TIP CLEARANCE CONTROL WITH FINNED CASE DESIGN

Abstract

An apparatus and methods for controlling tip clearance in gas turbine engines may be provided. The apparatus and methods may include situating fins on a surface of a turbine case included in a turbine section of the gas turbine engine. The fins may act as a means for maintaining tip clearance by, for example, controlling the thermal expansion of the turbine case. The turbine case may shroud turbine blades, and the turbine blades may include tips at a radial end of the blades. During operation of the gas turbine engine, the clearance between the tips and the turbine case is desirably as small as possible while avoiding contact in order to optimize efficiency of the gas turbine engine.

Description

TECHNICAL FIELD

This disclosure relates to gas turbine engines and, in particular, to turbine cases.

BACKGROUND

An aircraft, such as a helicopter, a tilt-rotor aircraft, or a plane, may have a gas turbine engine that includes turbine blades spinning within a turbine case. Efficiency of the turbine engine may depend, in part, on the proximity of tips of the turbine blades to the case during operation of the gas turbine engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views.

FIG. 1 illustrates an example of a gas turbine engine system including a turbine section;

FIG. 2 illustrates an isometric view of an example of a portion of a turbine section including a turbine case including fins, the fins shaped as pins;

FIG. 3 illustrates a side view of the turbine case example shown in FIG. 2;

FIG. 4 illustrates an isometric view of an example of a portion of a turbine section including a turbine case including fins, the fins shaped as wedges;

FIG. 5 illustrates a side view of the turbine case example shown in FIG. 4;

FIG. 6 illustrates an isometric view of an example of a portion of a turbine section including a turbine case including fins, the fins shaped as rectangular slabs of varying length;

FIG. 7 illustrates a side view of the turbine case example shown in FIG. 6;

FIG. 8 illustrates a side view of a turbine case having fins on radially inward structures supporting a blade track.

DETAILED DESCRIPTION

By way of an introductory example, a portion of a turbine section of a gas turbine engine including a turbine case having one or more fins is provided for use in a gas turbine engine. The fins may provide a means for maintaining tip clearance between turbine blade tips and a blade track in the turbine section. The fins may be situated on a surface of a turbine case or on structures radially inward from the surface of the turbine case in order to, for example, provide a means of thermal communication between an ambient fluid, such as air, and the turbine case.

One interesting feature of the systems and methods described below may be that the fins on the turbine case may facilitate control of the clearance between the turbine blades and the blade track during operation of an engine, thereby increasing efficiency of the engine. Alternatively, or in addition, an interesting feature of the systems and methods described below may be that facilitating the control of the tip clearance may help avoid the turbine blades contacting the blade track and causing wear on the tips of the turbine blades.

FIG. 1 illustrates a cross-sectional view of a gas turbine engine 100 for propulsion of, for example, an aircraft. Alternatively or in addition, the gas turbine engine 100 may be used to drive a propeller in aquatic applications, or to drive a generator in energy applications. The gas turbine engine 100 may include an intake section 120, a compressor section 160, a combustion section 130, a turbine section 110, and an exhaust section 150. During operation of the gas turbine engine 100, fluid received from the intake section 120, such as air, travels along the axial direction D1 and may be compressed within the compressor section 160. The compressed fluid may then be mixed with fuel and the mixture may be burned in the combustion section 130. The combustion section 130 may include any suitable fuel injection and combustion mechanisms. The hot, high pressure fluid may then pass through the turbine section 110 to extract energy from the fluid and cause a turbine shaft of a turbine 114 in the turbine section 110 to rotate, which in turn drives the compressor section 160. Discharge fluid may exit the exhaust section 150.

As noted above, the hot, high pressure fluid passes through the turbine section 110 during operation of the gas turbine engine 100. As the fluid flows through the turbine section 110, the fluid passes between adjacent blades 112 of the turbine 114 causing the turbine 114 to rotate. The rotating turbine 114 may turn a shaft 140 in a rotational direction D2, for example. The blades 112 may rotate around an axis of rotation, which may correspond to a centerline X of the turbine 114 in some examples.

FIG. 2 illustrates an isometric view of an example of a portion of the turbine section 110 that comprises a turbine case 210 including fins 220 having a pin shape. The turbine case 210 may include, for example, a radially outward facing surface 212, an aft section 216 and a fore section 218, the fin 220, and a flange 250. As noted above, during operation of the gas turbine engine 100, fluid may pass between adjacent blades 112 causing the blades 112 to rotate in the rotational direction D2 in some examples or in a direction opposite of the rotational direction D2 in other examples.

During operation of the gas turbine engine 100, the turbine case 210 may be subjected to a large amount of heat from a variety of sources. This heat may be absorbed into the turbine case 210 in a significant enough quantity to cause the turbine case 210 to substantially expand, resulting in an increase in a tip clearance 240. For example, the turbine case 210 may experience varying amounts of heat absorbed from operation of the gas turbine engine 100 at various stages of operation of the gas turbine engine 100. Examples of the various stages of operation may be, but are not limited to: idle, take-off, climb, cruise, descent, landing, and idle after landing. Referring to FIG. 3, the tip clearance 240 is preferably, during the various stages of operation, only as large as necessary to avoid contact between the blades 112 (more precisely, the tips 230 of the blades 112) and the radially inward facing surface 264 of the blade track 260. If the tip clearance 240 becomes larger than is needed to avoid the tips 230 contacting the radially inward facing surface 264 of the blade track 260, then it may be undesirable because, for example, the excessive tip clearance 240 allows fluid, such as gas, moving through the turbine section 110 to pass through the tip clearance 240 instead of past an airfoil portion of the turbine blades 112. If the fluid passes through the tip clearance 240, it results in a decreased overall efficiency of the gas turbine engine 100.

The turbine case 210 may include a shell surrounding the turbine blades 112. Alternatively or in addition, the turbine case 210 may include a ring-shaped body in which the turbine blades 112 are configured to rotate. During operation of the gas turbine engine 100, the turbine case 210 may surround fluid moving through the turbine section 110 of the gas turbine engine 100, thus promoting contact between the fluid and the blades 112. The turbine case 210 may include a variety of features, such as for example, a flange 250.

In some examples the turbine case 210 may be made of metal or metal alloy. Alternatively, or in addition, the turbine case 210 may made from a ceramic matric composite (“CMC”). In some examples, the turbine case 210 may taper smoothly along the axial direction D1 from the aft section 216 to the fore section 218, or vice versa. Alternatively or in addition, the turbine case 210 may be tapered along the axial direction D1 from the aft section 216 to the fore section 218, or vice versa, in a tiered fashion.

The fins 220 may be protrusions extending radially from the turbine case 210. The fins 220 may be in thermal communication with the turbine case 210. The fins 220 may be integral to the turbine case 210. Alternatively, the fins 220 may be coupled to the turbine case 210. The fins 220 may exchange heat between the turbine case 210 and, for example, an ambient fluid, such as cooling air. The fins 220 may have any shape or combination of shapes. For example, the fins 220 may be pins, wedges 320, rectangular slabs, polyhedrons, or non-polyhedrons.

In some examples, the fins 220 may be distributed uniformly or, alternatively, non-uniformly along either the radially outward facing surface 212 of the turbine case 212, structures 270 located radially inward from the turbine case 212, or both. If the fins 220 are along the structures 270 located radially inward from the turbine case 212, a stream of cooling fluid may be present with the fins 220 to allow for thermal communication between the cooling fluid and the fins 220. Alternatively or in addition, a variety of shapes of the fins 220 may be utilized in a single example. For example, the fins 220 may include pins and wedges, and both may be present on the turbine case 210.

In some examples, portions of the turbine case 210 may have a higher local thermal inertia than other portions. Thermal inertia may be the degree of slowness with which the temperature of a body approaches that of its surroundings. This difference in local thermal inertia may be due to, for example, differences in local material, local thickness T of the turbine case 210, proximity to features of the turbine case 210, such as the flange 250, or other reasons.

The turbine case 210 may have different local thermal inertias at some points of the turbine case 210. Additionally, these portions may have different mean local thermal inertias. For example, a portion of the turbine case 210 that includes the flange 250 may have a higher mean thermal inertia than a portion of the turbine case 210 that is further away from the flange 250. The location, the orientation, the size, and the shape of the fins 220 (protrusions) may be selected to make the temperature more uniform across portions of the turbine case 210. For example, if the fins 220 abut the flange 250 as shown in FIG. 4, such an arrangement may lower the thermal inertia of the portion of turbine case 210 that includes the flange 250 so that the thermal inertia is closer to the thermal inertia of the portion of the turbine case 210 that is further away from the flange 250. If both portions of the turbine case 210 are subjected to the same amount of heat, then the temperatures of the portions may be closer to each other as the turbine case 210 heats and cools than the portions would have been without the fins 220. Accordingly, the fins 220 may include or be a means for maintaining the tip clearance 240.

Local thermal inertia may be the thermal inertia at a particular point on the turbine case 210 while mean local thermal inertia may be the average thermal inertia in a portion of the turbine case 210. Despite differences in local thermal inertia or mean local thermal inertia, the turbine case 210 may obtain a substantial uniform temperature by various methods. An example of such a method may include distributing a plurality of fins 220 along the radially outer facing surface 212 at portions of the turbine case 210 in proportion with the local thermal inertia of the portions. Alternatively, or in addition, a method may include varying the height of the fins 220 in proportion with the local thermal inertia of the portions of the turbine case 210. Alternatively, or in addition, a method may include a blower providing a fluid adjacent to the fins 220. The fluid may include liquid, gas, or both. The fluid may be higher in temperature relative to the fins 220, thus transferring heat into the fins 220, or lower in temperature relative to the fins 220, thus transferring heat from the fins 220. Examples of fluids include, but are not limited to: ambient air from outside of the gas turbine engine 100, bleed air from the compressor section 160, or a liquid such as water, glycerin-based coolant, or other appropriate liquid coolant.

The flange 250 may be a protruding rim, edge, rib, or collar used to strengthen the turbine case 210, hold in place the turbine case 210, or attach the turbine case 210 to another part of the gas turbine engine 100. The flange 250 shown in FIG. 2 is situated at the end of the fore section 218 of the turbine case 210 without substantially extending axially along the radially outward facing surface 212 of the turbine case 210. Alternatively, the flange 250 may be situated on the aft section 216 of the turbine case 210. Alternatively, multiple flanges 250 may be situated on various potions of the turbine case 210. Fins 220 may be attached to the flange 250 and extend axially along the radially outward facing surface 212 of the turbine case 210. Alternatively or in addition, some or all of fins 220 may be completely separate from the flange 250.

FIG. 3 is a cross-sectional view of the turbine case 210 shown in FIG. 2. FIG. 3 is an example of the turbine case 210 having the fins 220 in the shape of pins. The pins may be, for example, cylindrical. The pins may vary in diameter, either within a single pin or in relation to other pins or both.

The tip clearance 240 may exist between a tip 230 of a respective one of the blades 112 and a radially inward facing surface 264 of the blade track 260. The tip clearance 240 may fluctuate during operation of the gas turbine engine 100. The fins 220 may serve as a means for maintaining tip clearance 240. The means for maintaining tip clearance 240 may change the mean local thermal inertia of portions of the turbine case 210 and include protrusions shaped as pins, wedges, slabs, polyhedrons, or non-polyhedrons.

The turbine case 210 has the thickness T defined by a radial length between the radially outward facing surface 212 and the radially inward facing surface 214 of the turbine case 210. The thickness T may vary along the axial direction D1.

FIG. 4 illustrates an isometric view of another example of a portion of the turbine case 210 that includes the fins 220 that are in the shape of wedges. The wedges may extend radially from the turbine case 210 resulting in the wedges having a wedge height 410 that may vary along the wedge length 420. The wedges may have varying wedge lengths 420 in relation to each other. The wedges may have a constant tapering along the wedge length 420. Alternatively or in addition, the wedges may have non-constant tapering.

FIG. 5 is a cross-sectional view of the turbine case 210 shown in FIG. 4. FIG. 5 is an example of the turbine case 210 having fins 220 in the shape of wedges. The wedges may have, for example, a triangular cross section. The wedges may abut the flange 250. Alternatively, the wedges may be situated along any portion in any direction of the radially outward facing surface 212.

FIG. 6 illustrates an isometric view of another example of a portion the turbine case 210 that includes the fins 220. The fins 220 in this example are substantially rectangular slabs. The rectangular slabs may have a slab length 620. FIG. 6 shows a plurality of rectangular slabs. The rectangular slabs may have varying slab lengths 620 in relation to each other. The rectangular slabs may abut the flange 250. Alternatively or in addition, the rectangular slabs may be situated along any portion in any direction of the radially outward facing surface 212.

FIG. 7 is a cross-sectional view of the turbine case 210 shown in FIG. 6. FIG. 7 is an example of the turbine case 210 having fins 220 in the shape of rectangular slabs.

FIG. 8 is a cross-sectional view of the turbine case 210 with the fins 220 located on the structures 270 located radially inward from the turbine case 212. The structures 270 may be supporting the blade track 260. Alternatively, the structures 270 may be independent of the blade track 260.

To clarify the use of and to hereby provide notice to the public, the phrases “at least one of <A>, <B>, . . . and <N>” or “at least one of <A>, <B>, . . . <N>, or combinations thereof” or “<A>, <B>, . . . and/or <N>” are defined by the Applicant in the broadest sense, superseding any other implied definitions hereinbefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, . . . and N. In other words, the phrases mean any combination of one or more of the elements A, B, . . . or N including any one element alone or the one element in combination with one or more of the other elements which may also include, in combination, additional elements not listed.

While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible. Accordingly, the embodiments described herein are examples, not the only possible embodiments and implementations.

The subject-matter of the disclosure may also relate, among others, to the following aspects:

• 1. An apparatus comprising:
  • a protrusion on a turbine case, the protrusion comprising a means for maintaining a tip clearance, the tip clearance being a space between a blade track and a tip of a turbine blade configured to rotate within the turbine case.
• 2. The apparatus of aspect 1, wherein the protrusion is included in a plurality of protrusions on the turbine case that each comprise a corresponding means for maintaining the tip clearance.
• 3. The apparatus of aspect 2, wherein the protrusions comprise a first protrusion and a second protrusion, the first protrusion extends a first distance radially from the turbine case and the second protrusion extends a second distance radially from the turbine case, wherein the first distance is greater than the second distance,
  • wherein the turbine case includes a first portion comprising a first local mean thermal inertia and a second portion comprising a second local mean thermal inertia, wherein the first local mean thermal inertia is greater than the second local mean thermal inertia, and
  • wherein the first protrusion is located on the first portion and the second protrusion is located on the second portion.
• 4. The apparatus of aspect 2, wherein the turbine case includes a first portion comprising a first local mean thermal inertia and a second portion comprising a second local mean thermal inertia, wherein the first local mean thermal inertia is greater than the second local mean thermal inertia, and wherein the first portion comprises a greater number of protrusions than the second portion.
• 5. The apparatus of aspect 1, wherein the protrusion has a height and a length, and wherein the means for maintaining tip clearance is configured to transfer heat from the turbine case to an ambient fluid, the heat transfer occurring at a rate, the rate varying with the height of the protrusion, the height varying along the length.
• 6. The apparatus of aspect 1, wherein the protrusion is integral to the turbine case.
• 7. The apparatus of aspect 1, wherein the protrusion is a first protrusion, and wherein a second protrusion comprising a means for maintaining a tip clearance is situated on a structure supporting the blade track, wherein the structure supporting the blade track is located radially inward from the turbine case.
• 8. An apparatus comprising:
  • a turbine case comprising a fin, wherein the fin comprises a protrusion extending a height radially from the turbine case and a width circumferentially along a surface of the turbine case, the fin extending a length along an axial direction of the turbine case, the length larger than the width.
• 9. The apparatus of aspect 8, wherein the fin is included in a plurality of fins, and the fins are distributed non-uniformly around the case.
• 10. The apparatus of aspect 8, wherein the fin extends radially inwardly from the turbine case.
• 11. The apparatus of aspect 8, wherein the fin extends radially outwardly from the turbine case.
• 12. The apparatus of aspect 8, wherein the height varies along the length.
• 13. The apparatus of aspect 8, wherein the fin is included in a plurality of fins on the turbine case, wherein a first fin extends a first distance radially from the turbine case and a second fin extends a second distance radially from the turbine case, and wherein the first distance is unequal to the second distance.

14. A system comprising:

• a turbine case for a gas turbine engine;
• a plurality of turbine blades configured to rotate within the turbine case; and
• a plurality of fins arranged on the turbine case, the fins extending radially from the turbine case, each of the fins comprising a means for maintaining a tip clearance, the tip clearance being a distance between a blade track and tips of the turbine blades as the tips pass the blade track.

15. The system of aspect 14, wherein the fins are attached to a flange at an edge of the turbine case.

16. The system of aspect 14, wherein the fins are non-polyhedron.

17. The system of aspect 16, wherein the fins are cylindrical, wherein a first fin of the plurality of fins has a first radius and a second fin of the plurality of fins has a second radius, and wherein the first radius is greater than the second radius.

18. The system of aspect 14, wherein a first fin of the plurality of fins has a first shape and a second fin of the plurality of fins has a second shape, and wherein the first shape is different from the second shape.

19. The system of aspect 18, wherein the first shape comprises a cylinder and the second shape comprises a polyhedron.

20. The system of aspect 14, wherein the turbine case has a length in an axial direction of the turbine case, and wherein the turbine case comprises a first flange and a second flange, wherein at least one fin of the plurality of fins extends from the first flange to the second flange.

Claims

1. An apparatus comprising: a protrusion on a turbine case, the protrusion comprising a means for maintaining a tip clearance, the tip clearance being a space between a blade track and a tip of a turbine blade configured to rotate within the turbine case.

2. The apparatus of claim 1, wherein the protrusion is included in a plurality of protrusions on the turbine case that each comprise a corresponding means for maintaining the tip clearance.

3. The apparatus of claim 2, wherein the protrusions comprise a first protrusion and a second protrusion, the first protrusion extends a first distance radially from the turbine case and the second protrusion extends a second distance radially from the turbine case, wherein the first distance is greater than the second distance, wherein the turbine case includes a first portion comprising a first local mean thermal inertia and a second portion comprising a second local mean thermal inertia, wherein the first local mean thermal inertia is greater than the second local mean thermal inertia, andwherein the first protrusion is located on the first portion and the second protrusion is located on the second portion.

4. The apparatus of claim 2, wherein the turbine case includes a first portion comprising a first local mean thermal inertia and a second portion comprising a second local mean thermal inertia, wherein the first local mean thermal inertia is greater than the second local mean thermal inertia, and wherein the first portion comprises a greater number of protrusions than the second portion.

5. The apparatus of claim 1, wherein the protrusion has a height and a length, and wherein the means for maintaining tip clearance is configured to transfer heat from the turbine case to an ambient fluid, the heat transfer occurring at a rate, the rate varying with the height of the protrusion, the height varying along the length.

6. The apparatus of claim 1, wherein the protrusion is integral to the turbine case.

7. The apparatus of claim 1, wherein the protrusion is a first protrusion, and wherein a second protrusion comprising a means for maintaining a tip clearance is situated on a structure supporting the blade track, wherein the structure supporting the blade track is located radially inward from the turbine case.

8. An apparatus comprising: a turbine case comprising a fin, wherein the fin comprises a protrusion extending a height radially from the turbine case and a width circumferentially along a surface of the turbine case, the fin extending a length along an axial direction of the turbine case, the length larger than the width.

9. The apparatus of claim 8, wherein the fin is included in a plurality of fins, and the fins are distributed non-uniformly around the case.

10. The apparatus of claim 8, wherein the fin extends radially inwardly from the turbine case.

11. The apparatus of claim 8, wherein the fin extends radially outwardly from the turbine case.

12. The apparatus of claim 8, wherein the height varies along the length.

13. The apparatus of claim 8, wherein the fin is included in a plurality of fins on the turbine case, wherein a first fin extends a first distance radially from the turbine case and a second fin extends a second distance radially from the turbine case, and wherein the first distance is unequal to the second distance.

14. A system comprising: a turbine case for a gas turbine engine;a plurality of turbine blades configured to rotate within the turbine case; anda plurality of fins arranged on the turbine case, the fins extending radially from the turbine case, each of the fins comprising a means for maintaining a tip clearance, the tip clearance being a distance between a blade track and tips of the turbine blades as the tips pass the blade track.

15. The system of claim 14, wherein the fins are attached to a flange at an edge of the turbine case.

16. The system of claim 14, wherein the fins are non-polyhedron.

17. The system of claim 16, wherein the fins are cylindrical, wherein a first fin of the plurality of fins has a first radius and a second fin of the plurality of fins has a second radius, and wherein the first radius is greater than the second radius.

18. The system of claim 14, wherein a first fin of the plurality of fins has a first shape and a second fin of the plurality of fins has a second shape, and wherein the first shape is different from the second shape.

19. The system of claim 18, wherein the first shape comprises a cylinder and the second shape comprises a polyhedron.

20. The system of claim 14, wherein the turbine case has a length in an axial direction of the turbine case, and wherein the turbine case comprises a first flange and a second flange, wherein at least one fin of the plurality of fins extends from the first flange to the second flange.