EP3094822B1

EP3094822B1 - Blade for a gas turbine and method for manufacturing said blade

Info

Publication number: EP3094822B1
Application number: EP15707775.1A
Authority: EP
Inventors: Luca Abba; Massimiliano Maritano
Original assignee: Ansaldo Energia SpA
Current assignee: Ansaldo Energia SpA
Priority date: 2014-01-13
Filing date: 2015-01-13
Publication date: 2021-10-06
Anticipated expiration: 2035-01-13
Also published as: CN106471214A; KR20160125952A; WO2015104695A1; CN106471214B; EP3094822A1

Description

TECHNICAL FIELD

The present invention concerns a blade for a gas turbine and a method for manufacturing said blade.
In particular, the present invention concerns a stator blade of a gas turbine installed in a plant for the production of electrical energy.

BACKGROUND ART

Stator blades of gas turbines are generally defined by an elongated main body inside which a cooling circuit is provided. A cooling fluid flows through the cooling circuit, generally air drawn from the plant compressor for the production of energy.
In the stator blades of gas turbines of known type, the air that flows through the cooling circuit has basically two functions: a cooling function and a sealing function.
The cooling function is performed by means of a plurality of cooling holes arranged along the main body of the blade supplied by the cooling circuit; the sealing function is performed by means of seal openings formed in the stator ring to which an anchoring portion of the blade is coupled; said seal openings are supplied by the cooling circuit. The seal openings are arranged so as to fill the cavity defined by the stator blade, by the stator ring and by the rotor with air coming from the cooling circuit and prevent the hot evolving gases in the turbine from occupying said cavity. Examples of cooling circuits of this type are disclosed in documents EP 2159376 , US 2009/185893 , EP 1070829 , WO 2010/139766 .
However, the air flow supplied to said cavity is often not sufficient to prevent inlet of the hot gases, with obvious drawbacks in terms of efficiency of the gas turbine and dependability of the gas turbine components.

DISCLOSURE OF INVENTION

One object of the present invention is therefore to produce a blade for a gas turbine which is free from the drawbacks of the known art highlighted here; in particular, one object of the invention is to produce a blade for a gas turbine able to optimise the sealing and cooling functions in a simple inexpensive manner, in both functional and construction terms.
In accordance with said objects, the present invention concerns a blade for a gas turbine as claimed in claim 1.
In this way the presence of two distinct channels having respective independent inlets allows regulation and optimisation of the cooling fluid flow which passes through the first outlet and the second outlet respectively in an independent manner.
Due to this, for example, in the design phases it is possible to size the inlets of the two channels so as to obtain a defined flow rate of cooling fluid which passes through the first outlet and the second outlet respectively.
According to the present invention, the blade comprises a first anchoring portion coupled to the main body and adapted, in use, to be coupled to a stator casing of the gas turbine; and a second anchoring portion coupled to the main body and adapted, in use, to be coupled to a respective stator ring of the gas turbine; the first inlet and the second inlet being formed in the first anchoring portion; the first outlet being formed in the second anchoring portion and the second outlet being formed along the main body.
The presence of the anchoring portion for anchoring to the stator casing and the anchoring portion for anchoring to the stator ring identifies a stator blade of a gas turbine. In this case the presence of two distinct channels having respective independent inlets allows independent regulation and optimisation of the seal flow rate and cooling flow rate of the cooling fluid, therefore preventing the cavity defined by the stator blade, the stator ring and the rotor from being filled with the hot evolving gases in the turbine.
According to the present invention, the first channel and the second channel are in communication.
In this way it is possible to further regulate the flow passing through the first outlet and the second outlet respectively by sizing the connection between the first channel and the second channel.
According to a preferred embodiment of the present invention, the first connecting conduit is configured in order to have a variable section. In this way the sizing of the connecting conduit is simplified.
According to a preferred embodiment of the present invention, the blade comprises at least one metering plate arranged in the area of one between the first inlet and the second inlet and configured to reduce the flow section of the first inlet or the second inlet.
In this way it is possible to further regulate the flow into the first or second channel. Due to this, it is possible to further regulate the values of the flow rate flowing through the first outlet and the second outlet respectively. Said aspect is very useful, for example, in the case of manufacturing defects on the connecting conduit between the first and the second channel or on the inlets and outlets of the first and second channel.
According to a preferred embodiment, the metering plate is provided with at least one first hole. In this way it is possible to further regulate the flow into the first or second channel via the sizing of the first hole.
According to a preferred embodiment, the metering plate is formed so that the first hole has a variable section.
In this way, regulation of the flow into the first or second channel is simplified.
A further object of the present invention is to provide a manufacturing method for a blade of a gas turbine which guarantees that the hot evolving gases in the turbine do not invade the cavity defined by the stator blade and the rotor.
In accordance with said objects, the present invention concerns a manufacturing method for manufacturing a blade for a gas turbine as claimed in claim 11.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will become clear from the following description of a non-limiting embodiment example thereof, with reference to the figures of the accompanying drawings, in which:

figure 1 is a schematic representation, with parts in section and parts removed for clarity, of a portion of a gas turbine comprising a blade according to the present invention;
figure 2 is a section view with parts removed for clarity, of the blade of figure 1 according to the present invention;
figure 3 is a perspective view, with parts in section and parts removed for clarity, of a detail of the blade of figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

In figure 1 the reference number 1 indicates a portion of a gas turbine 2 of a plant for the production of electrical energy (not illustrated for the sake of simplicity).
The electrical energy production plant is of known type and comprises a compressor (not illustrated), inside which is an air flow, a combustion chamber supplied with fuel and air from the compressor, the gas turbine 2 and a generator (not illustrated), mechanically connected to the shaft of the gas turbine 2 and of the compressor and connected to an electrical distribution network (not illustrated).
The gas turbine 2 extends along a longitudinal axis A and comprises a stator 4 and a rotor 5 (both partially illustrated in figure 1), which rotates about the axis A.
The stator 4 comprises a stator casing 7 (partially illustrated in figure 1), which extends around the axis A for the entire length of the gas turbine 2 and is static, a plurality of stator rings 8 centred on the axis A, supported by the stator casing 7 and arranged in sequence along the axis A, and a plurality of stator blades 10. The stator blades 10 are split into arrays and are arranged radially with respect to the axis A. Each stator blade 10 is fixed to the stator casing 7 and to a respective stator ring 8.
The rotor 5 comprises a plurality of rotor rings 12, coupled to one another so as to define one single element rotating about the axis A, and a plurality of rotor blades 13 split into arrays and arranged radially with respect to the axis A.
Each rotor blade 13 is provided with one free end 14 and one end 15 coupled to a respective rotor 12.
The stator rings 8 extend around the rotor rings 12 and are spaced from one another so that radial arrays of the rotor blades 13 and radial arrays of stator blades 10 alternate along the axis A.
The plurality of rotor rings 12, the stator rings 8 and the stator casing 7 define an expansion channel 16 inside which the hot gases coming from the combustion chamber flow.
Each stator blade 10 comprises an elongated main body 18, which extends along a respective axis with radial extension B with respect to the axis A, a first anchoring portion 19 coupled to one end 20 of the main body 18 and coupled, in use, to the stator casing 7, a second anchoring portion 21 coupled to one end 22 of the main body 18 opposite the end 20 and coupled, in use, to the respective stator ring 8.
In use, the second anchoring portions 21 of the adjacent stator blades 10 and the respective stator ring 8 define, when coupled, an annular seal chamber 23.
The stator ring 8 is provided with a plurality of seal openings 24, which establish communication between the seal chamber 23 and an open annular cavity 25. The annular cavity 25 is defined by the stator ring 8, by the anchoring portion 21 of the stator blades coupled to the stator ring 8 and by the rotor rings 12 adjacent to the stator ring 8.
With reference to figure 2, each stator blade 10 further comprises a cooling circuit 28 supplied with a cooling fluid.
The cooling circuit 28 comprises at least one first cooling channel 29, preferably bent in a U shape, and a second cooling channel 30.
The first cooling channel 29 is therefore defined by two branches 31, which extend mainly into the main body 18 substantially parallel to the axis B.
The second cooling channel 29 extends mainly into the main body 18 substantially along the axis B.
The first cooling channel 29 is provided with a first inlet 32 formed in the first anchoring portion 19 and a first outlet 33 formed in the second anchoring portion 21.
The second cooling channel 30 is provided with a second inlet 35 formed in the first anchoring portion 19 and a plurality of outlet holes 36 formed along the main body 18.
The first inlet 32 and the second inlet 35 are substantially arranged side by side.
The first cooling channel 29 and the second cooling channel 30 are preferably connected.
In particular, the first cooling channel 29 and the second cooling channel 30 are connected by means of two connecting conduits 37, which are preferably parallel and extend orthogonally to the axis B.
In a first variation not illustrated, there are more than two connecting conduits.
In a second variation not illustrated, the first cooling channel 29 and the second cooling channel 30 are connected by means of one single appropriately sized connecting conduit.
In a third variation not illustrated, the flow section of one or more connecting conduits between the first cooling channel 29 and the second cooling channel 30 is adjustable, for example by means of the use of a metering plate coupled to the connecting conduit having a variable section opening, or any other means able to shutter the section of the connecting conduit to which it is coupled.
With reference to figure 3, the second inlet 35 of the second cooling channel 30 formed in the first anchoring portion 19 is preferably coupled to a metering plate 40 configured so as to reduce the flow section of the second inlet 35.
In the non-limiting example described and illustrated here, the metering plate 40 is provided with two holes 41 and has a substantially identical shape to the section of the second inlet 35. The coupling of the metering plate 40 to the second inlet 35 determines a reduction in the flow section of the second inlet 35. The holes 41 are appropriately sized so as to obtain the desired reduction in flow section.
Preferably, the metering plate 40 is welded to the first anchoring portion 19.
In a first variation not illustrated, the metering plate is provided with one single flow hole.
In a second variation not illustrated there are more than two flow holes.
In a third variation not illustrated the metering plate is shaped so as to define one or more holes having an adjustable flow section. For example the metering plate could be provided with a mobile member configured to partially or completely close one or more holes of the metering plate. Alternatively, the metering plate could be defined by a first portion and a second portion couplable to each other and shaped so as to define, together, a variable section opening. For example the first portion and the second portion could be coupled geometrically in a plurality of positions to define the variable section opening.
In a further variation, the plate is without holes and completely closes the inlet to which it is coupled so as to reduce 100% the inlet flow rate.
With reference to figure 1, the cooling fluid that circulates in the cooling circuit 28 is preferably air coming from a draw-off circuit 41 (schematically illustrated), configured to draw air from the compressor of the electrical energy production plant and to feed it to a plurality of stator chambers 43 formed in the stator casing 7. Each stator chamber 43 communicates with the cooling circuit 28 of all the stator blades 10 of the same array through the first inlets 32 and the second inlets 35.
The cooling circuit 28 of each stator blade 10 receives, through the first inlet 32 and the second inlet 35, an overall air flow rate QTOT from the respective stator chamber 43 and supplies a cooling air flow rate QR to the expansion channel 26 through the plurality of outlet holes 36 formed along the main body 18 and a seal air flow rate QS to the seal chamber 23 through the first outlet 33.
At the design stage, the first inlet 32 and the second inlet 35, the first outlet 33, the outlet holes 36 and the connecting conduits 37 are sized so as to have a seal flow rate QS and a cooling flow rate QR equal to respective reference values.
However, the blade is usually produced by casting and the presence of manufacturing defects does not guarantee that the reference values of the seal flow rate QS and the cooling flow rate QR are actually observed.
To avoid this, a manufacturing method is used which involves the performance of tests on the blades just produced, during which the seal flow rate QS coming out of the first outlet 33 and the cooling flow rate QR which crosses the outlet holes 36 are detected.
If the seal flow rate QS and/or the cooling flow rate QR do not reflect the reference values, the manufacturing method provides for reduction of the flow section of one between the first inlet 32 and the second inlet 35 or both the inlets 32 and 35.
In particular, the method provides for reduction of the flow section of the second inlet 35 by coupling of the appropriately sized metering plate 40.
The sizing of the metering plate 40 contributes to further regulating the air supply to the second cooling channel 30 and therefore to regulating the flow rate of cooling air QR.
It is understood that if the seal flow rate QS and the cooling flow rate QR reflect the reference values, the metering plate 40 is not used.
Lastly it is obvious that modifications and variations can be made to the blade and method described here without departing from the scope of the attached claims.

Claims

Blade for a gas turbine (2) comprising:
a main body (18);

a first anchoring portion (19) coupled to the main body (18) and adapted, in use, to be coupled to a stator casing (7) of the gas turbine (2);

a second anchoring portion (21) coupled to the main body (18) and adapted, in use, to be coupled to a respective stator ring (8) of the gas turbine (2);

a cooling circuit (28) supplied with a cooling fluid and comprising a first channel (29) and at least a second channel (30) arranged, at least in part, inside the main body (18);

the first channel (29) being provided with a first inlet (32) and with a first outlet (33); the second channel (30) being provided with a second inlet (35), distinct from the first inlet (32), and with a plurality of second outlets (36) formed along the main body (18) and distinct from the first outlet (33); the first inlet (32) and the second inlet (35) being formed in the first anchoring portion (19); the first outlet (33) being formed in the second anchoring portion (21);

the blade being characterized in that the first channel (29) and the second channel (30) are in fluidic communication by means of at least one first connecting conduit (37) to allow the passage of a certain amount of cooling fluid.
Blade according to claim 1, wherein the first channel (29) and the second channel (30) are connected by means of at least one second connecting conduit (37).
Blade according to claim 1 or 2, wherein the flow section of the first connecting conduit (37) is adjustable.
Blade according to claim 2, wherein the first connecting conduit and the second connecting conduit (37) are substantially identical.
Blade according to any one of the foregoing claims, comprising at least one metering plate (40) coupled to the first inlet (32) and/or to the second inlet (35) and configured to reduce the flow section respectively of the first inlet (32) and/or of the second inlet (35).
Blade according to claim 5, wherein the metering plate (40) is provided with at least one first hole (41).
Blade according to claim 6, wherein the metering plate (40) is configured so that the first hole (41) has a variable section.
Blade according to claim 7, wherein the metering plate (40) comprises at least one mobile member configured to close, at least partially, at least the first hole (41).
Blade according to claim 7, wherein the metering plate (40) comprises a first portion and a second portion couplable one to the other and shaped so as to define, together, at least the first hole (41) having variable section.
Blade according to claim 9, wherein the first portion and the second portion are geometrically couplable in a plurality of positions for defining the first hole (41) having variable section.
Method for manufacturing a blade (10) for a gas turbine (2) comprising the steps of:
• manufacturing a blade (10) provided with a cooling circuit (28) comprising a first channel (29) and at least a second channel (30); the first channel (29) being provided with a first inlet (32) and with a first outlet (33); the second channel (30) being provided with a second inlet (35), distinct from the first inlet (32), and with a plurality of second outlets (36) formed along the main body (18) and distinct from the first outlet (33); the first channel (29) and the second channel (30) are in fluidic communication by means of at least one first connecting conduit (37) to allow the passage of a certain amount of cooling fluid;

• supplying a defined flow rate (QTOT) of a cooling fluid to both the first inlet (32) and the second inlet (35);

• detecting a first flow rate (QS) of cooling fluid flowing through the first outlet (33);

• detecting a second flow rate (QR) of cooling fluid flowing through the second outlet (36);

• comparing the first flow rate (QS) and the second flow rate (QR) of cooling fluid with respective reference values;

• reducing the flow section of at least one between the first inlet (32) and the second inlet (35) if the first flow rate (QS) and/or the second flow rate (QR) do not reflect the reference values.
Method according to claim 11 wherein the step of reducing the flow section of at least one between the first inlet (32) and the second inlet (35) comprises the step of coupling a metering plate (40) to at least one between the first inlet (32) and the second inlet (35)