EP2700788A1

EP2700788A1 - Vane or blade with tip cap

Info

Publication number: EP2700788A1
Application number: EP12181109.5A
Authority: EP
Inventors: Herbert Brandl; Marcel Koenig
Original assignee: Alstom Technology AG
Current assignee: GE Vernova GmbH
Priority date: 2012-08-21
Filing date: 2012-08-21
Publication date: 2014-02-26

Abstract

A hollow blade or vane body (2) of a turbine is joined at an open end to a plug or end body (5) by a cast securing ring (11), which is accommodated in an annular channel formed by corresponding annular grooves (7, 8) in the opposing surfaces of the connection area of the two bodies (2, 5).

Description

Technical area

The invention relates to vanes or blades for turbines or the like, having a blade body with at least one longitudinal end which is connected to an end or plug body, whereby both bodies are joined at a connection area in the manner of a male and female plug whereby an inner peripheral surface of one body overlaps an outer peripheral surface of the other body in the longitudinal direction of the blade.

Prior art

Such turbine blades with a hollow formed blade body are known from US 2005/0196277 A1 . According to this document a ring shaped flange with a stepped inner contour is formed in the inner periphery of the hollow blade body, whereby a correspondingly shaped plate-shaped cap can be placed onto the flange and then connected to it by electron beam welding. The plate-shaped cap can be provided with a plurality of openings in order to lead away the cooling air, which is flowing through the hollow blade during operation of the turbine, at defined positions.
A similarly designed blade is disclosed in US 2010/0080711 A1 . According to this document the plate-shaped cap, optionally provided with air outlet openings, can be connected to the blade body by welding or brazing.
Other similar turbine blades are known from US 2007/0258825 A1 and EP 1 772 593 A2 , however without the air outlet openings in the plate-shaped caps. It is also provided that these blade bodies can be connected to the caps by welding
The patent US 5,797,725 relates to the design of vane ring arrangements for turbines. Such ring arrangements comprise two ring surfaces arranged concentrically to one another and to the turbine axis, and are connected to one another by vanes arranged substantially radially to the turbine axis. Such vane ring arrangements are often arranged axially between rows of blades in a turbine in order to direct the gas or air flow optimally onto the following row of blades. In order to ensure a strong arrangement which can be dismantled, US 5,797,725 provides that the radially inner or outer ends of the vanes are inserted into recesses in the ring surfaces formed corresponding to the end profile of the vanes, and fixed with a securing ring which is moulded into ring grooves which correspond with each other on the outer periphery of the blade body and the inner periphery of the opening of the recess.
The said securing ring can be cut by EDM (electric discharge machining) for example. This allows separation of the parts.
The above described turbine blades are generally problematic because of the welded connections used. Welding of superalloys commonly used in turbine applications is problematic or even impossible. On the other hand it is generally desirable with turbine blades to be able to use hollow blade bodies with large end openings in order to simplify where possible the manufacturing of the blade body.

Summary of the invention

The invention addresses these problems, whereby departing from the general features of claim 1 the invention comprises the additional characterizing features of claim 1.
The invention is based on the general idea of using a form locking connection between the blade body and the cap or plug body, whereby the securing ring or clip providing the form locking connection is made by casting and arranged in an essentially annular channel between the bodies being connected together, the channel being practically only accessible by casting.
Through the invention a form locking connection with excellent sealing results can be achieved.
The excellent sealing effect is surprising as the region of the channel between the two bodies being connected must be strongly heated before introducing the casting material of the securing ring or clip into the essentially annular channel, whereby oxides form on the channel walls which then prevent a bonded connection between the channel walls and the material of the securing ring.
Furthermore it is advantageous that the sealing effect of the form locking connection increases during operation of the turbine with typical loads on the turbine blades.
Contrary to a welding process the connection process of the invention is not limited to specific materials to be connected. Therefore, the blade body and the cap or plug body can be produced of substantially different materials which can be optimally selected in view of any requirements for the blade and cap or plug bodies respectively.
According to an advantageous embodiment of the invention the cap or plug bodies can have any form and may be used to connect or arrange the turbine blades with or with respect to other turbine elements.
Preferred features of the invention can be found in the claims and the following description of the drawings, with the aid of which preferred embodiments of the invention are described in more detail.
The shown features can also fall under the scope of the invention when they are appropriately used in a combination which is different from that shown in the drawings.

Short description of the drawings

The drawings show in:

Fig. 1: an exemplary cross-section of a turbine blade,
Fig. 2: a sectional view of an assembled radially outer blade end with an inserted plug body, cf. sectional line II-II in Fig. 4,
Fig. 3: a perspective view of a radially outer blade end with plug bodies,

Fig. 4: a sectional view along the line IV-IV in Fig.3, whereby a plug body is inserted into the end opening,
Fig. 5: a perspective view of an open end of a turbine blade closed with a plug,
Fig. 6: a sectional view along the line VI-VI in Fig.5
Fig. 7: a perspective view of a turbine blade with a blade root at the radially inner blade end and a shroud part arranged at the radially outer blade end, the shroud part can form a closed segmented shroud ring with adjacent shroud parts.

Description of preferred embodiments

According to figure 1, a turbine blade 1 can have a hollow formed blade body 2, whereby in the example shown the inner cavity is divided by two cross walls 3 into three chambers 4 extending in the longitudinal direction of the blade, the chambers being open at the longitudinal ends of the blade body 2.
According to figure 2 the open end of a chamber 4 can be closed by a cap or plug 5. The plug has an outer periphery which corresponds to the profile of the chamber 4, so that the plug 5 can be inserted in the longitudinal direction of the chamber 4 into the chamber 4. In the example shown the plug 5 has an annular projection 6 on its outer periphery which extends in the longitudinal direction of the chamber 4, so that the outer periphery of the plug body 5 and the inner periphery of the chamber 4 overlap over the height of the annular projection. Cooperating essentially annular grooves 7 and 8 are formed in the outer periphery of the annular projection 6 and the inner periphery of the chamber 4. The annular grooves 7, 8 face each other with their open sides and form accordingly an essentially annular channel surrounding the plug 5. Half of the cross-section of the essentially annular channel is arranged in the essentially annular projection 6 of the plug 5 and the other half in the wall of the chamber 4. The essentially annular channel formed by the essentially annular grooves 7 and 8 is accessible from outside through openings which are formed, similarly to the annular channel, by grooves 9 and 10 which are substantially perpendicular to the essentially annular grooves 7 and 8. The grooves 9 and 10 being formed in the facing inner or outer peripheral surfaces of the plug body 5 or the chamber 4.
This makes it possible to arrange a securing ring or clip 11 inside of and filling the cross-section of the annular channel formed by the annular grooves 7 and 8, whereby a metal melt is poured into the openings formed by the grooves 9 and 10 into the essentially annular channel formed by the annular grooves 7 and 8. Venting holes (not shown) can be provided whenever required.
Before or also during the casting phase the blade body 2 and the plug body 5 are heated in order to avoid a too rapid cooling of metal melt which has been poured in. During this heating a thin oxide layer forms on the walls of the annular grooves 7 and 8, which prevents a bonded connection of the cast material with the material of the blade body 2 or with the plug body 5. As a result the cast securing ring 11 forms purely a form-locking connection between the blade body 2 and the plug body 5.
In the example in figure 2 the essentially annular groove 7 is arranged directly on the inner side of the wall of the blade body 2.
Figures 3 and 4 show that this must not always be the case. According to figures 3 and 4 a flange 12 in the form of a annular projection can be formed on the inner side of a chamber 4 of the blade body 2, the flange 12 surrounds an opening which is smaller than the cross-section of the chamber 4, whereby the opening can be closed by a correspondingly formed plug body 5. The said opening is smaller than the cross-section of the chamber 4, however it is large enough that the blade body 2 can be made from a cast material or a sinter material using moulding tools without excessive complexity or fragileness. The said opening has in particular a cross-section which facilitates a necessary, regular removal of a mould core.
The securing ring 11 again serves to fix the plug body 5 in the opening surrounded by the flange 12 in the form of the annular projection, whereby the essentially annular channel receiving the securing 11 is again formed by the essentially annular grooves 7 and 8 which in this case are formed on the inner peripheral edge of the flange 12 and in the outer peripheral edge of the plug body 5 respectively.
In the above described embodiments the plug body 5 is inserted in the way of a plug into an opening in the end of a blade body 2. This is appropriate and advantageous if the only or predominant function of the plug body 5 is a closing function.
If the plug body 5 is to have further functions it may be appropriate to form the plug body 5 as a cap over the open end of the blade body 2.
Figures 5 and 6 show such an embodiment.
According to these figures an essentially annular step 13 is formed on the outside of the open end of the blade body 2 which is filled by an annular projection 14 arranged on a plug body 5, so that the outer periphery of the essentially annular projection 14 is aligned with the outer periphery of the blade body under the essentially annular step 13. In order to have a sufficient blade body wall thickness in the area of the annular step 13 the cross-section of the chamber formed in the blade body 2 can narrow in the shape of a cone, as shown, in the direction of the open end of the blade body 2. The plug body 5 can have practically any form as a continuation of the blade body, whereby according to figures 5 and 6 it is possible to form the plug body 5 as a segment of a turbine shroud 17 or as a winglet of the respective blade, the turbine shroud or the winglets having ribs 15 which extend in the circumferential direction of the blades and cooperate with ribs or grooves in adjacent stationary parts of the turbine housing as a kind of labyrinth seal in order to ensure that the working medium in the form of a gas or steam flowing through the turbine blades cannot flow radially outside of the turbine blades.
It is also possible to connect the blade body 2 of a turbine blade 1 with an associated root 16 according to figure 7. This root 16 has an upside down fir tree shape with which the turbine blade 1 can be inserted into a correspondingly formed recess in the rotor shaft of a turbine. The connection of the blade body 2 and the root 16 can also be arranged similar to the arrangement in figure 6 where the plug body extends from the blade body 2 at its radially outer end.
The securing ring or clip 11 mentioned above can have an annular ring shape, but this must not always be the case. It is for example also possible to use an "open" ring shape like a C-shape ring or clip 11 in accordingly formed grooves 9 and 10.

List of references

1: blade / vane
2: blade body
3: cross wall
4: chamber
5: plug body
6: annular projection
7: annular groove
8: annular groove
9: groove
10: groove
11: securing ring or clip
12: flange
13: annular step
14: annular projection
15: rib
16: root
17: shroud

Claims

A vane or blade for turbines or the like, comprising a blade body (2) which is connected at at least one open longitudinal end with an end or plug body (5), whereby the two bodies (2, 5) have an inner and outer peripheral surface which overlap each other in the longitudinal direction in a connection area,
characterized in that,
an essentially annular groove (7, 8) is arranged in the inner and outer peripheral surfaces, the open side of one annular groove is arranged opposite the open side of the annular groove in the other peripheral surface, and that an annular channel formed by the two opposing annular grooves (7, 8) is filled by a cast securing ring or clip (11).
A vane or blade according to claim 1,
characterized in that,
the plug or end body (5) is inserted into an opening which has a smaller cross-section than that of an adjacent chamber (4) extending through the blade body (2).
A vane or blade according to claim 2,
characterized in that,
the opening is surrounded by an essentially annular projection (6) provided on the peripheral wall of the chamber (4).
A vane or blade according to one of claims 1 to 3,
characterized in that,
the inner peripheral surface is provided by the blade body (2) and the outer peripheral surface is provided by the end or plug body (5).
A vane or blade according to one of claims 1 to 3,
characterized in that,
the outer peripheral surface is provided by the blade body (2) and the inner peripheral surface is provided by the end or plug body (5).
A vane or blade according to one of claims 1 to 5,
characterized in that,
the radially outer end of the blade body (2), after mounting, is connected with a segment of a shroud (17) or with a winglet.
A vane or blade according to one of claims 1 to 6,
characterized in that,
the radially inner end of the blade body (2), after mounting, is connected to a root (16) which is arranged as an end or cap or plug body.
A vane or blade according to one of claims 1 to 7,
characterized in that,
the blade body (2) comprises a plurality of chambers (4) extending through the blade body in the longitudinal direction, the chambers being separated from each other by cross walls (3) in the blade body (2).
A vane or blade according to one of claims 1 to 8, characterized in that the vane or blade body and the end or plug body consist of different and/or not weldable materials.