Patent Description:
A gas turbine is a power engine that mixes air compressed by a compressor with fuel for combustion and rotates a turbine with hot gas produced by the combustion. The gas turbine is used to drive a generator, an aircraft, a ship, a train, etc..

A heat recovery steam generator (HRSG) is an energy recovery device that recovers heat from a hot gas stream to produce steam that is usable to drive a steam turbine (combined cycle). The HRSG typically includes four main components: an economizer, an evaporator, a superheater and a preheater.

In particular, a natural circulation HRSG includes piping to facilitate a proper rate of circulation within an evaporator tube, as well as evaporator heating surfaces and drums. A once-through HRSG includes a once-through evaporator that replaces a natural circulation component, thereby providing higher facility efficiency on site and further assisting in extending HRSG life in the absence of thick wall drums.

In the case of supercritical pressure vertical once-through HRSGs, it is difficult to ensure structural stability due to severe thermal expansion of an outlet head of a final superheater. Heating and thermal expansion of the outlet head by steam heated to a high temperature distorts tube arrangement and concentrates thermal stress, resulting in a high risk of breakage.

<CIT> present a recuperator that includes a heating gas duct; an inlet manifold; a discharge manifold; and a once-through heating area disposed in the heating-gas duct through which a heating gas flow is conducted. The once-through heating area is formed from a plurality of first single-row header-and-tube assemblies and a plurality of second single-row header-and-tube assemblies. Each of the plurality of first single-row header-and-tube assemblies including a plurality of first heat exchanger generator tubes is connected in parallel for a through flow of a flow medium therethrough and further includes an inlet header connected to the inlet manifold. Each of the plurality of second single-row header-and-tube assemblies including a plurality of second heat exchanger generator tubes is connected in parallel for a through flow of the flow medium therethrough from respective first heat exchanger generator tubes, and further includes a discharge header connected to the discharge manifold. Each of the inlet headers is connected to the inlet manifold via a respective at least one of a plurality of first link pipes and each of the discharge headers is connected to the discharge manifold via a respective at least one of a plurality of second link pipes. Each of the heat exchanger tubes of each of the first and second single-row header-and-tube assemblies have an inside diameter that is less than an inside diameter of any of the plurality of first and second link pipes.

<CIT> discloses a boiler that has an elongate base header, an elongate dome header, and a plurality of separate watertubes each having an intermediate section and opposite end sections. An upper one of the end sections of each watertube is connected to the dome header and a lower one of the end sections of each watertube is connected to the base header such that the intermediate section extends through a combustion chamber of the boiler. The intermediate section of each watertube has a substantially constant outer diameter along its full length and is closely spaced to adjacent watertubes within the combustion chamber. At least one of the end sections of each watertube has a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange. This arrangement permits close spacing of the connection sites of the watertubes to the header and permits the connection sites to be provided in a linear array. The structure of a watertube, an assembly of a watertube and header, and a method of assembling a boiler are also disclosed.

Aspects of one or more exemplary embodiments provide a once-through heat exchanger, a heat recovery steam generator, and a combined power generation system including the same, which are capable of minimizing damage caused by thermal expansion.

Additional aspects will be set forth in part in the description which follows and, in part, will become apparent from the description, or may be learned by practice of the exemplary embodiments.

One or more of these objects are solved by the invention set out by the features of the independent claim. According to an aspect of an exemplary embodiment, there is provided a once-through heat exchanger that includes a plurality of tubes (e.g. a tube stack including a plurality of tubes), a plurality of heads connected to the tubes and configured to accommodate heated steam, a manifold connected to the heads and configured to accommodate heated steam, and a first link pipe and a second link pipe configured to connect the heads and the manifold. the first link pipe and/or the second link pipe may include a variable pipe whose inner diameter gradually changes.

The heads may be spaced in a direction crossing a longitudinal direction thereof. The first link pipe and the second link pipe may include a first inclined link part or a second inclined link part, respectively, extending at an angle to each other.

The heads may be arranged parallel to each other and/or be positioned at the same distance from the manifold.

The heads may be spaced in a height direction of the once-through heat exchanger.

The first link pipe includes a first connection link part extending from an associated one of the heads toward the manifold. The first link pipe includes further a first inclined link part protruding obliquely from the first connection link part and coupled to the manifold.

The second link pipe may include a second connection link part extending from an associated one of the heads toward the manifold. The second link pipe may include a second inclined link part protruding obliquely from the second connection link part and coupled to the manifold.

The first connection link part and the second connection link part may be arranged parallel to each other. The first inclined link part may extend obliquely downward from the manifold, and/or the second inclined link part may extend obliquely upward from the manifold.

The first inclined link part includes a large diameter portion having a larger outer diameter than the first connection link part, a small diameter portion having the same inner diameter as the first connection link part, and the variable pipe configured to connect the large diameter portion and the small diameter portion.

The large diameter portion is connected to the manifold, and the inner diameter of the variable pipe gradually decreases from the large diameter portion to the small diameter portion.

The second inclined link part may include a large diameter portion having a larger outer diameter than the second connection link part, a small diameter portion having the same inner diameter as the second connection link part, and the variable pipe configured to connect the large diameter portion and the small diameter portion.

According to an aspect of another exemplary embodiment, there is provided a combined power generation system that includes a gas turbine configured to generate rotational force by burning fuel, a heat recovery steam generator configured to heat water using combustion gas discharged from the gas turbine and including a high-pressure section, a medium-pressure section, and a low-pressure section having different levels of pressure, and a steam turbine using steam heated by the heat recovery steam generator. The heat recovery steam generator includes a plurality of heat exchangers. Each of the heat exchangers includes a tube stack including a plurality of tubes, a plurality of heads connected to the tubes and configured to accommodate heated steam, a manifold connected to the heads and configured to accommodate heated steam, and a first link pipe and a second link pipe configured to connect the heads and the manifold. The first link pipe and/or the second link pipe may include a variable pipe whose inner diameter gradually changes.

The heads may be arranged parallel to each other and positioned at the same distance from the manifold.

The heads may be spaced in a height direction of the heat exchanger.

The first link pipe includes a first connection link part extending from an associated one of the heads toward the manifold. The first link pipe includes a first inclined link part protruding obliquely from the first connection link part and coupled to the manifold.

The large diameter portion is connected to the manifold. The inner diameter of the variable pipe gradually decreases from the large diameter portion to the small diameter portion.

The above and other aspects will become more apparent from the following description of the exemplary embodiments with reference to the accompanying drawings, in which:.

The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of the disclosure. In the disclosure, terms such as "comprises", "includes", or "have/has" should be construed as designating that there are such features, integers, steps, operations, components, parts, and/or combinations thereof, not to exclude the presence or possibility of adding of one or more of other features, integers, steps, operations, components, parts, and/or combinations thereof.

Exemplary embodiments will be described below in detail with reference to the accompanying drawings. It should be noted that like reference numerals refer to like parts throughout various drawings and exemplary embodiments. In certain embodiments, a detailed description of functions and configurations well known in the art may be omitted to avoid obscuring appreciation of the disclosure by those skilled in the art. For the same reason, some components may be exaggerated, omitted, or schematically illustrated in the accompanying drawings.

Hereinafter, a combined power generation system according to a first example will be described.

<FIG> is a configuration diagram illustrating the combined power generation system according to the first example. <FIG> is a configuration diagram illustrating a heat recovery steam generator according to the first example.

Referring to <FIG>, the combined power generation system, which is designated by reference numeral <NUM>, according to the first example includes a plurality of turbines to generate electric power. The combined power generation system <NUM> may include a gas turbine <NUM>, a steam turbine <NUM>, a first generator G1, a second generator G2, and a heat recovery steam generator <NUM>.

In the gas turbine <NUM>, thermal energy may be released by combustion of fuel in an isobaric environment after atmospheric air is sucked and compressed to a high pressure, hot combustion gas may be expanded to be converted into kinetic energy, and exhaust gas with residual energy may then be discharged to the atmosphere.

The gas turbine <NUM> may include a compressor <NUM>, a combustor <NUM>, and a main turbine <NUM>. The compressor <NUM> of the gas turbine <NUM> may suck air from the outside and compress the air. The compressor <NUM> may supply the combustor <NUM> with the air compressed by compressor blades and may also supply cooling air to a hot region required for cooling in the gas turbine <NUM>.

Meanwhile, the combustor <NUM> may mix the compressed air, which is supplied from the outlet of the compressor <NUM>, with fuel for isobaric combustion to produce combustion gas with high energy.

The high-temperature and high-pressure combustion gas produced by the combustor <NUM> is supplied to the main turbine <NUM>. In the main turbine <NUM>, the combustion gas applies impingement or reaction force to a plurality of turbine blades radially disposed on the rotary shaft of the main turbine <NUM> while expanding adiabatically, so that the thermal energy of the combustion gas is converted into mechanical energy for rotating the rotary shaft. Some of the mechanical energy obtained from the main turbine <NUM> is supplied as energy required to compress the air in the compressor <NUM>, and the rest is utilized as effective energy, such as for driving the first generator G1 to generate electric power.

After the combustion gas flowing out of the main turbine <NUM> is cooled through the heat recovery steam generator <NUM>, it is purified and discharged to the outside. The heat recovery steam generator <NUM> not only cools the combustion gas, but also produces high-temperature and high-pressure steam using the heat of the combustion gas to deliver the steam to the steam turbine <NUM>.

The steam turbine <NUM> rotates the blades thereof using the steam produced by the heat recovery steam generator <NUM> and transfers rotational energy to the second generator G2. The steam turbine <NUM> supplies cooled steam back to the heat recovery steam generator <NUM>.

The first generator G1 may be connected to the gas turbine <NUM> and the second generator G2 may be connected to the steam turbine <NUM> so as to generate electric power. However, the present disclosure is not limited thereto, and a single generator may be connected to the gas turbine <NUM> and the steam turbine <NUM>.

The combined power generation system may be equipped with a condenser <NUM> for condensing steam, a condensate reservoir <NUM> for storing condensed water, and a condensate pump <NUM> for supplying the heat recovery steam generator <NUM> with the condensed water stored in the condensate reservoir <NUM>.

The steam flowing in the heat recovery steam generator <NUM> may have two or three levels of pressure, so that the water is pressurized to two or three or more levels of pressure. In the exemplary embodiment, the heat recovery steam generator <NUM> is exemplified as having three levels of pressure.

The heat recovery steam generator <NUM> may include a low-pressure section H1 having a relatively low pressure, a medium-pressure section H2 having a medium pressure, and a high-pressure section H3 having a relatively high pressure. The high-pressure section H3 may be disposed adjacent to an inlet for introduction of combustion gas therethrough and be heated by high-temperature combustion gas. The low-pressure section H1 may be disposed adjacent to an outlet for discharge of combustion gas therethrough and be heated by low-temperature combustion gas.

The heat recovery steam generator <NUM> includes a condensate preheater <NUM>, a low-pressure evaporator <NUM>, a medium-pressure economizer <NUM>, a medium-pressure evaporator <NUM>, a high-pressure economizer <NUM>, and a high-pressure evaporator <NUM>, which are installed therein. In addition, an additional superheater (not shown) may be installed upstream of each evaporator. The combustion gas flowing out of the heat recovery steam generator <NUM> may be discharged via a stack.

The low-pressure section H1 includes a condensate preheater <NUM>, a low-pressure evaporator <NUM>, and a low-pressure drum <NUM>. The condensed water stored in the condensate reservoir <NUM> is delivered to the condensate preheater <NUM> by the condensate pump <NUM>. The condensate preheater <NUM> heats the condensed water by exchanging heat with combustion gas. The water heated by the condensate preheater <NUM> is delivered to a deaerator <NUM> so that gas is removed from the condensed water.

Water is supplied from the deaerator <NUM> to the low-pressure drum <NUM>. The low-pressure evaporator <NUM> may be connected to the low-pressure drum <NUM>, so that the water stored in the low-pressure drum <NUM> is converted into steam by heating and the steam is then supplied to the superheater after steam-water separation in the low-pressure drum <NUM>.

The medium-pressure section H2 includes a medium-pressure economizer <NUM>, a medium-pressure evaporator <NUM>, and a medium-pressure drum <NUM>. The water in the deaerator <NUM> is supplied to the medium-pressure economizer <NUM> by a medium-pressure pump <NUM>. The medium-pressure economizer <NUM> heats the water by exchanging heat with combustion gas. The water heated in the medium-pressure economizer <NUM> is supplied to the low-pressure drum <NUM>. The medium-pressure evaporator <NUM> may be connected to the medium-pressure drum <NUM>, so that the water stored in the medium-pressure drum <NUM> is converted into steam by heating and the steam is then supplied to the superheater after steam-water separation in the medium-pressure drum <NUM>.

The high-pressure section H3 includes a high-pressure economizer <NUM>, a high-pressure evaporator <NUM>, a high-pressure drum <NUM>, and a high-pressure superheater <NUM>. The water in the deaerator <NUM> is supplied to the high-pressure economizer <NUM> by a high-pressure pump <NUM>. The high-pressure economizer <NUM> heats the water by exchanging heat with combustion gas. The water heated in the high-pressure economizer <NUM> is supplied to the high-pressure drum <NUM>. The high-pressure evaporator <NUM> may be connected to the high-pressure drum <NUM>, so that the water stored in the high-pressure drum <NUM> is converted into steam by heating and the steam is then supplied to the high-pressure superheater <NUM> after steam-water separation in the high-pressure drum <NUM>.

The steam stored in the low-pressure drum <NUM>, the medium-pressure drum <NUM>, and the high-pressure drum <NUM> may be supplied to low-pressure, medium-pressure, and high-pressure steam turbines, respectively.

<FIG> is a perspective view illustrating a heat exchanger according to the first example. <FIG> is a side view illustrating the heat exchanger according to the first example.

Referring to <FIG>, the heat exchanger, which is designated by reference numeral <NUM>, according to the present example may be a once-through heat exchanger, and in particular, a vertical once-through heat exchanger applied to the heat recovery steam generator <NUM>. Alternatively, the heat exchanger <NUM> may be the high-pressure superheater <NUM> of the high-pressure section H3.

The heat exchanger <NUM> may include a plurality of tubes <NUM> and <NUM>, a plurality of heads <NUM>, a first link pipe <NUM>, a second link pipe <NUM>, and a manifold <NUM>. The heat exchanger <NUM> includes the tubes <NUM> and <NUM>, and steam flowing along the tubes <NUM> and <NUM> may be heated by high-temperature combustion gas.

A first tube <NUM> and a second tube <NUM> may be coupled to each of the heads <NUM>. The first tube <NUM> may protrude upward from the head <NUM>, and the second tube <NUM> may protrude downward from the head <NUM>. The first tube <NUM> may include a first inclined connection part 156a protruding obliquely downward from the head <NUM> and a first extension part 156b bent from the first inclined connection part 156a and extending horizontally to the ground. The second tube <NUM> may include a second inclined connection part 157a protruding obliquely upward from the head <NUM> and a second extension part 157b bent from the second inclined connection part 157a and extending horizontally to the ground.

Each head <NUM> is connected to the plurality of tubes <NUM> and <NUM> and accommodates steam delivered from the tubes <NUM> and <NUM>. The head <NUM> may be a pipe that extends parallel to the manifold <NUM> and has both longitudinal ends blocked.

The plurality of heads <NUM> may be arranged parallel to each other and may be spaced at the same distance from the manifold <NUM>. In addition, the heads <NUM> may be spaced in the height direction of the once-through heat exchanger.

The first link pipe <NUM> may include a first connection link part 152b extending from an associated one of the heads <NUM> toward the manifold <NUM> and a first inclined link part 152a protruding obliquely from the first connection link part 152b and coupled to the manifold <NUM>. The first link pipe <NUM> may have a larger outer diameter than the tubes <NUM> and <NUM>, and the first link pipe <NUM> may have a larger thickness than the tubes <NUM> and <NUM>.

The second link pipe <NUM> may include a second connection link part 153b extending from an associated one of the heads toward the manifold <NUM> and a second inclined link part 153a protruding obliquely from the second connection link part 153b and coupled to the manifold <NUM>. The second link pipe <NUM> may have a larger outer diameter than the tubes <NUM> and <NUM>, and the second link pipe <NUM> may have a larger thickness than the tubes <NUM> and <NUM>.

The first connection link part 152b and the second connection link part 153b may be arranged parallel to each other, and the first inclined link part 152a may be inclined at a preset angle of inclination A11 with respect to the second inclined link part 153a. The first inclined link part 152a may extend obliquely downward from the manifold <NUM> and the second inclined link part 153a may extend obliquely upward from the manifold <NUM>.

<FIG> is a graph illustrating a comparison of thermal stress distribution between the heat exchanger according to the first example and a conventional heat exchanger.

The conventional heat exchanger has a structure in which tubes are directly connected to a manifold. As illustrated in <FIG>, it can be seen in the conventional heat exchanger that a large thermal stress occurs in a portion where the manifold is connected to the tubes and the thermal stress is large even in a portion adjacent to the outer surface of that portion. However, in the heat exchanger <NUM> according to the present example, a large thermal stress occurs in a portion where the manifold <NUM> is connected to the first link pipe <NUM>, but it occurs only in a portion of the inner side thereof. In addition, the thermal stress is large in a portion less than half of the thickness of that portion, and the thermal stress is greatly reduced on the outer surface of that portion.

In particular, since the first inclined connection part 156a and the second inclined connection part 157a are inclined in different directions, steam can be introduced through the first and second inclined connection parts in a direction crossing each other into the manifold <NUM> and uniformly mixed within the manifold <NUM>. In addition, it is possible to prevent the concentration of heat in a portion of the heat exchanger.

As described above, the heat exchanger <NUM> according to the present example can significantly reduce piping breakage due to thermal stress.

Hereinafter, a heat exchanger according to the embodiment according to the invention will be described.

<FIG> is a perspective view illustrating the heat exchanger according to the embodiment. <FIG> is a side view illustrating the heat exchanger according to the embodiment.

Referring to <FIG> and <FIG>, the heat exchanger, which is designated by reference numeral <NUM>, according to the embodiment may include a plurality of tubes <NUM> and <NUM>, a plurality of heads <NUM>, a first link pipe <NUM>, a second link pipe <NUM>, and a manifold <NUM>.

Since the heat exchanger <NUM> according to the embodiment has the same structure as the heat exchanger according to the first example, with the sole exception of the first link pipe <NUM> and the second link pipe <NUM>, a redundant description thereof will be omitted.

A first tube <NUM> and a second tube <NUM> may be coupled to each of the heads <NUM>. The first tube <NUM> may protrude upward from the head <NUM>, and the second tube <NUM> may protrude downward from the head <NUM>. The first tube <NUM> may include a first inclined connection part 166a protruding obliquely upward from the head <NUM> and a first extension part 166b bent from the first inclined connection part 166a and extending in a horizontal direction. The second tube <NUM> may include a second inclined connection part 167a protruding obliquely downward from the head <NUM> and a second extension part 167b bent from the second inclined connection part 167a and extending in a horizontal direction.

The first link pipe <NUM> may include a first connection link part 162b extending from an associated one of the heads <NUM> toward the manifold <NUM> and a first inclined link part 162a protruding obliquely from the first connection link part 162b and coupled to the manifold <NUM>.

In addition, the first inclined link part 162a may include a large diameter portion 162aa having a larger outer diameter than the first connection link part 162b, a small diameter portion 162ac having the same inner diameter as the first connection link part 162b, and a variable pipe 162ab connecting the large diameter portion 162aa and the small diameter portion 162ac. The large diameter portion 162aa may be connected to the manifold <NUM>. The variable pipe 162ab may be formed such that the inner and outer diameters thereof gradually decrease from the large diameter portion 162aa to the small diameter portion 162ac.

The second link pipe <NUM> may include a second connection link part 163b extending from an associated one of the heads <NUM> toward the manifold <NUM> and a second inclined link part 163a protruding obliquely from the second connection link part 163b and coupled to the manifold <NUM>. The second link pipe <NUM> may have a larger outer diameter than the tubes <NUM> and <NUM>, and the second link pipe <NUM> may have a larger thickness than the tubes <NUM> and <NUM>.

The first connection link part 162b and the second connection link part 163b may be arranged parallel to each other, and the first inclined link part 162a may be inclined at a preset angle of inclination A11 with respect to the second inclined link part 163a. The first inclined link part 162a may extend obliquely downward from the manifold <NUM> and the second inclined link part 163a may extend obliquely upward from the manifold <NUM>.

In addition, the second inclined link part 163a may include a large diameter portion 163aa having a larger outer diameter than the second connection link part 163b, a small diameter portion 163ac having the same inner diameter as the second connection link part 163b, and a variable pipe 163ab connecting the large diameter portion 163aa and the small diameter portion 163ac. The large diameter portion 163aa may be connected to the manifold <NUM>. The variable pipe 163ab may be formed such that the inner diameter thereof gradually decreases from the large diameter portion 163aa to the small diameter portion 163ac.

<FIG> is a graph illustrating a comparison of thermal stress distribution between the heat exchanger according to the embodiment and a conventional heat exchanger.

The conventional heat exchanger has a structure in which tubes are directly connected to a manifold. As illustrated in <FIG>, it can be seen in the conventional heat exchanger that a large thermal stress occurs in a portion where the manifold is connected to the tubes and the thermal stress is large even in a portion adjacent to the outer surface of that portion. However, in the heat exchanger <NUM> according to the present embodiment, a large thermal stress occurs in a portion where the first link pipe <NUM> is connected to the manifold <NUM>, but it occurs only in a local portion of the inner side thereof. In addition, only a small thermal stress occurs in most of the connection portions.

In particular, since the first inclined link part 162a and the second inclined link part 163a include the variable tube 162ab and the variable tube 163ab, respectively, the pressure and speed of steam can be reduced in the variable tube 162ab and the variable tube 163ab. Therefore, it is possible to significantly reduce thermal stress and thermal damage compared to the prior art.

As is apparent from the above description, the once-through heat exchanger according to the exemplary embodiment can prevent breakage due to thermal stress since the first link pipe and the second link pipe include the first inclined link part and the second inclined link part, respectively, extending at an angle to each other.

Claim 1:
A once-through heat exchanger (<NUM>) comprising:
a plurality of tubes (<NUM>, <NUM>);
a plurality of heads (<NUM>) connected to the tubes (<NUM>, <NUM>) and configured to accommodate heated steam;
a manifold (<NUM>) connected to the heads (<NUM>) and configured to accommodate heated steam; and
a first link pipe (<NUM>) and a second link pipe (<NUM>) configured to connect the heads (<NUM>) and the manifold (<NUM>),
characterized in that:
the first link pipe (<NUM>) or the second link pipe (<NUM>) comprises a variable pipe (162ab, 163ab) whose inner diameter gradually changes;
wherein the first link pipe (<NUM>) comprises a first connection link part (162b) extending from an associated one of the heads (<NUM>) toward the manifold (<NUM>) and a first inclined link part (162a) protruding obliquely from the first connection link part (162b) and coupled to the manifold (<NUM>);
wherein the first inclined link part (162a) comprises a large diameter portion (162aa) having a larger outer diameter than the first connection link part (162b), a small diameter portion (162ac) having the same inner diameter as the first connection link part (162b), and the variable pipe (162ab) connecting the large diameter portion and the small diameter portion; and
wherein the large diameter portion (162aa) is connected to the manifold (<NUM>), and the inner diameter of the variable pipe (162ab) gradually decreases from the large diameter portion (162aa) to the small diameter portion (162ac).