Turbine bucket natural frequency tuning rib

• US 6,481,972 B2
• Filed: 12/22/2000
• Issued: 11/19/2002
• Est. Priority Date: 12/22/2000
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Jacala, Ariel Caesar-Prepena, Wang, John Zhiqiang, Barb, Kevin Joseph, Norton, Paul Francis
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): McAleenan, James M
• Application Number:
  US09/741,892
• Publication Number:
  US 20020081206A1
• Time in Patent Office: 697 Days
• Field of Search: 416/233, 416/96.R, 416/97.R, 416/232, 416/500, 415/115, 415/119, 298/892, 298/897.2, 294/070.1
• US Class Current: 416/233
• CPC Class Codes: F01D 5/16 for counteracting blade vibration
• CPC Class Codes: F01D 5/18 Hollow blades, i.e. blades with cooling or heating channels or cavities structure of hollow blades in general F01D5/147; Heating, heat-insulating or cooling means on blades
• CPC Class Codes: F05D 2230/21 by casting
• CPC Class Codes: Y10S 416/50 Vibration damping features
• CPC Class Codes: Y10T 29/4932 Turbomachine making
• CPC Class Codes: Y10T 29/49764 with testing or indicating

Abstract

A tuning rib is added preferably in the aft cavity of a cored turbine bucket to alter the bucket'"'"'s natural frequencies. The tuning rib may be a solid rib or a segmented rib and is particularly suited for altering high order frequency modes such as 2T, 4F and 1-3S. As such, detrimental crossings of natural bucket frequencies and gas turbine stimuli can be avoided to thereby improve the reliability of a gas turbine without impacting other features of the bucket that are important to the performance of the gas turbine.

Claims

1. A method of tuning a turbine bucket having an internal cavity, the method comprising:

(a) designing the turbine bucket construction;

(b) testing the turbine bucket for high cycle fatigue problems based on a natural frequency of the turbine bucket; and

(c) after steps (a) and (b), altering the natural frequency of the turbine bucket by adding a rib in the internal cavity.

2. A method according to claim 1, wherein step (c) is practiced by adding a rib in an aft cavity of the turbine bucket.

3. A method according to claim 1, wherein step (c) is practiced by adding a solid rib.

4. A method according to claim 1, wherein step (c) is practiced by adding a segmented rib.

5. A method according to claim 1, wherein step (c) is practiced by adding the rib to thereby alter high order frequency modes.

6. A method according to claim 5, wherein the high order frequency modes include at least one of 2T, 4F and 1-3S.

7. A turbine bucket that is tuned according to the method of claim 1.

8. A turbine bucket comprising a tuning rib within an internal cavity tuned according to the method of claim 1.

9. A turbine bucket according to claim 8, wherein the tuning rib is disposed in an aft cavity of the turbine bucket.

10. A turbine bucket according to claim 8, wherein the tuning rib is solid.

11. A turbine bucket according to claim 8, wherein the tuning rib is segmented.