Frequency-mistuned light-weight turbomachinery blade rows for increased flutter stability

• US 20020064458A1
• Filed: 11/30/2000
• Published: 05/30/2002
• Est. Priority Date: 11/30/2000
• Status: Active Grant

• Current Assignee: Raytheon Technologies Corporation d/b/a RTX
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Orosa, John A., Samit, Marc, Montgomery, Matthew
• Granted Patent: US 6,471,482 B2
• Time in Patent Office: Days
• US Class Current: 415/208.3
• CPC Class Codes: F01D 25/06 for preventing blade vibration means on blade-carrying members or blades F01D5/00
• CPC Class Codes: F01D 5/10 Anti- vibration means specially adapted for radial flow machines or engines F01D5/04
• CPC Class Codes: F01D 5/16 for counteracting blade vibration
• CPC Class Codes: F04D 29/666 by means of rotor construction or layout, e.g. unequal distribution of blades or vanes
• CPC Class Codes: F04D 29/668 damping or preventing mechanical vibrations
• CPC Class Codes: F05D 2260/96 Preventing, counteracting or reducing vibration or noise
• CPC Class Codes: F05D 2260/961 by mistuning rotor blades or stator vanes with irregular interblade spacing, airfoil shape
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10S 416/50 Vibration damping features

Abstract

The present invention relates to an array of flow directing elements having increased flutter stability for use in turbomachinery devices. The array comprises at least one high frequency flow directing element and at least one low frequency flow directing element. In a preferred embodiment, the array comprises a plurality of alternating high frequency and low frequency flow directing elements. Each high frequency flow directing element has its three lowest frequency vibratory modes at least 2.0% higher in frequency than the three lowest frequency vibratory modes of each low frequency flow directing element. The array of the present invention has particular utility in a turbomachinery device as part of a rotor stage.

Claims

1. An array of flow directing elements for use in turbomachinery devices to increase flutter stability comprising:

a plurality of flow directing elements mounted on a disk for rotation about an axis;

said plurality of flow directing elements including at least one high frequency first flow directing element and at least one second low frequency flow directing element; and

said at least one high frequency flow directing element having its three lowest frequency vibratory modes at least 2.0% higher in frequency than the three lowest frequency vibratory modes of said at least one low frequency flow directing element.

2. An array according to claim 1, wherein said plurality of flow directing elements includes a plurality of high frequency flow directing elements and a plurality of low frequency flow directing elements and wherein said high frequency flow directing elements and said low frequency flow directing elements are arranged in an alternating pattern around the circumference of said disk.

3. An array according to claim 2, wherein adjacent ones of said flow directing elements form passages for a working medium fluid.

4. An array according to claim 1, wherein the three lowest frequency vibratory modes of the at least one high frequency flow directing element are separated by at least 2.0% in frequency from any modes of the at least one low frequency blade.

5. An array according to claim 1, wherein said at least one high frequency flow directing element and said at least one low frequency flow directing element have substantially the same span, the same chord length distribution along the span, and the same axial position on the disk.

6. An array according to claim 1, wherein said array forms part of a rotor and wherein each of the at least one high frequency flow directing element and the at least one low frequency flow directing element have a resonant frequency of the lowest frequency vibratory mode which is between the first and the second harmonic of the rotor rotation frequency when operated at high speeds.

7. An array according to claim 6, wherein said second harmonic may be crossed by said resonant frequencies of the lowest frequency vibratory modes only in an operating speed range at relatively low speed conditions.

8. An array according to claim 1, wherein the at least one high frequency flow directing element has a different thickness distribution along its span than the at least one low frequency flow directing element.

9. An array according to claim 1, where each of the at least one high frequency flow directing element and the at least one low frequency flow directing element has a thickness distribution with a local maximum between 20 and 45% of the span.

10. An array according to claim 9, where the local maximum is the maximum thickness of the respective flow directing element.

11. An array according to claim 1, wherein the array forms part of a rotor and wherein the at least one low frequency flow directing element has a resonant frequency of the lowest frequency vibratory mode which is between a first and a second harmonic of rotor speed and wherein the at least one high frequency flow directing element has a resonant frequency of the lowest frequency vibratory mode which is between a second and third harmonic of said rotor speed.

12. An array according to claim 11, wherein the at least one high frequency flow directing element has a thickness distribution along its span which is different from a thickness distribution along a span of the at least one low frequency flow directing element.

13. An array according to claim 12, wherein the at least one low frequency flow directing element has a local maximum of thickness between 20 and 45% of its span.

14. An array according to claim 13, wherein the local maximum thickness is not the maximum thickness of the entire at least one low frequency flow directing element.

15. An array according to claim 13, wherein the local maximum thickness is the maximum thickness of the entire at least one low frequency flow directing element.