Intentionally frequency mistuned turbine blades
A new, more economical design for intentionally frequency mistuned turbine blades for more efficient turbine engines is disclosed. A rotating disk of a turbine engine includes first turbine blades that alternate between second turbine blades. The second turbine blades are thicker than the first turbine blades, within manufacturing tolerances, in sections from about their mean line to their airfoil tip. The first and second turbine blades can be cast using two different molds, resulting in an economical manufacturing method. As such, the natural frequency of the second turbine blades is about 3% less than the natural frequency of the first turbine blades. As a result of the intentional difference in natural frequencies of the two different turbine blades, the rotating disk does not experience flutter instability.
1. A rotating disk for a turbine engine having intentionally frequency mistuned turbine blades, comprising:
a rotating hub,
first turbine blades projecting from the circumference of the rotating hub; and
second turbine blades projecting from the circumference of the rotating hub, wherein:
the number of first turbine blades is equal to the number of second turbine blades,
the first turbine blades alternate between the second turbine blades,
the thickness of the second turbine blades from the mean line between their airfoil root and their airfoil tip to their airfoil tip is greater than the thickness of the first turbine blade from the mean line between their airfoil root and their airfoil tip to their airfoil tip, and
the natural frequency of the second turbine blades is lower than the natural frequency of the first turbine blades.
2. The rotating disk of claim 1 , wherein:
the first turbine blades are connected to the rotating hub at their blade root, and
the second turbine blades are connected to the rotating hub at their blade root.
3. The rotating disk of claim 1 , wherein first turbine blades and the second turbine blades have the same leading edge, trailing edge, and camber line.
4. The rotating disk of claim 1 , wherein the thickness of the second turbine blades on their pressure side is greater than the thickness of the first turbine blades on their pressure side.
5. The rotating disk of claim 1 , wherein the thickness of the second turbine blades on their suction side is greater than the thickness of the first turbine blades on their suction side.
6. The rotating disk of claim 1 , wherein:
the thickness of the second turbine blades on their pressure side is greater than the thickness of the first turbine blades on their pressure side, and
the thickness of the second turbine blades on their suction side is greater than the thickness of the first turbine blades on their suction side.
7. The rotating disk of claim 1 , wherein the first turbine blades and the second turbine blades are symmetric about their camber lines.
8. The rotating disk of claim 1 , wherein the difference in thickness between the second turbine blades and the first turbine blades ranges from 0.6% to 4% of the maximum blade thickness of the first turbine blades.
9. The rotating disk of claim 1 , wherein the difference in thickness between the first turbine blades and the second turbine blades is non-uniform along their camber lines.
10. The rotating disk of claim 1 , wherein the natural frequency of the second turbine blades is about 3% less than the natural frequency of the first turbine blades.
11. The rotating disk of claim 1 , wherein the height of the first turbine blades between their airfoil root and their airfoil tip is the same as the height of the second turbine blades between their airfoil root and their airfoil tip.
12. The rotating disk of claim 1 , wherein the width of the first turbine blades between their leading edge and their trailing edge is the same as the width of the second turbine blades between their leading edge and their trailing edge.
13. The rotating disk of claim 1 , wherein the first turbine blades and the second turbine blades are made of the same material.
14. The rotating disk of claim 13 , wherein the material is a nickel-based super alloy.
15. The rotating disk of claim 1 , wherein the first turbine blades and the second turbine blades are made of different materials.