# US 11,299,253 B2 · Transonic airfoil, wing, and aircraft

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- Number: US 11,299,253 B2
- Document ID: US11299253B2
- Status: Granted
- Kind: B2
- Application number: 16/771,414
- Filed: 2018-10-10
- Published: 2021-03-11
- Granted: 2022-04-12
- Earliest claimed: 2017-12-12
- Assignees: Japan Aerospace Exploration Agency
- Applicants: Japan Aerospace Exploration Agency
- Inventors: Naoko Tokugawa; Tatsunori Yuhara
- Web page: https://patentgrep.com/patent/US11299253B2

## CPC

- B64C 3/14: Aerofoil profile
- B64C 2003/149: {for supercritical or transonic flow}
- Y02T 50/10: Drag reduction
- B64C: AEROPLANES; HELICOPTERS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

[Object] To provide a transonic airfoil capable of reducing pressure drag more than before, a wing having such an airfoil, and an aircraft including such a wing. [Solving Means] An airfoil 11 has a shape in which a pressure coefficient Cp of a static pressure in a chord direction of a leading edge 12 of the airfoil 11 is −0.04 or less at z/c=0.015 (where z represents a coordinate in a direction perpendicular to an airflow direction within a plane that forms an airfoil, with a leading edge being as a reference (an upper wing surface direction is positive, and a lower wing surface direction is negative), and c represents a chord length). Thus, a pressure distribution has a sharp rise, which can decrease pressure drag.

## Claims

### Claim 1

A transonic airfoil, in which
κ has a local maximal value of 70 or more in an upwardly convex curve in a range of −0.08<s/c<0.08,
Ks is 2.2 or more in a range from s/c=−0.1 to s/c=0.02, and
κ is 0.3 or less in a range from s/c=0.3 to s/c=0.6,
where
s represents a surface length along a surface of the airfoil, with a leading edge being as a reference (an upper wing surface direction is positive, and a lower wing surface direction is negative),
c represents a chord length,
κ represents a curvature that is made dimensionless by a reciprocal of the chord length, and
Ks represents an integral value of the curvature κ.

### Claim 2 (depends on 1)

The transonic airfoil according to claim 1, wherein
κ is less than 0.3 at s/c=0.5, and the κ being less than 0.3 increases to be 0.45 or more at s/c=0.8.

### Claim 3 (depends on 1)

The transonic airfoil according to claim 1, wherein
κ has a local maximal value of 1 or more in an upwardly convex curve in a range from s/c=0.9 or more to a position of a trailing edge.

### Claim 4 (depends on 1)

The transonic airfoil according to claim 1, wherein
κ monotonically decreases in a range from a stagnation point to a crest position of a lower wing surface, and
Ks is 0.1 or more in a range from s/c=−0.1 to s/c=−0.2.

### Claim 5 (depends on 1)

The transonic airfoil according to claim 1, wherein
κ has a mean value of 0.45 or less in a range from s/c=−0.52 to s/c=−0.34, and
κ is 0.4 or less at s/c=−0.52.

### Claim 6 (depends on 1)

The transonic airfoil according to claim 1, wherein
a distribution of κ monotonically increases to 1 or more in a range from s/c=−0.9 or less to a position of a trailing edge.

### Claim 7 (depends on 1)

The transonic airfoil according to claim 1, wherein
the transonic airfoil has a shape in which a pressure coefficient Cp of a static pressure in a chord direction of a leading edge is −0.04 or less at z/c=0.015, where
z represents a coordinate in a direction perpendicular to an airflow direction within a plane that forms an airfoil, with the leading edge being as a reference (an upper wing surface direction is positive, and a lower wing surface direction is negative), and
c represents the chord length.

### Claim 8 (depends on 1)

The transonic airfoil according to claim 1, wherein
the transonic airfoil has a shape in which the pressure coefficient Cp of the static pressure in the chord direction of the leading edge is −0.07 or less at z/c=0.035.

### Claim 9

An aircraft comprising a main wing having a transonic airfoil, the transonic airfoil having:
κ with a local maximal value of 70 or more in an upwardly convex curve in a range of −0.08<s/c<0.08;
Ks of 2.2 or more in a range from s/c=−0.1 to s/c=0.02; and
κ of 0.3 or less in a range from s/c=0.3 to s/c=0.6,
where
s represents a surface length along a surface of the airfoil, with a leading edge being as a reference (an upper wing surface direction is positive, and lower wing surface direction is negative),
c represents a chord length,
κ represents a curvature that is made dimensionless by a reciprocal of the chord length, and
Ks represents an integral value of the curvature κ.