of the flow channel airfoils are arranged in a radiating manner in at least two immediately consecutive wreaths.

Axial compressors and gas turbines with axial compressors are known from the extensive state of the art in a variety of ways. For example, the shows EP 2 194 234 A1 an axial compressor of a gas turbine whose flow passage merges into a compressor outlet diffuser. Like any compressor stage, the last stage of the compressor, viewed in the direction of flow of the compressed air, includes a ring of blades followed by a ring of vanes downstream. According to the EP 2 194 234 A1 Following the vane ring of the last compressor stage another ring of blades, which are attached as well as the vanes to the radially outer boundary wall of the flow channel. The other wreath of blades is called Nachleitrad. The Nachleitschaufeln the stationary Nachleitrads have the task of exempting the air flow leaving the compressor as far as possible from swirl. Through the Entdrallung the air flow, this can build up the static pressure comparatively low loss in the compressor outlet diffuser. Although the Nachleitrad contributes no contribution to the compression of the air sucked by the axial compressor, this structurally belongs to the axial compressor.

Both the vanes of the last compressor stage and the Nachleitschaufeln the Nachleitrades are formed in accordance with the known axial compressor with freestanding blades, the free-ending inner peaks of a heat insulating ring each radial gap forming opposite.

The heat insulation ring is part of a rotationally fixed shaft cover of the compressor rotor, which also forms the inner boundary of the compressor outlet diffuser at the same time. The concentric to the central axis shaft cover is formed thin-walled because of the rather minor mechanical stress and connected to the diffuser exit side via struts not shown with the housing of the gas turbine.

The housing of the axial compressor, however, is relatively solid designed to withstand the pressure and temperature stresses during operation can. Furthermore, the housing is made relatively stiff. Thus, the load application to the housing during operation of the gas turbine leads only to small deformations. Characterized in that the shaft cover is formed with smaller wall thicknesses compared to the housing and typically has different material properties than the housing, the shaft cover heats up faster than the housing with the guide blade rows and Nachleitreihen attached thereto. This has the consequence that when starting and when the gas turbine shaft cover and the housing have a different thermal expansion rate, so that when starting and stopping the gas turbine, the size of the radial column changes, the radial gap when starting temporarily smaller and temporarily larger when starting be or are. So that during the operation of the gas turbine, the tips of the blades do not abut against the shaft cover and damage it, the radial gap is provided with such a dimensioned minimum height that in each operating state of the gas turbine, the blade tips touch the shaft cover almost never.

With the help of the heat insulating ring, the heat input from the compressed warm air is delayed in the shaft cover itself, which is equivalent to an adjustment of the temperature-induced thermal expansion rate of the shaft cover to the outer housing.

However, it has been found that this measure requires a comparatively complex attachment of the heat insulation ring to the shaft cover and a targeted coordination of the thermal behavior is still comparatively difficult.

The object of the invention is therefore to provide an annular flow channel for an axial compressor, which on the one hand bring about a particularly efficient and low-loss Entdrallung the last compressor stage leaving air flow and on the other hand has a comparatively simple construction in which the different rapidly expanding components in operation neither wear to be damaged.

The solution of the aforementioned object provides an annular flow channel, which corresponds to the features of claim 1. Advantageous embodiments are specified in the subclaims 2 to 8.

According to the invention it is provided that the annular flow channel is surrounded by an outer boundary wall on which in at least two successive wreaths blades are arranged radiating, wherein the blades of one of the two rings are connected with its radially inner end with a radially inner end bounding the flow channel inner ring , Wherein this has a radial extent such that the blades of the other of the two rings each with radial gap formation opposite this.

The invention has recognized that the radially inner boundary wall of the flow channel in the axial section of the last compressor stage and the Nachleitreihe should not be part of the shaft cover if possible, since the thermal coordination of the components is very difficult. Consequently, it is proposed to shorten the shaft cover, so that these only the inner boundary wall of the to the axial compressor then connecting the compressor outlet diffuser. For this reason, the inner boundary wall of the axial compressor in the region of the vane ring of the last compressor stage and the Nachleitrades must be supported by a different structure. For this purpose, it is provided that in this axial portion of the flow channel inside limiting flow wall is formed by an inner ring which is supported or supported by the housing via the blades. However, according to the invention, this concept of the inner ring supported by blades is only intended for a row of blades and not for both rings. The airfoils of the other wreath may remain free-standing when the inner ring comprises an extension which extends into the axial portion of the other wreath.

It is thus proposed a mixing concept: one of the two rings - preferably the vane ring of the last compressor stage - includes blades which are coupled on the head side via the inner ring and carry this and the other of the two wreaths - preferably the Nachleitschaufelkranz - is provided with freestanding blades. To realize this and to ensure a continuous shielding of the rotor, then the inner ring must have such an axial extent that this is also located in the axial portion of the free-ending blades.

This design has several advantages: on the one hand, it can also be used for existing axial compressors, without the housing of the axial compressor, in which the vanes of the last compressor stage and the guide vanes are fixed radially outward - foot side - must be changed. It is then only a modification of the previously used shaft cover required. Consequently, the design of the vanes of the last compressor stage alone has to be changed in order to retrofit existing machines to such constructions. Compared to a design where both the vanes and the guide vanes Head side are coupled together via a common inner ring, the invention has the advantage that it is relatively easy to manufacture. This is especially true when the Nachleitrad is formed in principle of two mutually axially overlapping rows of blades, which can also be referred to as two overlapping Nachleiträder. Such components are relatively complex to produce, if they are even produced in a milling process.

Due to the fact that the suspension of the inner ring takes place in almost the same axial section as the foot-side attachment of the guide vanes, the thermal behavior of the inner boundary wall of the flow channel (inner ring) and the Nachleitschaufel is much better matched to each other than in the prior art. This improved tunability allows for smaller radial gaps between the vanes of the idler vanes and the inner ring, which significantly reduces flow losses and also provides better unwinding of the airflow as it enters the compressor exit diffuser. Furthermore, wear between the inner ring and the free-standing airfoils can be reduced since the thermal behavior is far more predictable. Another advantage is that the isolation ring of the prior art can be omitted.

According to a first advantageous embodiment of the invention, the ring of blade blades connected to the inner ring is arranged upstream of the other ring, relative to the flow direction of the flow channel. Alternatively, the inside of the flow channel limiting inner ring may also be attached to the guide vanes. In this case, the guide vanes of the last compressor stage as freestanding blades can face this radial gap forming. However, since the vanes of the last compressor stage contribute to increasing the compressor pressure ratio, it is desirable to use them rather than bonded vanes equipped with an inner shroud - the inner ring - to avoid gap losses.

According to a further advantageous embodiment of the invention closes - viewed in the axial direction - the shaft cover to the inner ring, between which two components preferably a sealing means is arranged to prevent leakage flow from the flow channel in a remote space therefrom.

In order to be able to use the invention in particular in axial compressors and stationary gas turbines, it is provided that the outer boundary wall of the flow channel, an inner boundary wall of the flow channel and the inner ring each comprise at least two ring segments. Thus, the axial compressor is in total in a so-called. Dividing plane in which the machine axis is divided in half. Accordingly, both the inner ring and the outer boundary wall of the axial compressor need not be formed from one element. On the one hand, this simplifies the manufacture of the components and, on the other hand, the assembly of the axial compressor.

FIG 1

einen Längsschnitt durch einen ringförmigen Strömungskanal eines Axialverdichters im Bereich des Verdichterausgangs und

FIG 2

eine teilperspektivische Schnittansicht eines Kranzes mit Schaufelblättern und einem daran befestigten Innenring mit einer axialen Verlängerung.

Further features, advantages and features of the invention are explained in more detail in the following drawing. Show it:

FIG. 1

a longitudinal section through an annular flow channel of an axial compressor in the region of the compressor outlet and

FIG. 2

a partial perspective sectional view of a rim with blades and an attached inner ring with an axial extension.

FIG. 1 shows in a longitudinal section the outlet region 10 of an axial compressor 12 of a gas turbine 14. The axial compressor 12 comprises an annular flow channel 16, which in the illustrated embodiment, from left to right can be flowed through. The flow channel 16 is on the output side in a diffuser 18 via.

The axial compressor 12 comprises a housing 20, which simultaneously represents the outer boundary wall 22 for the flow channel 16 and for the diffuser 18. Both the flow channel 16 and the diffuser 18 are formed as annular channels, which extend concentrically around the machine axis 19. The axial compressor 12 further comprises a rotor 24, which may be designed, for example, in disc design. Part of a rotor disk is in FIG. 1 provided with the reference numeral 26. At the outer surface of blades 28 are hooked in a known manner with the aid of hammer-shaped feet 30.

Downstream of the blades 28, there is provided a rim 32 which includes a plurality of vanes 34 radiantly attached to the boundary wall 22. Each of these guide vanes 34 has an airfoil 36, which is located in the flow channel 16. At the inner end 38 of the airfoils 36, an inner ring 40 is arranged, which is supported by the vanes 34 and supported. Downstream of the vane ring 32, a further ring 42 is provided with a plurality of airfoils 44. The blades 44 of the ring 42 are not assigned to a compressor stage of the axial compressor 12. They are located in the flow channel 16 immediately downstream of the blades 36 of the vanes 34 and serve to Entdrallung the air flow, so that it can flow into the ring diffuser 18 largely swirl-free. These blades 44 are each components of Nachleitschaufeln 46, which are fastened via a corresponding entanglement in the boundary wall 22. The inner ring 40 comprises an axial extension 41 in a cylindrical shape, which faces the radially inner tips 48 of the airfoils 44 radial gap forming.

Downstream of the inner ring 40, a rotatably arranged shaft cover 50 is located as an inner boundary of the ring diffuser 18.

The shaft cover has a projection 54 on its front side surface 52. This overlaps axially, but radially further inside the inner ring 40 partially. This makes it possible to arrange the annular sealing plate 56 in two opposing grooves 58 and seal the gap between the shaft cover 50 and inner ring 40.

FIG. 2 shows in a perspective partial sectional view of the vane ring 32 with a plurality of circumferentially successive vanes 34, whose head-side end are hooked to the inner ring 40. Here are the from the description of the figures FIG. 1 known features in FIG. 2 provided with identical reference numerals.

Each vane 34 has at its radially outer end a dovetail-shaped blade root 37 which is inserted in a groove 39 arranged in a retaining ring. At the inner end of the airfoil 36, a hammer-shaped blade head 49 is provided, which is hooked in a correspondingly shaped groove 43 of the inner ring 40. The inner ring 40 comprises two parts 45, 47, which are connected to one another in the region of the blade head 49 to form the groove 43. In the FIG. 2 arrangement shown comprising the ring 39, the blades 36 of the vane 34 and the inner ring 40 is also referred to as a guide plate, which, like the outer boundary wall 20 of the axial compressor 12 is usually formed of two ring segments, the flange connected at opposite ends and can be screwed.

In particular, by the proposed construction, it is possible that thermal behavior of freestanding, attached to the outer housing wall 20 blades 44 of Nachleiträdern opposite to this opposite inner boundary of the flow channel 16 to be adjusted so that regardless of the operating state of the axial compressor or the gas turbine comparatively small radial gaps must be maintained or occur during operation.

Overall, the invention provides an annular flow channel 16 for an axial compressor 12, in which on the outer boundary wall 22 blades 36, 44 of two blade rings 32, 42 are attached. In order to achieve a particularly adapted thermal behavior of an inner ring 40 and the freestanding blades 44 and thus to allow comparatively small radial gaps, it is proposed that the inner ring 40 is held by the blades 36 of the one ring and has such an axial extent that the blades 44 of the other of the two rings 42 each with radial gap formation opposite this.

Claims (8)

Annular flow channel (16) for an axial compressor (12), in which on a outer boundary wall (22) of the flow channel (16) fixed blades (36, 44) are arranged in at least two immediately consecutive wreaths (32, 42) like a beam,
of which the blades (36, 44) of one of the two rings (32) are connected by their radially inner end (38) to an inner ring (40) bounding the flow channel (16) radially inwardly,
characterized,
in that the inner ring (40) has an axial extent such that the blades (44) of the other of the two rings (42) each have a radial gap formation opposite this. Flow channel (16) according to claim 1,
in which the ring (32) of blade leaves (36) connected to the inner ring (40) is arranged upstream of the other ring (42) relative to the flow direction of the flow channel (16). Flow channel (16) according to claim 1 or 2,
with at least three rings of airfoils, the blades of two wreaths - as viewed in longitudinal section of the axial compressor (12) - are partially located in the same axial section. Flow channel (16) according to claim 1, 2 or 3,
wherein the upstream rim (32) comprises vanes (34) of a compressor stage and the downstream rim (42) and downstream therefrom (42) comprise guide vanes. Axial compressor (12)
with a flow channel (16) according to one of the preceding claims and an annular compressor outlet diffuser (18) adjoining the flow channel (16), the inner boundary wall (22) of which forms a shaft cover (50) facing the inner ring (40) in a gap-forming manner. Axial compressor (12) according to claim 5,
wherein the gap is sealed by means of a sealant (56). Axial compressor (12) according to one of the preceding claims,
wherein the outer boundary wall (22) of the flow channel (16), an inner boundary wall of the flow channel (16) and the inner ring (40) each comprise at least two ring segments. Stationary gas turbine (14) with an axial compressor (12) according to one of claims 1 to 7.

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