Aircraft with an unducted fan propulsor
The present disclosure is generally related to aircraft having one or more unducted fan propulsors at locations within specific regions relative to an airfoil, such as a wing or horizontal stabilizer. More specifically, the specific regions are located where there is a relatively higher pressure air flow beneath the wings or above a horizontal stabilizer. That higher pressure air flow can be utilized to provide increased thrust from the unducted fan propulsor.
1. An aircraft comprising: a fuselage;
an airfoil extending from the fuselage,
the airfoil having an airfoil section defining a quarter-chord location (QC); an unducted fan propulsor mounted relative to the airfoil section on a high pressure side thereof, the unducted fan propulsor having a centerline (CL), a plurality of blades arranged in a forward array and a plurality of blades arranged in a rearward array, wherein only one of the forward and rearward array of blades are rotating blades and the rotating blades define a maximum outer diameter (D);
a point (P) located at the intersection of the CL and a line HP perpendicular to the axial centerline CL that passes through the axial midpoint between a rearward trailing edge at a root of a blade of the rearward array and a forward leading edge at a root of a blade of the forward array when the forward leading edge and rearward trailing edge of the respective blades are aligned with each other; and
a positioning line (R) having a length (RL) and extending from the QC to the point P of the unducted fan propulsor at an angle θ measured positive in a counter-clockwise direction when the high pressure side of the airfoil section is below the airfoil section, and measured positive in a clockwise direction when the high pressure side of the airfoil section is above the airfoil section, when viewed looking from an outboard position towards an inboard position; wherein 0.07≤RL/D≤2.0 and θ is between 187° and 342°.
2. The aircraft of claim 1 , wherein 0.15≤RL/D.
3. The aircraft of claim 1 , wherein 0.35≤RL/D, and preferably RL/D is about 0.72.
4. The aircraft of claim 1 , wherein 0 is between 198° and 310°, and preferably between 205° and 285°.
5. The aircraft of claim 1 , wherein the unducted fan propulsor operates at a cruise flight Mach M 0 of between 0.5 and 0.9, preferably between 0.7 and 0.9, and more preferably between 0.75 and 0.9.
6. The aircraft of claim 1 , wherein the unducted fan propulsor has a dimensionless cruise fan net thrust parameter expressed as follows:
0
.15
>
F
n
e
t
ρ
0
A
a
n
V
0
2
>
0
.
0
6
,
wherein F net is cruise fan net thrust, ρ 0 is ambient air density, V o is cruise flight velocity, and A an is annular cross-sectional area perpendicular to an axis of rotation of a rotor axis of rotation.
7. The aircraft of claim 1 , wherein the unducted fan propulsor is undermounted to the airfoil with one or more intermediate structures.
8. The aircraft of claim 1 , wherein the P of the unducted fan propulsor is variable to accommodate different operating conditions.
9. An aircraft, comprising:
a fuselage;
an airfoil extending from the fuselage, the airfoil having an airfoil section defining a quarter-chord location (QC);
an unducted fan propulsor mounted relative to the airfoil section on a high pressure side thereof, the unducted fan propulsor having a centerline (CL), a plurality of blades arranged in a forward array and a plurality of blades arranged in a rearward array, wherein only one of the forward and rearward array of blades are rotating blades and the rotating blades define a maximum outer diameter (D);
a point (P) located at the intersection of the CL and a line HP perpendicular to the axial centerline CL that passes through the axial midpoint between a rearward trailing edge at a root of a blade of the rearward array and a forward leading edge at a root of a blade of the forward array when the forward leading edge and rearward trailing edge of the respective blades are aligned with each other; and
an ellipse origin positioning line (EOR) having a length (EORL) extending from the QC to an ellipse origin (OR) at an angle θ measured positive in a counter-clockwise direction when the high pressure side of the airfoil section is below the airfoil section, and measured positive in a clockwise direction when the high pressure side of the airfoil section is above the airfoil section, when viewed looking for an outboard position towards an inboard position; wherein the P of the unducted fan propulsor is located within a first ellipse having a first major axis length (1MajAL) and a first minor axis length (1MinAL) with a first ellipse origin defined by EORL/D of 0.938 and θ of 253.6°, and where 1MajAL/D is 2.8 and 1 MinAL/D is 1.7.
10. The aircraft of claim 9 , wherein the P of the unducted fan propulsor is located in a second ellipse having a second major axis length (2MajAL) and a second minor axis length (2MinAL) with a second ellipse origin defined by EORL/D of 1.051 and θ of 248.8°, and where 2MajAL/D is 1.86 and 2MinAL/D is 1.56.
11. The aircraft of claim 9 , wherein the P of the unducted fan propulsor is located in a third ellipse having a third major axis length (3MajAL) and a third minor axis length (3MinAL) with a third ellipse origin defined by EORL/D of 0.870 and θ of 239.6°, where 3MajAL/D is 1.4 and 3MinAL/D is 0.9.
12. The aircraft of claim 9 , wherein the P of the unducted fan propulsor is located in a fourth ellipse having a fourth major axis length (4MajAL) and a fourth minor axis length (4MinAL) with a fourth ellipse origin defined by EORL/D of 0.763 and θ of 235.7°, and where 4MajAL/D is 0.94 and 4MinAL/D is 0.44.
13. An aircraft, comprising:
a fuselage;
an airfoil extending from the fuselage, the airfoil having an airfoil section defining a quarter-chord location (QC);
an unducted fan propulsor mounted relative to the airfoil section on a high pressure side thereof, the unducted fan propulsor having a centerline (CL), a plurality of blades arranged in a forward array and a plurality of blades arranged in a rearward array, wherein one of the forward and rearward array of blades are rotating blades and the rotating blades define a maximum outer diameter (D);
a point (P) located at the intersection of the CL and a line HP perpendicular to the axial centerline CL that passes through the axial midpoint between a rearward trailing edge at a root of a blade of the rearward array and a forward leading edge at a root of a blade of the forward array when the forward leading edge and rearward trailing edge of the respective blades are aligned with each other; and
a positioning line (R) having a length (RL) and extending from the QC to the point P of the unducted fan propulsor at an angle θ measured positive in a counter-clockwise direction when the high pressure side of the airfoil section is below the airfoil section, and measured positive in a clockwise direction when the high pressure side of the airfoil section is above the airfoil section, when viewed looking from an outboard position towards an inboard position (e.g. the fuselage) OR when viewed with the LE to the left of the TE; wherein 0.065<RL/D<1.98 and θ is between 187° and 340°; and wherein RL/D and θ of the P of the unducted fan propulsor adhere to the following expressions:
R
L
D
+
(
1.4161
*
[
1.88978
*
sin
2
(
θ
)
-
0.0875
*
cos
2
(
θ
)
+
0.477
*
sin
(
θ
)
*
cos
(
θ
)
]
+
1.764
*
sin
(
θ
)
+
0
.
1
9
1
4
6
*
cos
(
θ
)
)
1.96
*
sin
2
(
θ
)
+
0
.
7
2
2
5
*
cos
2
(
θ
)
>
0
and
R
L
D
+
(
-
1.4161
*
[
1.88978
*
sin
2
(
θ
)
-
0.0875
*
cos
2
(
θ
)
+
0.477
*
sin
(
θ
)
*
cos
(
θ
)
]
+
1
.
7
6
4
*
sin
(
θ
)
+
0
.
1
9
1
4
6
*
cos
(
θ
)
)
1.96
*
sin
2
(
θ
)
+
0
.
7
2
2
5
*
cos
2
(
θ
)
<
0.