Aircraft and BLI Propulsion Division

Abstract

To provide a technology capable of improving propulsion efficiency in a BLI propulsion technology.SOLUTION: An aircraft according to the present technology includes a torso part and a BLI propulsion part. The torso part has a cylindrical shape that is long in the axial direction and short in the width direction and vertical direction, and includes a rear end part in a rear part side of the axial direction. The BLI propulsion part is a BLI propulsion part provided in a rear part side of the torso part and having a suction port. The BLI propulsion part is arranged such that the center position of the suction port is offset from the center position of the rear end part in at least one of the vertical direction and the width direction.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present invention relates to technology for aircraft and the like having a BLI propulsion device on the rear side thereof. [Background technology]

[0002] In recent years, a device called a BLI (Boundary Layer Ingestion) thruster has become known as a type of thruster for generating thrust in aircraft (see Non-Patent Document 1 below).

[0003] The BLI thruster takes in slow-moving airflow near the surface of an aircraft, accelerates it backward, and expels it, thereby generating thrust in the direction of the aircraft's movement. BLI technology is based on the idea that it is more efficient to generate thrust by accelerating slow-moving airflow than to further accelerate fast-moving airflow. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Modeling Boundary Layer Ingestion Using a Coupled Aeropropulsive Analysis"JOURNAL OFAIRCRAFT Vol. 55, No. 3, May-June 2018 Summary of the Invention [Problem to be solved by the invention]

[0005] In BLI propulsion technology, there is a demand for technology that can improve propulsion efficiency.

[0006] In light of the above circumstances, the purpose of this technology is to provide a technology that can improve propulsion efficiency in BLI propulsion technology. [Means for solving the problem]

[0007] In order to achieve the above object, the aircraft according to the present technology includes a fuselage section and a BLI propulsion section. The body portion is tubular and long in the axial direction and short in the width direction and vertical direction, and has a rear end portion on the rear side in the axial direction. The BLI propulsion unit is a BLI propulsion unit provided on the rear side of the body unit and having an air intake port, and the center position of the air intake port is offset from the center position of the rear end portion in at least one of the vertical direction and the width direction.

[0008] In this way, by offsetting the center position of the air intake from the center position of the rear end of the fuselage, slow-speed airflow can be efficiently taken in through the air intake, thereby improving propulsion efficiency.

[0009] In the aircraft, the fuselage may have a shape in which an outer diameter gradually decreases toward the rear end on the rear side of the fuselage.

[0010] In the above aircraft, a center position of the rear end portion may be located higher than a center position of the fuselage portion in the vertical direction.

[0011] In the above aircraft, a center position of the air intake may be offset downward in the vertical direction from a center position of the rear end portion.

[0012] In the above aircraft, a center position of the intake port may be disposed between a center position of the fuselage section and a center position of the rear end section in the up-down direction.

[0013] In the above-mentioned aircraft, the area of ​​a non-overlapping region where a projection surface when parallel light parallel to the axial direction is irradiated onto the fuselage section does not overlap with a projection surface when the parallel light is irradiated onto the air intake port may be less than 60%.

[0014] In the above aircraft, when the length of the intake port in the width direction is 2a and the area of ​​the intake port is Sfan, AR=(2a) 2 The value of AR expressed as / Sfan may be 1.3 or greater.

[0015] In the above aircraft, the BLI propulsion unit may include at least one blade unit that is rotatable about an axis that faces the axial direction.

[0016] In the above aircraft, the BLI propulsion unit may include a first impeller and a second impeller aligned in the width direction, and the first impeller and the second impeller may rotate in opposite directions.

[0017] In the aircraft, the first impeller and the second impeller may each have a rotation direction corresponding to an inboard-up rotation direction.

[0018] In the above aircraft, the BLI propulsion unit may include a third impeller disposed between the first impeller and the second impeller in the width direction and below the first impeller and the second impeller in the up-down direction.

[0019] In the above aircraft, the impeller may be arranged such that a position of a central axis of rotation is higher than a center position of the intake port in the vertical direction.

[0020] In the above aircraft, the impeller may be arranged such that a position of a central axis of rotation is located outside a central position of the intake port in the width direction.

[0021] The above aircraft may further comprise a landing section provided below the fuselage section, and in the shape of a projection plane when the fuselage section and the landing section are irradiated with parallel light parallel to the width direction, the angle formed by a tangent line connecting the contact point of the landing section with the ground and the lowest point of the BLI propulsion section and the axial direction may exceed 10.5°.

[0022] In the above-mentioned aircraft, in the shape of the projection plane when parallel light parallel to the width direction is irradiated onto the fuselage section, the shape of the curve indicating the underside of the rear side of the fuselage section may be a shape that is twice differentiable and has an inflection point.

[0023] In the above aircraft, the intake port may be arranged after the inflection point in the axial direction.

[0024] In the aircraft, the intake port may be arranged in the axial direction after a position where the width of the fuselage portion is 50% of the maximum width of the fuselage portion.

[0025] In the above aircraft, a portion of the BLI thruster corresponding to a center position of the intake port may be unjoined to the fuselage.

[0026] In the above aircraft, the intake port may be arranged in the axial direction after a position where a cross-sectional area of ​​the fuselage section perpendicular to the axial direction is 25% of a maximum cross-sectional area.

[0027] In the above aircraft, the aircraft may further include a main power generating unit having a generator, and the BLI propulsion unit may be driven by electric power from the generator.

[0028] In the aircraft, the generator may be operated at an extraction torque of not more than 100% and not less than 90% of a maximum torque of the generator, regardless of an operating state of the aircraft.

[0029] In the above aircraft, when at least one of the conditions that the altitude of the aircraft is equal to or less than a predetermined altitude and the speed of the aircraft is equal to or less than a predetermined speed is satisfied, the power extracted from the generator may be limited to a predetermined value or less.

[0030] In the above aircraft, the main power generating unit may include a plurality of main engines each having the generator, and when, in addition to the condition that at least one of the two conditions is satisfied, a condition that at least one of the main engines has stopped, the power extracted from the generator may be limited to a predetermined value or less.

[0031] In the above aircraft, the main generator may include an engine shaft that rotates to cause the generator to generate electricity, and when the rotation speed of the engine shaft of the main generator is 60% or less of the maximum rotation speed of the engine shaft at that altitude, the extracted torque from the generator may be limited to 10% or less of the maximum extracted torque.

[0032] In the above aircraft, when the engine output of the main engine unit is 60% or less of the maximum engine output at that altitude, the extracted torque extracted from the engine may be limited to 10% or less of the maximum extracted torque.

[0033] The BLI propulsion unit according to the present technology is a BLI propulsion unit having a cylindrical shape that is long in the axial direction and short in the width and up-down directions, and that has an air intake provided on the rear side of a body section that has a rear end on the rear side in the axial direction, and the center position of the air intake is offset from the center position of the rear end in at least one of the up-down direction and the width direction. [Effects of the Invention]

[0034] As described above, according to the present invention, it is possible to provide a technology that can improve propulsion efficiency in BLI propulsion technology. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a top view showing an aircraft according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a side view of an aircraft. [Figure 3] FIG. 1 is a front view of an aircraft. [Figure 4]FIG. 2 is a block diagram showing the internal configuration of the main generator and the electrical connection between the main generator and the BLI propulsion unit. [Figure 5] FIG. 10 is a diagram showing the results of a simulation of the speed of airflow near the rear end of the fuselage. [Figure 6] FIG. 10 is a diagram showing the average velocity of the airflow taken in through the air intake port when the center position of the air intake port is changed in the vertical direction. [Figure 7] FIG. 10 is a diagram showing the projection surface of the fuselage section and the projection surface of the intake port in the BLI propulsion section. [Figure 8] FIG. 10 is a diagram showing the average velocity of the airflow into the intake port when the center position of the intake port in the BLI propulsion unit is changed in the vertical direction and the area of ​​the non-overlapping region is changed. [Figure 9] FIG. 10 is a diagram showing a state where the shape of the intake port is changed to an ellipse. [Figure 10] FIG. 10 is a diagram showing the average velocity of airflow into the intake port when the AR ratio of the intake port (ellipse) is changed. [Figure 11] FIG. 10 is a diagram showing the average velocity of airflow into the intake port when the AR ratio of the intake port (super ellipse) is changed. [Figure 12] FIG. 10 is a diagram showing the average velocity of airflow into the intake port when the AR ratio of the intake port (rectangular) is changed. [Figure 13] FIG. 1 is a diagram showing the position of the impeller relative to the air intake and the direction of rotation of the impeller, as viewed from the rear of the aircraft. [Figure 14] This is a diagram showing the airflow flowing near the surface of an aircraft's fuselage, viewed from diagonally behind the aircraft. [Figure 15] FIG. 10 is a diagram showing another example of the BLI propulsion unit, as viewed from the rear. [Figure 16] FIG. 10 is a diagram showing another example of the BLI propulsion unit, as viewed from the rear. [Figure 17] FIG. 10 is a diagram showing another example of the BLI propulsion unit, as viewed from the rear. [Figure 18]FIG. 10 is a diagram showing a projection plane when parallel light parallel to the width direction (Y-axis direction) is irradiated onto the body part. [Figure 19] 10 is a diagram showing a projection view when parallel light parallel to the axial direction is irradiated onto the body portion and the intake port. FIG. [Figure 20] FIG. 10 is a diagram showing the speed of the airflow when it is sucked into the BLI propulsion section, accelerates rearward, and is then discharged. [Figure 21] FIG. 10 is a diagram showing the width of the body portion 10 at a certain point in the axial direction when the maximum value of the width of the body portion is used as a reference, and the area of ​​the body portion at a certain point in the axial direction when the maximum value of the cross-sectional area of ​​the body portion is used as a reference. [Figure 22] FIG. 10 is a diagram showing a range in which the power extracted by the BLI propulsion unit from the main generator is set to a predetermined value or less. [Figure 23] FIG. 23 is a diagram showing the relationship between the rotation speed of the engine shaft of the main power generating unit and the extracted torque extracted from the generator by the BLI propulsion unit. [Figure 24] FIG. 24 is a diagram showing the relationship between the engine output of the main power generating unit and the torque extracted from the generator by the BLI propulsion. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0037] First Embodiment <Overall configuration of aircraft 100> Fig. 1 is a top view showing an aircraft 100 according to a first embodiment of the present invention, Fig. 2 is a side view of the aircraft 100, and Fig. 3 is a front view of the aircraft 100.

[0038] As shown in FIGS. 1 to 3, the aircraft 100 includes a fuselage section 10, a main wing section 20, a main engine section 30, a BLI propulsion section 40, and a landing section 50.

[0039] The body 10 has a cylindrical shape that is long in the axial direction (X-axis direction) and short in the width direction (Y-axis direction) and the up-down direction (Z-axis direction). The body 10 has a rear end 11 on its rear side in the axial direction, and the rear side of the body 10 is formed so that its outer diameter gradually decreases toward the rear end 11.

[0040] The main wing section 20 includes a pair of left and right main wings 21, 22 provided on the fuselage section 10. The two main wings 21, 22 are provided so as to extend outward in the width direction (Y-axis direction) from the left and right sides of the fuselage section 10.

[0041] Although omitted for clarity of illustration, a tail is provided near the rear end 11 of the fuselage 10. The tail may be of any type, such as a T-tail, a cruciform tail, or a V-tail.

[0042] The main engine section 30, together with the BLI propulsion section 40, generates thrust for flight of the aircraft 100. The main engine section 30 includes two main engines 31, 32. The two main engines 31, 32 are provided below the left and right main wings 21, 22, respectively. The number of main engines may be two or more, and is not particularly limited.

[0043] 4 is a block diagram showing the internal configuration of the main generator 30 and the electrical connection state between the main generator 30 and the BLI propulsion unit 40. The main engines 31, 32 are, for example, jet engines, and include a fan 33, a compressor 34, a combustion engine 35, a turbine 36, a generator 37, and an engine shaft 38. In this example, a turbofan engine is given as an example of the main generator 30, but the type of main generator 30 is not particularly limited.

[0044] The fan 33 draws in air in front of it as it rotates, generating a jet. The compressor 34 compresses (a portion of) the jet from the fan and sends it to the combustor 35 at the rear. The combustor 35 burns fuel in a combustion chamber, expands the compressed air, and sends the high-temperature jet to the turbine 36 at the rear. The turbine 36 is rotated by the high-temperature jet from the combustor 35, and exhausts the jet rearward.

[0045] The rotation of the turbine 36 rotates the engine shaft 38. The rotational force of the engine shaft 38 is used to power the rotation of the fan 33 and the compressor 34, and is also used to power the generator 37. The electric power generated by the generator 37 is also used to drive the motor 43 of the BLI propulsion unit 40.

[0046] Between the main engines 31, 32 and the BLI propulsion unit 40, a first circuit breaker 1, an AC / DC converter 2, a DC / AC inverter 3, and a second circuit breaker 4 are interposed.

[0047] The first circuit breaker 1 and the second circuit breaker 4 switch between an electrically connected state and a disconnected state as necessary. The AC / DC converter 2 converts the AC voltage from the generator 37 into a DC voltage and outputs it to the DC / AC inverter 3. The DC / AC inverter 3 converts the DC voltage from the AC / DC converter 2 into an AC voltage and outputs it to the motor 43.

[0048] 1 to 3 again, the BLI propulsion unit 40, together with the main engine unit 30, generates thrust for flight of the aircraft 100. The BLI propulsion unit 40 includes one BLI thruster 41. The BLI thruster 41 is provided near the rear end 11 on the rear side of the fuselage 10 in the axial direction (X-axis direction). The number of BLI thrusters 41 may be two or more, and is not particularly limited.

[0049] The BLI propulsion device 41 is a fan that generates thrust for flight of the aircraft 100, and includes an impeller 42 (see FIG. 13, etc.), a motor 43 (see FIG. 4) that rotates the impeller 42, and a nacelle 44 (see FIG. 4) that houses the impeller 42 and the motor 43. The number of BLI propulsion devices 41 may be one or two or more, and there is no particular limitation on the number.

[0050] The impeller 42 is configured to be rotatable around an axis facing the axial direction (X-axis direction) as the central axis of rotation. The impeller 42 includes a plurality of fan blades (not shown) regularly arranged along the circumferential direction (direction around the X-axis). The number of impellers 42 per BLI propeller 41 may be one, or may be two or more, and there is no particular limitation on the number.

[0051] The motor 43 rotates the impeller 42 based on electric power from the generator 37 in the main generator 30. The nacelle 44 is cylindrical with its axis facing the axial direction (X-axis direction), and has an intake port 45 on the front side in the axial direction that draws in airflow, and an exhaust port 46 on the rear side in the axial direction that exhausts the airflow accelerated by the impeller 42.

[0052] <Center position of intake port 45> The BLI method is based on the idea that propulsion can be obtained more efficiently (in terms of energy efficiency and fuel consumption rate) by accelerating the relatively slow airflow flowing near the surface of the aircraft, rather than by further accelerating the relatively fast airflow away from the aircraft. In other words, it is better for the airflow that should be taken in through the intake port 45 of the BLI propulsion unit 40 to be a relatively slow airflow.

[0053] The inventors performed a simulation to determine the speed of airflow near the rear end 11 of the fuselage 10 of the aircraft 100. Figure 5 is a diagram showing the results of the simulation to determine the speed of airflow near the rear end 11 of the fuselage 10.

[0054] Figure 5 shows the aircraft 100 as seen from the rear. In Figure 5, the maximum diameter of the shape of the fuselage 10 of the aircraft 100 is shown by a large circle, and the shape of the intake 45 of the BLI propulsion unit 40 is shown by a small circle. The speed of the airflow is shown in grayscale, with darker black indicating slower airflow.

[0055] In addition, in Figure 5, the center position (width direction and up-down direction (YZ direction)) of the rear end portion 11 of the body portion 10 is indicated by an x ​​mark, and the center position (width direction and up-down direction (YZ direction)) of the intake port 45 is indicated by a black circle.

[0056] As shown in FIG. 5, the airflow speed is slower in the region below the center position (see the x mark) of the rear end 11 of the body 10, particularly in the region diagonally downward to the right and the region diagonally downward to the left when viewed from the center position of the rear end 11 of the body 10 (see the dark areas in the gray scale).

[0057] Therefore, in this embodiment, in the BLI propulsion section 40, in order to take in a slower airflow through the intake port 45, the center position of the intake port 45 is offset downward from the center position of the rear end portion 11 of the body section 10.

[0058] FIG. 6 is a diagram showing the average speed of the airflow taken in through air intake port 45 when the center position of air intake port 45 (see the black circle in FIG. 5) is changed in the vertical direction.

[0059] In Fig. 6, the horizontal axis indicates the center position of the intake port 45 in the vertical direction (Z-axis direction). Note that the point 1 m below the lowest point of the maximum diameter of the fuselage 10 (the lowest point of the large circle in Fig. 5) is used as the reference point, which is 0 m. Also, in Fig. 6, the vertical axis indicates the average velocity Vave of the airflow taken in through the intake port 45 when the velocity V0 of the aircraft 100 is used as the reference point.

[0060] 6 shows the results when the diameter of the intake port 45 is changed in five patterns: 0.4 m, 0.8 m, 1.2 m, 1.6 m, and 2 m. In the description of this embodiment, the size of the body portion 10, the size of the intake port 45, etc. are sometimes described using specific numbers, but these are merely examples. In other words, the size of the body portion 10, the size of the intake port 45, etc. are not limited to the examples and can be changed as appropriate.

[0061] 6, when the center position of air intake port 45 is changed in the vertical direction between 4 m and 6 m from the reference point (1 m below the lowest point of the maximum diameter of body portion 10), the average velocity Vave / V0 of the airflow taken in through air intake port 45 gradually increases as the center position of air intake port 45 rises. This tendency appears regardless of the diameter of air intake port 45.

[0062] 6, a dashed vertical line is shown where the center position of intake port 45 is 4.7 m from the reference (1 m below the lowest point of the maximum diameter of body section 10). At the point where the center position of intake port 45 is 4.7 m, the center position of intake port 45 (black circle in FIG. 5) approximately coincides with the center position of rear end portion 11 of body section 10 (x mark in FIG. 5).

[0063] Furthermore, if the center position of the intake port 45 is less than 4.7 m from the reference (1 m below the lowest point of the maximum diameter of the body section 10), the center position of the intake port 45 is offset downward from the center position of the rear end section 11 of the body section 10. Conversely, if the center position of the intake port 45 is more than 4.7 m from the reference, the center position of the intake port 45 is offset upward from the center position of the rear end section 11 of the body section 10.

[0064] In FIG. 6, the area shown to the left of the dashed vertical line, where the center position of the air intake 45 is less than 4.7 m from the reference (1 m below the lowest point of the maximum diameter of the body portion 10), corresponds to this embodiment.

[0065] 6, when the center position of air intake 45 is 4.7 m or more from the reference (1 m below the lowest point of the maximum diameter of body 10) and the center position of air intake 45 is offset upward from the center position of rear end 11 of body 10, the average velocity Vave / V0 of the airflow taken in through air intake 45 becomes relatively faster. This tendency appears regardless of the diameter of air intake 45.

[0066] On the other hand, when the center position of intake port 45 is less than 4.7 m from the reference (1 m below the lowest point of the maximum diameter of body section 10) and the center position of intake port 45 is offset below the center position of rear end section 11 of body section 10, the average velocity Vave / V0 of the airflow taken in through intake port 45 becomes relatively slow. This tendency appears regardless of the diameter of intake port 45.

[0067] That is, as in this embodiment, by offsetting the center position of the intake port 45 downward from the center position of the rear end portion 11 of the fuselage section 10, it is possible to slow down the average velocity Vave / V0 of the airflow taken in through the intake port 45. This allows the BLI propulsion section 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0068] <Downward offset ratio of intake port 45> Next, we will explain how far the intake port 45 of the BLI propulsion unit 40 should be offset downward. Figure 7 is a diagram showing the projection plane of the body unit 10 and the projection plane of the intake port 45 of the BLI propulsion unit 40.

[0069] In Fig. 7, the outer ring of the projection plane when parallel light parallel to the axial direction (X-axis direction) is irradiated onto the body section 10 is shown by a large circle (corresponding to the maximum diameter of the body section 10). Also in Fig. 7, the outer ring of the projection plane when parallel light parallel to the axial direction (X-axis direction) is irradiated onto the intake port 45 of the BLI propulsion section 40 is shown by a small circle.

[0070] 7, the non-overlapping region where the projection plane of the fuselage 10 and the projection plane of the intake port 45 of the BLI propulsion unit 40 do not overlap is shown in gray. In the explanation here, the downward offset rate of the intake port 45 of the BLI propulsion unit 40 is defined as the rate of the non-overlapping region (see gray region) described above.

[0071] FIG. 8 is a diagram showing the average velocity of the airflow into the intake port 45 when the center position of the intake port 45 in the BLI propulsion unit 40 is changed in the vertical direction (Z-axis direction) and the area of ​​the non-overlapping region is changed.

[0072] 8, the horizontal axis indicates the ratio of the area Sfa_pro of the non-overlapping region to the overall area Sfan of the projection surface of air intake port 45. That is, a value of 0 on the horizontal axis means that the non-overlapping region is 0%, and a value of 1 on the horizontal axis means that the non-overlapping region is 100%.

[0073] In addition, in FIG. 8, the vertical axis represents the average velocity Vave of the airflow taken in through the intake port 45 when the velocity V0 of the aircraft 100 is used as the reference velocity.

[0074] FIG. 8 also shows the results when the diameter of the intake port 45 is changed in five patterns: 0.4 m, 0.8 m, 1.2 m, 1.6 m, and 2 m.

[0075] As shown in Figure 8, the center position of the intake port 45 in the BLI propulsion section 40 is changed in the vertical direction (Z-axis direction), and the non-overlapping area between the projection plane of the body section 10 and the projection plane of the intake port 45 is changed between 0% and 100%. As a result, a tendency is observed in which the average velocity Vave / V0 of the airflow taken in through the intake port 45 gradually increases as the proportion of the non-overlapping area increases. This tendency appears regardless of the diameter of the intake port 45.

[0076] On the other hand, if the non-overlapping area between the projection plane of the fuselage 10 and the projection plane of the air intake 45 of the BLI propulsion unit 40 is less than 60%, the average velocity Vave / V0 of the airflow taken in from the air intake 45 will be appropriately slowed down regardless of the diameter of the air intake 45.

[0077] For this reason, in this embodiment, the center position of the intake port 45 is offset downward so that the non-overlapping area between the projection plane of the fuselage section 10 and the projection plane of the intake port 45 is less than 60%. This allows the BLI propulsion section 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0078] <Shape of intake port 45> Next, the shape of the intake port 45 of the BLI propulsion unit 40 will be described. Fig. 9 is a diagram showing the state when the shape of the intake port 45 is changed to an ellipse. In Fig. 9, the ellipse is (y / a) n +(z / b) n = 1, n = 2, and a > b > 0. Note that n = 2 is an ellipse, and n > 2 is a hyperellipse.

[0079] The center position of the intake port 45 (see black circle), i.e., the origin of the ellipse, is located below the center position of the rear end portion 11 of the body portion 10 in the vertical direction (see x mark), and is located at a position corresponding to the center position of the rear end portion 11 of the body portion 10 in the width direction.

[0080] 9, the y-axis corresponds to the width direction, and the z-axis corresponds to the up-down direction. Furthermore, a represents the radius of the major axis (y-axis direction) of the ellipse, and b represents the radius of the minor axis (z-axis direction) of the ellipse.

[0081] FIG. 10 is a diagram showing the average velocity of the airflow into the intake port 45 when the AR ratio of the intake port 45 (elliptical) is changed.

[0082] In FIG. 10, the horizontal axis represents the AR ratio (aspect ratio) of the (elliptical) air intake port 45. The AR ratio is expressed as AR=(2a) 2It is defined as / Sfan, which indicates the horizontal length of the air intake port 45 (ellipse). Note that 2a is the length of the air intake port 45 in the width direction (the length of the major axis of the ellipse), and Sfan is the area of ​​the air intake port 45 (YZ plane).

[0083] In FIG. 10, the vertical axis indicates the average velocity Vave of the airflow taken in through the intake port 45 when the velocity V0 of the aircraft 100 is used as the reference velocity.

[0084] Figure 10 also shows the results when the center position of the air intake 45 is changed in the vertical direction (Z-axis direction) from the reference (1 m below the lowest point of the maximum diameter of the body portion 10) in seven patterns: 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, 4.65 m, and 4.8 m.

[0085] The six patterns in which the center position of intake port 45 is lower than the center position of rear end 11 of body 10 are 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, and 4.65 m from the reference (1 m below the lowest point of the maximum diameter of body 10), and these correspond to this embodiment. On the other hand, the pattern in which the center position of intake port 45 is 4.8 m from the reference (1 m below the lowest point of the maximum diameter of body 10) corresponds to the comparative example, since the center position of intake port 45 is higher than the center position of rear end 11 of body 10.

[0086] As shown in FIG. 10, when the AR ratio is changed between 0 and 5, as the AR ratio increases (air intake port 45 becomes longer horizontally), the average velocity Vave / V0 of the airflow taken in through air intake port 45 gradually decreases.

[0087] This tendency appears in six patterns in which the center position of air intake 45 corresponding to this embodiment is 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, and 4.65 m from the reference (1 m below the lowest point of the maximum diameter of body portion 10). On the other hand, in a pattern in which the center position of air intake 45 is 4.8 m from the reference (1 m below the lowest point of the maximum diameter of body portion 10) corresponding to the comparative example, air intake 45 also draws in fast airflow, and as the AR ratio increases, the average velocity Vave / V0 of the airflow taken in through air intake 45 tends to gradually increase.

[0088] 10, the vertical axis is indicated by a dashed line where the AR ratio is 1.3. In this embodiment, if the AR ratio is 1.3 or greater, the average velocity Vave / V0 of the airflow taken in from the intake port 45 becomes appropriately slow. This allows the BLI propulsion unit 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0089] FIG. 11 is a diagram showing the average velocity of the airflow into the intake port 45 when the AR ratio of the intake port 45 (super ellipse) is changed. In FIG. 11, the shape of the intake port 45 is a super ellipse. Here, the ellipse is expressed as (y / a) n +(z / b) n =1, n=5, and a>b>0.

[0090] In Figure 11, the horizontal axis represents the AR ratio (aspect ratio) of the intake port 45 (superellipse), and the vertical axis represents the average velocity Vave of the airflow taken in from the intake port 45 when the velocity V0 of the aircraft 100 is used as the reference velocity.

[0091] Figure 11 also shows the results when the center position of the air intake 45 is changed in the vertical direction (Z-axis direction) in seven patterns: 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, 4.65 m, and 4.8 m from the reference point (1 m below the lowest point of the maximum diameter of the body portion 10).

[0092] The six patterns in which the center position of the intake port 45 is 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, and 4.65 m from the reference (1 m below the lowest point of the maximum diameter of the body portion 10) correspond to this embodiment. On the other hand, the pattern in which the center position of the intake port 45 is 4.8 m from the reference (1 m below the lowest point of the maximum diameter of the body portion 10) corresponds to the comparative example.

[0093] As shown in FIG. 11, when the AR ratio is changed between 0 and 5, as the AR ratio increases (air intake port 45 becomes longer horizontally), the average velocity Vave / V0 of the airflow taken in through air intake port 45 gradually decreases.

[0094] This tendency appears in six patterns in which the center position of air intake 45 corresponding to this embodiment is 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, and 4.65 m from the reference (1 m below the lowest point of the maximum diameter of body portion 10). On the other hand, in a pattern in which the center position of air intake 45 is 4.8 m from the reference (1 m below the lowest point of the maximum diameter of body portion 10) corresponding to the comparative example, air intake 45 also draws in fast airflow, and as the AR ratio increases, the average velocity Vave / V0 of the airflow taken in through air intake 45 tends to gradually increase.

[0095] 11, the vertical axis is indicated by a dashed line where the AR ratio is 1.3. In this embodiment, if the AR ratio is 1.3 or greater, the average velocity Vave / V0 of the airflow taken in from the intake port 45 becomes appropriately small. This allows the BLI propulsion unit 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0096] FIG. 12 is a diagram showing the average velocity of the airflow into the intake port 45 when the AR ratio of the intake port 45 (rectangular) is changed. In FIG. 12, the shape of the intake port 45 is rectangular. Here, when the shape of the intake port 45 is rectangular, the AR ratio is expressed as AR=(2a), similarly to the case of an ellipse and a superellipse. 2 It is defined by / Sfan, where the value 2a means the length of the long side of the rectangle (in the y-axis direction).

[0097] In Figure 12, the horizontal axis represents the AR ratio (aspect ratio) of the intake port 45 (rectangle), and the vertical axis represents the average velocity Vave of the airflow taken in from the intake port 45 when the velocity V0 of the aircraft 100 is used as the reference velocity.

[0098] Also, Figure 12 shows the results when the center position of the air intake 45 (rectangle) is changed in the vertical direction (Z-axis direction) in seven patterns: 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, 4.65 m, and 4.8 m from the reference (1 m below the lowest point of the maximum diameter of the body portion 10).

[0099] The six patterns in which the center position of the intake port 45 is 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, and 4.65 m from the reference (1 m below the lowest point of the maximum diameter of the body portion 10) correspond to this embodiment. On the other hand, the pattern in which the center position of the intake port 45 is 4.8 m from the reference (1 m below the lowest point of the maximum diameter of the body portion 10) corresponds to the comparative example.

[0100] As shown in FIG. 12, when the AR ratio is changed between 0 and 5, as the AR ratio increases (air intake port 45 becomes longer horizontally), the average velocity Vave / V0 of the airflow taken in through air intake port 45 gradually decreases.

[0101] This tendency appears in six patterns in which the center position of air intake 45 corresponding to this embodiment is 3.9 m, 4.05 m, 4.2 m, 4.35 m, 4.5 m, and 4.65 m from the reference (1 m below the lowest point of the maximum diameter of body portion 10). On the other hand, in a pattern in which the center position of air intake 45 is 4.8 m from the reference (1 m below the lowest point of the maximum diameter of body portion 10) corresponding to the comparative example, air intake 45 also draws in fast airflow, and as the AR ratio increases, the average velocity Vave / V0 of the airflow taken in through air intake 45 tends to gradually increase.

[0102] 12, the vertical axis is indicated by a dashed line where the AR ratio is 1.3. In this embodiment, if the AR ratio is 1.3 or more, the average velocity Vave / V0 of the airflow taken in from the intake port 45 becomes appropriately slow. This allows the BLI propulsion unit 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0103] <Position and Rotation Direction of Impeller 42> Next, we will explain the position of the impeller 42 relative to the intake port 45 and the rotation direction of the impeller 42. Figure 13 is a diagram showing the position of the impeller 42 relative to the intake port 45 and the rotation direction of the impeller 42, as seen from the rear of the aircraft 100.

[0104] 13, air intake 45 is indicated by a solid line, and impeller 42 is indicated by a dashed line. Furthermore, the center position of air intake 45 is indicated by a black circle, and the central axis of impeller 42 is indicated by a white circle.

[0105] Here, the BLI propulsion unit 40 draws in a slow-speed airflow through the intake port 45, and then expels the airflow, the total pressure of which has been increased by the impeller 42, rearward to generate thrust. Therefore, the larger the area (YZ plane) of the impeller 42, the higher the efficiency that can be obtained.

[0106] On the other hand, if the impeller 42 is made larger and given a shape that differs from the shape of the intake port 45, the drag of the BLI propulsion unit 40, including the nacelle 44, will increase. In this case, fuel efficiency will be impaired and separation will be induced inside the BLI propulsion unit 40, reducing efficiency. Therefore, it is desirable for the impeller 42 to have a shape that is close to the shape of the intake port 45.

[0107] For this reason, in FIG. 13, two impellers 42 are arranged in the width direction for an elliptical intake port 45 that has a high AR ratio and is horizontally long (or, as shown in FIG. 16 described later, three impellers 42 are arranged in a V-shape for an inverted triangular intake port 45).

[0108] As shown in Fig. 13, the BLI propulsion unit 40 includes two impellers 42. For convenience, in the description of Fig. 13, the right-side impeller 42 will be referred to as the first impeller 42a, and the left-side impeller 42 will be referred to as the second impeller 42b.

[0109] The first impeller 42a and the second impeller 42b are arranged side by side along the width direction (Y axis). The central axes of rotation of the first impeller 42a and the second impeller 42b (see white circles) are offset upward in the vertical direction (Z axis direction) from the center position (see black circles) of the air intake port 45. The central axes of rotation of the first impeller 42a and the second impeller 42b (see white circles) are offset outward in the width direction from the center position (see black circles) of the air intake port 45.

[0110] The first impeller 42a and the second impeller 42b rotate in opposite directions. Specifically, the first impeller 42a (right side) rotates clockwise (as viewed from the rear), while the second impeller 42b (left side) rotates counterclockwise (as viewed from the rear).

[0111] Here, we will explain that the central axes of rotation of the first impeller 42a and the second impeller 42b are offset in the vertical and horizontal directions relative to the center position of the air intake 45, and that the first impeller 42a and the second impeller 42b rotate in opposite directions.

[0112] FIG. 14 is a diagram showing the airflow flowing near the surface of the aircraft 100, viewed obliquely from behind the aircraft 100. In FIG.

[0113] 14, attention is focused on the region near the lower right of the rear end portion 11 of the fuselage portion 10. In this region, the airflow flowing near the surface of the fuselage rotates clockwise (as viewed from the rear) and flows rearward (inboard up). Therefore, in this embodiment, the first impeller 42a (right side) rotates clockwise in accordance with the rotation direction of this airflow (a rotation direction corresponding to inboard up).

[0114] On the other hand, although not shown, in the lower left region of the rear end 11 of the fuselage 10, the airflow flowing near the surface of the fuselage rotates counterclockwise and flows rearward (inboard up). Therefore, in this embodiment, the second impeller 42b (left side) rotates counterclockwise in accordance with the flow of this airflow (a rotation direction corresponding to inboard up).

[0115] Additionally, the airflow flowing near the lower right of rear end portion 11 of body portion 10 rotates clockwise while spiraling upward and flows into the right side of intake port 45. Therefore, in this embodiment, the central axis of first impeller 42a is disposed above the center position of intake port 45 in the vertical direction and outside the center position of intake port 45 in the width direction.

[0116] This allows the first impeller 42a (right side) to efficiently capture the airflow flowing in clockwise while being rolled up, thereby generating thrust more efficiently. Also, by setting the rotation direction of the first impeller 42a to correspond to the inboard-up direction, the angle of the airflow acting on the first impeller 42a can be alleviated, and the torque required of the motor 43 that drives the first impeller 42a can be reduced, allowing the weight of the aircraft 100 to be reduced and fuel efficiency to be further improved.

[0117] Similarly, the airflow flowing near the lower left of rear end 11 of body 10 rotates counterclockwise while spiraling upward and flows into the left side of intake port 45. Therefore, in this embodiment, the central axis of second impeller 42b is disposed above the center position of intake port 45 in the vertical direction and outside the center position of intake port 45 in the width direction.

[0118] This allows the second impeller 42b (left side) to efficiently capture the airflow flowing in counterclockwise while being rolled up, thereby enabling more efficient thrust generation. Also, by setting the rotation direction of the second impeller 42b to correspond to the inboard-up direction, the angle of the airflow acting on the second impeller 42b can be alleviated, and the torque required of the motor 43 that drives the second impeller 42b can be reduced, allowing the weight of the aircraft 100 to be reduced and fuel efficiency to be further improved.

[0119] In the above description, the first impeller 42a and the second impeller 42b are rotated in accordance with the rotation direction of the airflow flowing in from the air intake port 45. However, the first impeller 42a (counterclockwise) and the second impeller 42b (clockwise) can also be rotated in the direction opposite to the rotation direction of the airflow flowing in from the air intake port 45.

[0120] In the explanation given here, a case has been described in which one BLI propeller 41 is provided with two impellers 42. However, the BLI propulsion unit 40 may be provided with two BLI propellers 41, and each of the two BLI propellers 41 may have one impeller 42.

[0121] 15 is a diagram showing another example of the BLI propulsion unit 40, as viewed from the rear. The BLI propulsion unit 40 has two BLI thrusters 41 arranged side by side in the width direction (Y-axis direction). The first BLI thruster 41a (right side) has a first air intake 45a and a first impeller 42a. Similarly, the second BLI thruster 41b (left side) has a second air intake 45b and a second impeller 42b.

[0122] The center position (black circle) of the first air intake 45a in the first BLI thruster 41a (right side) is offset downward in the vertical direction from the center position (see x mark) of the rear end 11 of the fuselage section 10, and is also offset outward (to the right) from the center position of the rear end 11 of the fuselage section 10 in the width direction.

[0123] In addition, the center position (black circle) of the second air intake 45b in the second BLI thruster 41b (left side) is offset downward in the vertical direction from the center position (see x mark) of the rear end 11 of the fuselage section 10, and is also offset outward (left side) from the center position of the rear end 11 of the fuselage section 10 in the width direction.

[0124] 15, as in the case shown in Fig. 14, the first impeller 42a (right side) typically rotates clockwise (inboard up). The central axis of rotation of the first impeller 42a (see white circle) is located above the center position (see black circle) of the first air intake port 45a in the vertical direction and outside the center position of the first air intake port 45a in the width direction.

[0125] Similarly, the second impeller 42b (left side) typically rotates counterclockwise (inboard up). The central axis of rotation of the second impeller 42b (see white circle) is located above the center position of the second air intake port 45b (see black circle) in the vertical direction and outside the center position of the second air intake port 45b in the width direction.

[0126] Here, the AR ratio of the entire intake port 45 including the first intake port 45a and the second intake port 45b will be described. In this case, if the diameter of the circle representing the first intake port 45a and the second intake port 45b is D, the AR ratio of the entire intake port 45 is given by AR=(2D 2 ) / (2πD 2 / 4)≈2.55, which is equal to or greater than the above-mentioned 1.3. Therefore, the average velocity of the airflow taken in from the intake port 45 is appropriately slowed, enabling the BLI propulsion unit 40 to generate thrust efficiently (with good energy efficiency and fuel consumption rate).

[0127] That is, when the BLI propulsion unit 40 has a plurality of intake ports 45, the AR ratio is calculated as the AR ratio of the entire intake port 45 including the plurality of intake ports, and this value should be 1.3 or more.

[0128] FIG. 16 is a diagram showing another example of the BLI propulsion unit 40, as viewed from the rear of the aircraft 100.

[0129] 16, the BLI propulsion section 40 has one BLI thruster 41. The shape of the air intake 45 of this BLI thruster 41 is an inverted triangle (heart-like). The center position of this air intake 45 is offset downward in the vertical direction from the center position (see x mark) of the rear end 11 of the fuselage section 10, and is located at a position corresponding to the center position of the rear end 11 of the fuselage section 10 in the width direction.

[0130] 16, for convenience, the right-side impeller 42 will be referred to as the first impeller 42a, the left-side impeller 42 as the second impeller 42b, and the lower impeller 42 as the third impeller 42c. The first impeller 42a and the second impeller 42b are the same as those in FIG.

[0131] The central axis of rotation of third impeller 42c (see white circle) is offset downward from the center position of air intake port 45 in the vertical direction, and is located at a position in the width direction corresponding to the center position of air intake port 45. The rotation direction of third impeller 42c may be clockwise or counterclockwise (as viewed from the rear).

[0132] 17 is a diagram showing another example of the BLI propulsion unit 40, as viewed from the rear. The BLI propulsion unit 40 has a first BLI propulsion device 41a (right side) and a second BLI propulsion device 41b (left side) arranged along the width direction (Y-axis direction), and a third BLI propulsion device 41c arranged below the first BLI propulsion device 41a and the second BLI propulsion device 41b.

[0133] The first BLI thruster 41a and the second BLI thruster 41b are the same as those in Fig. 15. The third BLI thruster 41c has a third air intake 45c and a third impeller 42c. The center position of the third air intake 45c (see black circle) is offset downward in the vertical direction from the center position (see x mark) of the rear end 11 of the body section 10, and is located at a position corresponding to the center position of the rear end 11 of the body section 10 in the width direction.

[0134] The central axis of rotation of third impeller 42c (see white circle) coincides with the central position (black circle) of third air intake port 45c. The central axis of rotation of third impeller 42c may be offset in at least one of the vertical and horizontal directions from the central position of third air intake port 45c. The rotation direction of third impeller 42c may be clockwise or counterclockwise (as viewed from the rear).

[0135] <Width-direction projection shape of the body portion 10, etc.> Next, the shape of the projection plane when parallel light parallel to the width direction (Y-axis direction) is irradiated onto the body portion 10 will be described.

[0136] Fig. 18 is a diagram showing a projection plane when parallel light parallel to the width direction (Y-axis direction) is irradiated onto the fuselage section 10. In Fig. 18, in addition to the fuselage section 10, the BLI propulsion section 40 and the landing section 50 are also shown. Fig. 19 is a diagram showing a projection diagram when parallel light parallel to the axial direction (X-axis direction) is irradiated onto the fuselage section 10 and the intake port 45.

[0137] 18 and 19, the top diagram shows an aircraft 100 according to this embodiment. In addition, in Fig. 18 and 19, the central diagram shows an aircraft 101 according to a first comparative example, and the bottom diagram shows an aircraft 102 according to a second comparative example.

[0138] 18 and 19, in the aircraft 100 according to this embodiment, the fuselage 10 is formed so that the lower side of its aft portion is rounded up, and the diameter of the aft portion gradually decreases toward the rear. The center position of the aft end 11 of the fuselage 10 is located near the upper end of the fuselage 10 where the diameter is greatest.

[0139] Furthermore, in the aircraft 100 according to this embodiment, the center position of the intake port 45 of the BLI propulsion section 40 (see the black circle in Figure 19) is offset downward in the vertical direction from the center position of the rear end portion 11 of the fuselage section 10 (see the X mark in Figure 19), and is located at a position corresponding to the center position of the fuselage section 10 in the width direction.

[0140] 18 and 19, in an aircraft 101 according to a first comparative example, a fuselage section 110 is formed symmetrically about a central axis in the axial direction (X-axis direction), and is formed so that the diameter on the aft side gradually decreases toward the rear. In addition, the center position of a rear end 111 of the fuselage section 110 substantially coincides with the center position of the fuselage section 110 itself.

[0141] Furthermore, in the aircraft 101 according to the first comparative example, the center position (see black circle in Figure 19) of the intake port 145 of the BLI propulsion section 140 is located at a position corresponding to the center position (see X mark in Figure 19) of the rear end portion 111 of the fuselage section 110 in the vertical and width directions.

[0142] 18 and the bottom diagram of Fig. 19, in an aircraft 102 according to a second comparative example, a fuselage section 210 is formed so that the lower side of its aft portion is rounded up, and the diameter of the aft portion gradually decreases toward the rear. Furthermore, the center position of an aft end portion 211 of the fuselage section 210 is located near the upper end portion of the fuselage section 210 where the diameter is greatest.

[0143] Furthermore, in the aircraft 102 according to the second comparative example, the center position (see black circle in Figure 19) of the intake port 245 of the BLI propulsion section 240 is located at a position corresponding to the center position (see X mark in Figure 19) of the rear end portion 211 of the fuselage section 210 in the vertical and width directions.

[0144] In Figure 18, the ground contact surfaces of the landing sections 50, 150, and 250 of the aircraft 100, 101, and 102 are indicated by dashed lines, and the roll angle required for takeoff relative to the ground contact surface is indicated by a solid straight line. Also in Figure 18, a dotted line connects the ground contact points of the landing sections 50, 150, and 250 of the aircraft 100, 101, and 102 with the lowest points of the BLI propulsion sections 40, 140, and 240.

[0145] The roll-up angle is the angle required to ensure that the rear side of the aircraft 100, 101, 102 does not even touch the ground when the aircraft 100, 101, 102 take off, and in this example, is set to 10.5° relative to the ground surface.

[0146] In the first and second comparative examples, the line connecting the ground contact points of the landing sections 150, 250 of the aircraft 101, 102 and the lowest points of the BLI propulsion sections 140, 240 coincides with the line indicating the tilt angle, and is therefore 10.5° with respect to the axial direction (X-axis direction).

[0147] On the other hand, in this embodiment, the line connecting the ground contact point on the landing section 50 of the aircraft 100 and the lowest point of the BLI propulsion section 40 is above the line indicating the raising angle, and therefore exceeds 10.5° with respect to the axial direction (X-axis direction).

[0148] 18, attention will be focused on the curved line on the lower rear side of the aircraft 100 according to this embodiment in the plane of the width direction projection of the fuselage 10. This curve is rounded up at a steeper angle than those of the first and second comparative examples. This curve is also twice differentiable and has an inflection point.

[0149] In the top diagram of Figure 18, an asterisk is added to the inflection point where this curve changes from a downward convex to an upward convex. In this embodiment, the BLI propulsion unit 40 (intake port 45) is located at a location where the lower side of the body unit 10 is recessed after the inflection point.

[0150] Here, when the aircraft has a shape like that of the first and second comparative examples, the position of the BLI propulsion units 140, 240 is a determining factor in the roll-up angle. Therefore, in the first and second comparative examples, in order to ensure a roll-up angle of 10.5° at takeoff, the landing units 150, 250 of the aircraft 101, 102 must be made larger.

[0151] The ratio of the weight of the landing section 50 to the overall weight of the aircraft 100 is relatively large, so if the landing section 50 becomes large and heavy, the overall weight of the aircraft 100 will increase, resulting in reduced fuel efficiency.

[0152] In contrast, in this embodiment, the BLI propulsion unit 40 is disposed in a recess aft of the inflection point, and the line connecting the ground contact point on the landing section 50 of the aircraft 100 and the lowest point of the BLI propulsion unit 40 is above the line indicating the roll-up angle. This makes it possible to appropriately ensure a roll-up angle of 10.5° or more without increasing the size of the landing section 50, and prevents a decrease in the fuel efficiency of the aircraft 100.

[0153] Furthermore, in this embodiment, the slow-moving airflow on the rear side of the fuselage section 10 can be appropriately drawn in through the intake port 45, while at the same time a raising angle of 10.5° or more can be appropriately ensured, thereby achieving both high propulsion performance and high takeoff performance. In particular, by positioning the intake port 45 of the BLI propulsion section 40 after the inflection point in the axial direction (X-axis), it is possible to more effectively guide decelerated airflow into the intake port 45, enabling further improvement in propulsion efficiency.

[0154] In this embodiment, in the BLI propulsion section 40, a portion corresponding to the center position of the intake port 45 (for example, a core portion in the center of the nacelle including a fan hub, motor, etc.) is not joined to the fuselage section (upper side of FIG. 18). On the other hand, in the first comparative example and the second comparative example, a portion corresponding to the center position of the intake ports 145, 245 (for example, a core portion in the center of the nacelle including a fan hub, motor, etc.) in the BLI propulsion sections 140, 240 is joined to the fuselage section (center, lower side of FIG. 18).

[0155] Therefore, in the first and second comparative examples, the propulsion efficiency is poor because the configuration is such that a relatively fast airflow flowing over the upper side of the fuselage of the aircraft 101, 102 is taken in through the intakes 145, 245. Furthermore, in the first and second comparative examples, the impellers of the BLI propulsion units 140, 240 are subjected to a high-speed airflow in the upper rotation phase of the fuselage units 110, 120, and a low-speed airflow in the lower rotation phase of the fuselage units 110, 120. Therefore, fatigue failure is induced in the impellers of the BLI propulsion units 140, 240 when they are subjected to a severe cyclic load.

[0156] In contrast, in this embodiment, the center position of the air intake 45 is offset downward from the center position of the rear end of the fuselage section 10, and the portion of the BLI propulsion section 40 corresponding to the center position of the air intake 45 (the core portion at the center of the nacelle) is not joined to the fuselage section 10. Therefore, high-speed airflow from the upper part of the fuselage section 10 is less likely to enter the air intake 40, which improves propulsion efficiency and prevents the above-mentioned fatigue failure.

[0157] Fig. 20 is a diagram showing the speed of the airflow when it is sucked into the BLI propulsion section 40, accelerates rearward, and is then discharged. In Fig. 20, the top diagram shows the aircraft 100 according to this embodiment, the middle diagram shows the aircraft 101 according to the first comparative example, and the bottom diagram shows the aircraft 102 according to the second comparative example.

[0158] 20, in the first and second comparative examples, a relatively slow airflow from the rear side of the fuselage sections 110 and 210 is taken in through the intake ports 145 and 245, but the speed of the taken-in airflow is faster than in this embodiment. Therefore, the first and second comparative examples have lower propulsion performance than this embodiment.

[0159] On the other hand, in this embodiment, a relatively slow airflow from the rear side of the fuselage 10 is taken in through the intake port 45, and the speed of the taken-in airflow is slower than in the first and second comparative examples, so this embodiment has higher propulsion performance than the first and second comparative examples.

[0160] In other words, with the BLI technology of this embodiment, thrust can be obtained by efficiently drawing in slow-speed airflows (see also Figures 5, 14, etc.) that occur not only on the surface of the airframe but also on the rear side of the airframe due to interference with various parts of the airframe, into the BLI propulsion unit 40. Therefore, the BLI propulsion unit of this embodiment can obtain higher propulsion efficiency than the BLI propulsion units 140 and 240 of the first and second comparative examples. <How far back should the intake port 45 be positioned in the axial direction (X-axis direction)?> Next, how far rearward in the axial direction (X-axis direction) the intake port 45 of the BLI propulsion section 40 should be positioned relative to the body section 10 will be described.

[0161] In this embodiment, the intake port 45 is located axially after any one of the following three points. (1) In the axial direction, after the inflection point (2) In the axial direction, after the position where the width of the body part 10 (Y-axis direction) becomes 50% of the maximum width of the body part 10 (3) In the axial direction, after the position where the cross-sectional area perpendicular to the axial direction (X-axis direction) of the body portion 10 becomes 25% of the maximum cross-sectional area

[0162] As (1) has been described above, (2) and (3) will be explained below. Fig. 21 is a diagram showing the width of the body portion 10 at a certain point in the axial direction when the maximum value of the width of the body portion 10 is used as a reference, and the area of ​​the body portion 10 at a certain point in the axial direction when the maximum value of the cross-sectional area of ​​the body portion 10 is used as a reference.

[0163] In FIG. 21, the black-filled area indicates a cross section (YZ plane) perpendicular to the axial direction of the body section 10, and the white circle indicates the intake port 45 of the BLI propulsion section 40.

[0164] In each diagram in Fig. 21, the position in the axial direction (X-axis direction) is changed, and the position of the tip of the body part 10 is set to x = 0. Also in Fig. 21, the speed of the airflow flowing near the surface of the body part 10 is shown in gray scale (darker black means slower airflow).

[0165] As shown in Fig. 21, by shifting the position of intake port 45 rearward in the axial direction, it becomes possible to gradually properly take in slower airflow from intake port 45. Here, attention is focused on the right-hand diagram in the second row from the top of Fig. 21 and the left-hand diagram in the bottom row of Fig. 21.

[0166] The second diagram from the top on the right side of Figure 21 shows the cross-sectional area of ​​the fuselage section 10 at a point 30 m from the tip of the fuselage section 10. Furthermore, at a point 30 m from the tip of the fuselage section 10, the width of the fuselage section 10 is 57% of the maximum width of the fuselage section 10, and the cross-sectional area of ​​the fuselage section 10 is 32% of the maximum area of ​​the fuselage section 10. If the intake port 45 is placed at this point, it will not be able to take in the slow-speed airflow (dark gray area) very efficiently.

[0167] On the other hand, the diagram on the left side of the bottom row in Figure 21 shows the cross-sectional area of ​​the fuselage section 10 at a point 31 m from the tip of the fuselage section 10. Furthermore, at a point 31 m from the tip of the fuselage section 10, the width of the fuselage section 10 is 49% of the maximum width of the fuselage section 10, and the cross-sectional area of ​​the fuselage section 10 is 20% of the maximum area of ​​the fuselage section 10. If the intake port 45 is located at this point, it can efficiently take in slow-speed airflow.

[0168] Therefore, in this embodiment, the intake port 45 is provided in the axial direction after a position where the width (Y-axis direction) of the body section 10 is 50% of the maximum width of the body section 10. Alternatively, the intake port 45 is provided in the axial direction after a position where the cross-sectional area of ​​the body section 10 perpendicular to the axial direction (X-axis direction) is 25% of the maximum cross-sectional area. This allows slow-velocity airflow to be efficiently taken in through the intake port 45, and enables the BLI propulsion section 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0169] <Other> The BLI propulsion unit 40 can achieve higher propulsion efficiency than the main engine unit 30 installed on the underside of the main wing 20. Therefore, by increasing the thrust distribution of the BLI propulsion unit 40 with respect to the thrust of the entire aircraft 100, the propulsion efficiency can be increased.

[0170] On the other hand, increasing the thrust allocation of the BLI propulsion unit 40 increases the weight of the electric propulsion system, which is shown in Figure 4 and is composed of the generator 37, converter 2, inverter 3, motor 43, power wiring, etc., impairing the fuel efficiency of the entire aircraft 100. Furthermore, since the power of the engine shaft 38 is less during takeoff than during cruising, it is possible to increase the extracted torque in the BLI propulsion unit 40 during takeoff, but to do so, it is necessary to enlarge the electronic components of the generator 37 to a corresponding size. On the other hand, since such a large extracted torque is not required during cruising, the weight of the enlarged electronic components of the generator 37 becomes deadweight during cruising.

[0171] In contrast, in this embodiment, the extracted torque at takeoff is adjusted to the extracted torque corresponding to the thrust distribution that maximizes the fuel efficiency of the entire aircraft 100 during cruising. In other words, the generator 37 is configured to maintain the extracted torque at 100% to 90% of the maximum torque of the generator 37 regardless of whether it is during takeoff or cruising. This makes it possible to ensure operation during cruising while preventing the above-mentioned increase in dead weight.

[0172] Furthermore, in this embodiment, because the power of the motor 43 of the BLI propulsion unit 40 is extracted from the engine shaft 38 of the main generator unit 30, if a malfunction occurs in the electric propulsion system, it is possible that the BLI propulsion unit 40 may fall into a state where it does not generate thrust, even though it is extracting power from the main generator unit 30. In this case, if one of the main engines 31, 32 stops during takeoff, there is a risk that the thrust will be insufficient and the aircraft 100 will crash.

[0173] Therefore, in this embodiment, when the altitude H and speed V of the aircraft 100 are within a predetermined range, the power (electricity) extracted by the BLI propulsion unit 40 from the main generator 30 is limited to a predetermined value (zero, or a value at which the BLI propulsion unit 40 does not generate drag on the main generator 30) or less.

[0174] Fig. 22 is a diagram showing the range (see gray area) in which the power extracted by the BLI propulsion unit 40 from the main engine unit 30 is set to a predetermined value or less (zero, or a value at which the BLI propulsion unit 40 generates no drag). In Fig. 22, the trajectories of the speed and altitude of the aircraft 100 at takeoff are shown by dotted curves.

[0175] As shown in Figure 22, when at least one of the two conditions is met, namely, that the altitude H of the aircraft 100 is equal to or less than a predetermined altitude, and that the speed V is equal to or less than a predetermined speed, the power extracted by the BLI propulsion unit 40 from the main engines 31, 32 is limited to a predetermined value (zero, or a range in which the BLI propulsion unit 40 does not generate drag) or less.

[0176] Furthermore, when the condition that at least one of the above two conditions is satisfied and at least one of the multiple prime movers 31, 32 has stopped is satisfied, the power extracted by the BLI propulsion unit 40 from the prime movers 31, 32 may be limited to a predetermined value (zero, or a range in which the BLI propulsion unit 40 does not generate drag) or less.

[0177] This reduces the probability of failure of the electric propulsion system in the event that one of the main engines 31, 32 stops, and ensures the reliability of the aircraft 100.

[0178] Furthermore, when the aircraft 100 is descending, the thrust or rotation speed of the main engine unit 30 can be reduced to near idle. However, if the BLI propulsion unit 40 extracts power from the engine shaft 38 at this time, even a slight fluctuation in the extracted power could cause the engine to stop.

[0179] Therefore, in this embodiment, when the rotation speed N1 of the engine shaft 38 of the main generator 30 is 60% or less of the maximum rotation speed of the engine shaft 38 (a value determined according to the flight altitude), the extracted torque τgen extracted by the BLI propulsion unit 40 from the generator 37 is limited to 10% or less.

[0180] Alternatively, if the engine output of the main engine unit 30 falls below 60% of the maximum engine output (a value determined according to the flight altitude), the extracted torque τgen extracted by the BLI propulsion unit 40 from the generator 37 is limited to 10%.

[0181] 23 is a diagram showing the relationship between the rotation speed N1 of the engine shaft 38 of the main generator 30 and the extracted torque τgen extracted by the BLI propulsion unit 40 from the generator 37. As shown in Fig. 23, when the rotation speed N1 of the engine shaft 38 of the main generator 30 is 60% or less of the maximum rotation speed of the engine shaft 38, the extracted torque τgen extracted by the BLI propulsion unit 40 from the generator 37 is limited to 10% or less of the maximum value of the extracted torque. This makes it possible to eliminate problems such as the main generator 30 suddenly stopping during descent, for example.

[0182] Fig. 24 is a diagram showing the relationship between the engine output of the main generator 30 and the extracted torque τgen that the BLI propulsion unit 40 extracts from the generator 37. As shown in Fig. 24, when the engine output of the main generator 30 is 60% or less of the maximum engine output value (a value determined according to the flight altitude), the extracted torque τgen that the BLI propulsion unit 40 extracts from the generator 37 is limited to 10% or less of the maximum extracted torque. This makes it possible to eliminate the problem of the main generator 30 stopping unexpectedly during descent.

[0183] <Effect, etc.> As described above, in this embodiment, the center position of the air intake 45 of the BLI propulsion unit 40 is offset downward in the vertical direction from the center position of the rear end 11 of the fuselage 10. This makes it possible to appropriately slow down the average speed of the airflow taken in from the air intake 45, thereby enabling the BLI propulsion unit 40 to generate thrust efficiently (energy efficiency, fuel consumption rate).

[0184] Furthermore, in this embodiment, the body section 10 has a shape in which the outer diameter gradually decreases toward the rear end 11 on the rear side of the body section 10, and the center position of the rear end 11 of the body section 10 is located above the center position of the body section 10 in the up-down direction. In this embodiment, the center position of the intake port 45 of the BLI propulsion section 40 is located between the center position of the body section 10 and the center position of the rear end 11 in the up-down direction. This allows the BLI propulsion section 40 to generate thrust more efficiently.

[0185] Here, the shape of the projection plane in the width direction of the fuselage section 10 in this embodiment is such that the lower side of the rear side of the fuselage section 10 is rounded off. Therefore, in this embodiment, the region below the center position of the rear end 11 of the fuselage section 10 is the region where slow airflow flows. However, the region where slow airflow flows may differ depending on the shape of the aircraft 100. For example, the region where slow airflow flows may be the region above, below, to the right, or to the left of the center position of the rear end 11 of the fuselage section 10, depending on the shape of the aircraft 100.

[0186] Therefore, it is only necessary to analyze the location of the region where slow airflow flows as viewed from the center position of the aft end 11 of the fuselage section 10 according to the shape of the aircraft 100, and determine the direction (YZ direction) in which to offset the center position of the intake port 45 accordingly. In other words, typically, the center position of the intake port 45 of the BLI propulsion section 40 should be offset from the center position of the aft end 11 of the fuselage section 10 in at least one of the vertical and width directions.

[0187] For example, as shown in FIG. 15, in a configuration in which the first BLI thruster 41a and the second BLI thruster 41b are aligned in the width direction, the center positions (see black circles) of the first air intake 45a of the first BLI thruster 41a and the second air intake 45b of the second BLI thruster 41b are offset from the center position (see cross marks) of the rear end portion 11 of the body section 10 in both the up-down direction and the width direction.

[0188] Furthermore, in this embodiment, the area of ​​the non-overlapping region where the projection plane when parallel light parallel to the axial direction (X-axis direction) is irradiated onto the body section 10 and the projection plane when parallel light is irradiated onto the air intake 45 do not overlap is set to less than 60% (the percentage by which the center position of the air intake 45 is offset downward). This allows slow-speed airflow to be appropriately taken in through the air intake 45, and enables the BLI propulsion section 40 to generate thrust more efficiently.

[0189] In this embodiment, when the width direction length of the intake port 45 of the BLI propulsion unit 40 is 2a and the area of ​​the intake port 45 is Sfan, AR=(2a) 2 The aspect ratio (AR) value, expressed as / Sfan (how horizontally long the intake port 45 is), is set to 1.3 or less. This allows slow airflow to be appropriately taken in through the intake port 45, enabling the BLI propulsion unit 40 to generate thrust more efficiently.

[0190] Furthermore, in this embodiment, when the BLI propulsion section 40 includes a first impeller 42a and a second impeller 42b aligned in the width direction, the rotation directions of the first impeller 42a and the second impeller 42b are reversed, and the rotation directions of the first impeller 42a and the second impeller 42b are each set to a rotation direction corresponding to inboard-up. This reduces the torque required of the motor 43 that drives the first impeller 42a and the second impeller 42b, thereby reducing the weight of the aircraft 100 and further improving fuel efficiency.

[0191] Furthermore, in this embodiment, the positions of the central axes of rotation of the first impeller 42a and the second impeller 42b are arranged above the center of the air intake 45 in the vertical direction, and are also arranged outside the center of the air intake 45 in the width direction. This allows the first impeller 42a and the second impeller 42b to efficiently capture the airflow that flows up into the air intake 45, and therefore allows the BLI propulsion unit 40 to generate thrust more efficiently.

[0192] Furthermore, in this embodiment, when parallel light parallel to the width direction is irradiated onto the fuselage section 10 and the landing section 50, the shape of the projection plane forms an angle of more than 10.5° between the axial direction (X-axis direction) and a tangent line connecting the contact point of the landing section 50 with the ground and the lowest point of the BLI propulsion section 40. This makes it possible to achieve both high propulsion performance and high takeoff performance.

[0193] In this embodiment, in the shape of the projection plane when parallel light parallel to the width direction is irradiated onto the fuselage section 10, the shape of the curve indicating the lower side at the rear side of the fuselage section 10 is twice differentiable and has an inflection point, and the intake port 45 is positioned after the inflection point in the axial direction (X-axis direction). This makes it possible to achieve both high propulsion performance and high takeoff performance.

[0194] Furthermore, in this embodiment, the intake port 45 of the BLI propulsion unit 40 is positioned in the axial direction (X-axis direction) after the position where the width of the body section 10 is 50% of the maximum width of the body section 10. This allows slow-speed airflow to be efficiently taken in through the intake port 45, and allows the BLI propulsion unit 40 to efficiently generate thrust.

[0195] Furthermore, in this embodiment, the intake port 45 of the BLI propulsion unit 40 is positioned in the axial direction after the position where the cross-sectional area perpendicular to the axial direction of the body section 10 is 25% of the maximum cross-sectional area. This allows slow-speed airflow to be efficiently taken in through the intake port 45, enabling the BLI propulsion unit 40 to efficiently generate thrust.

[0196] Furthermore, in this embodiment, in the cross section of the body section 10 and the cross section of the intake port 45 in a direction perpendicular to the front axial direction at the position where the intake port 45 is provided in the axial direction (X-axis direction), the cross section of the body section 10 and the cross section of the intake port 45 are non-overlapping. This allows the BLI propulsion section 40 to generate thrust more efficiently.

[0197] Furthermore, in this embodiment, the generator 37 of the main generator unit 30 is operated at an extracted torque of 90% or more and 100% or less of the maximum torque of the generator 37, regardless of the operating state (takeoff, cruising, etc.) of the aircraft 100. This makes it possible to ensure operation during cruising while preventing an increase in deadweight.

[0198] Furthermore, in this embodiment, when at least one of the conditions that the altitude of the aircraft 100 is equal to or lower than a predetermined altitude and the speed of the aircraft 100 is equal to or lower than a predetermined speed is satisfied, the power extracted from the generator 37 is limited to a predetermined value or lower. This makes it possible to reduce the probability of failure of the electric propulsion system when one of the main engines 31, 32 stops, and ensures the reliability of the aircraft 100.

[0199] Furthermore, in this embodiment, when the rotation speed of the engine shaft 38 of the main generator 30 is 60% or less of the maximum rotation speed of the engine shaft 38 at that altitude, the torque extracted from the generator is limited to 10% or less of the maximum value of the torque to be extracted. This makes it possible to eliminate the problem of the main generator 30 stopping unexpectedly during descent, for example.

[0200] In this embodiment, when the engine output of the main generator 30 is 60% or less of the maximum engine output at that altitude, the torque extracted from the generator is limited to 10% or less of the maximum extracted torque. This eliminates the problem of the main generator 30 stopping unexpectedly during descent, for example. [Explanation of symbols]

[0201] 10...Torso 20...Main wing 30...Main drive unit 40…BLI Promotion Department 42...impeller 45...Air intake 50...Accretion part 100...Aircraft

Claims

1. a body portion having a cylindrical shape that is long in an axial direction and short in a width direction and a vertical direction, a rear end portion on a rear side in the axial direction, and an outer diameter that gradually decreases toward the rear end portion on the rear side, wherein a center position of the rear end portion is located at an upper end of a maximum diameter of the body portion in the vertical direction; a BLI (Boundary Layer Ingestion) propulsion unit provided on the rear side of the fuselage unit and having an intake port, wherein the center position of the intake port is offset downward from the center position of the rear end portion in the vertical direction; An aircraft equipped with:

2. 10. The aircraft of claim 1, The center of the intake port is disposed between the center of the body and the center of the rear end in the up-down direction. aircraft.

3. 3. An aircraft according to claim 1 or 2, The BLI propulsion unit includes at least one impeller that is rotatable about an axis facing the axial direction, and the position of the central axis of rotation is located above the center position of the intake port in the vertical direction. aircraft.

4. An aircraft according to any one of claims 1 to 3, The aircraft further includes a landing section provided on the underside of the fuselage section, In the shape of a projection plane when the parallel light parallel to the width direction is irradiated onto the fuselage section and the landing section, the angle formed by a tangent line connecting the contact point of the landing section with the ground and the lowest point of the BLI propulsion section and the axial direction exceeds 10.5°. aircraft.

5. An aircraft according to any one of claims 1 to 4, In the shape of the projection plane when the body portion is irradiated with parallel light parallel to the width direction, the shape of the curve showing the lower side of the rear side of the body portion is twice differentiable and has an inflection point. aircraft.

6. 6. An aircraft according to claim 5, The intake port is disposed after the inflection point in the axial direction. aircraft.

7. An aircraft according to any one of claims 1 to 6, The intake port is disposed in the axial direction after a position where the width of the body portion is 50% of the maximum width of the body portion. aircraft.

8. a body section having a cylindrical shape that is long in the axial direction and short in the width direction and the vertical direction, a rear end portion on the rear side in the axial direction, and an outer diameter that gradually decreases toward the rear end portion on the rear side, the center position of the rear end portion being located at an upper end of the body section with the largest diameter in the vertical direction; and a BLI propulsion section having an air intake port provided on the rear side of the body section, the center position of the air intake port being offset downward from the center position of the rear end portion in the vertical direction. BLI Promotion Department.

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