Patent Description:
Dual cycle power plants include a power generation system that creates excess heat that can be used for other purposes. For example, a cogeneration plant creates power and excess heat that can be used for other purposes. Similarly, combined cycle power plants (CCPP) include a gas turbine (GT) system that creates power and excess heat that can be used to create steam for a steam turbine (ST) system that also creates power. In a simple cycle operation of the CCPP, the GT system is operated alone to generate power, and exhaust therefrom is directed via a diverter or bypass damper through a bypass exhaust stack. The bypass exhaust stack may include any variety of environmental exhaust treatment systems that treat the exhaust gas prior to exiting it to the atmosphere. In the combined cycle operation of the CCPP, the hot exhaust from the GT system is directed by the bypass damper to a heat recovery system, e.g., a heat recovery steam generator, to create steam for the ST system, prior to it being exhausted to the atmosphere. In the combined cycle, both the GT system and the ST system generate power.

An ST system startup ideally includes gradually increasing temperature of the system to prevent damage to the system. The ST system temperature is increased through, among other things, controlling the amount of steam created by the heat recovery system and applied to the ST system. The bypass damper used to re-direct GT system exhaust from the exhaust stack to the heat recovery system may include a single or double blade closure or a flap valve. The blade(s) either swing open or closed on an end pivot point or slide open/closed (the latter may be referred to as a guillotine damper). The bypass damper is typically designed to be in an open or a closed position.

In operation, the GT system creates hot exhaust and, when the ST system is ready to start, the bypass damper is opened, exposing the heat recovery system to the hot exhaust to create steam for the ST system. This all-or-nothing approach makes a gradual, controlled startup of the ST system challenging and exposes the components upstream of the heat recovery system and in the heat recovery system to potentially severe thermal stress during rapid heating. The severe stresses can reduce the usable lifetime of these components. By way of example, <CIT> describes an emissions reduction system for a combined cycle power plant having a gas turbine engine and a heat recovery steam generator (HRSG). Further, <CIT> describes an H-beam tandem damper for blocking high pressure and high temperature gas for blocking environmental contamination due to the leak of the toxic gas and prevent damage to and thermal expansion deformation of a damper and a blade due to hot air current and gas.

In order to address these challenges, in one approach, exhaust temperature control is provided by controlling the output of the GT system, but this approach may disadvantageously reduce plant output and power availability. In another approach, the bypass damper is used to attempt to control, among other aspects, the mass flow of the exhaust to the heat recovery system by positioning the bypass damper in a partially open position, e.g., <NUM>%, <NUM>%, etc. This method and structure pose a number of shortcomings. Notably, the blade bypass damper does not provide sufficient control of the exhaust flow because it includes no more than one or two blades that are only really capable of either an open or closed position. In any of the partially open positions, the one or two blades lack sufficient control of the application of back pressure in the GT system, which is advantageous during fast start or cycling operation. In addition, in between the closed and opened settings, current bypass dampers can cause, among other issues, reverse flow or turbulence in the exhaust, creating uneven heat transfer in the heat recovery system. The inability to control the rate of heating of the heat recovery system caused by the current bypass damper thus presents difficult challenges to controlling the temperature of an ST system, e.g., during startup.

Another shortcoming of current bypass dampers is the minimal mass flow control for the exhaust entering the heat recovery system. The lack of better mass flow control can also lead to difficulty controlling the heating of the heat recovery system and volume of steam it generates.

An exhaust control damper system for a combined cycle power plant in accordance with the invention as hereinafter claimed comprises the features of claim <NUM> below.

A power plant in accordance with the invention as hereinafter claimed comprises the features of claim <NUM> below.

The drawings are intended to depict only typical aspects of the disclosure and therefore should not be considered as limiting the scope of the disclosure.

As an initial matter, in order to clearly describe the subject matter of the current disclosure, it will become necessary to select certain terminology when referring to and describing relevant machine components within a power plant. To the extent possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.

In addition, several descriptive terms may be used regularly herein, and it should prove helpful to define these terms at the onset of this section. These terms and their definitions, unless stated otherwise, are as follows. As used herein, "downstream" and "upstream" are terms that indicate a direction relative to the flow of a fluid, such as the exhaust from a gas turbine or, for example, the flow of exhaust from a damper system towards a heat exchanger. The term "downstream" corresponds to the direction of flow of the fluid, and the term "upstream" refers to the direction opposite to the flow (i.e., the direction from which the flow originates). The terms "forward" and "aft," without any further specificity, refer to directions, with "forward" referring to the front or compressor end of the engine, and "aft" referring to the rearward section of the turbomachine.

It is often required to describe parts that are disposed at differing radial positions with regard to a center axis. The term "radial" refers to movement or position perpendicular to an axis. For example, if a first component resides closer to the axis than a second component, it will be stated herein that the first component is "radially inward" or "inboard" of the second component. If, on the other hand, the first component resides further from the axis than the second component, it may be stated herein that the first component is "radially outward" or "outboard" of the second component. The term "axial" refers to movement or position parallel to an axis. Finally, the term "circumferential" refers to movement or position around an axis. It will be appreciated that such terms may be applied in relation to the center axis of the turbine.

It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. "Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur or that the subsequently describe component or element may or may not be present, and that the description includes instances where the event occurs or the component is present and instances where it does not or is not present.

Where an element or layer is referred to as being "on," "engaged to," "connected to" or "coupled to" another element or layer, it may be directly on, engaged to, connected to, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present.

Embodiments of the disclosure provide an exhaust control damper system for a power plant, such as a cogeneration plant or a combine cycle power plant (CCPP). The damper system includes a frame configured to be fluidly coupled in an exhaust flow path from a gas turbine (GT) system to a heat recovery system. The damper system includes at least two sets of louvered dampers in the frame, which collectively cover the exhaust flow path. Each set of louvered dampers includes a plurality of blades collectively angularly positionable in one of a fully open position, a fully closed position, and a partially open position. The sets of louvered dampers can be modulated to control gas flow distribution to a heat recovery system, such as a heat recovery steam generator. The damper system also provides improved mass flow control of exhaust to the heat recovery system by controlling the position of the different sets of louvered dampers. The damper system can be added to a conventional bypass system or can replace a conventional bypass system in a retrofit setting.

An air insertion system is operatively coupled to the frame and configured to insert an airflow into the exhaust flow path. The air insertion system may mix air with the exhaust flow to the heat recovery system to control the exhaust temperature entering the heat recovery system. The air insertion system allows reduction of thermal stresses on components and provides controlled temperature startup of the ST system without degrading efficiency of the GT system. Hence, the GT system can be started in simple cycle mode, and later the heat recovery system can be started with controlled gas temperature and mass flow according to the heat recovery system and the ST system requirements (gradually higher temperatures, lower thermal stress, etc.).

<FIG> illustrates a power plant <NUM> according to an embodiment of the present disclosure. Power plant <NUM> may include a gas turbine (GT) system <NUM> and a steam turbine (ST) system <NUM>. GT system <NUM> may include a compressor <NUM>, a combustor <NUM>, and a gas turbine <NUM>. Power plant <NUM> may also include a bypass stack <NUM> and a heat recovery system <NUM>. While single components are illustrated in <FIG>, embodiments of this disclosure are not so limited and may include a plurality of compressors, combustors, turbines, bypass stacks, and/or heat recovery systems connected in series and/or in parallel. In one embodiment, GT system <NUM> is a 7HA. <NUM> engine, commercially available from General Electric Company, Greenville, S. The present disclosure is not limited to any one particular GT system and may be implanted in connection with other engines including, for example, the other HA, F, B, LM, GT, TM and E-class engine models of General Electric Company, and engine models of other companies.

Gas turbine <NUM> may be coupled to compressor <NUM> and/or a generator <NUM> through one or more shafts <NUM>. During operation, compressor <NUM> may receive air via an inlet filter <NUM>, compress the air, and supply compressed air to combustor <NUM>. In combustor <NUM>, fuel such as natural gas may be introduced and burned to generate hot combustion gases. The combustion gases may be discharged to gas turbine <NUM> that is rotationally driven due to the expansion of the combustion gases. The rotation of gas turbine <NUM> may be used to rotate generator <NUM> through shaft <NUM> to generate power.

Gas turbine <NUM> may be coupled to exhaust bypass stack <NUM> and heat recovery system <NUM> via an exhaust duct <NUM>. Exhaust duct <NUM> may include an inlet coupled to the exhaust outlet of gas turbine <NUM> to receive the high temperature exhaust gas from gas turbine <NUM>. Exhaust duct <NUM> may include a first outlet coupled to exhaust bypass stack <NUM> and a second outlet coupled to heat recovery system <NUM>. Exhaust bypass stack <NUM> may receive the high temperature exhaust gas and direct it outside of power plant <NUM>, e.g., through any now known or later developed cleaning systems.

Heat recovery system <NUM> may receive the high temperature exhaust gas (hereinafter "exhaust"), recover heat from the exhaust, heat water, and produce steam. Heat recovery system may also be referred to as a heat recovery steam generator (HRSG), where appropriate. Heat recovery system <NUM> may include a boiler <NUM> to generate the steam. In one embodiment, heat recovery system <NUM> may include a supplementary fire duct burner <NUM> in boiler <NUM>. The steam may be directed to a ST system <NUM> configured to rotate due to the steam. The rotation of a steam turbine <NUM> of ST system <NUM> may rotate a generator <NUM> through shaft <NUM> to generate additional power. In other embodiments, the steam from heat recovery system <NUM> may be used for other applications (e.g., heating or desalination).

As illustrated in <FIG>, exhaust duct <NUM> may include a bypass damper <NUM> inside of exhaust duct <NUM>. Bypass damper <NUM> may be a sandwich-type flap, with independent expandable double skin blades. The blades may be actuated by a toggle lever system and powered by hydraulics controls. Bypass damper <NUM> and the drive components for bypass damper <NUM> may be manufactured from materials that can withstand the exhaust gas environment. Bypass damper <NUM> may be controlled to direct the flow of exhaust to exhaust bypass stack <NUM> or to heat recovery system <NUM>. Bypass damper <NUM> may be configured to completely shut off the flow of exhaust gas to exhaust bypass stack <NUM> or to heat recovery system <NUM>. For example, a controller <NUM> may control the position of bypass damper <NUM> to be in a first position (vertical) to shut off the flow of exhaust to heat recovery system <NUM>. Controller <NUM> may control the position of bypass damper <NUM> to be in a second potion (horizontal) to shut off the flow of the exhaust to exhaust bypass stack <NUM>.

While a flat type bypass damper <NUM> is illustrated in <FIG>, the embodiments of this disclosure are not so limited, and other types of dampers may be used to stop the flow of exhaust to exhaust bypass stack <NUM> and/or to heat recovery system <NUM>. For example, a bi-plane damper may be installed at the outlets of exhaust duct <NUM> and/or the inlets to exhaust bypass stack <NUM> and/or to heat recovery system <NUM>. In another embodiment, a guillotine damper or blanking plate may be used to control the flow of the exhaust.

Power plant <NUM> may include one or more sensors <NUM> to monitor the operation of the power plant. Sensors <NUM> may monitor the temperature, moisture, flow speed, and/or exhaust composition. Controller <NUM> of power plant <NUM> may receive data from sensors <NUM>, analyze the data to determine the operating state of the power plant, and generate controls for the power plant based on the received data from sensors <NUM>.

Power plant <NUM> may further include an exhaust control damper system <NUM> (hereinafter "damper system <NUM>") to provide additional control over exhaust prior to its introduction to heat recovery system <NUM>. <FIG> shows a perspective view, <FIG> shows an end view, and <FIG> shows an enlarged perspective view of damper system <NUM> fluidly coupled to exhaust duct <NUM>.

Damper system <NUM> includes a frame <NUM> configured to be fluidly coupled in an exhaust flow path from GT system <NUM> (<FIG>) to heat recovery system <NUM>. The exhaust flow path may include any now known or later developed duct or enclosed pathway. Frame <NUM>, which may be configured to direct the flow of exhaust between bypass damper <NUM> (<FIG>) and heat recovery system <NUM>, houses portions of damper system <NUM>. Frame <NUM> may be positioned adjacent to and downstream of bypass damper <NUM>. Frame <NUM> may be included in exhaust duct <NUM> or in heat recovery system <NUM>.

As shown in <FIG>, frame <NUM> may provide the outermost part of exhaust duct <NUM>, i.e., it is inserted as part of exhaust duct <NUM>, or as shown in <FIG>, <FIG> and <FIG>, it may be mounted within a portion of exhaust duct <NUM>, e.g., spaced within exhaust duct <NUM> by supports <NUM>. In either case, frame <NUM> may include any number of plate members <NUM> configured to create a duct of the same or similar shape and dimensions as the location in which it is positioned. In <FIG>, for example, one plate member <NUM> creates each of the bottom and top of frame <NUM>, and three plate members <NUM> create each of the sides of frame <NUM>. Frame <NUM> may be made of any material capable of withstanding the environment of the exhaust.

Frame <NUM> may be coupled to a new power plant <NUM> or may be retrofitted to an existing power plant <NUM>. To this end, frame <NUM> has an adjustment member <NUM> configured to allow adjustment of a size of the frame. Adjustment member(s) <NUM> may include any now known or later developed structure for allowing frame <NUM> to have different sizes to accommodate different sized exhaust ducts <NUM> and/or heat recovery systems <NUM>. In one non-limiting example, adjustment member <NUM> may include a selection from a variety of different length plate members.

Damper system <NUM> also includes at least two sets of louvered dampers <NUM> in frame <NUM>, which collectively cover the exhaust flow path. Each set of louvered dampers <NUM> includes a plurality of blades or vanes <NUM> collectively angularly positionable in one of: a fully open position (shown in outer two in <FIG>), a fully closed position (shown in outer two in <FIG>), and a partially open position (shown in middle two in <FIG>). The partially open position may include any angular position of blades <NUM> between the fully open and fully closed position, e.g., <NUM>%, <NUM>%,<NUM>%, etc. Sets of louvered dampers <NUM> may have the same setting or may have different settings. Each set of louvered dampers <NUM> may include a position transmission <NUM> configured to adjust an angular position of a respective plurality of blades <NUM> independently of the other set(s) of louvered dampers <NUM>. Position transmission <NUM> may include any now known or later developed mechanism for simultaneously changing the angular position of a plurality of blades <NUM>, such as, but not limited to, an elongated member pivotally coupled to each vane and linearly movable to change the angular position.

Each set of louvered dampers <NUM> may also include an actuator <NUM> configured to control operation of position transmission <NUM> to position the respective set of louvered dampers <NUM> in the one of: the fully open position, the fully closed position, and the partially open position. Controller <NUM> may control each actuator <NUM> to control, among other things, the mass flow of exhaust through frame <NUM>. Actuator(s) <NUM> may include any appropriate motorized actuator, e.g., electric, hydraulic, pneumatic, etc., capable of moving the position transmission <NUM>. For example, actuator(s) <NUM> may be rotational actuators (shown in <FIG>) capable of pivotally coupling to and linearly moving position transmissions <NUM> vertically to change the angular position of blades <NUM>, or they could be linear actuators coupled to and linearly moving position transmissions <NUM> vertically to change the angular position of blades <NUM>. Other varieties of actuators may also be employed depending on the type of position transmission <NUM>.

While four sets of louvered dampers <NUM> are shown in each of <FIG>, any number of sets may be employed. For example, at least two or at least three sets of louvered dampers <NUM> may be employed. Plurality of blades <NUM> of each set of louvered dampers <NUM> includes any number capable of providing the desired mass flow controls for the exhaust. That is, blades <NUM> have sufficient numbers to provide more than just an open/closed passage; they provide controlled flow restriction capable of controlling the mass flow of exhaust to heat recovery system <NUM> and back pressure on GT system <NUM>. In one non-limiting example, plurality of blades <NUM> includes at least ten vertically spaced damper blades, but any number sufficient to provide the desired flow restriction is possible.

In the example shown, blades <NUM> are vertically spaced and rotate about a horizontal axis. It is readily understood that the blades <NUM> could also be horizontally spaced and rotate about a vertical axis, i.e., with actuators <NUM> on the side of frame <NUM>. As shown for example in <FIG> and <FIG>, each set of louvered dampers <NUM> may be separated by a section <NUM> of frame <NUM>, but this is not necessary in all cases (see <FIG>).

Damper system <NUM> also includes an air insertion system <NUM> (<FIG>) operatively coupled to frame <NUM> and configured to insert an airflow into the exhaust flow path. Air insertion system <NUM> may include an air pump <NUM> having an output, and a conduit <NUM> fluidly coupling the output of air pump <NUM> to at least one opening <NUM> in frame <NUM> in fluid communication with the exhaust flow path. Conduit <NUM> can include any form of piping capable of withstanding the environment within power plant <NUM> and of directing the airflow to the desired locations. <FIG> shows one opening <NUM>, and <FIG>, <FIG> and <FIG> show a plurality of openings <NUM> spaced along at least a portion of frame <NUM>, e.g., one side. While particular arrangements of openings have been illustrated, any number of openings <NUM> can be provided in any arrangement about frame <NUM>. Each opening <NUM> is configured to insert an airflow from air pump <NUM> into the exhaust flow path.

In <FIG>, air pump <NUM> is disposed aside frame <NUM>, and in <FIG>, <FIG> and <FIG>, air pump(s) <NUM> are mounted on frame <NUM>. Any number of air pumps <NUM> may be used. <FIG> and <FIG> show one air pump <NUM>, and <FIG> and <FIG> show a pair of air pumps <NUM>. The air can be taken from the atmosphere about power plant <NUM> or from compressor <NUM> (<FIG>). In one embodiment, sensor <NUM> measures the temperature of the exhaust flow (gas). Based on the temperature, controller <NUM> can control air pump <NUM> to deliver an amount of air that, when mixed with the rest of the exhaust flow in and/or downstream of frame <NUM>, creates a desired exhaust temperature for heat recovery system <NUM>.

As shown in <FIG>, power plant <NUM> may also include isolator <NUM> to isolate air or air/gas mixture from heat recovery system <NUM>. Isolator <NUM> may be a guillotine damper or blanking plate that is configured to isolate bypass damper <NUM> and damper system <NUM> from heat recovery system <NUM>. Isolator <NUM> may be positioned adjacent to damper system <NUM> (shown) or bypass damper <NUM>. Isolator <NUM> may be included in exhaust duct <NUM> or in heat recovery system <NUM>. Isolator <NUM> may be a bolted plate supplied along with diverter bypass damper <NUM> and/or damper system <NUM> and may remain in place before operating heat recovery system <NUM> to allow power plant <NUM> to operate in the simple cycle. In one embodiment, isolator <NUM> may not provide thermal insulation.

During operation, power plant <NUM> may be controlled to operate in a simple cycle to generate energy only from the operation of gas turbine <NUM> or in a combined cycle to generate energy from the operation of gas turbine <NUM> and heat recovery system <NUM>. In the simple cycle, bypass damper <NUM> may be controlled to be in the first position (vertical) to shut off the flow of exhaust to heat recovery system <NUM>. In the simple cycle, the exhaust from gas turbine <NUM> may flow to exhaust bypass stack <NUM> via exhaust duct <NUM>.

In the combined cycle, bypass damper <NUM> may be controlled to be in the second position (horizontal) to shut off the flow of exhaust to exhaust bypass stack <NUM>. In the combined cycle, the exhaust from gas turbine <NUM> may flow to damper system <NUM>, and eventually to heat recovery system <NUM> via exhaust duct <NUM>, to recover additional energy from the exhaust gas. Damper system <NUM> controller <NUM> is configured to control the position of sets of louvered dampers <NUM> and the operation of air insertion system <NUM> to control at least one of: an exhaust flow temperature downstream of frame <NUM>; an exhaust mass flow rate downstream of frame <NUM>; and a back pressure upstream of frame <NUM>, i.e., on GT system <NUM>. Controller <NUM> may be part of power plant <NUM> control system or a separate controller.

When starting up power plant <NUM>, the power plant may be set in simple cycle or combined cycle. For startup in the simple cycle, bypass damper <NUM> may be set in the first position (vertical) to shut off the flow of exhaust to heat recovery system <NUM> and to allow the generated exhaust to flow to exhaust bypass stack <NUM>. After the start-up of gas turbine <NUM>, the exhaust is introduced into exhaust duct <NUM> and all of the exhaust flows outside of power plant <NUM> via exhaust bypass stack <NUM>. After predetermined conditions are satisfied (e.g., predetermined time period, temperature, composition of the exhaust gas), bypass damper <NUM> may be controlled to transition to a second position (horizontal) to allow the exhaust to flow to heat recovery system <NUM> and to block the exhaust from flowing to exhaust bypass stack <NUM>.

During the transition from the first position to the second position, a portion of the exhaust may flow to heat recovery system <NUM> and a portion of the exhaust may flow to exhaust bypass stack <NUM>. By controlling the speed of the transition, the amount of exhaust introduced into heat recovery system <NUM> may be controlled in a limited manner by bypass damper <NUM> to reduce stress on the components of heat recovery system <NUM> due to a drastic temperature change. In accordance with embodiments of the disclosure, damper system <NUM> may be operated to provide further control of the exhaust flow to reduce stress on components of heat recovery system <NUM>, both during the transition and after the transition. Thus, damper system <NUM> may reduce hazards to heat recovery system <NUM> of power plant <NUM>, created by the lack of fine-tuned control of bypass damper <NUM>.

For example, damper system <NUM> can guard against over-pressure or under-pressure in exhaust duct <NUM>. Damper system <NUM> can also remove turbulence and better control mass flow of exhaust to heat recovery system <NUM>. Air insertion system <NUM> allows control of exhaust temperature, providing further protection against thermal stress to heat recovery system <NUM> or upstream components. Damper system <NUM> may also be controlled with bypass damper <NUM> and stack damper <NUM> of heat recovery system <NUM>, e.g., to reduce the possibility of overpressure in exhaust duct <NUM>.

In another embodiment, shown in <FIG>, damper system <NUM>, perhaps in conjunction with isolator <NUM>, may replace bypass damper <NUM>, thus removing any disadvantage provided by bypass damper <NUM>. In another embodiment, shown in <FIG>, only two sets of louvered dampers <NUM> are used.

Claim 1:
An exhaust control damper system (<NUM>) for a combined cycle power plant (<NUM>), the damper system (<NUM>) comprising:
a frame (<NUM>) configured to be fluidly coupled in an exhaust flow path from a gas turbine (<NUM>) (GT) system to a heat recovery system (<NUM>);
at least two sets of louvered dampers (<NUM>) in the frame (<NUM>) and collectively covering the exhaust flow path, each set of louvered dampers (<NUM>) including a plurality of blades (<NUM>) collectively angularly positionable in one of: a fully open position, a fully closed position and a partially open position; and
an air insertion system (<NUM>) operatively coupled to the frame (<NUM>) and configured to insert an airflow into the exhaust flow path; characterized in that
the frame (<NUM>) has an adjustment member (<NUM>) configured to allow adjustment of a size of the frame (<NUM>).