EP0236337B1

EP0236337B1 - Seal ring means for a bladed rotor assembly

Info

Publication number: EP0236337B1
Application number: EP19860901729
Authority: EP
Inventors: Philip J. Cederwall; Charles T. Darragh; Warren W. Davis; Boris Glezer; Philip J. Hengen
Original assignee: Solar Turbines Inc
Current assignee: Solar Turbines Inc
Priority date: 1985-09-12
Filing date: 1985-12-06
Publication date: 1989-03-01
Also published as: CA1235071A; EP0236337A1; WO1987001761A1; JPS63500879A; DE3568465D1

Abstract

Bladed rotor assemblies having removable blades are used with gas turbines to reduce costs and increase serviceability. Complex structures were used in the past to retain the blades within the rotor and seal the space therebetween. Complex tooling and methods were required for replacement of worn or damaged blades. Replacement of such blades by using the present invention reduces the complexity of the service required and reduces maintenance costs. The bladed rotor assembly (10) of the present invention has a rotor (14) with slots (40), an outward facing groove (62) and an opening (23) in the rotor (14). The blades (16) are mounted in the slots (40) and have an inward facing groove (64) therein. The grooves (62, 64) form an annular T-slot (20). A ring segment (74) and a spacer (82) are rotatably trapped in the T-slot (20) and a device (26) prevents relative rotation between the ring segment (74) and/or the spacer (82), and the rotor (14). The rotor assembly (10) enables replacement of damaged blade (16) on an individual basis by a simple disassembly-assembly technique which is inexpensive and requires low cost tooling. The device (26) preventing rotation is removed from the rotor (14) and the ring segment (74) and the spacer (82) are rotated to align the opening (23) and the spacer (82). The spacer (82) is slipped from the T-slot (20). The ring segment (74) is aligned so that each damaged blade (16) is replaced. After all the damaged blades (16) are replaced, the ring segment (74) is aligned with the opening (23), the spacer (82) reinserted and the ring segment (74) and spacer (82) rotated to a position where prevention device (26) is fixedly attached to the rotor (14).

Description

This invention relates generally to gas turbine engine rotors and more particularly to the device for retaining the blades of a bladed rotor against axial movement on the rotor, sealing the gaps at the roots of the blades, dampening blade vibration and to the method of assembling the retaining device.
Turbine rotor assemblies having removable blades have been used in gas turbine engines and turbochargers to reduce cost and increase serviceability over one-piece rotors. The ability to replace worn or damaged blades rather than replacing the entire rotor has allowed the engineer to strive for greater efficiency by reducing the gap or space between the tip of the turbine blade and the surrounding shroud. However, during actual operation of the engine, thermal variation (expansion from heat and retraction from cooling) at start-up and running modes will vary the clearance and efficiency.
The current rotor assemblies consist of a forged rotor hub which is machined to accept a plurality of individual blades. The root portion of the blades are assembled on the hub to prevent centrifugal force from extracting the blade from the hub. A seal ring is attached to the hub to prevent the blades from moving axially out of the hub and to prevent the passage of working gases between the hub and the root portion of the blade. By blocking the space between the root portion of the blade and the hub, the seal causes all the working gas to pass through the working portion of the blade and increases the operating efficiency of the engine.
A large variety of structures and methods have been devised to attach the seal ring to the rotor. US-A-3,807,898 discloses a bladed rotor assembly which has a segmented sealing plate, a groove in the blades, a half-round groove in the plate segments, and a half-round groove which cooperates with the half-round groove in the segments. The blades are assembled in the rotor; the segments are inserted in the groove of the blade and a lock wire is circumferentially inserted into the two half-round grooves. The seal plate retains the blades in position and seals the flow of working gas from passing between the rotor and the blades. The segments overlap one another to prevent leakage past the segments. US-A-4,344,740 discloses a rotor assembly which consists of a plurality of attaching slots and lugs on the disk, a plurality of blades equal in number to the slots and a one-piece sideplate has lugs thereon. The sideplate is positioned on the rotor with the blades secured in the slots, and the lugs on the rotor and the lugs on the sideplate interleaved. The sideplate is forced against the rotor, the lugs are caused to elastically deform and the sideplate is rotated until the lugs on the sideplate are captured beneath the lugs on the rotor. An antirotation pin is used to prevent relative movement between the sideplate and the disc. Furthermore, US-A-4,523,890 discloses an end seal for a turbine blade base. The seal consists of a seal ring and a plurality of seal plate segments. The seal ring is positioned between the seal plate segments and the blade at one end, and between the seal plate segments and the turbine wheel at the other end. After installation of the seal ring each of the seal plate segments are conventionally installed.
The disadvantages of the above noted rotor assembly constructions are that they increase the manufacturing cost, are difficult to service, and reduce the dependability of the rotor assembly. For example, US-A-3,807,898 involves increased manufacturing and assembly costs by requiring two half-round grooves and two lock wires which must be fed into the two half-round grooves and bent radially inwardly to prevent the wire form passing too far into the groove. US-A-4,344,740 involves increased manufacturing and assembly costs by using a plurality of lugs on both the rotor and the sideplate. The lugs require machined tapers to mate with each other and the assembly technique requires special tooling such as heating facilities and a press. US-A-4,523,890 involves increased manufacturing and assembly costs due to the addition of a complex shaped seal ring and a complex machining configuration of the turbine wheel retainer area. The above patents describe expensive bladed rotor assembly employing complex machining and assembly techniques. The seal ring must be removed from the rotor to replace a single failed blade and then requires that the complex assembly technique be followed to reassembly.
In accordance with the invention, a bladed rotor assembly comprising a rotor having opposed faces, a rim and a plurality of circumferentially arrayed retention slots in the rim, the slots passing from one of the faces to the other of the faces and having radial retention means, a plurality of blades mounted on the rotor with each of the blades having a root portion received in a corresponding one of the slots, the root portion being shaped so that it engages the radial retention means to prevent movement of the blade radially outwards of the rotor; means on the rotor and on each of the plurality of blades for defining an annular T-slot at one of the faces; means defining an opening in the means on the rotor which forms a portion of the T-slot; seal means rotatably trapped in the T-slot and including ring segment means having first and second ends circumferentially spaced apart to define therebetween a space wide enough for the passage of a blade root portion, and a spacer positioned between the ends of the ring segment means, the arcuate length of the opening being at least equal to the length of the spacer, and the seal means being indexable to a position at which the spacer is out of alignment with the opening in the rotor; and means for preventing rotation between the seal means and the rotor; (as disclosed in GB-A-905582); is characterised in that the ring segment means comprises a single ring segment.
The invention also includes a method of assembling a bladed rotor assembly, the rotor assembly including a rotor having opposed faces, a rim and a plurality of circumferentially arrayed retention slots in the rim, the slots passing from one of the faces to the other of the faces and having radial retention means; and a plurality of blades mounted on the rotor with each of the blades having a root portion received in a corresponding one of the slots, the root portion being shaped so that it engages the radial retention means to prevent movement of the blade radially outward of the rotor; means on the rotor for forming a circumferentially extending, radially outwardly facing groove on the rotor; and means on each of the plurality of blades for forming a circumferentially extending inwardly facing groove; the method comprising the steps of:

a) positioning a ring segment means in the groove formed in the rotor, so that a space defined between circumferentially spaced apart first and second ends is aligned with one of the slots in the rotor;
b) inserting the root portion of a blade through the space in the ring segment means and into one of the slots in the rim so that an arcuate portion of an annular T-slot is formed;
c) indexing the segment means into the arcuate portion of the T-slot to align the space in the segment with another one of the slots in the rotor;
d) inserting the root portion of a second one of the plurality of blades through the space in the ring segment means and into the another one of the slots in the rim so that the arcuate portion of the annular T-slot is increased in length; and
e) progressively repeating steps c) and d) until all of the retention slots contain a blade; closing the space so that no blade is retractable from its slot; and fixing the ring segment means against further indexing in the T-slot; (as disclosed in FR-A-1580473);
is characterised in that the ring segment means comprises a single ring segment which is initially positioned in the groove; in that the space is closed by a spacer which is introduced through an opening in the groove-forming means on the rotor with the space aligned with the opening, the spacer and the ring segment means being indexed until the spacer is trapped in the T-slot; and in that a hole extending through one of the spacer and ring segment is aligned with a hole in the face of the rotor and means are inserted in the hole for preventing further indexing between the seal means and the rotor.

The present invention provides a simple and inexpensive method of replacing individual worn or damaged blades of a rotor assembly. The means for preventing rotation are removed and the seal means which is rotatably trapped in the T-slot is indexed so that the ends of the ring segment means align with the opening in the rotor and the spacer is removed. The ring segment means is rotated until the ends align with the worn or damaged blades to be removed and replaced. After replacing the blades, the ring segment means is indexed to align the ends with the opening and the spacer is inserted, the seal means is indexed to a position at which the spacer is out of alignment with the opening in the rotor, and the means for preventing rotation is secured to the rotor. The present invention provides for a simple and inexpensive means to attach a plurality of blades to a rotor while providing a seal to ensure the flow of working gases through the working portion of the turbine blades and for dampening blade vibration. The assembly technique is simple and easy to employ. The use of heavy presses for assembly or disassembly and complex machining configuration have been eliminated. The present invention is simple to employ, allows for the flexibility of replacing a single or a plurality of worn or damaged blades and does not require a complexity of machining or assembly fixtures.
In the accompanying drawings:

Figure 1 is a view of a gas turbine engine employing the present invention;
Figure 2 is an end view of a rotor assembly constructed in accordance with the present invention; and
Figure 3 is a sectional view along lines III-III of Fig. 2 showing a detailed view of the rotor, blade and ring means.

Referring to Figure 1, a bladed rotor assembly 10 is shown in a gas turbine engine 12. As shown in Figure 2, the rotor assembly 10 comprises a rotor 14, a plurality of blades 16, means 18 on the rotor and on each of the plurality of blades for defining an annular T-slot 20, means 22 defining an opening 23 in the rotor 14 to provide access to a portion of the T-slot 20, means 24 for sealing positioned in the T-slot 20 and means 26 for preventing relative rotation between the means 24 for sealing and the rotor 14.
The rotor 14, as shown in Figures 2 and 3, has a center hub 28 and a rim 30 at its perimeter. A web 32 connects the hub 28 to the rim 30. The rotor 14 has opposite first and second faces 34, 36, of which the first face 34 is stepped or multilevel, a plurality of blind holes 38 in the first face 34 and a plurality of circumferentially arrayed retention slots 40 positioned in the rim 30. The slots 40 extend from one face 34 to the other face 36 and have a radial retention means 42 which includes a pair of side walls 43 which are undercut in a conventional manner to provide at least one inwardly directed abutment face 44 on each side wall.
The plurality of blades 16 are mounted on the rotor 14. Each of the plurality of blades has a root section 46 which engages a corresponding slot 40 and is spaced away from a bottom 50 of the slot 40 in the rotor 14. The root portion 46 is shaped so that it engages the abutment face 44 of the rotor 14. Each blade 16 has a platform section 52 disposed radially outwardly from the periphery of the rim 30 by an extended neck region 54 of the blade 16. Each blade has a lip 56 projecting radially inward from the root section 46 and abuts a portion of the multilevel surface of the first face 34.
The means 18 on the rotor 14 for defining a portion of the T-slot 20 includes a circumferentially extending radially outwardly facing groove 62 which extends axially outward from the first face 34 of the rotor 14. The means 18 on each blade 16 for defining a portion of the T-slot 20 includes a circumferentially extending radially inwardly facing groove 64 formed on each blade 16 intermediate the root section 46 and the platform section 52 and on the same side as the lip 56.
The opening 23 in said means 18 on the rotor 14 which forms a portion of the T-slot 20 opens into the groove 62 and has an arcuate length D₂ for purposes to be defined later.
The means 24 for sealing includes a ring segment means 74 having first and second ends 76, 78 circumferentially spaced apart to define a space 80 therebetween, and a segment shaped spacer 82 positioned in the space 80. The spacer 82 has a circumferential length slightly less than the circumferential length of the space to define a controlled gap 84 or clearance between the spacer 82 and on both of the ends 76, 78 for a later defined purpose. The arcuate length D2of the opening 23 is at least equal to the length of the spacer 82.
The ring segment means 74 is a single ring segment 86 with the ends 76, 78 being the ends thereof.
The ring segment means 74 and the spacer 82 each have an inner edge 88 and an outer edge 90. The inner edges 88 are received in the outwardly facing groove 62 of the rotor 14 and the outer edges 90 are received in the inwardly facing groove 64 of each blade 16. The inner edge 88 of the ring segment means 74 has an inner leg portion 92 which is angled away from the first face 34 on the rotor 14 and the outer edge 90 has an outer leg portion 94 which angles away from the root portion 46 of the blade 16. The means 26 for preventing relative rotation between the means for sealing 24 and the rotor 14 as shown in Fig. 2 includes a hole 100 extending through one of the spacers 82 and ring segment means (74), one of the blind holes 38 in the first face of the rotor 14, and a pin 102 having a diameter slightly smaller than the holes 100, 38. The pin 102 has a hollow recess in one end. As an alternative, the pin 100 could be a rivet or a bolt inserted through the holes 100 in the spacer 82 and the blind holes would be through drilled in rotor 14.

Industrial Applicability

The bladed rotor assembly 10 is preassembled prior to assembly into a gas turbine engine 12. The single ring segment 86 is assembled into the groove 62 by spreading the ends 76, 78 of the single ring segment 86 over the rotor and releasing the ends with the single ring segment 86 positioned in the groove 62. As an alternate, one end of the single ring segment 86 could be inserted through the opening 23 in the rotor 14 and threaded around the groove 62 so that the inner leg portion 88 of the segment 76 is trapped within the groove 62 in the rotor 14. The space 80 between the first and second ends 76, 78 of the segment 86 is aligned with one of the slots 40 in the rim 30 of the rotor 14 so that the root portion 46 of the blade 16 will pass therethrough. The root portion 46 of one of the plurality of turbine blades 16 is inserted into that slot 40 from the first face 34 side until the lip 56 contacts the first face 34. With the blade 16 in the slot 40, the groove 64 is radially aligned with the groove 62 to form a short portion of the T-slot 20. At this point, the segment 86 is indexed to align the space 80 with another of the slots 40 in the rotor 14. In so doing, a portion of the segment 86 enters the short portion of the T-slot and locks the blade to the rotor in an axial direction. The root portion 46 of a second blade 16 is then inserted into the slot 40 aligned with the space 80 and the segment 86 is again indexed to lock the second blade to the rotor 14 and the space 80 is aligned with the next adjacent slot. The sequence of inserting a blade 16 in the slot 40 and indexing the segment 86 is repeated until all the slots 40 contain a blade 16. The single ring segment 86 is then rotated to align the space 80 with the opening 23 in the rotor 14. The leg portion 94 of the outer edge 90 of the spacer 82 is positioned in the inwardly facing groove 64 formed by the blades 16. The segment 86 and spacer 82 are rotated within the T-slot 20 until the hole 100 in the spacer 82 aligns with one of the blind holes 38 in the rotor 14 at which position the spacer 82 is out of alignment with the opening 23 in the rotor 14 and the gap 84 is positioned so that the space between the rotor 14 and the bottom 50 of the blade 16 do not coincide. The pin 102 is inserted through the hole 100 in the spacer 82 into the blind hole 38 in the rotor 14 with the hollow end toward the rotor and fixedly attached to the rotor 14 using a punch and a hammer. The hollow end is expanded in the hole 38 by tapping the punch againstthe pin 102 with the hammer.
After completing the assembly, the bladed rotor assembly 10 will be assembled by a conventional manner into a gas turbine engine 12. During operation of the gas turbine engine 12, heat is absorbed in the thin spacer 82 and the single ring segment 86 at a high rate wherein the mass of the rotor absorbs heat at a slower rate. Therefore, the controlled gap 84 between the single ring segment 86 and the spacer 82 will be filled due to the difference in the rate of heat absorbed in the masses in the start up mode. As the engine continues to warm up and enters the steady state mode, the controlled gap 84 will reoccur.
The primary advantage of the bladed rotor assembly 10 of this invention is in the unique construction of the ring segment means 74 and the spacer 82, and the simple assembly technique which can be used to make a new rotor or repair a damaged rotor. For example, when the bladed rotor assembly 10 has a failed blade 16 and requires that the blade be replaced the rotor assembly 10 will be removed from the engine using conventional disassembly techniques. The pin 102 which prevents the means for sealing 24 from rotating relatively to the rotor 14 is removed. The ends 76, 78 of the single ring segment 86 are aligned with the opening 23 in the rotor 14 and the spacer 82 is removed from the inwardly facing groove 64 formed by the blades 16. The ends 76, 78 of the single ring segment 86 are rotated to align with the damaged blade 16, the blade 16 is removed from the slot 40 in the rotor 14 and a new blade 16 is replaced in the slot 40. The single ring segment 86 can be rotated to align with each damaged blade 16 and the blade 16 can be replaced. This process continues until all of the worn or damaged blades 16 are replaced. The spacer 82 is repositioned and the pin or pins 102 are secured as discussed earlier. Thus a simple inexpensive repair to the bladed rotor assembly 10 can be employed when using the present invention.

Claims

1. A bladed rotor assembly (10) comprising a rotor (14) having opposed faces (34, 36), a rim (30) and a plurality of circumferentially arrayed retention slots (40) in the rim (30), the slots (40) passing from one of the faces (34) to the other of the faces (36) and having radial retention means (42), a plurality of blades (16) mounted on the rotor (14) with each of the blades (16) having a root portion (46) received in a corresponding one of the slots (40), the root portion (46) being shaped so that it engages the radial retention means (42) to prevent movement of the blade (16) radially outwards of the rotor (14); means (18) on the rotor (14) and on each of the plurality of blades (16) for defining an annular T-slot (20) at one of the faces (34); means defining an opening (23) in the means (18) on the rotor (14) which forms a portion of the T-slot (20); seal means (24) rotatably trapped in the T-slot (20) and including ring segment means (74) having first and second ends (76,78) circumferentially spaced apart to define therebetween a space (80) wide enough for the passage of a blade root portion (46), and a spacer (82) positioned between the ends (76, 78) of the ring segment means (74), the arcuate length of the opening (23) being at least equal to the length of the spacer (82), and the seal means (24) being indexable to a position at which the spacer (82) is out of alignment with the opening (23) in the rotor (14); and means (26) for preventing rotation between the seal means (24) and the rotor (14); characterised in that the ring segment means (74) comprises a single ring segment (86).

2. An assembly (10) according to claim 1, wherein the means (18) for forming a T-slot (20) comprises a circumferentially extending, radially inwardly facing groove (64) formed on each of the plurality of blades (16) and a circumferentially extending, radial outwardly facing groove (62) on the rotor (14).

3. An assembly (10) according to claim 1 or claim 2, wherein the means (26) for preventing relative rotation between the seal means (24) and the rotor (14) comprises a hole (100) extending through one of the spacer (82) and the ring segment means (74), a hole (38) in the face (34) of the rotor (14), and a pin (102) extending through the hole (100) and into the hole (38) in the rotor (14) and fixed to the rotor (14).

4. An assembly (10) according to any one of the preceding claims, wherein the spacer (82) is slightly smaller than the space (80) between the ends (76, 78) of the ring segment means (74) when the bladed rotor assembly (10) is at ambient temperature to compensate for differences in the rate of thermal expansion between the spacer (82) and ring segment means (74), and the rotor (14).

5. A method of assembling a bladed rotor assembly (10), the rotor assembly (10) including a rotor (14) having opposed faces (34, 36), a rim (30) and a plurality of circumferentially arrayed retention slots (40) in the rim (30), the slots (40) passing from one of the faces (34) to the other of the faces (36) and having radial retention means (42); and a plurality of blades (16) mounted on the rotor (14) with each of the blades (16) having a root portion (46) received in a corresponding one of the slots (40), the root portion (46) being shaped so that it engages the radial retention means (42) to prevent movement of the blade (16) radially outward of the rotor (14); means (18) on the rotor (14) for forming a circumferentially extending, radially outwardly facing groove (62) on the rotor (14); and means on each of the plurality of blades (16) for forming a circumferentially extending inwardly facing groove (64); the method comprising the steps of:

a) positioning a ring segment means (74) in the groove (62) formed in the rotor (14), so that a space (80) defined between circumferentially spaced apart first and second ends (76, 78) is aligned with one of the slots in the rotor (14);

b) inserting the root portion (46) of a blade (16) through the space (80) in the ring segment means (74) and into one of the slots (40) in the rim (30) so that an arcuate portion of an annular T-slot (20) is formed;

c) indexing the segment means (74) into the arcuate portion of the T-slot (20) to align the space (80) in the segment (74) with another one of the slots (40) in the rotor (14);

d) inserting the root portion (46) of a second one of the plurality of blades (16) through the space (80) in the ring segment means (74) and into another one of the slots (40) in the rim (30) so that the arcuate portion of the annular T-slot (20) is increased in length; and

e) progressively repeating steps c) and d) until all of the retention slots (40) contain a blade (16); closing the space (80) so that no blade is retractable from its slot; and fixing the ring segment means (74) against further indexing in the T-slot; characterised in that the ring segment means (74) comprises a single ring segment (86) which is initially positioned in the groove (62); in that the space (80) is closed by a spacer (82) which is introduced through an opening (23) in the groove-forming means (18) on the rotor (14) with the space (80) aligned with the opening (23), the spacer (82) and the ring segment means (74) being indexed until the spacer (82) is trapped in the T-slot (20); and in that a hole (100) extending through one of the spacers (82) and ring segment (86) is aligned with a hole (38) in the face (34) of the rotor (14) and means (26) are inserted in the hole for preventing further indexing between the seal means (24) and the rotor (14).

6. A method according to claim 5, wherein the step of positioning the ring segment (86) in the groove (64) formed in the rotor (14) includes spreading the ends (76, 78) of the ring segment means (74) over a portion of the rotor (14) and releasing the ends (76, 78) when the ring segment means (74) is positioned in the groove (62).

7. A method according to claim 5, wherein the step of positioning the ring segment (86) in the groove (64) formed in the rotor (14) includes the step of inserting an end of the ring segment (86) through the opening (23) and threading the ring segment around the groove (62).