MISTUNED FAN
First Claim
1. A mistuned fan for a gas turbine engine, the fan comprising fan blades circumferentially distributed around and extending a 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, 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.
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Accused Products
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.
34 Citations
40 Claims
- 1. A mistuned fan for a gas turbine engine, the fan comprising fan blades circumferentially distributed around and extending a 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, 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.
- 15. 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 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.
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28. A compressor for a gas turbine engine, the compressor comprising:
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a plurality of first blades having a first airfoil thickness distribution defining a first natural vibration frequency; a plurality of second blades having a second airfoil thickness distribution different from the first airfoil thickness distribution and defining a second natural vibration frequency different from the first natural vibration frequency; the first airfoil thickness distribution including a first frequency modifier on the pressure side of the first blades at a first span distance away from the central hub and the second airfoil thickness distribution defining a second first frequency modifier on the pressure side of the second blades at a second span distance away from the central hub, the second span distance different from the first span distance, wherein first and second pressure side airfoil thicknesses are respectively defined by the first and second first frequency modifiers, wherein the first pressure side airfoil thickness of the first blades is less than a thickness of the second blades at the first span distance, and the second pressure side airfoil thickness of the second blades is less than a thickness of the first blades 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.
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29. A method of mitigating supersonic flutter in a compressor rotor, the rotor having a plurality of circumferentially disposed blades, the method comprising the steps of:
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providing a nominal airfoil having a nominal airfoil definition; determining a first span location associated with a region of high strain energy expected on the airfoil while in use on the compressor rotor; determining a second span location associated with a region of low strain energy expected on the airfoil while in use on the compressor rotor; providing a first blade airfoil definition substantially the same as the nominal airfoil definition but having a different thickness at the first span location associated with the region of high strain energy; providing a second blade airfoil definition substantially the same as the nominal airfoil definition but having a different thickness at the second span location associated with the region of low strain energy; and providing the compressor rotor where the blades are providing with the first and second blade airfoil definitions in an alternating fashion around the circumference of the rotor. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A method of mitigating supersonic flutter for a fan of a turbofan gas turbine engine, the method comprising:
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providing the fan with a plurality of fan blades, the fan blades composed of a plurality of pairs of circumferentially alternating first and second fan blades each having a different airfoil thickness distribution on a pressure side of the fan blades, the airfoil thickness distributions creating different natural vibrational frequencies of each of the first and second fan blades; selecting a desired frequency separation between natural vibration frequencies of the first and second fan blades in use, the frequency separation selected to mistune the pairs of fan blades to reduce the occurrence of supersonic flutter of the fan blades; determining respective first and second airfoil thickness distributions of the first and second fan blades to provide said desired frequency separation; and providing the first airfoil thickness distribution on the pressure side of the first fan blade and providing the second airfoil thickness distribution on the pressure side of the second fan blade, wherein the first airfoil thickness distribution includes a first frequency modifier at a first span distance on the first fan blades, and the second airfoil thickness distribution including a second frequency modifier located on the second fan blades at a second span distance different from the first span distance, and selecting the first span distance to correspond to a span-wise location of high strain energy and selecting the second span distance to correspond to a span-wise location of low strain energy. - View Dependent Claims (40)
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Specification