Adjustable blade root spring for turbine blade fixation in turbomachinery

Patent metadata

Field	Value
Publication number	US-9739160-B2
Application number	US-201414457504-A
Country	US
Kind code	B2
Filing date	Aug 12, 2014
Priority date	Oct 18, 2013
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

An adjustable blade root spring device for turbine blade fixation in turbomachinery. The device is designed to be placed in a space in a rotor disk cavity adjacent to a tip of a blade root fir tree, where the device applies a radial outward force on the turbine blade to fix the blade position in the rotor disk. The device includes an accordion-shaped spring which is compressed by a bolt and a coil spring. When the accordion spring is compressed in length, it increases in height and makes contact with the rotor disk and the turbine blade. The force of the accordion spring on the turbine blade can be adjusted via the bolt, and the coil spring provides an increased compliance range. The device can be inserted into the space without scraping against the blade root or the rotor disk, and expanded once it is in position.

First claim

What is claimed is:

1. An adjustable blade root spring device for fixing a turbine blade in position in a rotor disk in a gas turbine, said device comprising:
an outer body including opposing side walls and first and second end blocks;
an accordion spring characterized by a plurality of straight segments folded in an alternating fashion into an accordion shape, with an apex point between each of the straight segments;
a spring bracket attached to a first end of the accordion spring;
an L-bracket attached to a second end of the accordion spring;
a coil spring;
an elongated washer; and
a bolt, said bolt arranged to pass through the elongated washer, through the coil spring and through a hole in the spring bracket, said bolt being threaded into a hole in the first end block of the outer body, where threading the bolt into the hole in the first end block compresses the coil spring against the spring bracket and causes the accordion spring to increase in height such that the accordion spring presses the turbine blade radially outward relative to the rotor disk.

2. The device of claim 1 wherein the turbine blade includes a root portion having an inverted fir tree shape, the rotor disk includes a cavity shaped to receive the root portion of the turbine blade, and the cavity further includes a space adjacent to the root portion of the turbine blade where the device can exert a force radially outward on the turbine blade and radially inward on the rotor disk.

3. The device of claim 2 wherein the elongated washer has a shape which fits within the space adjacent to the root portion of the turbine blade but does not permit rotation of the elongated washer within the space.

4. The device of claim 2 wherein the accordion spring presses the turbine blade radially outward relative to the rotor disk with a force of at least 150 pounds, and the force fixes the turbine blade position in the rotor disk.

5. The device of claim 4 wherein the coil spring has a stiff-ness which causes the coil spring to compress by a compression amount when the bolt is tightened during installation of the device, and the compression amount is sufficient to absorb any relaxation of the accordion spring due to increased height of the space adjacent to the root portion of the turbine blade during turbine operation, while still maintaining the force within the range of 150-250 pounds.

6. The device of claim 5 wherein the stiffness of the coil spring is in a range of 150-200 pounds/inch.

7. The device of claim 2 further comprising a fixed washer attached to the second end block of the outer body, said fixed washer having an elongated shape which fits within the space adjacent to the root portion of the turbine blade but does not permit rotation of the fixed washer within the space, thus preventing rotation of the outer body within the space when the bolt is being tightened.

8. The device of claim 7 further comprising a bent tab washer located between a head of the bolt and the elongated washer, said bent tab washer including an engagement tab which engages a notch in the elongated washer and prevents rotation of the bent tab washer relative to the elongated washer, where tabs on the bent tab washer can be bent into a position which prevents rotation of the head of the bolt after the device has been installed in the gas turbine.

9. The device of claim 1 wherein the accordion spring is fabricated from a nickel-based alloy strip having a width in a range of 0.25-0.35 inches and a nominal thickness of 0.025 inches.

10. The device of claim 1 wherein the accordion spring is shaped so that three upper apex points contact the turbine blade and four lower apex points contact the rotor disk.

11. The device of claim 10 wherein the three upper apex points each provide a substantially equal contact force on the turbine blade, and the four lower apex points each provide a substantially equal contact force on the rotor disk.

12. A gas turbine engine rotor assembly, said assembly comprising:
a plurality of turbine blades, each turbine blade including a blade root portion having an inverted fir tree shape;
a rotor disk designed to hold the plurality of turbine blades in a circumferential arrangement around an outer periphery of the rotor disk, said rotor disk including a plurality of cavities, with one of the cavities for each of the turbine blades, where each of the cavities has a fir tree shape designed to receive the blade root portion of one of the turbine blades, and where each of the cavities also includes a space adjacent to and radially inward from the blade root portion; and
an adjustable blade root spring device inserted into the space in each of the cavities, where the adjustable blade root spring device includes;
an outer body including opposing side walls and first and second end blocks;
an accordion spring characterized by a plurality of straight segments folded in an alternating fashion into an accordion shape, with an apex point between each of the straight segments;
a spring bracket attached to a first end of the accordion spring;
an L-bracket attached to a second end of the accordion spring;
a coil spring;
an elongated washer; and
a bolt, said bolt arranged to pass through the elongated washer, through the coil spring and through a hole in the spring bracket, said bolt being threaded into a hole in the first end block of the outer body, where threading the bolt into the hole in the first end block compresses the coil spring against the spring bracket and causes the accordion spring to increase in height such that the accordion spring presses the turbine blade radially outward relative to the rotor disk.

13. The rotor assembly of claim 12 wherein the elongated washer has a shape which fits within the space adjacent to the blade root portion but does not permit rotation of the elongated washer within the space.

14. The rotor assembly of claim 12 wherein the coil spring has a stiffness which causes the coil spring to compress by a compression amount when the bolt is tightened during installation of the adjustable blade root spring device, and the compression amount is sufficient to absorb any relaxation of the accordion spring due to increased height of the space adjacent to the blade root portion during turbine operation, while still maintaining a force on the turbine blade of at least 150 pounds.

15. The rotor assembly of claim 12 wherein the accordion spring is shaped so that three upper apex points contact the turbine blade and four lower apex points contact the rotor disk, and the three upper apex points each provide a substantially equal contact force on the turbine blade, and the four lower apex points each provide a substantially equal contact force on the rotor disk.

16. The rotor assembly of claim 12 further comprising a fixed washer attached to the second end block of the outer body, said fixed washer having an elongated shape which fits within the space adjacent to the blade root portion but does not permit rotation of the fixed washer within the space, thus preventing rotation of the outer body within the space when the bolt is being tightened.

17. The rotor assembly of claim 16 further comprising a bent tab washer located between a head of the bolt and the elongated washer, said bent tab washer including an engagement tab which engages a notch in the elongated washer and prevents rotation of the bent tab washer relative to the elongated washer, where tabs on the bent tab washer can be bent into a position which prevents rotation of the head of the bolt after the adjustable blade root sprin

Assignees

• Siemens Ag

Inventors

• Kain Jeffrey A
• Gupta Mohit
• Meyer Leonard J
• Yamane Ryan S
• Chonody James A
• Polyzopoulos Charalambos

Classifications

• F01D5/3007

  of axial insertion type · CPC title

• F01D5/30

  Fixing blades to rotors; Blade roots {; Blade spacers} · CPC title

• F01D5/323 Primary

  Locking of axial insertion type blades by means of a key or the like parallel to the axis of the rotor · CPC title

• F01D5/16

  for counteracting blade vibration · CPC title

• F05D2220/32

  in gas turbines · CPC title