Turbine stator, turbine, and gas turbine including the same

A turbine stator, into which combustion gas supplied from a combustor of a gas turbine flows, has an improved structure capable of preventing circumferential movement of turbine vanes. The turbine stator, which may be included in a turbine of a gas turbine having the improved structure, includes a casing including first and second casings constituting respective casing halves, the first and second casings having a fastening groove formed on at least one contact surface between the first casing and the second casing; a plurality of vane airfoils configured to be installed on an inner peripheral surface of the casing and arranged in a multi-stage manner in a flow direction of the combustion gas; and a stop configured to be fixed with respect to a vane airfoil of the plurality of vane airfoils and to be inserted into the fastening groove to fix the vane airfoil to the casing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 10-2017-0121199, filed on Sep. 20, 2017, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

Exemplary embodiments of the present disclosure relate to a turbine stator, a turbine, and a gas turbine including the same, and more particularly, to a turbine stator into which combustion gas supplied from a combustor flows, a turbine, and a gas turbine including the same.

Description of the Related Art

A gas turbine generally includes a compressor, a combustor, and turbine. The compressor has a compressor inlet scroll strut for the introduction of air, and includes a plurality of compressor vanes and compressor blades alternately arranged in a compressor casing. The combustor mixes fuel with the air compressed by the compressor to ignite the mixture with a burner, thereby producing high-temperature and high-pressure combustion gas.

The turbine includes a plurality of turbine vanes and turbine blades alternately arranged in a turbine casing. A tip clearance is defined as a gap between the turbine casing and each of the turbine blades. In addition, a tie rod is arranged to pass through the centers of the compressor, combustor, turbine and exhaust chamber. The tie rod is rotatably supported at both ends by bearings. A plurality of disks are fixed to the tie rod, and the blades are connected to each of the disks. A drive shaft of a generator or the like is connected to the end of the exhaust chamber.

This gas turbine is advantageous in that it consumes a very small amount of lubricant, has a significantly reduced amplitude which is a characteristic of reciprocating machines, and operates at a high speed because it does not have a reciprocating device such as a piston in a four-stroke engine to have no friction portion between the piston and the cylinder causing deterioration.

Briefly, the gas turbine is operated in such a manner that the air compressed by the compressor is mixed with fuel for combustion to produce hot combustion gas and the produced combustion gas is injected into the turbine. The injected combustion gas generates torque while flowing through the turbine vanes and the turbine blades, thereby rotating a rotor.

Each of the turbine vanes included in the gas turbine includes a turbine vane airfoil and a turbine vane shroud. The turbine vane airfoil is fixed on the inner peripheral surface of the turbine casing by the turbine vane shroud installed between the turbine vane airfoil and the turbine casing.

In this case, the turbine vane has a limitation in that the turbine vane shroud allows the axial movement of the turbine vane to be fixed but cannot provide for its circumferential movement to be fixed. Hence, the gas turbine is problematic in that vibration occurs in the turbine as the turbine vane moves circumferentially, resulting in a reduction in turbine efficiency.

SUMMARY OF THE INVENTION

The present disclosure has been made in view of the above-mentioned problems, and an object thereof is to provide a turbine stator having an improved structure capable of preventing circumferential movement of turbine vanes. The present disclosure has a further object to provide a turbine and a gas turbine including the turbine stator having the improved structure.

In accordance with one aspect of the present disclosure, there is provided a turbine stator into which combustion gas supplied from a combustor flows. The turbine stator may include a casing including first and second casings constituting respective casing halves, the first and second casings having a fastening groove formed on at least one contact surface between the first casing and the second casing; a plurality of vane airfoils configured to be installed on an inner peripheral surface of the casing and arranged in a multi-stage manner in a flow direction of the combustion gas; and a stop configured to be fixed with respect to a vane airfoil of the plurality of vane airfoils and to be inserted into the fastening groove to fix the vane airfoil to the casing.

In accordance with another aspect of the present disclosure, there is provided a turbine to generate power for generation of electric power by passing combustion gas supplied from a combustor. The turbine may include a stator into which combustion gas supplied from the combustor flows, and a rotor installed inside the stator and configured to rotate by the flow of the combustion gas. Here, the stator is consistent with the above turbine stator.

In accordance with another aspect of the present disclosure, a gas turbine may include a compressor to suck and compress air, a combustor to mix compressed air supplied from the compressor with fuel for combustion, and a turbine to generate power for generation of electric power by passing combustion gas supplied from the combustor. Here, the turbine is consistent with the above turbine.

The turbine stator may further include a flange protruding radially outward from either end of an outer peripheral surface of the casing, for coupling together the first and second casings; and a first vane airfoil of the plurality of vane airfoils disposed on an inner peripheral surface of the casing corresponding to a position of the flange.

The turbine stator may further include a plurality of vane shrouds arranged between the casing and the plurality of vane airfoils and configured to be coupled to the plurality of vane airfoils, respectively; and an inner peripheral groove circumferentially formed on the inner peripheral surface of the casing and configured to receive the vane shrouds in order to fix the vane airfoils to the casing.

The turbine stator may further include a first vane shroud of the plurality of vane shrouds coupled to the first vane airfoil, wherein the stop extends outward radially from the first vane shroud.

The turbine stator may further include a plurality of fixing pins inserted inward from an outer peripheral surface of the casing, ends of the fixing pins respectively configured to penetrate, and fix to the casing, only the vane shrouds of the plurality of vane shrouds excluding the first vane shroud.

The first shroud may be fixed to the casing using a force applied in a circumferential direction of the casing, and the vane shrouds of the plurality of vane shrouds excluding the first vane shroud may be fixed to the casing using in a force applied in an axial direction toward the tie rod.

Each vane shroud may include a base plate; a front end protrusion extending outward radially from the base plate so as to be contiguous with a front-stage vane airfoil; and a rear end protrusion extending outward radially from the base plate so as to be contiguous with a rear-stage vane airfoil. The first vane airfoil and the first vane shroud may each be disposed to the right, in the flow direction of the combustion gas, with the stop installed at the front end protrusion of the first vane shroud. Alternatively, the first vane airfoil and the first vane shroud may each be disposed to the left, in the flow direction of the combustion gas, with the stop installed at the front end protrusion of the first vane shroud.

The turbine stator may further include a fastening bolt configured to penetrate the stop in order to fix the stop to the casing.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. The present disclosure may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present disclosure.

Hereinafter, a turbine stator, a turbine, and a gas turbine including the same according to exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

FIG. 1illustrates an example of a gas turbine1according to the present disclosure. The gas turbine1includes a casing and a turbine diffuser disposed behind the casing for discharge of combustion gas having passed through a turbine10. A combustor4is disposed in front of the turbine diffuser for combustion of compressed air supplied from a compressor3. In terms of airflow direction, the compressor3is disposed upstream of the turbine10.

The casing of the gas turbine1includes a compressor casing and a turbine casing110. The compressor casing accommodates compressor vanes and compressor rotors, and the turbine casing110accommodates turbine vanes and turbine rotors11. A torque tube as a torque transmission member is disposed between the compressor3and the turbine10to transmit a rotational torque generated in the turbine10to the compressor.

Each of the compressor rotors includes a compressor disk and compressor blades. A plurality of compressor disks (e.g., fourteen disks) is accommodated in the compressor casing, and these individual compressor disks are fastened by a tie rod2so as not to be axially separated from each other.

In detail, the compressor disks are axially aligned in the state in which the tie rod2passes through the substantial centers of the respective compressor disks. Here, the compressor disks are arranged so that the facing surfaces of adjacent compressor disks, pressed together by the tie rod2, are not rotatable relative to each other.

A plurality of compressor blades are radially coupled to the outer peripheral surface of each compressor disk. A plurality of compressor vanes are fixedly arranged in the compressor casing, alternately with the compressor disks, so as to be respectively disposed between adjacent compressor disks. The compressor vanes are fixed so as not to rotate, unlike the compressor disks, and serve to align the flow of compressed air having passed through upstream compressor blades and to guide the compressed air to compressor blades arranged downstream. In this case, the compressor casing and the compressor vanes may define a comprehensive compressor stator, to distinguish the compressor stator from the compressor rotor.

The tie rod2is disposed to pass through the centers of the compressor disks and the turbine disks12. One end of the tie rod2is fastened to a compressor disk positioned at the most upstream side, and the other end is fastened by a fastening nut.

The tie rod2is not limited to the structure shown inFIG. 1and may be variously configured according to the gas turbine1. That is, one tie rod may pass through the centers of compressor disks and turbine disks (as shown), a plurality of tie rods may be arranged circumferentially, or a combination of these may be used.

Although not illustrated in the drawings, a deswirler serving as a guide vane may be installed in the compressor of the gas turbine in order to adapt the angle of flow of fluid, entering into the inlet of the combustor after the pressure of the fluid is increased, to a design angle of flow.

The combustor mixes the compressed air introduced thereinto with fuel for combustion to produce high-temperature and high-pressure combustion gas with high energy, and increases the temperature of the combustion gas to a temperature at which the combustor and turbine components are able to be resistant to heat in a constant-pressure combustion process.

The constituent combustor of the combustion system of the gas turbine may consist of a plurality of combustors arranged in a combustor casing in the form of a cell, and includes a nozzle for injection of fuel, a liner that forms a combustion chamber, and a transition piece that is a connection between the combustor and the turbine.

In detail, the liner defines a combustion space in which the fuel injected from the fuel nozzle is mixed with the compressed air from the compressor for combustion. The liner may include a combustion chamber as the combustion space in which the fuel mixed with air is burned, and a liner annular passage that defines an annular space while surrounding the combustion chamber. The nozzle for injection of fuel is coupled to the front end of the liner, and an igniter is coupled to the side wall of the liner.

The compressed air, which is introduced through a plurality of holes arranged in the outer wall of the liner, flow in the liner annular passage, and the compressed air used to cool the transition piece, which will be described later, also flows through the liner annular passage. Since the compressed air flows along the outer wall of the liner, it is possible to prevent thermal damage to the liner due to heat generated by combustion of fuel in the combustion chamber.

The transition piece is connected to the rear end of the liner to send the combustion gas burned by an ignition plug to the turbine. Similar to the liner, the transition piece has a transition piece annular passage surrounding the internal space thereof, and the outer wall of the transition piece is cooled by the compressed air flowing along the transition piece annular passage, thereby preventing damage to the transition piece due to the high temperature of combustion gas.

Meanwhile, the high-temperature and high-pressure combustion gas discharged from the combustor is supplied to the turbine. The high-temperature and high-pressure combustion gas supplied to the turbine gives impingement or reaction force to turbine blades while expanding, to generate a rotational torque. The obtained rotational torque is transmitted via the torque tube to the compressor, and the power beyond that for driving the compressor is used to drive a generator or the like.

The turbine10basically has a structure similar to the compressor. That is, the turbine10includes a plurality of turbine rotors11similar to the compressor rotors of the compressor. Thus, each of the turbine rotors11similarly includes a turbine disk12and a plurality of turbine blades13arranged radially. A plurality of turbine vanes fixed to the turbine casing110are each arranged between the turbine blades13to guide the flow direction of combustion gas having passed through the turbine blades13. In this case, the turbine casing110and the turbine vanes may define a comprehensive turbine stator100, to distinguish the turbine stator100from the turbine rotor11.

Referring toFIG. 2, the turbine casing110(hereinafter referred to as a “casing”) includes first and second casings111and112which constitute the respective halves of casing110, which are centered about the tie rod2. As shown, the first casing111may constitute the upper portion of the casing110and the second casing112may constitute the lower portion of the casing110, but the converse is also possible. That is, the first casing111may constitute the lower portion of the casing110and the second casing112may constitute the upper portion of the casing110.

The first casing111has first flanges113protruding radially outward from either end of the casing's outer periphery, for coupling to the second casing112. The second casing112has second flanges114protruding radially outward from either end of the casing's periphery, for coupling to the first casing111. The first and second casings111and112are fixed to each other, using separate fastening means (not shown) that pass through the first and second flanges113and114in close contact with each other.

Each of the turbine vanes consists of a turbine vane airfoil120(hereinafter referred to as an “airfoil”) and a turbine vane shroud130(hereinafter referred to as a “shroud”). InFIG. 2, the view is from a front stage looking downstream toward a rear stage. The airfoil120serves to guide combustion gas such that the combustion gas having passed through a front-stage turbine blade13may be supplied to a rear-stage turbine blade13. The shroud130is disposed between the airfoil120and the casing110to be coupled to the airfoil120. The shroud130is inserted into an inner peripheral groove circumferentially formed on an inner peripheral surface of the casing110and fixes the airfoil120to the casing110.

Here, the shroud130is kept fixed in the axial direction of the tie rod2, but is not fixed in the circumferential direction of the casing110. If the turbine vane moves circumferentially relative to the casing110during the operation of the gas turbine1, the airfoil120may vibrate by impinging against combustion gas flowing in the turbine10. In this case, the airfoil120does not properly guide combustion gas to a next-stage turbine blade13. Hence, a force applied to the turbine blade13is reduced due to expansion of combustion gas, which may lead to a reduction in overall efficiency of the turbine10.

Accordingly, the stator100may further include a fixing pin140in order for the shroud130and the airfoil120coupled thereto to be circumferentially fixed to the casing110. The fixing pin140penetrates inward from the outer peripheral surface of the casing110, and the end of the fixing pin140is inserted into the shroud130so that the shroud130and the airfoil120are fixed to the casing110. In this case, since the turbine vane is also fixed in the circumferential direction of the casing110, it is possible to reduce the occurrence of vibration in the turbine10and enhance the efficiency of the turbine10.

As illustrated inFIG. 2, the first flanges113and the second flanges114are disposed between the first casing111and the second casing112. In this case, due to the presence of the first and second flanges113and114, the fixing pin140may not be inserted through the outer peripheral surfaces of the first and second casings111and112at locations corresponding to the thicknesses of the first and second flanges113and114. Accordingly, as illustrated inFIG. 3, the stator100may further include stops150to fix to the casing110the airfoils120that are disposed in correspondence to the positions of the first and second flanges113and114.

Hereinafter, the embodiment of the present disclosure will be described with respect to the first casing111. However, the embodiment of the present disclosure may be equally applied to the second casing112and associated components in the same manner.

Referring toFIGS. 2 and 3, the airfoils120may include first vane airfoils121(hereinafter referred to as “first airfoils”) disposed on the inner peripheral surface of the first casing111corresponding to the positions of the respective first flanges113. In addition, the stops150may include first stops151provided to the respective first airfoils121.

In this case, the first stops151extend outward radially from first vane shrouds131(hereinafter referred to as “first shrouds”) coupled to the first airfoils121, respectively. In more detail, each of the shrouds130may further include a base plate134, a front end protrusion135extending outward radially from the base plate134so as to be contiguous with a front-stage airfoil, and a rear end protrusion136extending outward radially from the base plate134so as to be contiguous with a rear-stage airfoil. Each of the first stops151is installed at the front or rear end protrusion135or136of the associated first shroud131.

Referring toFIGS. 4 to 6, fastening grooves110aare formed on the contact surface of the first casing111coming into contact with the second casing112. The first stops151are inserted into the respective fastening groove110ato fix the turbine vanes to the first casing111. In this case, the stator100may further include fastening bolts160for fixing the first stops151to the first casing111by penetrating the first stops151. That is, the first shrouds131are fixed to the first casing111by the fastening bolts160penetrating the first stops151and the first casing111from the direction of the second casing112, instead of by the fixing pins140inserted through the outer peripheral surface of the first casing111. Therefore, the first shrouds131are fixed to the first casing111using a force applied in the circumferential direction of the first casing111, and the remainder of the shrouds130are fixed to the first casing111using in a force applied in the axial direction toward the tie rod2.

In the case where the first airfoils121are fixed to the first casing111by the first stops151and the fastening bolts160, it is possible to reduce costs to manufacture products and simplify the structure of the turbine10since there is no need for separate fixing pins large enough to penetrate the first flanges113.

When the flow direction of the combustion gas (or the viewpoint ofFIG. 4) is taken as a reference, the first airfoils121may include a first right vane airfoil122(hereinafter referred to as a “first right airfoil”) disposed to the right of the flow direction of the combustion gas, and a first left vane airfoil123(hereinafter referred to as a “first left airfoil”) disposed to the left of the flow direction of the combustion gas. Similarly, the first shrouds131may include a first right vane shroud132(hereinafter referred to as a “first right shroud”) and a first left vane shroud133(hereinafter referred to as a “first left shroud”).

In addition, the first stops151may include a first right stop152installed at the front end protrusion135of the first right shroud132, and a first left stop153installed at the rear end protrusion136of the first left shroud133. That is, the first right stop152is installed adjacent to the front-stage turbine vane and the first left stop153is installed adjacent to the rear-stage turbine vane.

Although not illustrated in the drawing, among the stops150fixed to the second casing112, the stop150installed at the airfoil120facing the first right airfoil122may be installed adjacent to the rear-stage turbine vane, and the stop150installed at the airfoil120facing the first left airfoil123may be installed adjacent to the front-stage turbine vane.

In this case, a pair of stops150is provided at each of front and rear end sides on the contact surface between the first casing111and the second casing112with respect to the same stage. Thus, in the turbine stator100, the turbine10, and the gas turbine1including the same according to the present disclosure, when the first casing111is coupled to the second casing112, it is possible to prevent impingement between the stops150and fastening bolts160fixed to the first casing111and the stops150and fastening bolts160fixed to the second casing112.

As described above, in accordance with the turbine stator100, the turbine10, and the gas turbine1including the same of the present disclosure, it is possible to reduce occurrence of vibration in the turbine10and enhance the efficiency of the turbine10since the turbine vanes are circumferentially fixed. In addition, in accordance with the turbine stator100, the turbine10, and the gas turbine1including the same of the present disclosure, it is possible to simplify the structure of the turbine10and reduce costs incurred by using separate fixing pins since the turbine vanes positioned inside the flanges113and114are fixed to the casing by means of the stops150.

While the present disclosure has been described with respect to the embodiments illustrated in the drawings, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It will be understood by those skilled in the art that various modifications and other equivalent embodiments may be made without departing from the spirit and scope of the disclosure as defined in the following claims. Therefore, the true technical protection scope of the present disclosure should be defined by technical concepts of the appended claims.