Turbine blade and damper retention

Abstract

A gas turbine engine rotor assembly has a plurality of blades spaced apart from each other for rotation about an axis. Each of the blades includes a platform having an inner surface and an outer surface. The inner surfaces of adjacent platforms define a pocket having a radially outer wall, a pressure side wall, and a suction side wall. The pocket includes a leading edge wall portion and a trailing edge wall portion, and a shelf extending in a tangential direction relative to the axis from the pressure side of the pocket. The shelf is spaced apart from the radially outer wall.

Claims

1. A gas turbine engine rotor assembly comprising: a plurality of blades spaced apart from each other for rotation about an axis, each of the blades including a platform having an inner surface and an outer surface, and wherein the inner surfaces of adjacent platforms define a pocket having a radially outer wall, a pressure side wall, and a suction side wall, and wherein the pocket includes a leading edge wall portion and a trailing edge wall portion, and including a first shelf extending in a tangential direction relative to the axis from the pressure side of the pocket, the first shelf being spaced apart from the radially outer wall, and including a second shelf extending axially inward from the leading edge wall portion on a suction side of the pocket.

2. The gas turbine engine rotor assembly according to claim 1, wherein the first shelf is adjacent the leading edge wall portion.

3. The gas turbine engine rotor assembly according to claim 2, wherein the first shelf is spaced apart from the leading edge wall portion by a gap.

4. The gas turbine engine rotor assembly according to claim 1, wherein the first and second shelves are configured to restrict radial, axial and tangential movement of a damper seal positioned within the pocket.

5. The gas turbine engine rotor assembly according to claim 1, wherein the first shelf is positioned adjacent the leading edge wall portion and spaced apart from the radially outer wall by a first gap, and wherein the first shelf is spaced apart from the leading edge wall portion by a second gap, and including a damper seal positioned within the pocket and supported by the shelf.

6. The gas turbine engine rotor assembly according to claim 5, wherein the second shelf extends axially inward from the leading edge wall portion to a distal end that overlaps, in a radial direction, a leading edge of an airfoil associated with the platform, and wherein the first and second shelves are configured to restrict radial, axial and tangential movement of the damper seal within the pocket.

7. The gas turbine engine rotor assembly according to claim 6, wherein the damper seal comprises an axially elongated body having a leading edge, a trailing edge, a pressure side, and a suction side, and wherein the elongated body includes a tab that extends axially outward from the leading edge.

8. The gas turbine engine rotor assembly according to claim 7, wherein the damper seal is defined by a length and a width that continuously varies between the leading edge and trailing edge, and wherein the width is at a maximum near the leading edge and is at a minimum at the tab.

9. The gas turbine engine rotor assembly according to claim 7, wherein the plurality of blades are mounted for rotation with a disk about the axis, and wherein the tab is visible at each damper seal location when the blades are finally mounted to the disk to indicate that the damper seals are correctly mounted within the pockets.

10. The gas turbine engine rotor assembly according to claim 9, wherein a width of the damper seal is greater at the leading edge than the trailing edge, and wherein the trailing edge at each damper seal location is flush or below an aft face of the blades and disk when the blades are finally mounted to the disk to indicate that the damper seals are correctly mounted within the pockets.

11. The gas turbine engine rotor assembly according to claim 7, wherein the damper seal includes a first enlarged portion formed on the pressure side of the leading edge and a second enlarged portion formed on the suction side adjacent the trailing edge.

12. The gas turbine engine rotor assembly according to claim 10, wherein the first and second enlarged portions comprise added mass portions with the first enlarged portion having a greater mass than the second enlarged portion.

13. A method of assembling a rotor assembly for a gas turbine engine comprising the following steps: (a) partially installing a blade within a disk; (b) inserting a damper seal into a pocket defined by the blade, wherein the damper seal has an axially elongated body having a leading edge, a trailing edge, a pressure side, and a suction side, and wherein the elongated body includes a tab that extends axially outward from the leading edge, wherein the tab defines a minimum width of the elongated body; (c) repeating steps (a) and (b) until all blades and damper seals are installed into the disk; (d) simultaneously seating all of the blades in the disk as a unit to a final installation position; and (e) inspecting the tab of each damper seal to determine that the damper seals are correctly engaged in the pockets.

14. The method according to claim 13, wherein step (e) includes determining that the damper seal is correctly installed when the tab is visible from a leading edge end face of the disk.

15. The method according to claim 14, wherein step (e) further includes verifying that the trailing edge of each damper seal is flush or below an aft face of the blades and disk.

16. The method according to claim 15, including installing a cover plate to an aft end of the disk.

17. The method according to claim 13, wherein the blades rotate about an axis, and wherein the pocket has a radially outer wall, a pressure side wall, and a suction side wall, and wherein the pocket includes a leading edge wall portion and a trailing edge wall portion, and including providing a first shelf extending in a tangential direction relative to the axis from the pressure side of the pocket, the first shelf being spaced apart from the radially outer wall, and including a second shelf extending axially inward from the leading edge wall portion on a suction side of the pocket, and including supporting the damper seal on the first and second shelves to restrict radial, axial and tangential movement of the damper seal within the pocket.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

(2) FIG. 1 schematically illustrates a geared turbofan engine embodiment.

(3) FIG. 2 illustrates a front perspective view of a blade mounted to a turbine disk.

(4) FIG. 3 is a perspective view of a portion of the turbine disk and blade of FIG. 2 which schematically shows a damper.

(5) FIG. 4A is a side view of a pressure side pocket side of a blade.

(6) FIG. 4B is a perspective view of the blade of FIG. 4A as viewed from a trailing edge location.

(7) FIG. 4C is bottom view of FIG. 4A.

(8) FIG. 4D is an enlarged view of FIG. 4C.

(9) FIG. 5 is side view of a suction side pocket of a blade.

(10) FIG. 6A is a perspective view of a prior art damper seal.

(11) FIG. 6B is a perspective view of a damper seal incorporating the subject invention.

(12) FIG. 7A is a side view of assembling a blade to a disk.

(13) FIG. 7B shows a side view of a partially installed blade and a fully installed damper seal.

(14) FIG. 7C is a leading edge end view showing a correctly installed damper seal.

(15) FIG. 7D is a side view showing a fully installed blade, damper seal and cover plate.

(16) FIG. 7E is a perspective view of FIG. 7D.

(17) FIG. 8 is a top view of a blade and damper seal.

(18) FIG. 9A is a cross-sectional view taken along 9A-9A of FIG. 8.

(19) FIG. 9B is a cross-sectional view taken along 9B-9B of FIG. 8.

(20) FIG. 9C is a cross-sectional view taken along 9C-9C of FIG. 8.

(21) FIG. 9D is a cross-sectional view taken along 9D-9D of FIG. 8.

(22) FIG. 10 is an end view showing tangential rotation restriction in one direction.

(23) FIG. 11 is a view similar to FIG. 10 but showing tangential rotation restriction in an opposite direction.

DETAILED DESCRIPTION

(24) FIG. 1 schematically illustrates an example gas turbine engine 20 that includes a fan section 22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section 22 drives air along a bypass flow path B while the compressor section 24 draws air in along a core flow path C where air is compressed and communicated to a combustor section 26. In the combustor section 26, air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section 28 where energy is extracted and utilized to drive the fan section 22 and the compressor section 24.

(25) Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section.

(26) The example engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided.

(27) The low speed spool 30 generally includes an inner shaft 40 that connects a fan 42 and a low pressure (or first) compressor section 44 to a low pressure (or first) turbine section 46. The inner shaft 40 drives the fan 42 through a speed change device, such as a geared architecture 48, to drive the fan 42 at a lower speed than the low speed spool 30. The high-speed spool 32 includes an outer shaft 50 that interconnects a high pressure (or second) compressor section 52 and a high pressure (or second) turbine section 54. The inner shaft 40 and the outer shaft 50 are concentric and rotate via the bearing systems 38 about the engine central longitudinal axis A.

(28) A combustor 56 is arranged between the high pressure compressor 52 and the high pressure turbine 54. In one example, the high pressure turbine 54 includes at least two stages to provide a double stage high pressure turbine 54. In another example, the high pressure turbine 54 includes only a single stage. As used herein, a high pressure compressor or turbine experiences a higher pressure than a corresponding low pressure compressor or turbine.

(29) The example low pressure turbine 46 has a pressure ratio that is greater than about 5. The pressure ratio of the example low pressure turbine 46 is measured prior to an inlet of the low pressure turbine 46 as related to the pressure measured at the outlet of the low pressure turbine 46 prior to an exhaust nozzle.

(30) A mid-turbine frame 58 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 58 further supports bearing systems 38 in the turbine section 28 as well as setting airflow entering the low pressure turbine 46.

(31) The core airflow C is compressed by the low pressure compressor 44 then by the high pressure compressor 52 mixed with fuel and ignited in the combustor 56 to produce high speed exhaust gases that are then expanded through the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 58 includes vanes 60, which are in the core airflow path and function as an inlet guide vane for the low pressure turbine 46. Utilizing the vane 60 of the mid-turbine frame 58 as the inlet guide vane for low pressure turbine 46 decreases the length of the low pressure turbine 46 without increasing the axial length of the mid-turbine frame 58. Reducing or eliminating the number of vanes in the low pressure turbine 46 shortens the axial length of the turbine section 28. Thus, the compactness of the gas turbine engine 20 is increased and a higher power density may be achieved.

(32) The disclosed gas turbine engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine 20 includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example geared architecture 48 is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3.

(33) In one disclosed embodiment, the gas turbine engine 20 includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor 44. It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines.

(34) A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight conditiontypically cruise at about 0.8 Mach and about 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft., with the engine at its best fuel consumptionalso known as bucket cruise Thrust Specific Fuel Consumption (TSFC)is the industry standard parameter of pound-mass (lbm) of fuel per hour being burned divided by pound-force (lbf) of thrust the engine produces at that minimum point.

(35) Low fan pressure ratio is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (FEGV) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.50. In another non-limiting embodiment the low fan pressure ratio is less than about 1.45.

(36) Low corrected fan tip speed is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram R)/(518.7 R)].sup.0.5. The Low corrected fan tip speed, as disclosed herein according to one non-limiting embodiment, is less than about 1150 ft/second.

(37) The turbine section 28 includes one or more turbine rotor assemblies 66 as shown in FIG. 2. Each rotor assembly 66 includes a plurality of adjacent turbine blades 68 (only one is shown in FIG. 2) mounted to a turbine rotor disk 70 for rotation about the engine axis A. Each of the turbine blades 68 includes a root 72 that is fit into a corresponding slot 74 of the turbine rotor disk 70. Radially outward of the root 72 is a platform 76. The platform 76 defines an outer platform surface 78 and an inner platform surface 80. The inner platform surface 80 is disposed radially inward of the outer platform surface 78. An airfoil 82 extends outward from the platform 76.

(38) As shown in FIG. 3, a gap 84 extends axially between adjacent turbine blades 68. Hot gas H flows around the airfoil 82 and over the outer platform surface 78 while relatively cooler high pressure air (C) pressurizes a cavity or pocket 86 under the platform 76. The gap 84 between adjacent blades prevents contact and allows for thermal growth between adjacent turbine blades 68.

(39) As shown in FIG. 4A, the pocket 86 has a radially outer wall portion defined by the inner platform surface 80, a leading edge wall portion 88, a trailing edge wall portion 90, and a pressure side wall portion 92 as viewed in FIG. 4A.

(40) A shelf 94 extends outwardly from the pressure side wall portion 92 in a tangential direction relative to axis A. The shelf 94 is spaced from the leading edge wall portion 88 by a gap 96a as shown in FIG. 4C and is spaced apart from the radially outer wall portion 80 by a gap 96b as shown in FIG. 4A. The shelf 94 is defined by an axially extending width W and a tangentially extending length L as shown in FIG. 4D. In one example the length L is greater than the width W. The shelf 94 assists in assembly, axially and radially retains a damper seal 98 (FIG. 6), and prevents rotation of the damper seal 98 into the pressure side neck. This will be discussed in greater detail below.

(41) As shown in FIG. 5, a leading edge shelf 100 extends in an axial direction from the leading edge wall portion 88 of a suction side 101 of the pocket 86. The leading edge shelf 100 extends axially inwardly into the pocket 86 such that a distal end 102 of the shelf is in overlapping engagement with the leading edge of the airfoil 82 in a radial direction. This suction side leading edge damper shelf 100 prevents the damper seal 98 from disengaging the shelf axially during assembly and operation.

(42) A prior damper seal 200 is shown in FIG. 6A. The damper seal 200 includes a leading edge 202, a trailing edge 204, a pressure side 206, and a suction side 208. A tab portion 210 extends outwardly from the pressure side 206 of the damper seal 200. The purpose of the tab portion 210 was to facilitate assembly, but was not always effective. Further, this damper seal configuration exhibited tangential movement within the pocket during engine operation, which led to permanent distortion of the shape of the damper seal from its initial shape.

(43) The subject damper seal 98 is shown in greater detail in FIG. 6B. The damper seal 98 is sized to provide sufficient mass and rigidity to dissipate vibrations from the turbine blade. In the example shown, the damper seal 98 has an axially elongated body having a leading edge 98a, a trailing edge 98b, a pressure side 98c, and a suction side 98d. The damper seal 98 is defined by a length 98e and a width 98f. The width 98f varies between the leading edge 98a and trailing edge 98b. The width 98f is greater at the leading edge end than the trailing edge end of the damper seal.

(44) In the example shown, a leading edge tab 110 extends axially outward from the leading edge 98a. The tab 110 defines the minimum width of the elongated body. The tab 110 facilitates assembly and aids in the correct positioning of the damper seal within the pocket 86.

(45) In the example shown, a first enlarged portion 112 is provided on the pressure side 98c adjacent the leading edge 98a. A second enlarged portion 114 is provided on the suction side 98d adjacent the trailing edge 98b. These enlarged portions 112, 114 add mass at these locations as compared to prior designs. The first enlarged portion 112 has a greater mass than the second enlarged portion 114. Further, the width at the first enlarged portion 112 defines the maximum width of the elongated body. The added mass decreases freedom of movement of the damper seal in the pocket during engine operation. This will be discussed in greater detail below.

(46) The method of assembly for the damper seal 98 is shown in FIGS. 7A-7E. In a first step, a blade 68 is partially installed within the disk 70 from the rear as shown in FIG. 7A. In one example, the blade 68 is engaged approximately 0.125 inches (3.175 mm) in the disk 70. Next, the damper seal 98 is inserted into a corresponding pocket 86 as shown in FIG. 7B. It is important to ensure that the damper seal is correctly engaged in the leading edge pocket portion as shown in FIG. 7B. This process is then repeated for each blade 68.

(47) Once all of the blades 68 are partially installed in the disk 70, the blades are all simultaneously seated as a unit against a minidisk (not shown). Next, a visual inspection is performed to ensure that the damper seals are correctly engaged in the leading edge pocket portions. As shown in FIG. 7C, when the damper seal 98 is installed correctly, the leading edge tab 110 is visible from an end view of the blade and disk assembly. If the damper seal is not properly installed at the leading edge, i.e. the leading edge tab 110 is not properly positioned within the leading edge pocket portion, the damper seal will not fit properly and the blade will not be able to fully engage the disk without the damper seal protruding from the trailing edge. The visual inspection is performed for each damper seal 98. The next step performed is to verify that the trailing edge 98b of each damper seal 98 is flush or below an aft face of the blades and disk 70.

(48) Then, a cover plate 120 is installed as shown in FIGS. 7D-E. The disk 70 and shelf 94 support the damper seal 98 radially as shown in FIG. 7D. The cover plate 120 supports the damper seal axially and seals off the back of the blades. The leading edge tab 110 additionally serves to decrease damper rotation during assembly as shown in FIG. 7E.

(49) As discussed above, the damper seal mass was increased to improve damper durability and retention. A top view of a blade 68, platform 96, and damper seal 98 is shown in FIG. 8. A plurality of cross-sections have been taken along the length of the damper seal 98 as indicated by sections 9A-9D in FIG. 8. The sections at these axial locations show the variance in mass distribution in the pocket 86 for the loads that are shared by adjacent platforms 76.

(50) As shown in FIG. 9A, a first platform 76a is separated from an adjacent second platform 76b by the gap 84. A pressure side/leading edge pocket section is shown at 121 and a suction side/leading edge is shown at 122. At the leading edge of the blade 68 (9A-9A cross-sectional location), the majority of the mass of the damper seal 98 is located in the pressure side/leading edge pocket section 121, while only a small portion of the mass is located in the suction side/leading edge pocket section 122. Thus, the load carried by the first platform 76a is significantly greater at this location than the load carried by the second platform 76b.

(51) FIG. 9B shows a cross-section location that is just aft of the leading edge of the blade. The mass distribution is similar to that of FIG. 9A, however, the second platform 76b carries a slightly greater load than that shown in FIG. 9B.

(52) FIG. 9C shows a cross-section location that is aft of 9B and which is just forward of the trailing edge of the blade 68. At this location, the mass distribution has shifted as compared to that shown in FIG. 9A. The majority of the mass of the damper seal 98 at this axial location is located in the suction side pocket portion as indicated at 130, while only a lesser extent of the mass is located in the pressure side pocket section as indicated at 132. Thus, the load carried by the second platform 76b is significantly greater at this location than the load carried by the first platform 76a.

(53) FIG. 9D shows a cross-section that is located at the trailing edge of the blade. At this location the mass distribution is generally centered within the pocket 86. Thus, the loads between the first 76a and second 76b platforms are generally equal at the trailing edge.

(54) FIGS. 10 and 11 show two examples of how added damper mass decreases rotational freedom of the damper seal 98 within the pocket 86. As shown in FIG. 10, the damper seal is limited from rotating in a counter-clockwise direction due to the interference between the damper seal and pocket as indicated at 140. In one example, the interference points limit the damper seal to six degrees or less of relative rotation. As shown in FIG. 11, the damper seal is limited from rotating in a clockwise direction due to the interference between the damper seal and pocket as indicated at 150, and between the damper seal and disk as indicated at 152.

(55) The blade pocket shelf 94 holds the damper seal 98 radially, axially, and tangentially during engine operation and assembly. The damper seal slides in between the shelf on the pressure side of the blade pocket and the blade leading edge, which prevents the damper seal from sliding excessively in the axial direction. The damper seal also fills the blade pocket to the neck of the blade and down to the shelf 94, which prevents any excessive tangential rotation. The damper seal also seats onto the shelf 94, which prevents radial drop into the disk 70.

(56) The assembly process for the damper seal is also significantly improved compared to prior configurations. At assembly, the added damper features, such as the leading edge tab for example, add mistake proofing to ensure that the damper seal is installed correctly. The damper seal is also configured to prevent the damper seals from becoming disengaged during assembly. Further, the added damper mass helps prevent the damper seal from rotating too far into the pressure side blade pocket.

(57) Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.