Mistuned fan

Patent metadata

Field	Value
Publication number	US-10215194-B2
Application number	US-201514976701-A
Country	US
Kind code	B2
Filing date	Dec 21, 2015
Priority date	Dec 21, 2015
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

A compressor rotor for a gas turbine engine is described which includes sets of blades having different airfoil thickness distributions, each including a frequency modifier forming a thickness differential relative to a baseline blade thickness. The frequency modifiers provide different natural vibration frequencies for each of the blades, and facilitate modifying natural vibration frequency separation between adjacent blades of the compressor rotor.

First claim

The invention claimed is:

1. A mistuned fan for a gas turbine engine, the fan comprising fan blades circumferentially distributed around and extending a total span length from a central hub, the fan blades including successively alternating first and second fan blades each having airfoil with a pressure side and a suction side disposed on opposed sides of a median chord line, the pressure side and suction side extending on opposed sides of the airfoils between a leading edge and a trailing edge, the first and second fan blades respectively having different first and second airfoil thickness distributions, the first airfoil thickness distribution including a first baseline thickness and a first frequency modifier on the pressure side, the first frequency modifier defining an airfoil thickness differential relative to the first baseline thickness and being located at a first span distance away from the central hub, and the second airfoil thickness distribution including a second baseline thickness and a second frequency modifier on the pressure side, the second frequency modifier defining an airfoil thickness differential relative to the second baseline thickness and being located at a second span distance away from the central hub, the second span distance being different from the first span distance, both the first span distance and the second span distance being between 60% and 100% of the total span length of the first and second fan blades, the first and second frequency modifiers generating different natural vibration frequencies for each of the first and second fan blades, wherein a thickness of the airfoil of the first fan blade at the first span distance is less than the thickness of the second fan blade at the first span distance, and a thickness of the airfoil of the second fan blade at the second span distance is less than the thickness of the first fan blade at the second span distance, and the first span distance corresponds to a span-wise location of high strain energy and the second span distance corresponds to a span-wise location of low strain energy.

2. The mistuned fan according to claim 1 , wherein the first natural vibration frequency of the first fan blades is less than a baseline frequency and the second natural vibration frequency of the second fan blades is greater than the baseline frequency, wherein the baseline frequency is defined as the natural vibration frequency of a fan blade having corresponding size and shape but absent said first and second frequency modifiers.

3. The mistuned fan according to claim 1 , wherein the first and second frequency modifiers comprise at least one of a local region of reduced thickness relative to the first and second baseline thicknesses, respectively, and a local region of increased thickness relative to said first and second baseline thicknesses.

4. The mistuned fan according to claim 3 , wherein the first and second frequency modifiers both comprise regions of reduced thickness relative to their respective baseline thicknesses, the thickness of the first and second fan blades at the respective first and second span distances are both less than their respective baseline thicknesses.

5. The mistuned fan according to claim 4 , wherein the airfoil thickness of the first fan blades at the first span distance is between 40% and 60% of said baseline thickness of the pressure side.

6. The mistuned fan according to claim 4 , wherein the thickness of the second fan blades at the second span distance is between 40% and 60% of said baseline thickness of the pressure side.

7. The mistuned fan according to claim 1 , wherein a frequency separation between the first and second natural vibration frequencies is between 3 and 10%.

8. The mistuned fan according to claim 7 , wherein the frequency separation between the first and second natural vibration frequencies is greater than or equal to 5%.

9. The mistuned fan according to claim 1 , wherein the second span distance is greater than the first span distance.

10. The mistuned fan according to claim 1 , wherein the first span distance of the first frequency modifier is disposed between 65% and 100% of the total span length, and the second span distance of the second frequency modifier is disposed between 80% and 100% of the total span length.

11. The mistuned fan according to claim 10 , wherein the first span distance of the first frequency modifier is disposed between 65% and 90% of the total span length, and the second span distance of the second frequency modifier is disposed between 90% and 100% of the total span length.

12. The mistuned fan according to claim 1 , wherein the first frequency modifier extends over a greater chord-wise extent of the pressure side of the first fan blades than does the second frequency modifier of the second fan blades.

13. The mistuned fan according to claim 12 , wherein the first frequency modifier extends in a chord-wise direction substantially the entire cord-wise width of the first fan blades, and the second frequency modifier extends in the chord-wise direction from 10% to 90% of the entire chord-wise width of the second fan blades.

14. A mistuned compressor rotor assembly for a gas turbine engine, the mistuned compressor rotor assembly comprising a hub to which a plurality of airfoil blades are mounted, the airfoil blades having a full span length extending from the hub to tips of the airfoil blades, the airfoil blades each having an airfoil selected from at least first and second airfoil types and arranged as generally alternating with one another around the circumference of the rotor, the first airfoils having an airfoil thickness less than an airfoil thickness of the second airfoils at a first selected span of the respective blades, and the second airfoils having an airfoil thickness less than an airfoil thickness of the first airfoil at a second selected span of the respective blades different from the first selected span, both the first selected span and the second selected span being located within a radially outermost 40% of the full span length of airfoil blades.

15. The mistuned compressor rotor assembly of claim 14 , wherein the first and second airfoils have substantially identical thickness distribution profiles but for in regions immediately adjacent the first and second selected spans.

16. The mistuned compressor rotor assembly of claim 14 , wherein the first airfoil thickness at the first selected span at least partially provides the first airfoil blade with a lower natural vibration frequency than the second airfoil blade.

17. The mistuned compressor rotor assembly of claim 16 , wherein the second airfoil thickness at the second selected span at least partially provides the second airfoil blade with a higher natural vibration frequency than the first airfoil blade.

18. The mistuned compressor rotor assembly of claim 17 , wherein the second selected span corresponds in use to a span of a region of strain energy in the second airfoil blade lower than an average strain energy in the second airfoil blade.

19. The mistuned compressor rotor assembly of claim 14 , wherein the first selected span corresponds in use to a span of a region of strain energy in the first airfoil blade higher than an average strain energy in the first airfoil blade.

20. The mistuned compressor rotor assembly of claim 19 , wherein the second selected span corresponds in use to a span of a region of strain energy in the second airfoil blade lower than an average strain energy in the second airfoil blade.

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Assignees

• Pratt & Whitney Canada

Inventors

• Theratil Ignatius
• Balike Krishna Prasad
• Ivakitch Richard
• Kelly Sean Michael
• Townsend Peter
• Dutton Ronald
• Stone Paul
• Venditti Robert
• Fudge Daniel
• Kojovic Milica
• Abate Aldo

Classifications

• F04D29/384

  characterised by form · CPC title

• F01D5/141 Primary

  Shape, i.e. outer, aerodynamic form (F01D5/148 - F01D5/20 take precedence; blade construction F01D5/147) · CPC title

• F01D5/16

  for counteracting blade vibration · CPC title

• F04D29/666 Primary

  by means of rotor construction or layout, e.g. unequal distribution of blades or vanes · CPC title

• F04D29/324

  Blades · CPC title