Low-noise airfoil for an open rotor
An airfoil section of a blade for an open rotor includes: a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein a chord of the airfoil section is defined as a straight-line distance between the leading edge and the trailing edge; the airfoil section has a meanline defined midway between the pressure side and the suction side; and the meanline is shaped such that, in the presence of predetermined transonic or supersonic relative velocity conditions, maximum and minimum ideal Mach numbers on the suction side will lie within a 0.08 band, between 25% and 80% percent of the chord.
1. An airfoil section of a blade for an open rotor, comprising: a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein a chord of the airfoil section is defined as a straight-line distance between the leading edge and the trailing edge;
the airfoil section has a meanline defined midway between the pressure side and the suction side; and
the meanline is shaped such that, in the presence of predetermined transonic or supersonic relative velocity conditions, maximum and minimum ideal Mach numbers on the suction side will lie within a 0.08 band, between 25% and 80% percent of the chord.
2. The airfoil section according to claim 1 , wherein a maximum camber rise of the meanline is located forward of 50% of the chord.
3. The airfoil section according to claim 1 , wherein a thickness of the airfoil section is defined as a distance measured normal to the meanline between the pressure side and the suction side, and wherein a maximum value of the thickness occurs at a location between about 20% to about 30% of the chord.
4. The airfoil section according to claim 1 , wherein the airfoil section has a maximum thickness of about 2% to about 4% of the chord.
5. The airfoil section according to claim 1 , wherein the airfoil section is configured to operate at a flight speed between about Mach 0.7 and about Mach 0.8.
6. An airfoil section of a blade for an open rotor, comprising: a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein a chord of the airfoil section is defined as a straight-line distance between the leading edge and the trailing edge;
the airfoil section has a meanline defined midway between the pressure side and the suction side;
the meanline is shaped such that it includes a predetermined total turning;
the meanline is shaped such that less than 15% of the total turning occurs from 40% to 75% of the chord; and
the meanline is shaped such that greater than 35% of the total turning occurs in the aft 25% of the chord.
7. The airfoil of claim 6 wherein the total turning is greater than 10°.
8. The airfoil section of claim 6 wherein the meanline is shaped such that less than 13% of the total turning occurs from 40% to 75% of the chord.
9. The airfoil section of claim 6 wherein:
an inlet angle is defined as an angle between a tangent to the meanline and a centerline of the open rotor at the leading edge;
an exit angle is defined as an angle between a tangent to the meanline and a centerline of the open rotor at the trailing edge; and
the total turning is defined as an absolute value of the difference between the inlet angle and the exit angle.
10. The airfoil section according to claim 6 , wherein a maximum camber rise of the meanline is located forward of 50% of the chord.
11. The airfoil section according to claim 6 , wherein a thickness of the airfoil section is defined as a distance measured normal to the meanline between the pressure side and the suction side, and wherein a maximum value of the thickness occurs at a location between about 20% to about 30% of the chord.
12. The airfoil section according to claim 6 , wherein the airfoil section has a maximum thickness of about 2% to about 4% of the chord.
13. The airfoil section according to claim 6 , wherein the airfoil section is configured to operate at a flight speed between about Mach 0.7 and about Mach 0.8.
14. A blade for an open rotor, comprising: an airfoil body having spaced-apart pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges, the airfoil body comprising at least one airfoil section according to claim 6 .
15. The apparatus of claim 14 further comprising a disk rotatable about an axial centerline and carrying a first airfoil row of the blades.
16. An open rotor apparatus, comprising:
a first airfoil row including a first disk rotatable about an axial centerline and carrying an annular array of airfoil-shaped blades, wherein each of the blades has spaced-apart pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges, wherein each of the blades of the first airfoil row includes at least one airfoil section in which:
a meanline of the airfoil section is shaped such that it includes a predetermined total turning; and
the meanline is shaped such that greater than 35% of the total turning occurs in the aft 25% of the chord;
the meanline is shaped such that less than 15% of the total turning occurs from 40% to 75% of the chord; and
a second airfoil row disposed downstream of the first airfoil row.
17. The apparatus of claim 16 wherein the total turning is greater than 10°.
18. The apparatus of claim 16 wherein the at least one airfoil section is located within an outer half of the span of the blade.
19. The apparatus of claim 16 wherein:
an inlet angle is defined as an angle between a tangent to the meanline and a centerline of the open rotor at the leading edge;
an exit angle is defined as an angle between a tangent to the meanline and a centerline of the open rotor at the trailing edge;
the total turning is defined as an absolute value of the difference between the inlet angle in the exit angle.
20. The apparatus according to claim 16 , wherein the meanline is shaped such that less than 13% of the total turning from occurs from 40% to 75% of the chord.
21. The apparatus according to claim 16 , wherein a maximum camber rise of the meanline is located forward of 50% of the chord.
22. The apparatus according to claim 16 , wherein a thickness of the airfoil section is defined as a distance measured normal to the meanline between the pressure side and the suction side, and wherein a maximum value of the thickness occurs at a location between about 20% to about 30% of the chord.
23. The apparatus according to claim 16 , wherein the airfoil section has a maximum thickness of about 2% to about 4% of the chord.
24. The apparatus according to claim 16 , wherein the airfoil section is configured to operate at a flight speed between about Mach 0.7 and about Mach 0.8.
25. The apparatus according to claim 16 wherein the second airfoil row comprises an annular array of airfoil-shaped outlet guide vanes, wherein each of the outlet guide vanes includes spaced-apart pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges.
26. The apparatus according to claim 16 wherein the second airfoil row comprises a second disk disposed aft of the first disk, the second disk rotatable about the axial centerline and carrying a row of airfoil-shaped blades, wherein each of the blades of the second airfoil row includes spaced-apart pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges, and wherein the blades of the second airfoil row are configured for rotation opposite to those of the first airfoil row.