CASING FOR TURBINE ENGINE HAVING A COOLING UNIT

Abstract

A turbine inner shell for a turbine engine includes one or more mounting grooves, each of which receives a fluid conduit. A temperature controlling fluid is circulated through fluid conduit to selectively heat or cool surrounding portions of the turbine inner shell, to thereby control the thermal growth of those portions of the turbine inner shell. This makes it possible to selectively control a clearance between the tips of rotating turbine blades and the surrounding shrouds of the turbine.

Description

BACKGROUND OF THE INVENTION

Industrial turbine engines include a compressor section, a combustor section and a turbine section. In the turbine section, multiple rows of turbine blades (or buckets) mounted on a rotor rotate between corresponding rows of stationary nozzles. For each row of turbine blades, a circumferential shroud is mounted on the turbine casing, the shroud being positioned just outside the tips of the turbine blades in the radial direction.

A clearance must be maintained between the tips of the turbine blades and shroud to prevent the tips of the turbine blades from rubbing the shroud as the turbine blades rotate. However, it is desirable to keep the clearance as small as possible to prevent the motive gas from escaping around the tips of the blades. Generally speaking, the smaller the clearance, the more efficient the turbine.

During transient periods, such as when the turbine is starting, or when the turbine increases or decreases load or rotational speed, various elements within the turbine section can increase or decrease in temperature. Unfortunately, the various elements do not tend to increase and decrease in temperature at the same rate. For example, during startup operations, the turbine blades tend to increase in temperature more rapidly than the turbine casing, which holds the shroud surrounding the tips of the turbine blades. The turbine blades are mounted on disks, and the disks also heat up and expand outward in the radial direction.

When one portion of the turbine increases in temperature more rapidly than other portions, the portions that are heated more rapidly can experience more rapid thermal expansion/growth than the portions that are increasing in temperature more slowly. During startup operations, if the turbine blades increase in temperature more rapidly than the turbine casing holding the shrouds, the turbine blades can experience more rapid thermal growth in the radial direction than the turbine casing.

Moreover, the different parts of the turbine mare made of different materials which have different coefficients of thermal expansion. Even if all the elements increased in temperature at the same rate, the differences in the coefficients of thermal expansion of the various materials would still cause the various elements to grow different amounts relative to each other.

Another factor is the loading applied to the various elements. The turbine blades, and the disks upon which they are mounted, experience mechanical centripetal forces due to the fact that the blades and disks are rotating. This also can cause the disks and turbine blades to grow in the radial direction. At relatively low rotational speeds, there is relatively little growth due to this mechanical loading. However, as the rotational speed increases, the blades and disks tend to grow longer. In contrast, the shroud surrounding the turbine blades is not rotated and does not experience any growth due to centripetal forces.

Designers must take all of these factors into account when specifying the dimensions of the elements of the turbine to ensure that at any given point in time, the turbine blades do not grow so long in the radial direction that they begin to rub against the shroud. However, when the elements of the turbine are designed to ensure that a clearance is maintained between the tips of the turbine blades and the shroud at all times, this can result in the clearance being larger than desirable during steady state operations, which can negatively impact the efficiency of the turbine engine.

To address this issue, selected portions of the turbine casing can be heated and/or cooled during transient periods, or during steady state operations, to control the position of the shroud in the radial direction. This, in turn, controls the clearance between the tips of the turbine blades and shroud. Selective heating or cooling of portions of the turbine casing during a transient period can ensure that a clearance is maintained between the tips of the turbine blades and the shroud during the transient period. Selective heating and/or cooling of the turbine casing during steady state operations can decrease the clearance between the tips of the turbine blades and the shroud to a desired minimum dimension, to thereby maximize the efficiency of the turbine engine.

Prior art attempts to selectively heat and/or cool the turbine casing have required that coolant passages be formed in the turbine casing at selected locations, such as just outside the shrouds in the radial direction. Manufacturing the turbine casing in this fashion can be expensive and difficult. Also, it is impossible to retrofit such designs into existing turbine engines. The turbine casing must be manufactured from the start to include the coolant passages.

SUMMARY OF THE INVENTION

In a first aspect, the invention may be embodied in an inner shell for the turbine section of a turbine engine that includes a plurality of arcuate casing portions that are configured to be attached to one another to form a generally cylindrical inner shell. Each arcuate casing portion includes at least one shroud hook portion that extends along an interior side of the arcuate casing portion in a circumferential direction, and at least one mounting groove that extends along the arcuate casing portion in the circumferential direction. Each at least one mounting groove is located adjacent to one of the at least one shroud hook portions. At least one conduit having at least one internal passageway for a temperature controlling fluid is mounted within one of the at least one mounting grooves. The at least one conduit is configured to be slid into a mounting groove in the circumferential direction.

In another aspect, the invention may be embodied in a temperature controlling fluid conduit that is configured to be mounted on an arcuate-shaped portion of an inner shell of a turbine section of a turbine engine. The fluid conduit includes an elongated, arcuate-shaped body having an interior passageway for a temperature controlling fluid, and at least one inlet aperture that is configured to admit a flow of a temperature controlling fluid into the interior passageway

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the interface between rotating turbine blades in the turbine section of a turbine engine and surrounding portions of the turbine shell;

FIG. 2 is a diagram illustrating a fluid conduit that is partially slid into a mounting groove of a turbine inner shell;

FIG. 3 is a diagram illustrating a fluid conduit fully installed in a mounting groove of a turbine inner shell;

FIG. 4 is a cross-sectional view of a first embodiment of a fluid conduit installed in a mounting groove of a turbine inner shell;

FIG. 5 is a cross-sectional view of a second embodiment of a fluid conduit installed in a mounting groove of a turbine inner shell;

FIG. 6 is a partial perspective view of a portion of a first embodiment of a temperature controlling fluid conduit having protrusions on exterior surfaces;

FIG. 7 is a partial perspective view of a portion of a second embodiment of a temperature controlling fluid conduit having protrusions on exterior surfaces; and

FIG. 8 is a cross sectional view of a third embodiment of a fluid conduit installed in a mounting groove of a turbine inner shell.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a diagram illustrating a portion of a turbine section of a turbine engine. FIG. 1 shows the turbine outer shell 100 and the turbine inner shell 110. The tips of two rows of turbine blades 122 and 124 are shown. The rows of turbine blades 122, 124 are mounted on a rotor of the turbine and the turbine blades rotate relative of the inner surface of the turbine inner shell 110. A row of stationary nozzles 130 is mounted on the turbine inner shell 110 between the two rows of turbine blades 122, 124.

Circumferentially extending shrouds 142, 144 are mounted on the turbine inner shell 110 at positions opposite the tips of the rotating turbine blades 122, 124. The shrouds 142, 144 are mounted on shroud hooks in the turbine inner shell 110. As explained in the Background section above, it is necessary to maintain a clearance between the tips of the rotating turbine blades 122, 124 and the stationary shrouds 142, 144. However, it is also desirable to minimize the clearance to maximize the efficiency of the turbine engine.

FIG. 1 illustrates that temperature controlling fluid passageways 150, 152 are formed in the turbine inner shell 110. Heated fluid can be circulated in the temperature controlling fluid passageways 150, 152 to raise the temperature of the turbine inner shell, which will cause the inner shell 110 to expand outward radially, increasing the clearance between the shrouds 142, 144 and the tips of the turbine blades 122, 124. At the same time, increasing the temperature of the shrouds tends to cause thermal growth of the shrouds, which tends to decrease the clearance. These factors must be balanced to ensure that a proper temperature fluid is used to cause the clearance to be adjusted in the proper way.

Conversely, a cooling fluid can be circulated through the temperature controlling fluid passageways 150, 152 to lower the temperature of the turbine inner shell 110, which will cause the turbine inner shell 110 to contract inward radially, decreasing the clearance between the shrouds 142, 144 and the tips of the turbine blades 122, 124. At the same time, cooling the shrouds causes the shrouds to contract, which tends to increase the clearance. Here again, the temperature of the fluid must be carefully controlled to ensure the proper clearance is maintained.

At different times it may be advantageous to increase or decrease the clearance using an appropriate temperature fluid. However, a design as illustrated in FIG. 1 requires that fluid passageways be formed in the turbine inner shell, which can be expensive.

FIG. 2 illustrates a design embodying the invention for a turbine inner shell 110 of a turbine engine that includes a fluid conduit 200 that can carry a flow of temperature controlling fluid. The turbine inner shell of a turbine engine is typically comprised of two or more arcuate-shaped sections that are bolted together to form a generally cylindrical turbine inner shell. FIG. 2 illustrates a portion of one arcuate-shaped section of the turbine inner shell 110. FIG. 2 also illustrates that several shroud hooks 114 are formed on the radially inner surface of the turbine inner shell 110. Shrouds that would confront the tips of rotating turbine blades are mounted on the shroud hooks 114.

A mounting groove 120 is formed in the turbine inner shell 110 at a location that is radially outside and immediately adjacent to one of the sets of shroud mounting hooks 114. An elongated, arcuate-shaped conduit 200 is mounted in the mounting groove 120. FIG. 2 shows the fluid conduit 200 partially inserted into the mounting groove 120. FIG. 3 illustrates the fluid conduit 200 fully inserted into the mounting groove 120. FIGS. 2 and 3 also illustrate that a mounting block portion 240 on the fluid conduit is aligned with a mounting block portion 112 of the turbine inner shell 110 when the fluid conduit 200 is fully inserted into the turbine inner shell 110.

FIG. 4 illustrates a cross-sectional view of a first embodiment of a fluid conduit 200 mounted in a mounting groove 120 of a turbine inner shell 110. The fluid conduit 200 has a lower surface portion 210 that abuts a wall 116 separating the mounting groove 120 from the location where a shroud is mounted on shroud mounting hooks 114.

The fluid conduit 200 has a stepped shape that includes an upper portion 230 having a smaller cross-sectional area which encloses a first interior passageway 232 and a lower portion having a larger cross-section that encloses a second interior passageway 220. A separation wall 222 with a plurality of apertures 234 separates the first interior passageway 232 from the second interior passageway 220.

The upper portion 230 also provides stiffness and rigidity to the structure, which helps the lower portion to retain its shape. This, in turn, helps to prevent any deformation of the lower portion from affecting the shape and position of the underlying shroud.

A supply pipe 250 is attached to the upper, portion 230 of the fluid conduit 200. The supply pipe 250 delivers a flow of temperature controlling fluid into the first interior passageway 232. The temperature controlling fluid can flow in a circumferential direction along the first interior passageway 232. The temperature controlling fluid can also pass through the apertures 234 in the separation wall 222 to enter the second interior passageway 220. The separation wall 222 with apertures 234 helps to cause a flow of temperature controlling fluid that is delivered into the first interior passageway 232 to be evenly distributed circumferentially around the turbine inner shell 110 before the temperature controlling fluid enters the second interior passageway 220 via the apertures 234.

The flow of temperature controlling fluid that enters the second interior passageway 220 escapes from the fluid conduit 200 via a plurality of apertures 212 that pass through the lower wall 210 of the fluid conduit 200. As will be explained in greater detail below, the exterior walls of the fluid conduit 200 are spaced from the interior walls of the mounting groove 120. As a result, the temperature controlling fluid can pass along the gap between the exterior walls of the fluid conduit 200 and the interior walls of the mounting groove 120, and ultimately escape to a location radially outside the turbine inner shell 110. The arrows in FIG. 4 illustrate the flow of the temperature controlling fluid as it passes from the supply pipe 250 into the first interior passageway 232, from the first interior passageway 232 to the second interior passageway 220, out the apertures 212, around the exterior sides of the fluid conduit 200 and out to the location radially outside the turbine inner shell 110.

In alternate embodiments, the fluid that is circulated through the first and second interior passageways need not be routed to a location radially outside the inner shell 110. Instead, the fluid could be collected and used for other purposes inside the turbine inner shell 110.

The configuration illustrated in FIG. 4 results in the temperature controlling fluid impinging on the wall 116 that is adjacent the shroud mounting hooks 114. As a result, the temperature controlling fluid can heat or cool the portions of the turbine inner shell and the shrouds that are directly opposite the tips of the rotating turbine blades. This provides rapid and effective control over the thermal growth of these portions of the turbine, and thus the clearance between the turbine blades and the shroud.

The stepped shape of the mounting groove 120 and the corresponding stepped shape of the fluid conduit 200 allow the fluid conduit 200 to be easily mounted on the turbine inner shell 110. The stepped shape, where the radially outer portion has a smaller cross-sectional shape than the radially inner portion, ensures that the fluid conduit is trapped on the turbine inner shell 110 without the use of mounting hardware. Other shapes for the mounting groove 120 and fluid conduit 200 could achieve similar functions. For example, the mounting groove 120 and fluid conduit 200 could have a trapezoidal or triangular shape, where the radially outer portions have a smaller dimension than the radially inner portions. Also, in some embodiments, the shape of the mounting groove need not match the shape of the fluid conduit.

FIG. 5 illustrates an alternate configuration for the fluid conduit 200. In this embodiment, no separation wall is provided between the first fluid passageway 232 and the second fluid passageway 220. This embodiment may be advantageous in embodiments where ensuring that the temperature controlling fluid is circumferentially distributed is not as important. The lack of the separation wall would decrease the flow restrictions.

FIG. 6 illustrates that a plurality of protrusions 242, 244, 246 could be formed on exterior walls of a fluid conduit 200 embodying the invention. The protrusions 242, 244, 246 serve to space the exterior walls of the fluid conduit 200 from the interior walls of a mounting groove 120 in the turbine inner shell 110. Maintaining a spacing allows the temperature controlling fluid to pass along the space between the exterior walls of the fluid conduit 200 and the interior walls of the mounting groove 120, as illustrated in FIGS. 4 and 5. Although not shown in FIG. 6, similar protrusions would be formed on the bottom wall of the fluid conduit 200.

In the embodiment illustrated in FIG. 6, the protrusions 242, 244, 246 are elongated in the length direction of the fluid conduit 200. Also, the leading and trailing edges of the protrusions are tapered. The tapered, elongated shape of the protrusions 242, 244, 246 is designed to facilitate sliding of the fluid conduit 200 into a mounting groove 120 of the turbine inner shell 110.

FIG. 7 illustrates an alternate embodiment of a fluid conduit 200. In this embodiment, the protrusions are formed as ridges 248 that extend around the exterior walls of the fluid conduit 200. Although only a single ridge 248 is illustrated in FIG. 7, multiple ridges 248 would be located along the length of the fluid conduit 200. The ridges 248 extend in essentially the same direction that the temperature controlling fluid flows along the exterior sides of the fluid conduit 200. Thus, the ridges 248 would not impede the flow, and may serve to guide the flow of the temperature controlling fluid.

FIG. 8 illustrates another embodiment of a fluid conduit 300 mounted in a mounting groove 320 of a turbine inner shell 110. In this embodiment, no protrusions are formed on the exterior walls of the fluid conduit 300. As a result, the bottom wall 310 and the side exterior walls of the fluid conduit 300 may be in direct contact with the inner walls of the mounting groove 320.

When an embodiment of a fluid conduit as illustrated in FIG. 8 is used in a turbine inner shell 110, one or more of the pipes coupled to the interior passageway 320 of the fluid conduit 300 would be used to deliver an incoming flow of temperature controlled fluid into the interior passageway 320, and one or more of the pipes coupled to the interior passageway 320 would remove a flow of the temperature controlling fluid. The pipes used to deliver an incoming flow and the pipes used to withdraw an outgoing flow would be positioned around the fluid conduit to cause a predetermined flow pattern through the interior passageway 320 of the fluid conduit 300.

A fluid conduit as described above can be easily mounted to a turbine inner shell to help control a clearance between the tips of the turbine blades and the surrounding shrouds. The fluid conduits can be easily inserted into and removed from the corresponding mounting grooves when the sections of the turbine inner shell are separated for maintenance and repair. Also, mounting grooves for the fluid conduits described above can be machined into existing turbine inner shells, making it possible to retrofit such fluid conduits into existing turbines which lack any way to actively control the clearance between the tips of the turbine blades and the surrounding shrouds.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An inner shell for the turbine section of a turbine engine, comprising:

a plurality of arcuate casing portions that are configured to be attached to one another to form a generally cylindrical inner shell, wherein each arcuate casing portion includes: at least one shroud hook portion that extends along an interior side of the arcuate casing portion in a circumferential direction, and at least one mounting groove that extends along the arcuate casing portion in the circumferential direction, wherein each at least one mounting groove is located adjacent to one of the at least one shroud hook portions; and

at least one conduit having at least one internal passageway for a temperature controlling fluid, each conduit being mounted within one of the at least one mounting grooves, wherein the at least one conduit is configured to be inserted into a mounting groove.

2. The inner shell of claim 1, wherein a radial inner side of the at least one mounting groove has a larger width than a radial outer side of the at least one mounting groove.

3. The inner shell of claim 1, wherein each at least one mounting groove is located on a radially outer side of one of the at least one shroud hook portions.

4. The inner shell of claim 1, wherein the internal passageway of each at least one conduit extends in a length direction of the conduit.

5. The inner shell of claim 4, wherein each at least one conduit includes a plurality of apertures that extend from the interior passageway to an exterior of the conduit.

6. The inner shell of claim 5, wherein the plurality of apertures are formed on a side of the conduit that faces the at least one shroud hook portion.

7. The inner shell of claim 5, wherein each at least one conduit includes a plurality of protrusions that are formed on an exterior surface of the conduit.

8. The inner shell of claim 7, wherein the plurality of protrusions are configured to space exterior surfaces of the conduit from interior surfaces of the at least one mounting groove.

9. The inner shell of claim 1, wherein each at least one conduit includes:

a first interior passageway that extends in a length direction of the conduit;

a second interior passageway that extends in a length direction of the conduit, wherein the first interior passageway is located on a radial outer side of the second interior passageway; and

a plurality of radially extending apertures that extend between the first and second interior passageways.

10. The inner shell of claim 1, wherein each at least one conduit further includes at least one inlet aperture that is configured to admit a flow of a temperature controlling fluid into the interior passageway.

11. The inner shell of claim 1, wherein the at least one conduit is configured to be slid into a mounting groove in a circumferential direction.

12. A temperature controlling fluid conduit that is configured to be mounted on an arcuate-shaped portion of an inner shell of a turbine section of a turbine engine, comprising:

an elongated, arcuate-shaped body having an interior passageway for a temperature controlling fluid; and

at least one inlet aperture that is configured to admit a flow of a temperature controlling fluid into the interior passageway.

13. The temperature controlling fluid conduit of claim 12, wherein a radial inner side of the elongated body has a larger width than a radial outer side of the elongated body.

14. The temperature controlling fluid conduit of claim 12, wherein the at least one inlet aperture is located on a radial outer side of the elongated, arcuate-shaped body.

15. The temperature controlling fluid conduit of claim 12, wherein the interior passageway extends in a length direction of the elongated arcuate-shaped body.

16. The temperature controlling fluid conduit of claim 15, wherein a plurality of apertures extend through the elongated, arcuate-shaped body from the interior passageway to an exterior of the body.

17. The temperature controlling fluid conduit of claim 16, wherein the plurality of apertures are formed on a radial inner side of the elongated, arcuate-shaped body.

18. The temperature controlling fluid conduit of claim 16, wherein a plurality of protrusions are formed on at least one exterior surface of the elongated, arcuate-shaped body.

19. The temperature controlling fluid conduit of claim 12, wherein the interior passageway comprises:

a first interior passageway that extends in a length direction of the elongated, arcuate-shaped body;

a second interior passageway that extends in the length direction of the elongated, arcuate-shaped body, wherein the first interior passageway is located on a radial outer side of the second interior passageway; and

a plurality of radially extending apertures that extend between the first and second interior passageways.