Turbomachine supports having thermal control system   

Abstract: Supports for a first casing of a turbomachine are disclosed that each include a thermal control system to control thermal expansion thereof. The thermal control system may include: a sealed duct surrounding a support column of the turbomachine, the duct being coupled to a source of a cooling fluid flow, and/or a hollow leg supporting the inner casing on the support column with a conduit supplying operative fluid, e.g., steam, from a stage of turbomachine to the hollow leg.

BACKGROUND OF THE INVENTION

The disclosure relates generally to turbo-machinery, and more particularly, to turbomachine supports having a thermal control system.

In a steam turbine, after the steam has been used, it is exhausted from the turbine through an outer casing or exhaust hood. For example, a low pressure (LP) exhaust hood for a side exhaust unit houses the inner casing of the turbine. The inner casing is typically supported by various combinations of transverse and vertical plates which form a complex support structure for the inner casing\'s vertical support. Since the weight of the inner casing and related diaphragms is very large, this supporting structure needs to be very stiff. Consequently, the hood is very heavy and causes airflow blockages, reducing the effective area for diffusion.

Another way of supporting an inner casing in a side exhaust design is to bring a pedestal from the bottom of the hood so that the hood is supported from the bottom and the base of the hood is the foundation or plant floor. In this complex internal structure, the load of the inner casing is directly transmitted to the foundation. However, in this case, the thermal expansion of the pedestal is very large. Further, with the change in back pressure and the resulting change in exhaust temperature, the thermal expansion of the pedestal varies over time. This varying thermal expansion of the pedestal causes clearance problems as the movement of rotor does not vary since the bearings are supported on standards mounted on the foundation.

A first aspect of the disclosure provides a turbomachine comprising: a plurality of supports for a first casing of the turbomachine, each support including a thermal control system to control thermal expansion thereof

A second aspect of the disclosure provides a support for a turbomachine, the support comprising: a support column fixedly attached to a foundation; and a thermal control system to control thermal expansion of the support.

A third aspect of the disclosure provides a steam turbomachine comprising: a plurality of stages; a first casing enclosing the plurality of stages, the first casing including a plurality of supports therefor, each support including a support column fixedly attached to a foundation and a hollow leg coupled to the first casing and configured to be slidingly coupled to the support column; a thermal control system for each support, each thermal control system including: a duct surrounding the support column, the duct coupled to a source of a cooling fluid flow, a seal between the support column and the duct sealing a space between the duct and the support column, and a conduit configured to supply steam from a stage of the plurality of stages to the hollow leg.

The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:

FIG. 1 shows a perspective partial cut-away illustration of a steam turbine.

FIG. 2 shows a side, partial cross-sectional view of a turbomachine having supports according to embodiments of the invention.

FIG. 3 shows a partial end, cross-sectional view of the turbomachine of FIG. 2 through line A-A.

FIG. 4 shows an enlarged perspective view of a portion of a support according to embodiments of the invention.

FIG. 5 shows an end, cross-sectional view of a portion of a support according to embodiments of the invention.

It is noted that the drawings of the disclosure are not to scale. 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. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

Referring to the drawings, FIG. 1 shows a perspective partial cut-away view of an illustrative turbomachine 100 in the form of a steam turbine. Although the embodiments of the invention will be described relative to a steam turbine, it will be understood that the teachings are also applicable to any form of turbomachine, e.g., a gas turbine, compressor, etc. Further, the embodiments of the invention may be applied to any kind of system where an inner casing is inside an outer casing or hood, e.g., for side exhaust, down exhaust or axial exhaust. The illustrative turbomachine 100 includes a rotor 102 that includes a rotating shaft 114 and a plurality of axially spaced rotor wheels 118. A plurality of rotating blades 120 are mechanically coupled to each rotor wheel 118. More specifically, blades 120 are arranged in rows that extend circumferentially around each rotor wheel 118. A plurality of stationary vanes 122 extends circumferentially around shaft 114, and the vanes are axially positioned between adjacent rows of blades 120. Stationary vanes 122 cooperate with blades 120 to form a stage and to define a portion of a steam flow path through turbomachine 100. A casing 130 surrounds the rotor wheels 118. Casing 130 is supported by a plurality of supports 132 (FIG. 2), each support including a thermal control system 150 (FIG. 2) to control thermal expansion thereof

In operation, steam 124 enters an inlet 126 of the steam turbine and is channeled through stationary vanes 122. Vanes 122 direct steam 124 downstream against blades 120. Steam 124 passes through the remaining stages imparting a force on blades 120 causing shaft 114 to rotate. At least one end of turbine 100 may extend axially away from rotor 112 and may be attached to a load or machinery (not shown) such as, but not limited to, a generator, and/or another turbine.

Referring to FIGS. 2 and 3, FIG. 2 shows a side, partial cross-sectional view of turbomachine 100 having a plurality of supports 132 for a first (inner) casing 130 of turbomachine 100. FIG. 3 shows a partial, end, cross-sectional view of the turbomachine of FIG. 2 through line A-A, with the right side set of supports 132 removed for clarity. As noted above and as will be described in greater detail herein, each support 132 includes a thermal control system 150 to control thermal expansion thereof.

As shown in FIGS. 2 and 3, each support 132 may include a support column 134 fixedly attached to a foundation 136, e.g., of a plant, for supporting first, inner casing 130. As illustrated, four columns 134 are used to support inner casing 130; however, other than four columns may be employed. Columns 134 are designed to support the entire load of inner casing 130, any diaphragm (not shown) within inner casing 130 and any dynamic loading during operation. They may be made of, for example, steel, concrete, or a combination thereof. Foundation 136 may also include vertical columns 138 that support, for example, bearings 140 for shaft 114 (FIG. 1) and/or a second, outer casing 142 (also referred to as a hood). Each support column 134 may extend through second, outer casing 142 that surrounds first, inner casing 130.

A thermal control system 150 according to embodiments of the invention may take a number of forms, which may be used alone or in combination.

In one embodiment, as shown in FIGS. 2 and 3, thermal control system 150 may include a duct 152 surrounding support column 134. Duct 152 may be made, for example, of the same material as second, outer casing 142 (e.g., steel). A seal 154 may be provided between support column 134 and duct 152 for sealing a space 155 (FIGS. 3 and 4 only, FIG. 4 without the seal) between duct 152 and support column 134. Seal 154 may take any variety of forms for coupling a duct to a surface, e.g., a polymer sheet or diaphragm sealed to duct 152 and column 134. As illustrated in FIG. 3, in one embodiment, seal 154 is provided on an upper end of duct 152 just below where support column 134 is coupled to support first, inner casing 130, e.g., by a standard mount 156. Seal 154 seals the upper end of duct 152 and isolates any exchange of force between second, outer casing 142 and hollow legs 170, described below. Consequently, supports 132 isolate columns 134 from being exposed to exhaust steam within second, outer casing 142.

Under steady state operation, space 155 may eventually attain the same temperature as within second, outer casing 142. Duct 152, however, may be coupled to a source of a cooling fluid flow to cool support column 134. In one embodiment, the source of cooling fluid flow includes atmospheric air. For example, source of cooling fluid flow may include exposure to atmospheric air from outside of second, outer casing 142 through duct 152, the latter of which is open at a lower end through second, outer casing 142. That is, each support column 134 extends through second, outer casing 142 that surrounds first, inner casing 130 and the source of cooling fluid flow includes atmospheric air from outside of the second casing. Alternatively, a pump 156 such as a fan arrangement may be provided for propelling the cooling fluid flow along support column 134 within duct 152. In this case, the cooling fluid flow may be forced to move along the dashed line 158 in FIG. 3. A pump 156 may be desired to ensure continuous air circulation in space 155. Constant air circulation may be required to maintain the air temperature in space 155 close to atmospheric temperature so as to prevent an increased temperature for column 134 and thermal expansion thereof even though the back pressure may change. In one embodiment, the volume of cooling fluid flow can be controlled by pump 155 based on feedback from any variety of sensors (not shown), e.g., temperature sensors within duct 152, on support column 134, within second, outer casing 142, etc. Consequently, the movement of supports 132 will be completely isolated from the back pressure changes. As a result, this arrangement can be used for variable back pressure operation, especially under high back pressure where exhaust temperature is significantly high such as in power plants where air-cooled condensers are used.

Referring to FIGS. 2 and 4, in another embodiment, each support 132 includes a hollow leg 170 extending from first, inner casing 130 and configured to slidingly couple to support column 134. In this case, each thermal control system 150 includes a conduit 172 supplying operative fluid, e.g., gas or steam, from a stage of turbomachine 100 (FIG. 1) to hollow leg 170. The pressure within hollow leg 170 is thus that of the selected stage(s) P(L-1) and the pressure outside of hollow leg 170 is the exhaust pressure P(exh). Numerous parameters relative to this embodiment can be selected so as to assist in cooling support 132. For example, the height of hollow leg 170 and operative fluid\'s temperature (out of various stages) can be chosen such that net thermal growth of the entire stationary structure matches rotor 102 growth. One advantage of this concept is that the operative fluid temperature within turbomachine 100 does not vary substantially with back pressure change, which means that under all operating condition of turbomachine 100, the stationary structure will move by approximately the same amount. Conduit 172 may take operative fluid from any stage(s) at which the conditions of the operative fluid may be advantageous in cooling support 132. Although conduit 172 is shown in an external position relative to first, inner casing 130, it is understood that conduit 172 may be positioned internally of casing 130 with appropriate openings being provided to hollow leg 170 for fluid communication of the operative fluid thereto.

Hollow leg 170 may be slidingly coupled to support column 134 in any now known or later developed fashion, e.g., a slide bearing 180, to allow fairly free movement but prevent disconnect due to thermal expansion and/or other operational conditions. As shown in FIG. 5, intervening structure 182, e.g., of steel, may be provided between hollow leg 170 and slide bearing 180 to provide for proper alignment. In order to provide proper drainage of condensed operative fluid, e.g., water, hollow leg 170 may include a drain opening 184. Drain opening 184 also assists in maintaining a high heat transfer co-efficient inside hollow leg 170, which promotes legs\' 170 response to the chosen operative fluid temperature rather than to the exhaust temperature. Further, an insulation layer 186 may be provided about hollow leg 170 to prevent condensation on an exterior of hollow leg 170 and/or adjust thermal conditions within hollow leg 170. Insulation layer 186 may include, for example, a thin sheet metal or any other thermally insulated blanket which will maintain a low heat transfer co-efficient on an outer surface of hollow leg 170 so as to further reduce the impact of the exhaust temperature (within second, outer casing 142) on the hollow legs. If provided, drain opening 184 may extend through insulation layer 186. Hollow leg 170 may be made of any material capable of withstanding the environmental and structural loads applied thereto, e.g., steel.

As is typical, a finite amount of clearance is given between rotor 102 and stationary structure thereabout to avoid rubs. This clearance is essential because the relative thermal growth and deflection of rotor 102 and stationary structure is not zero. Because any clearance essentially gives an extra path for steam to escape without being used for power generation, the clearance used is minimized as much as possible. Hollow legs 170, among other things, reduce thermal expansion between rotor 102 (FIG. 1) and stationary structure thereabout. In particular, using the described arrangement, rotor 102 (FIG. 1) which is supported on foundation 136 by supports 132 will grow vertically from an aligned position, which is usually the horizontal dividing plane for the entire steam turbomachine. Here, rotor 102 thermal growth will be primarily due to support 132 thermal growth, oil film rise and growth of rotor 102 due to steam temperature. Consequently, the clearance between rotor 102 (FIG. 2) and the surrounding stationary structure can be further minimized, resulting in improved turbomachine 100 performance.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 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.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.