Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
  • F01D11/08—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator

Definitions

• This invention relates generally to turbine engines and more particularly to an expansion control ring mounted about the gasifier turbine in a gas turbine engine.
• Gas turbine engines in order to operate efficiently / must maintain a relatively close tolerance between the turbine blades and the surrounding engine. This is necessary in order to minimize the loss of power due to expanding gases passing between the end of the turbine blade and the surrounding shroud.
• expansion of the turbine wheel relative the engine shroud is a problem which must be dealt with during design and in some cases, during engine operation. While this invention deals specifically with a gas turbine environment, it would be equally applicable to a steam turbine environment.
• the abradable portion of the shroud structure is made softer than the turbine blade so that upon, such contact, the shroud structure is worn away.
• the tip of the turbine blade is designed so that a certain amount of a turbine blade tip will wear away.
• These type turbine blades are commonly called “squealer tips” stemming from the fact that the contact of the blade with the turbine shroud causes a “squeal.”
• a unique disadvantage of a "squealer tip” blade is that the cooling passages normally found in gasifier turbine blades are easily blocked by the abrasion of the turbine tip. Once the cooling passages are blocked in the turbine blade, the turbine blade is subject to overheating and subsequent failure.
• the clearance between the turbine wheel and the shroud structure is permanently increased every time there is contact between the turbine wheel and the shroud structure that is sufficient to cause abrading of the metal, either on the shroud structure or the turbine tip.
• a floating expansion control ring in a turbine shroud assembly that includes a pair of manifold rings, a spacer ring positioned between the manifold rings.
• the spacer ring further defines a plurality of notches on its inner perimeter with each notch having a depth D and a width W.
• the expansion control ring has a plurality of lugs extending outward from the outer perimeter thereof with each lug having a width less than the width W of a corresponding notch in the spacer ring so that the lugs may be received in the notches.
• This invention permits the shroud structure through a floating expansion control ring to move eccentrically to the axis of the engine thereby maintaining concentricity with the turbine wheel.
• Figure 1 is a portion of a turbine shroud assembly which forms an embodiment of the present invention.
• Figure 2 is. a cross-sectional view of the turbine shroud assembly with the associated mounting elements which form an embodiment of the present invention along with a turbine blade.
• Figure 3 is a detailed view of a portion of the spacer ring and the expansion control ring that form an embodiment of the present invention.
• Figures 4A-E includes a sequence of schematic views of a turbine wheel and the associated shroud structure in the present embodiment and the prior art.
• FIG. 1 a portion of a turbine shroud assembly 10 is illustrated.
• a turbine shroud assembly such as the shroud assembly 10 shown
• Figure 1 is applicable for use in a turbine engine, in particular in a gas turbine engine, to surround the turbine wheel 11 (shown schematically in Figures 4A-E) which has extending outwardly therefrom a plurality of blades 12 upon which a stream of hot gases, as indicated by the arrow G, impinge.
• the shroud assembly 10 is comprised of three major portions, a spacer ring 14, a pair of manifold rings 28 and 30, and an expansion control ring 20.
• the spacer ring 14 is the outermost portion and has formed therein a plurality of nothces 16, each adapted to receive a corresponding lug 18 formed on an outwardly extending web 32 of expansion control ring 20.
• Expansion control ring 20 has positioned thereon a plurality of shroud segments 22.
• Shroud segments 22 and expansion control 20 provide the floating interface between the spacer ring 14 which is fixed to the surrounding engine and the rotating turbine blades 12.
• expansion control ring 20 and the associated shroud segments 22 are floatingly affixed to the engine casing 24.
• Spacer ring 14 is formed with a plurality of holes 26 through which a corresponding plurality of bolts 27 may be passed.
• manifold rings 28 and 30, respectively are on either side of spacer ring 14. The purpose of these manifold rings is more clearly set forth in U.S. Patent No. 4,251,185. Suffice it to say these rings in addition to providing support for the shroud assembly direct cooling air to the shroud assembly.
• Spacer ring 14 has a slightly thicker dimension T, than the thickness 2 of the web 32 of expansion control ring 20. This greater thickness permits movement of expansion control ring 20 relative the manifold rings 28 and 30 and spacer ring 14.
• Expansion control ring 20 has an outer perimeter 34 which has a radius R, while spacer ring 14 has an inner perimeter 36 having a radius R 2 . It should be apparent that radius R 2 is greater than radius R, by a predetermined amount. Similarly, in Figure 3 it can be seen that each lug 18 has a width W, while each notch 16 has a width 2 . Further, the depth of each notch is equal to a predetermined amount D, while the height of each lug is equal to H.
• the expansion control ring 20 in a gas turbine engine may move eccentrically as described in the following paragraphs.
• Figure 4A the expansion control ring as shown schematically as a circle at 20,
• FIG. 4A A schematic turbine wheel 11 with associated turbine blades 12 is shown in an at rest position at Figure 4A.
• Prior art devices having abradable shroud segments such as is described in U.S. Patent 4,251,185 noted above, will take the configuration shown in Figure 4B should there be a lack of concentricity between the turbine shroud 20' and the turbine wheel 11' upon start-up or during operation of the engine. Tn particular, in Figure 4B- it can be seen that the turbine wheel 11' has moved downwardly so that the associated turbine blades 12' will come in contact with expansion control ring 20'. With an abradable structure, the expansion control ring then becomes out of round as indicated in Figure 4C. This out of round condition will result in loss of efficiency in the turbine engine due to the increased gap between the blades and the turbine wheel, as shown in Figure 4C. It is understood that the illustrations in Figures 4A-E are exaggerated to better define the problem.
• the present invention is shown schematically
• the expansion control ring 20 is free to move in a radial direction and to a certain extent, to rotate axially. Concurrently, sufficient gap is maintained between the expansion control ring 20 and the spacer ring 14 so that any variation in the rate of expansion between the expansion control ring and the spacer ring 14 may take place without serious injury to the internal portions of the engine. It is appropriate to make the clearances between the sides of the lugs 18 and notches 16 less than the clearances between the end of the notches 16 and lugs 18 so that the radial movement of the expansion ring will be controlled by the side clearance. It is also important to understand that the clearance between the sides of the lugs and notches is not made so large so that there will be excessive movement, rather the fit should be sufficiently tight so that movement is dampened between the two portions.
• the aforedescribed invention has particular advantages in that it overcomes the necessity for using either an abradable shroud or a "squealer tip" as described in the background of this invention.
• abradable shrouds have been subject to oxidation and corrosion due to the high gas temperatures and have further suffered from erosion due to the high gas velocities after a short period of time.
• the actual clearance between the turbine wheel and the expansion control ring 20 will increase due to this erosion and corrosion problem.
• the "squealer tips" are used on all blades of the turbine wheel, there is a permanent increased clearance between all the blades and the shroud structure as shown in Figure 4D.
• the abrasion around the end of the "squealer tip” may block off the air flow through the turbine blade, thereby having a deleterious effect on the cooling of the engine itself.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=22161182

Family Applications (1)

Country Status (7)

Cited By (6)

Citations (4)

Family Cites Families (7)

• 1981
  • 1981-04-10 DE DE8181901830T patent/DE3174911D1/de not_active Expired
  • 1981-04-10 WO PCT/US1981/000481 patent/WO1982003657A1/en active IP Right Grant
  • 1981-04-10 JP JP50226581A patent/JPS58500489A/ja active Granted
  • 1981-04-10 EP EP19810901830 patent/EP0076256B1/en not_active Expired
  • 1981-11-24 CA CA000390737A patent/CA1173368A/en not_active Expired
• 1982
  • 1982-03-12 BE BE0/207543A patent/BE892463A/fr not_active IP Right Cessation
• 1987
  • 1987-12-31 MY MY1987851A patent/MY8700851A/xx unknown

Patent Citations (5)

Non-Patent Citations (1)

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