Combustor and gas turbine including the same

A combustor includes a fuel injector to inject fuel; a cooling passage configured to pass compressed air for cooling an outer surface of a liner forming a combustion chamber for containing combustion gas; and a nozzle part that is coupled to the liner and has a rear surface facing the combustion chamber, the nozzle part configured to mix the compressed air with the fuel from the fuel injector and to discharge some of the compressed air in the cooling passage to the rear surface in order to block an introduction of the combustion gas into the nozzle part. Before the compressed air introduced through air introduction holes formed in a nozzle casing is discharged through through-holes formed in a nozzle cap, some of the compressed air may be introduced through bypass holes formed in a bypass tube and then discharged to the combustion chamber through the gap.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No. 10-2017-0142542, filed on Oct. 30, 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 combustor and a gas turbine including the same.

Description of the Related Art

A gas turbine is a power engine that mixes air compressed in a compressor with fuel for combustion and rotates a turbine using high-temperature gas produced by the combustion. The gas turbine is used to drive a generator, an aircraft, a ship, a train, etc.

This gas turbine typically includes a compressor, a combustor, and a turbine. The compressor sucks and compresses outside air, and then transmits it to the combustor. The air compressed in the compressor is in a high-pressure and high-temperature state. The combustor mixes the compressed air introduced from the compressor with fuel and burns the mixture. Combustion gas produced by the combustion is discharged to the turbine. Turbine blades in the turbine are rotated by the combustion gas, thereby generating power. The generated power is used in various fields, such as generating electric power and driving machines.

The combustor is provided with a combustion duct assembly that transmits high-temperature combustion gas produced in a combustion chamber to the turbine. The combustion duct assembly includes a liner and a transition piece connected to the liner to guide the produced combustion gas to the turbine. The combustor includes a nozzle part and a head part, which are installed over the liner. The head part includes a plurality of fuel injectors supported by an end plate, and the nozzle part includes a plurality of nozzles supported by a nozzle casing, a nozzle shroud, and the like.

In this case, the surface of the nozzle part faces the high-temperature environment of the combustion chamber and is thus always directly exposed to the combustion gas in the combustion chamber and to its high temperatures. Hence, if some of the combustion gas is introduced into the nozzle part through a minute gap, the durability of the nozzle part may be deteriorated.

SUMMARY OF THE INVENTION

An object of the present disclosure is to provide a combustor capable of blocking the introduction of combustion gas into a nozzle part, and a gas turbine including the same.

In accordance with one aspect of the present disclosure, a combustor may include a fuel injector to inject fuel; a cooling passage configured to pass compressed air for cooling an outer surface of a liner forming a combustion chamber for containing combustion gas; and a nozzle part that is coupled to the liner and has a rear surface facing the combustion chamber, the nozzle part configured to mix the compressed air with the fuel from the fuel injector and to discharge some of the compressed air in the cooling passage to the rear surface in order to block an introduction of the combustion gas into the nozzle part.

The nozzle part may include a nozzle installed at one end of the fuel injector and surrounded by a nozzle shroud for introducing the compressed air from the cooling passage into a space between the nozzle and the nozzle shroud in which the compressed air and the fuel are mixed; a nozzle casing for supporting the nozzle shroud at one end and including an open side at the other end, the nozzle casing further including a side in which an air introduction hole is formed; a nozzle cap installed in the open side of the nozzle casing between the nozzle shroud and the nozzle casing, the nozzle cap having a plurality of through-holes formed to discharge the compressed air introduced through the air introduction hole; and an annular bypass tube installed between the nozzle shroud and the nozzle cap to form a gap between the nozzle shroud and an inner circumferential surface of the nozzle cap, the annular bypass tube having a bypass hole formed to discharge to the gap some of the compressed air introduced through the air introduction hole.

The nozzle shroud may have a tubular shape that is longer than the nozzle, and the installed nozzle may have one end concealed within the nozzle shroud.

The nozzle part may further include a swirler installed inside the nozzle shroud.

The combustor may further include a plurality of fixing brackets formed on an outer circumference of the nozzle casing to be radially coupled inside the combustor casing.

The may further include a spring seal provided on an outer circumference of the nozzle casing to be pressed into the liner.

The air introduction hole may consists of a plurality of air introduction holes circumferentially formed in the nozzle casing.

The combustor may further include a holder interposed between the nozzle cap and the nozzle casing to fix the nozzle cap inside the open side of the nozzle casing.

The nozzle cap may have a flat surface facing the combustion chamber, and the through-holes may be formed throughout the flat surface.

The annular bypass tube may be supported inside the nozzle cap.

The bypass hole may consist of a plurality of bypass holes circumferentially formed in the annular bypass tube.

The annular bypass hole may be inclined with respect to a longitudinal direction of the bypass tube.

In accordance with another aspect of the present disclosure, a gas turbine may include a compressor to compress air, a combustor to produce combustion gas by mixing fuel with the compressed air and combusting the mixture, and a turbine configured to be rotated by the combustion gas to generate power. The combustor of the gas turbine may include the fuel injector of the above combustor; the cooling passage of the above combustor; and a nozzle part including a nozzle installed at one end of the fuel injector and surrounded by a nozzle shroud for introducing the compressed air from the cooling passage into a space between the nozzle and the nozzle shroud in which the compressed air and the fuel are mixed; a nozzle casing for supporting the nozzle shroud at one end and including an open side at the other end, the nozzle casing further including a side in which an air introduction hole is formed; a nozzle cap installed in the open side of the nozzle casing between the nozzle shroud and the nozzle casing, the nozzle cap having a plurality of through-holes formed to discharge the compressed air introduced through the air introduction hole; and an annular bypass tube installed between the nozzle shroud and the nozzle cap to form a gap between the nozzle shroud and an inner circumferential surface of the nozzle cap, the annular bypass tube having a bypass hole formed to discharge to the gap some of the compressed air introduced through the air introduction hole.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present disclosure may be subjected to various modifications and have various embodiments. Specific embodiments are illustrated in the drawings and will be described in the detailed description of the present disclosure. However, this is not intended to limit the present disclosure to specific embodiments. It should be understood that the present disclosure includes all modifications, equivalents or replacements that fall within the spirit and technical range of the present disclosure, and the scope of the present disclosure is not limited to the following embodiments.

The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. As used in the disclosure and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless context clearly indicates otherwise. It will be further understood that the terms “comprises/includes” and/or “comprising/including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Exemplary embodiments of the present disclosure will be described below in more detail with reference to the accompanying drawings. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present disclosure. In certain embodiments, detailed descriptions of functions and configurations well known in the art may be omitted to avoid obscuring appreciation of the disclosure by a person of ordinary skill in the art. For the same reason, some components may be exaggerated, omitted, or schematically illustrated in the accompanying drawings.

FIG. 1illustrates the structure of a gas turbine1000according to the present disclosure.FIG. 2illustrates a combustor1200included in the gas turbine ofFIG. 1.

Referring toFIGS. 1 and 2, a compressor1100of the gas turbine1000serves to suck and compress air, and mainly serves to supply cooling air to a high-temperature region required for cooling in the gas turbine1000while supplying combustion air to the combustor1200. Since the air sucked into the compressor1100is subject to an adiabatic compression process, the pressure and temperature of the air passing through the compressor1100increase. The compressor1100of the large gas turbine1000as inFIG. 1is a multistage axial compressor configured such that a large amount of air is compressed to a desired compression ratio while passing through each stage.

The combustor1200mixes the compressed air, which is supplied from the outlet of the compressor1100, with fuel for isobaric combustion to produce high-energy combustion gas. The combustor1200, which in actuality consists of a plurality of combustors1200arranged around a casing of the gas turbine100, is disposed downstream of the compressor1100. Each combustor1200includes a plurality of head parts1220arranged in an annular combustor casing1210and supported by an end plate1221. Each head part1220includes a plurality of fuel injectors1222, and the fuel supplied from the fuel injectors1222is mixed with air at an appropriate rate to be suitable for combustion.

The gas turbine1000may use gas fuel, liquid fuel, or composite fuel combining them. It is important to make a combustion environment for reducing an amount of emission such as carbon monoxide or nitrogen oxide that is subject to legal regulations. Accordingly, pre-mixed combustion has been increasingly used in recent years in that it can accomplish uniform combustion to reduce emission by lowering a combustion temperature even though it is relatively difficult to control combustion.

In the pre-mixed combustion, compressed air is mixed with the fuel injected from the fuel injectors1222and then introduced into a combustion chamber1240. When combustion is stable after pre-mixed gas is initially ignited by an igniter, the combustion is maintained by the supply of fuel and air.

The combustor1200needs to be suitably cooled since it operates at the highest temperature in the gas turbine1000. Especially, a turbine inlet temperature (TIT) is very important in the gas turbine1000because the efficiency of the gas turbine1000is typically increased as the turbine inlet temperature becomes high. In addition, the increase of the turbine inlet temperature is advantageous for gas turbine combined power generation. For this reason, the gas turbine1000is also classified based on the turbine inlet temperature.

Ultimately, the temperature of combustion gas must be increased to increase the turbine inlet temperature. Accordingly, it is important that a combustion duct assembly, which forms the combustion chamber1240and passage of the combustor1200for the flow of hot combustion gas, be designed to be made of a high heat-resistant material and desirably cooled.

Compressed air flows along the outer surface of the combustion duct assembly, which connects the combustor1200to a turbine1300so that hot combustion gas flows through the combustion duct assembly, and is supplied to the fuel injectors1222. In this process, the combustion duct assembly heated by the hot combustion gas is properly cooled.

The combustion duct assembly may consist of a liner1250and a transition piece and is formed by coupling the liner1250and the transition piece, which each have a double-tube structure, through an elastic support (not shown) provided to accommodate the effects of thermal expansion. In this case, the transition piece consists of an inner transition piece1260and an outer transition piece1270. The inner transition piece1260connected to the liner1250is connected to the inlet of the turbine1300to guide hot combustion gas to the turbine1300.

The liner1250is a tubular member connected to a nozzle part1290, which will be described later, and defines an internal space forming the combustion chamber1240. It is necessary to suitably cool the liner1250and the transition piece because their inner surfaces are in direct contact with hot combustion gas. To this end, a plurality of cooling holes or inlets (not shown) may be provided in the outer peripheral surfaces of the outer transition piece1270and the liner1250. The number and arrangement of such cooling holes is not particularly limited and may be determined by design requirements.

The liner1250may consist of an inner liner1251forming the combustion chamber1240, and an outer liner1252surrounding the inner liner1251to form a cooling passage C for the flow of compressed air introduced via cooling holes/inlets. The air introduced into the cooling passage C through the inlet holes may be compressed air supplied from the compressor1100of the gas turbine. While the outer liner1252is separated from the inner liner1251, the inner liner1251is in direct contact with hot combustion gas produced in the combustion chamber1240so that heat is directly transferred from the combustion gas to the inner liner1251.

The liner1250may be included within a casing can (not shown) and the compressed air produced in the compressor may be introduced into the casing can and then introduced into the cooling passage C through the inlet holes while flowing along the outer surface of the liner1250. The compressed air flowing through the cooling passageC comesinto contact with the inner liner1251and thus cools the inner liner1251.

FIG. 3illustrates a portion of the combustor ofFIG. 2, andFIG. 4is a section view of a region “A” ofFIG. 3. Here, the individual fuel injectors1222are combined with the nozzle part1290to mix compressed air with fuel for injection.FIG. 5illustrates the external appearance of the nozzle part1290in which a plurality of nozzles1291are arranged. The nozzle part1290has a rear side that faces the combustion chamber1240(FIG. 2).

Referring toFIGS. 3 to 5, the nozzle part1290includes the nozzles1291, a nozzle shroud1292, a nozzle casing1293, a nozzle cap1294, and an annular bypass tube1295. Each nozzle1291is installed at one end of the fuel injectors1222and is surrounded by the nozzle shroud1292forming a compressed air inlet (facing the fuel injectors1222, refer toFIG. 7) for introducing compressed air into a space between the nozzle1291and the nozzle shroud1292in which fuel is mixed with the compressed air. The nozzle casing1293, which encloses the plurality of nozzles1291, is coupled to the combustor casing1210while supporting the nozzle shroud1292at one end and has an open side at the other end. An air introduction hole1293ais formed in the side of the nozzle casing1293. The nozzle cap1294is installed in the open side of the nozzle casing1293and closes the open areas around the nozzle shroud1292, between the nozzle shroud1292and the nozzle casing1293. A plurality of through-holes1294aare formed in the nozzle cap1294to discharge the compressed air introduced through the air introduction hole1293a. The annular bypass tube1295is installed between the nozzle shroud1292and the nozzle cap1294to form a gap G around the nozzle shroud1292, between the nozzle shroud1292and an inner circumferential surface of the nozzle cap1294. A bypass hole1295ais formed in the bypass tube1295to discharge to the gap G some of the compressed air introduced through the air introduction hole1293a(refer toFIG. 6).

The end of the nozzle1291may be recessed to a certain depth so as to be concealed within the nozzle shroud1292to be protected from the hot gas produced by combustion. The configuration is not limited only to the double-tube shape illustrated in the drawings.

On the other hand, one end of the nozzle shroud1292has a tubular shape and may be slightly longer than the nozzle1291, thereby enabling the nozzle1291to be restrictively protected from hot gas. The other end of the nozzle shroud1292is a portion for receiving compressed air and has a relatively large inner diameter. A swirler (not shown) may be additionally installed inside the other end of the nozzle shroud1292.

Referring toFIG. 5, the nozzle casing1293has an outer circumference on which a plurality of fixing brackets1293-1are formed and radially coupled inside the combustor casing1210. The air introduction hole1293amay consist of a plurality of air introduction holes circumferentially (radially) formed in the nozzle casing1293, but the present disclosure is not limited thereto.

The outer circumference of the nozzle casing1293is provided with a spring seal1293-2that presses into the inner liner1251as shown inFIG. 4. Here, the nozzle cap1294is fixed inside the open end of the nozzle casing1293by a holder1294-1interposed therebetween. The nozzle cap1294has a flat surface, throughout which are formed the through-holes1294a, facing the combustion chamber1240so that compressed air is supplied to the combustion chamber1240through the through-holes1294ato protect the nozzle part1290from hot gas.

As illustrated inFIG. 6, the bypass tube1295may be supported inside the inner circumferential surface of the nozzle cap1294. The bypass hole1295aformed in the bypass tube1295may consists of a plurality of bypass holes1295aarranged circumferentially around the bypass tube1295for the introduction of some of the compressed air to be discharged through the through-holes1294aof the nozzle cap1294. The compressed air introduced through the bypass holes1295amay be discharged to the combustion chamber1240through the gap G formed outside the nozzle shroud1292. To facilitate airflow, the bypass holes1295amay be inclined at a certain angle with respect to the longitudinal direction of the bypass tube1295.

Hereinafter, the operation of the combustor according to the embodiment of the present disclosure will be described with reference toFIG. 7.

Referring toFIG. 7, compressed air flows in the direction of the arrow through the cooling passage C formed between the inner liner1251and the outer liner1252, and is supplied into the nozzle shroud1292for the purpose of cooling. Meanwhile, some of the compressed air flowing into the nozzle shroud1292may be introduced in the direction of the vertical, dotted line arrow ofFIG. 7through the air introduction holes1293aformed in the nozzle casing1293. Most of the compressed air introduced through the air introduction holes1293ais discharged to the combustion chamber1240through the through-holes1294aformed in the nozzle cap1294to protect the nozzle part1290from the high-temperature combustion chamber1240.

In the present disclosure, before the compressed air introduced through the air introduction holes1293ais discharged through the through-holes1294a, some of the compressed air may be introduced in the direction of the inclined, dotted line arrows through the bypass holes1295aformed in the bypass tube1295, and then discharged to the combustion chamber1240through the gap G as inFIG. 6.

The high-temperature and high-pressure combustion gas produced in the combustor1200in this process is supplied to the turbine1300through the combustion duct assembly. In the turbine1300, the thermal energy of combustion gas is converted into mechanical energy to rotate a rotary shaft by applying impingement and reaction force to a plurality of blades radially arranged on the rotary shaft of the turbine1300through the adiabatic expansion of the combustion gas. Some of the mechanical energy obtained from the turbine1300is supplied as energy required for compression of air in the compressor, and the remainder is used as effective energy required for driving a generator to produce electric power or the like.

As described above, the combustor and the gas turbine including the same according to the present disclosure are advantageous in that the durability of the nozzle part can be enhanced by blocking the introduction of combustion gas into the nozzle part through the gap.

While the specific embodiments have been described with reference to the drawings, the present disclosure is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the disclosure as defined in the following claims.