Propulsion fan

Abstract

A propulsion fan and a drive system with reduced noise are disclosed. The propulsion fan includes a blade fan having a plurality of blades. The blades can include a double pin root design for fixing the blade fan to the hub and a shroud at the blade tip. The blades can include one or more knife edge seals protruding from the surface of the shroud.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 356,852, filed on June 29, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure generally relates to a propulsion fan and a drive system, and more particularly, to a tension - type blade fan having one or more knife - edge seals.

Background Art

[0003] (Description of Related Art) Conventional propulsion fans generally include an open rotor and a propeller. These types of propulsion fans have reached their acoustic limits. In conventional propellers, the blades are supported at one end, which limits the number of blades to five or less. To lower the frequency emitted by a conventional propeller to a band that is less perceptible to the human ear, the rotational speed of the fan has to be increased. However, since a conventional propeller is only supported by a one - end structure, it cannot be driven at a higher speed. Furthermore, since a conventional propulsion fan is supported only at one end, the angle of the fan blades may change as the blade fan rotates at high speed, and as a result, the sound heard by the human ear changes. As a result, noise pollution increases. Since a conventional propulsion fan incorporates a plurality of arranged propulsion fans, the noise pollution further increases.

[0004] Furthermore, the fan designs of conventional propulsion fans assume applications with medium to high fan pressure ratios (PR) (1.3 PR to 1.75 PR). Generally, the lower the fan PR, the lower the aspect ratio (AR) of the fan. As a result, high aspect ratio blades become high pressure ratio fans and are made of titanium (or a stronger material). For structural reasons, such conventional fan designs include one or two span shrouds to control the vibration modes of the fan blades. As a result, the performance of the fan is reduced (loss is about 1% with one span shroud and twice that with two). For example, the open tip clearances used in conventional fan designs are designed to rub against materials that are prone to wear over time due to maneuvers, hard landings, and erosion, further reducing the performance of the fan.

Summary of the Invention

[0005] A propulsion fan with reduced noise is disclosed. The propulsion fan includes a blade fan having a plurality of blades. The plurality of blades have an interlocking tip shroud design to increase the structural rigidity of the airfoil at high revolutions per minute (RPM) and to limit the angle of attack movement of the airfoil.

[0006] In one embodiment, the tips of the blade fan are tensioned by an interlocking tip design such that the pitch of the blades during thrust generation is substantially the same as the pitch of the blades at rest. Each blade includes a shroud segment configured to connect to the shroud segments of other blades. The connected shroud segments collectively form a tip shroud at the outer periphery of the blade fan and apply tension to the tips of the blades. By applying tension to the tips of the blades, the same shape and twist of the blades are maintained during both thrust generation and at rest, reducing the noise caused by changes in the angle of the blades.

[0007] In one embodiment, each blade can also include a plurality of knife-edge segments that protrude from the upper surface of the shroud segment of the blade. The knife-edge segments of each blade are configured to connect to the knife-edge segments of other blades. The connected knife-edge segments collectively form one or more knife-edge seals on the outer periphery of the tip shroud. The knife-edge seals improve the control of tip air leakage, improve the clearance-to-span ratio of the fan blades, and improve performance and retention.

[0008] In one embodiment, each blade includes a pin root structure for connecting the blade to the hub. The pin root structure can include a plurality of mounting tabs that are offset from each other. The mounting tabs of each blade are inserted into the hub and connected to the hub using a plurality of fasteners. Since there is an offset in the mounting tabs of each blade, when connecting a plurality of blades to the hub with a plurality of fasteners, a plurality of fasteners are used to connect each blade to the hub. By applying tension to the root of the blade, the same shape and twist of the blade can be maintained both during thrust generation and at rest, and the noise caused by changes in the blade angle can be reduced.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0010] The figures, and the following description, describe certain embodiments by way of example only. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods described herein can be used without departing from the principles described herein. Here, several embodiments are referred to in detail, and these examples are described in the accompanying drawings. Note that whenever similar or like reference numbers are used in the drawings, they can indicate similar or like functions.

[0011] Propulsion Fan and Drive System In one embodiment, a propulsion fan and a drive system are disclosed. Generally, the propulsion fan and the drive system are configured to generate thrust. The propulsion fan and the drive system can generate thrust for various applications, from an aircraft to a hand tool such as a leaf blower. However, the applications of the propulsion fan and the drive system are not limited to those described herein.

[0012] FIG. 1 is a perspective view of a propulsion fan 100 according to one embodiment. Generally, the propulsion fan 100 includes a plurality of components that collectively reduce the noise generated by the propulsion fan 100 during thrust generation. Thereby, the propulsion fan 100 reduces noise pollution. For example, the propulsion fan 100 includes a tension blade fan including a plurality of fan blades. By applying tension to the blade fan, the angle of the fan blade can be maintained substantially the same as when it is not operating (e.g., in a stationary state), even when the propulsion fan is generating maximum thrust. As a result, noise pollution is reduced and thrust efficiency is improved compared to conventional propulsion fans. The propulsion fan 100 reduces noise pollution on the premise that the angle of the fan blade is maintained within a predetermined allowable range. For example, the propulsion fan 100 emits noise of less than 65 dBA at 300 feet sideline / 5,000 lbf.

[0013] Figure 2A is a first exploded view of a propulsion fan 100 according to an embodiment, and Figure 2B is a second exploded view of the propulsion fan 100 according to an embodiment. As shown in Figures 2A and 2B, the propulsion fan 100 includes a plurality of different components. In one embodiment, the propulsion fan 100 includes a duct lip 201, a nose cone 203, a hub 205, a blade fan 209, a lock ring 210 (shown in Figures 8A - 8C), a tension ring 211, a motor 215, a body housing 217, a plurality of outer casings 213A and 213B, a stator 219, and a tail cone 221. Other embodiments of the propulsion fan 100 may include components other than those shown in Figures 2A and 2B. In one embodiment, a part of the duct lip 201, the outer casing 213, and the stator 219 (e.g., 219C) collectively form a circulation duct that houses the components of the propulsion fan, as shown in Figure 1.

[0014] Figures 3A, 3B, 3C, and 3D are respectively a perspective view, a front view, a side view, and a cross - sectional view of the duct lip 201 of the propulsion fan 100 according to an embodiment. In one embodiment, the duct lip 201 is configured to provide a clean air flow to the propulsion fan 100. In one embodiment, the duct lip 201 is configured to connect to the body housing 217. The duct lip 201 can include a plurality of mounting holes 223 on the rear surface of the duct lip 201, as shown in Figure 2B. As will be further described below, fasteners (e.g., nuts and bolts, rivets, etc.) are placed in the mounting holes 223 to connect the duct lip 201 to the first end 1001 of the body housing 217.

[0015] The duct lip 201 can be composed of a plurality of panels that collectively form the duct lip 201. For example, the duct lip 201 may include a first plurality of panels that collectively form the inner surface 309 of the duct lip 201 and a second plurality of panels that collectively form the outer surface 307 of the duct lip 201 such that air flows to the blade fan 209 at the hollow central portion. The first and second pluralities of panels may be connected to each other via various fastening means such as fasteners (e.g., screws, nuts, bolts) or via welding. The first and second pluralities of panels may be made of a metal such as aluminum or titanium, or a composite material such as carbon fiber. Alternatively, the duct lip 201 may be made of a single piece of material and may be, for example, 3D printed.

[0016] In one embodiment, the duct lip 201 includes a first end 303 (e.g., an inlet) and a second end 305 (e.g., an outlet). The first end 303 receives air and the air exits from the second end 305. As shown in FIG. 3C, the diameter of the first end 303 is smaller than the diameter of the second end 305, but in other embodiments they may be the same. The diameters of the first end 303 and the second end 305 of the duct lip 201 depend on the use of the propulsion fan 100. For example, the diameters of the first end 303 and the second end 305 of the duct lip 201 are larger for aircraft use compared to leaf blower use.

[0017] Figure 3D is a cross-sectional view of the duct lip 201 along the plane A-A' shown in Figure 3B according to one embodiment. As described above, the duct lip 201 includes an outer surface 307 and an inner surface 309. Both the outer surface 307 and the inner surface 309 extend from the first end 303 of the duct lip 201 towards the second end 305 of the duct lip 201. Air flows through the inner surface 309 of the duct lip 201. The curvature 311A of the inner surface 309 of the duct lip 201 and the curvature 311B of the outer surface 307 of the duct lip 301 are designed to balance various factors such as different conditions (e.g., flight conditions such as cruising, takeoff, landing, etc.) and Reynolds numbers. Those skilled in the art can adjust the pressure gradient according to the speed range and flight mode by adjusting the radius of the duct lip.

[0018] Figures 4A, 4B, 4C, and 4D respectively show a perspective view, a front view, a cross-sectional view, and a perspective view of a cross-section of the nose cone 203 of the propulsion fan 100 according to one embodiment. The nose cone 203 is configured to adjust the behavior of the oncoming airflow and reduce air resistance. Further, the nose cone 203 may be provided with an impeller for assisting in cooling the air mass flow without significantly affecting broadband noise or tonal noise.

[0019] In one embodiment, the nose cone 203 is configured to connect to the motor 215 with the hub 205 disposed between the nose cone 203 and the motor 215. The nose cone 203 can include a plurality of mounting holes on the rear surface of the nose cone 203 as shown in Figure 2B. Fasteners 207 (e.g., nuts and bolts, rivets, etc.) are disposed in the mounting holes to connect the nose cone 203 to the first end of the hub 205. As described later, the fasteners 207 extend through the hub 205 and are connected to the first end of the motor 215.

[0020] In one embodiment, the nose cone 203 is conical. However, the nose cone 203 may have a different shape in other embodiments. As shown in FIGS. 4A - 4D, the nose cone 203 includes an opening 403 (e.g., a hole) at a first end of the nose cone 203. When the blade fan 209 rotates, air is drawn through the opening 403 of the nose cone 203 to cool the motor 215. The inner diameter of the opening 403 of the nose cone 203 is determined by the secondary mass flow rate required to cool the internal components. One of ordinary skill in the art could derive this diameter given the thermal requirements of various electric motors and the air required to cool the electric motor under the most restrictive conditions (generally under maximum continuous operation).

[0021] FIG. 4C is a cross - sectional view of the nose cone 203 along the plane B - B' shown in FIG. 4B according to one embodiment. In one embodiment, the nose cone 203 is not solid and includes a cavity. For example, in one embodiment, the nose cone 203 forms an air flow path 405. The air flow path 405 extends from the opening 403 of the nose cone 203 to a plurality of openings 407 disposed on the circumference of a second end (e.g., the rear surface) of the nose cone 203. Air flows through the air flow path 405 from the opening 403 and exits through the plurality of openings 407 to cool the motor 215. In one embodiment, the air flow path 405 is formed between the outer surface 409 of the nose cone 203 and a protrusion 411 formed within the nose cone 211, as shown in FIGS. 4C and 4D.

[0022] In one embodiment, the protrusion 411 protrudes inwardly from the second end of the nose cone 203 towards the opening 403 of the nose cone 203. The protrusion 411 may have a shape similar to that of the nose cone 203. For example, the protrusion 411 is also conical. However, in other embodiments, the protrusion 411 may have a shape different from that of the nose cone 203.

[0023] Generally, the protrusion 411 has a size and shape adjusted according to the mass air flow rate for cooling the motor 215. In one embodiment, the protrusion 411 includes an air flow path 413 formed therethrough, whereby air flows from the opening 415 of the air flow path 413 to the opening 417 at the second end of the nose cone 203. In one embodiment, the center of the air flow path 413 is aligned with the center of the opening 403 of the nose cone 203.

[0024] Figures 5A and 5B are a front view and a side view, respectively, of the hub 205 of the propulsion fan 100 according to the first embodiment. The hub 205 is the central portion of the propulsion fan 100 and is disposed at the center of the blade fan 209, as further described below. In one embodiment, the hub 205 is configured to connect to the nose cone 203, the lock ring 210, and the motor 215.

[0025] As shown in FIGS. 5A-5C, the hub 205 according to one embodiment is cylindrical. The diameter of the first end 507 of the hub 205 coincides with the diameter of the second end of the nose cone 203 in one embodiment. The first end 507 (e.g., the front surface) of the hub 205 includes a plurality of mounting holes 501A-501F formed through the thickness of the hub 205. The positions of the mounting holes 501 are such that when the second end of the nose cone 203 is fitted to the first end 507 of the nose hub 205, the mounting holes 501 are aligned with the mounting holes of the nose cone 203. The fasteners 207 are configured to pass through the mounting holes 501A-501F and connect to the first end (e.g., the front surface) of the motor 215. For example, the fasteners 207 are screwed into the screw holes 225 at the first end of the motor 215.

[0026] In one embodiment, the hub 205 also includes a plurality of openings 503 that penetrate the thickness of the hub 205, such as openings 503A and 503B. The plurality of openings 503 have a shape and size that match (e.g., are the same as) the opening 407 behind the nose cone 203. The openings 503 are configured to be aligned with the opening 407 behind the nose cone 203 when the nose cone 203 and the hub 205 are fitted to each other. Accordingly, the air that exits the opening 407 of the nose cone 203 flows through the openings 503 included in the hub 205. In one embodiment, the plurality of openings 503 included in the hub have different sizes. For example, the opening 503A is smaller than the opening 503B.

[0027] In one embodiment, the hub 205 also includes an opening 505 that penetrates the thickness of the hub 205. The opening 505 is located at the center of the hub 205. In one embodiment, the center of the opening 205 is configured to be aligned with the center of the air flow path 413 of the nose cone 203. Accordingly, the air flow that exits the air flow path 413 of the nose cone 203 flows through the opening 505 of the hub 205 to cool the motor 215.

[0028] In one embodiment, the second end 511 of the hub 205 on the opposite side of the first end 507 includes a connection mechanism 509 on its outer periphery. The connection mechanism 509 is configured to connect the hub 205 to the locking ring 210. In one embodiment, the connection mechanism 509 is configured to screw the hub 205 into the locking ring 210. When the hub 205 is connected to the locking ring 210, the locking ring 210 surrounds the outer periphery of the hub 205. The motor 215 is configured to fit onto the outer surface of the second end 511 of the hub 211.

[0029] In one embodiment, the hub 205 includes an intermediate region 511 disposed between the first end 507 and the second end 511 of the hub 205. In one embodiment, the blade fan 209 is configured to be disposed on the circumference of the intermediate region 511, and the hub 205 is disposed through the center of the blade fan 209.

[0030] Figures 6A and 6B are a perspective view and a front view, respectively, of the blade fan 209 of the propulsion fan 100 according to the first embodiment. As shown in FIGS. 6A and 6B, the blade fan 209 includes a plurality of blades 601. The total number of blades 601 included in the blade fan 209 is significantly larger than the number of blades included in a conventional propulsion fan having 2 to 5 blades. In one embodiment, the blade fan 209 can include from 20 to a maximum of 100 to 150 blades 601 having a hub / tip ratio (H / t) of 0.3 to 0.5. However, the number of blades can be any number as long as it is 5 or more. Generally, the total number of blades 601 included in the blade fan 209 depends on the application. In one embodiment, the material of the blades of the multi-blade fan also depends on its application. The blades can be made of a metal such as aluminum or titanium, or a composite material such as carbon fiber.

[0031] In one embodiment, the blade fan 209 rotates at a low tip speed (about 300 to 450 feet per second) to reduce the noise of the entire blade. As described herein, the tension fan blade 209 enables more blades to be arranged within the limits of mechanical materials and pushes the noise into the ultrasonic band to achieve a low subsonic tip speed. Furthermore, because the number of blades 601 is large, the voice noise can be raised to an ultrasonic frequency exceeding the upper limit of the human audible range (for a general adult, 16,000 Hz or higher). Additionally, because the number of blades is large, the blade load is low, and the intensity of the collision between vortices, which causes broadband noise, is also reduced.

[0032] As shown in FIGS. 6A and 6B, a plurality of blades 601 are arranged to form an annular shape having a hollow center in which the hub 205 is disposed. Each blade 601 is arranged such that at least a part of the leading edge and the trailing edge of the blade 601 overlaps with an adjacent blade 601. For example, the leading edge of a certain blade overlaps with the trailing edge of the blade on the left side of that blade, and the trailing edge of a certain blade overlaps with the leading edge of the blade on the right side of that blade. By arranging the plurality of blades 601 to overlap each other, the robustness against the inflowing air flow is improved. This robustness can be adjusted in consideration of local aerodynamic effects and the Reynolds number effect that affects the laminar flow adhesion of the flow within and between the blades.

[0033] FIGS. 7A, 7B, 7C, and 7D are respectively a perspective view, a front view, a side view, and a top view of the blade 601 included in the blade fan 209 shown in FIGS. 6A and 6B according to the first embodiment. In one embodiment, each blade 601 includes a first locking end 605, a second locking end 603, and an airfoil portion 607 disposed between the first locking end 605 and the second locking end 603. The blade 601 may include features other than those described herein in other embodiments.

[0034] In one embodiment, the first locking end 605 is located at the tip of the blade 601. The first locking end 605 is inserted into the tension ring 211 to lock the blade 601 to the tension ring 211 so as to apply tension to the tip of the blade 601. By applying tension to the tip of the blade 601, the pitch (e.g., angle) of the tip of the blade 601 is substantially the same during thrust generation as well as when the propulsion fan 100 is stationary, thereby reducing noise pollution.

[0035] As shown in FIGS. 7A-7D, the first lock end 605 is rectangular with a chamfered edge, but may be of other shapes. In one embodiment, the first lock end 605 has a width and thickness greater than the width and thickness of the tip of the airfoil portion 607. However, in other embodiments, the first lock end 605 may have the same width as the tip of the blade 601 or may be narrower than that. Those skilled in the art can adjust the edge, chamfer, surface finish, beveling, etc. in consideration of local stress and strain due to tension.

[0036] In one embodiment, the second lock end 603 is located at the root of the blade 601. The second lock end 606 is configured to be inserted into the lock ring 210 and lock the blade 601 to the lock ring 210. By applying tension to the root of the blade 601, the pitch (e.g., angle) of the root of the blade 601 is substantially the same whether during thrust generation or at rest of the propulsion fan 100, thereby reducing noise pollution. As shown in FIGS. 7A-7D, the second lock end 603 has a plurality of different surfaces (e.g., a straight surface and a curved surface) to increase the surface area in contact with the lock ring 210 for the purpose of reducing blade deflection. In one embodiment, the second lock end 603 has a width wider than the root of the blade 601 and wider than the width of the first lock end 605. However, in other embodiments, the second lock end 603 may have the same width as the root of the blade 601 or may be narrower than that.

[0037] The airfoil portion 607 is disposed between the first locking end portion 605 and the second locking end portion 603. In one embodiment, the airfoil portion 607 includes a geometric twist 609 of the airfoil portion 607. The geometric twist 609 is a change in the angle of incidence of the airfoil portion measured with respect to the root of the blade 601. That is, due to the geometric twist 609, the airfoil portion 607 includes a plurality of different angles of incidence over the length of the airfoil portion 607. For example, the airfoil portion 607 may have a first angle of incidence on a first side of the geometric twist 609 (e.g., below the geometric twist 609 in FIGS. 7A-7C), and may have a second angle of incidence on a second side of the geometric twist 609 (e.g., above the geometric twist 609 in FIGS. 7A-7C).

[0038] As a result of the geometric twist 609, as shown in FIG. 7D, when viewed from the top view of the blade 601, the first locking end portion 605 and the second locking end portion 609 are offset from each other. In one embodiment, the geometric twist 609 begins at a portion of the airfoil portion 607 closer to the root than the tip of the blade 601. The geometric twist 609 between the root and tip chord may vary up to 45 degrees.

[0039] Referring to FIGS. 6A and 6B, in one embodiment, the blades 601 are arranged such that the second locking end portions 603 are parallel to each other around the circumference, thereby forming a hole at the center of the blade fan 209. As a result, the first locking end portions 605 are also arranged parallel to each other, and the airfoil portions 607 of each blade 601 overlap with another airfoil portion of an adjacent blade 601 due to the geometric twist 609 of the airfoil portion 607.

[0040] Figures 8A, 8B, and 8C are respectively a perspective view, a front view, and a side view of the locking ring 201 of the propulsion fan 100 according to one embodiment. Generally, the locking ring 210 is connected to the blade fan 209 and the hub 205 and is configured to apply beneficial tension to the root of the blade 601. Thus, the blades 601 of the blade fan 209 are tensioned both at the tip and at the root to maintain the angle of the blades 601 during operation. The locking ring 201 may be made of a metal such as aluminum or titanium, or a composite material such as carbon fiber.

[0041] The locking ring 210 includes a first end 801 and a second end 803. In one embodiment, the first end 801 has a diameter smaller than the diameter of the second end 803, thereby forming a conical shape. This shape is adjusted by the need for a primary internal flow (i.e., not a cooling flow) to the fan, and the boundary layer pressure gradient along the hub in the presence of the fan can also be considered. In one embodiment, the first end 801 of the locking ring 210 is configured to directly connect the blade fan 209 to the locking ring 210, whereby the blade fan 209 is locked to the locking ring 210. The first end 801 of the locking ring 210 includes a plurality of locking teeth 805. In one embodiment, the locking teeth 805 are protrusions extending from the body of the locking ring 210 at an angle with respect to a plane perpendicular to the second end 803 of the locking ring.

[0042] A plurality of slots 807 are formed between the locking teeth 805. For example, the slot 807 is formed between a pair of locking teeth including the locking tooth 805A and the locking tooth 805B. The slot 807 has a width and a depth that match the dimensions of the second locking end 603 of the blade fan 209. The slot 807 extends partially through the thickness of the locking ring 210, such as 3 / 4 of the thickness of the locking ring 210.

[0043] In one embodiment, each of the plurality of slots 807 is configured to connect to a corresponding one of the plurality of blades 601 of the blade fan 209. In particular, the second locking end 603 of each blade 601 is inserted into one of the slots 807 to fix the blade 601 to the locking ring 210 through the directional contact between the surface of the second locking end 603 and the locking teeth 805 forming the slot. In one embodiment, in order to further strengthen the connection between the blade 601 and the locking ring 210, a fastener such as an epoxy resin is also used at the second locking end 603 of each blade 601. By locking the second locking end 603 of the blade 601 to the locking ring 210, the pitch at the root of the blade 601 is maintained substantially the same as at rest even during thrust generation, thereby reducing the pitch change perceptible to the human ear, i.e., the audible noise emitted from the propulsion fan 100.

[0044] In one embodiment, the second end 803 of the locking ring 210 includes a connection mechanism 809 on its inner circumference. The connection mechanism 809 is configured, for example, to connect the locking ring 210 to the connection mechanism 509 of the hub 205. In one embodiment, the connection mechanism 809 is a thread that matches the thread of the connection mechanism 509 of the hub 205, whereby the hub 205 can be screwed into the locking ring 210. Since the motor 215 is connected to the hub 205, when the hub 205 rotates, the locking ring 210 and the blade fan 209 also rotate accordingly.

[0045] Figures 9A and 9B are a perspective view and a side view, respectively, of a tension ring 211 of a propulsion fan 100 according to an embodiment. The tension ring 211 is arranged on the outer periphery of a blade fan 209 and configured to be connected to the blade fan 209. More specifically, according to an embodiment, the tension ring 211 is configured to be connected to all first lock ends 605 of the blade fan 209. By locking the first lock end 605 of the blade 601 to the tension ring 211, the pitch of the tip of the blade 601 is maintained substantially the same as when stationary even during thrust generation, thereby reducing a pitch change perceptible to the human ear, that is, audible noise emitted from the propulsion fan 100. Thus, by applying pretension to the blade 601 using the tension ring 211, it is possible to reduce the efficiency reduction due to the tip clearance. In one embodiment, the tension ring 211 is made of a metal such as aluminum or titanium, or a composite material such as carbon fiber. However, in other embodiments, other materials may be used.

[0046] As shown in FIGS. 9A and 9B, the tension ring 211 includes a first end 903 and a second end 905. In one embodiment, the first end 903 has substantially the same diameter as the diameter of the second end 905. The body 909 of the tension ring 211 is arranged between the first end 903 and the second end 905.

[0047] In one embodiment, the body 909 of the tension ring 211 includes a plurality of openings (for example, slots) 907 penetrating through the entire thickness of the tension ring 211. Each opening 907 is configured to be connected to a first lock end 605 of one of the plurality of blades 601. Therefore, there is a one-to-one relationship between each opening 907 of the tension ring 211 and the blade 601. In one embodiment, in order to further strengthen the connection between the blade 601 and the tension ring 211, a fastener such as epoxy is also used at the first lock end 605 of each blade 601.

[0048] In one embodiment, the plurality of openings 907 are formed at an angle with respect to a plane perpendicular to the first end 903 or the second end 905. The angle formed by the openings 907 is consistent with the pitch of the first locking end 605 of the blade 601. The dimensions of the openings 907 are such that when the first locking end 605 is inserted into the opening 907 of the tension ring 211 and the first locking end 605 is in direct contact with the tension ring 211, the first locking end 605 is locked to the tension ring 211, and are substantially consistent with the dimensions of the first locking end 605.

[0049] Figures 10A, 10B, and 10C are a perspective view, a front view, and a side view, respectively, of an inner duct body housing 217 (hereinafter referred to as the "body housing") of a propulsion fan 100 according to one embodiment. The body housing 217 according to one embodiment is configured to house (e.g., partially surround) the components of the propulsion fan 100. For example, the blade fan 209, the hub 205, the tension ring 211, the lock ring 210, and the motor 215 are housed within the body housing 217 in one embodiment. In other embodiments, other components of the propulsion fan 100 may be housed within the body housing 217. In one embodiment, the body housing 217 is made of a metal such as aluminum or titanium, or a composite material such as carbon fiber. However, in different embodiments, other materials may be used.

[0050] In one embodiment, the body housing 217 is cylindrical and includes a first end 1001 (e.g., an inlet) and a second end 1003 (e.g., an outlet). In one embodiment, the first end 1001 has a diameter larger than the diameter of the second end 1003. The first end 1001 includes a plurality of mounting holes 1005 formed on the circumference of the first end 1001 of the body housing 217. In one embodiment, the first end 1001 of the body housing 217 is connected to the second end 305 of the duct lip 201 such that the mounting holes 223 of the duct lip 201 are aligned with the mounting holes 1005 of the body housing 217. As described above, the fastener 207 can be used to fix the duct lip 201 to the first end 1001 of the duct body housing 217.

[0051] In one embodiment, the second end portion 1003 of the main body housing 217 includes a plurality of mounting holes 1007 formed on the circumference of the second end portion 1003 of the main body housing 217. In one embodiment, the second end portion 1003 of the main body housing 217 is configured to be connected to the first end portion (e.g., the inlet) of the stator 219. When the second end portion 1003 of the main body housing 217 is connected to the first end portion of the stator 219, the mounting holes 1007 provided in the second end portion 1003 of the main body housing 217 are aligned with the mounting holes provided in the first end portion of the stator 219. A fastener (e.g., a nut, a bolt, a rivet) can be used to fix the second end portion 1003 of the main body housing 217 to the first end portion of the stator 219.

[0052] In one embodiment, the main body housing 217 includes a plurality of intermediate portions 1009 configured to accommodate different components of the propulsion fan. The plurality of intermediate portions 1009 includes a first intermediate portion 1009A extending from the first end portion 1001 and a second intermediate portion 1009B extending from the second end portion 1003. The intermediate portion 1009 of the main body housing 217 is disposed between the first end portion 1001 and the second end portion 1003 of the main body housing 217.

[0053] As shown in FIG. 10C, the first intermediate portion 1009A has a diameter different from the diameter of the second intermediate portion 1009B. For example, the diameter of the first intermediate portion 1000A is larger than the diameter of the second intermediate portion 1000B. Further, the first intermediate portion 1009A has a diameter smaller than the first end portion 1001, and the second intermediate portion 1009B has a diameter smaller than the second end portion 1003.

[0054] In one embodiment, the first intermediate portion 1009A is configured to accommodate the hub 205, the blade fan 209, the lock ring 210, and the tension ring 211. Since the tension ring 211 has the largest diameter among the components accommodated in the first intermediate portion 1009A, the diameter 1009A of the first intermediate portion 1009A is based on the diameter of the tension ring 211. In one embodiment, the diameter of the first intermediate portion 1009A is substantially the same as the diameter of the tension ring 211, whereby the tension ring 211 is firmly fixed within the first intermediate portion 1000A, for example, by press fitting.

[0055] In one embodiment, the second intermediate portion 1009B is configured to accommodate the motor 215 and a part of the stator 219. The length of the second intermediate portion 1009B is based on the length of the motor 215 and the length of a part of the stator 219 accommodated in the intermediate portion. The second intermediate portion 1000B has at least the same length as the motor 215 and a part of the stator 219 in order to accommodate the motor 215 and a part of the stator 219 in the second intermediate portion 1009B. In one embodiment, the diameter of the second intermediate portion 1009B is based on the mass air flow rate of the air entering and leaving the stator 219. Those skilled in the art would be able to adjust the diameter in order to induce an advantageous pressure gradient over a plurality of design speeds of interest for the purpose of minimizing flow separation or swirl. The internal cavity of the second intermediate portion 1009B can also be adjusted to reduce noise.

[0056] Figures 11A, 11B, 11C, and 11D are respectively a perspective view, a front view, a side view, and a cross-sectional view of the stator 219 of the propulsion fan 100 according to one embodiment. In one embodiment, the stator 219 is composed of a plurality of stator blades 219A, a motor housing 219B, and a stator housing 219C. The stator 219 may include components other than those shown in Figures 11A to 11D in other embodiments.

[0057] In one embodiment, the motor housing 219B is cylindrical and includes a first end portion 1101 and a second end portion 1103 as shown in FIG. 11D. FIG. 11D is a cross-sectional view of the stator 219 along the plane C-C' of FIG. 11B according to one embodiment. As shown in FIG. 11D, the motor housing 219B includes a cavity 1105 disposed between the first end portion 1101 and the second end portion 1103. The cavity 1105 may extend from the first end portion 1101 toward the second end portion 1103, but does not extend to the second end portion 1103. In one embodiment, the cavity 1105 is configured to accommodate the motor 215. That is, the motor 215 is disposed within the cavity 1105 of the motor housing 219B. Therefore, the shape and size of the cavity 1105 depend on the shape and size of the motor 215. Since the motor 215 is disposed within the cavity 1105 and the motor 215 is indirectly connected to the hub 205, the stator 219 also serves as a structural component that supports the hub 205 and other components of the thruster 100.

[0058] In one embodiment, the motor housing 219B includes a hole 1113 that passes through the center of the motor housing 219B as shown in FIGS. 11B and 11D. The diameter of the hole 1113 is smaller than the diameter of the motor 215 in order to prevent the motor 215 from falling through the hole 1113. The hole 1113 is disposed in the motor housing 219B to assist in heat dissipation and cools the motor 215.

[0059] Referring to FIG. 11B, the stator 219 includes a plurality of stator blades 219. The stator blade 219A extends radially from the motor housing 219B. That is, the root of each blade 219A is connected to the motor housing 219B, and the airfoil portion of the stator blade 219 extends outward away from the motor housing 219B. In one embodiment, each blade 219A extends away from the motor housing 219B at an angle measured with respect to a reference line that extends perpendicular to the point on the motor housing 219B from which the stator blade 219A extends.

[0060] In one embodiment, the stator blade 219 conducts heat from the motor 215. Since the blade 219 is in contact with the motor housing 219B that houses the motor 215, the air passing over the blade 219 dissipates the heat generated from the motor 215. In one embodiment, the arrangement of the blade 219 also reduces the noise generated by the blade fan 209 and controls the thrust generated by the propulsion fan 100. The number of blades of the stator blade 219 can be selected such that the harmonics of the stator cancel out the harmonics of the blade fan 209. In the case of a ultrasonic fan, since the Reynolds number becomes locally low along the blade, those skilled in the art will understand that the blade fan 209 may carry a plurality of blades 601 having a larger number (total amount) than the stator blade 219 as a noise countermeasure. In order to reduce the noise in a specific band, the number of blades may increase by 50% to 200%.

[0061] In one embodiment, the stator housing 219C is configured to house the stator blade 219 and the motor housing 219B. That is, the stator blade 219 is disposed within the stator housing 219C such that the stator housing 219C surrounds the blade 219. In one embodiment, the stator housing 219C includes a first end 1107 (e.g., an inlet) and a second end 1109 (e.g., an outlet). As shown in FIG. 11C, the first end 1107 has a diameter larger than the diameter of the second end 1109. Accordingly, the stator housing 219C may be conical in shape. However, the stator housing 219C may have other shapes in other embodiments.

[0062] Referring to FIG. 11D, in one embodiment, the tip of the blade 219A is in contact with the inner surface 1111 of the stator housing 219C. Accordingly, the stator blade 219A is stationary. By the blade 219A contacting the inner surface 1111 of the stator housing 219C, the position of each blade 219A is stationary.

[0063] Figures 12A, 12B, 12C, and 12D are respectively a perspective view, a front view, a side view, and a cross-sectional view of the tail cone 221 of the propulsion fan 100 according to one embodiment. In one embodiment, the tail cone 221 is configured to accurately vary the area of the stator housing 219C from which air exits the propulsion fan 100. The tail cone 221 may be made of a metal such as aluminum or titanium, or a composite material such as carbon fiber.

[0064] The tail cone 221 includes a first end 1201 (e.g., an inlet) and a second end 1203 (e.g., an outlet). In one embodiment, the first end 1201 has a diameter larger than the diameter of the second end 1203. In one embodiment, the diameter of the tail cone 221 varies over the length of the tail cone 221. As shown in FIG. 12C, the diameter of the tail cone 221 decreases from the first end 1201 toward the second end 1203 until it reaches an intermediate point 1205. From the intermediate point 1205 to the second end 1203, the diameter of the tail cone 221 is relatively constant.

[0065] In one embodiment, the first end 1201 of the tail cone 221 is configured to connect to the second end 1103 of the motor housing 219B of the stator 219. Accordingly, the diameter of the second end 1201 of the tail cone 221 substantially matches the diameter of the second end 1103 of the motor housing 219B of the stator 219. In one embodiment, the first end 1201 of the tail cone 221 includes a mounting surface 1209 that mates with (e.g., contacts) the second end 1103 of the motor housing 219B. The mounting surface 1209 can be attached to the motor housing 219B using, for example, fasteners. However, in other embodiments, other attachment mechanisms may be used.

[0066] FIG. 12D is a cross-sectional view of the tail cone 221 along the plane D-D' shown in FIG. 12B. In one embodiment, the tail cone 221 includes a cavity 1207 formed throughout the length of the tail cone 221 from a first end 1201 of the tail cone to a second end 1203 of the tail cone. The shape of the rear end of the tail cone 221 is determined by the secondary flow exhausted from the interior of the tail cone 221 in relation to the expansion of the jet airflow exiting the blade disk and / or the stator.

[0067] In one embodiment, the propulsion fan 100 includes a center hub drive motor 215. That is, in one embodiment, a single motor 215 is used to drive the propulsion fan 100. An example of a motor used for the propulsion fan 100 is an electric motor. However, in other embodiments, other types of motors such as gas motors or jet turbines can also be used for the propulsion fan 100. Generally, motors of different types and sizes can be used according to the application of the propulsion fan 100.

[0068] Multi-motor drive system In another embodiment, the propulsion fan 100 may be driven not only by the single motor 215 described above but also by a plurality of motors. FIGS. 13A, 13B, and 13C are respectively a perspective view, a front view, and a side view of a circumferential multi-motor drive system of the propulsion fan 100 according to one embodiment.

[0069] Instead of driving the thrust with a single motor 215, a plurality of auxiliary motors 1301A, 1301B, 1301C, 1301D are arranged in the main body housing 217 and drive the blade fan 209 via a ring gear 1303. The plurality of auxiliary motors 1303 may be electric motors in one embodiment. However, other types of motors can also be used.

[0070] In one embodiment, the ring gear 1303 may be connected to the tension ring 211. The auxiliary motor 1303 can replace the above-described motor 215 or can be used in combination with the motor 215. Due to the redundancy of the multi-motor, the propulsion fan 100 system can ensure excellent fault tolerance. For example, when there are four auxiliary motors 1303, even if one auxiliary motor stops, it becomes a level that can be almost ignored in the normal operation of the thruster. Even if another motor stops, it may be possible to ensure sufficient thrust by simply operating the remaining auxiliary motors 1303 at overspeed.

[0071] As shown in FIGS. 13A to 13C, the auxiliary motors 1301A to 1301D are not concentrated and arranged on the hub 205 of the thruster 100, but radially spread on the circumference of the thruster 100. Each end of the auxiliary motor 1301 includes a gear connected to the ring gear 1303. The radial arrangement does not need to be limited to equal angular intervals. For example, the fan is driven by three motors, and these motors are arranged biased to the lower side of the duct. Furthermore, the thruster does not need the stator 219 to support the hub 205 to support the motor 215 housed in the center, but can utilize the duct structure itself to support the motor and its load. This not only reduces weight and resistance, but also reduces broadband noise generated by the interaction of the stator flow. In one embodiment, the auxiliary motor 1303 can operate more at a high rotation speed of 20,000 RPM and generate an excellent specific output of 15 kW / kg compared to a heavier low-speed motor with a specific output of 5 kW / kg. The auxiliary motor 1303 integrally drives the ring gear 1303 to eliminate gear slip (axial and radial). This low bearing reduces gear noise.

[0072] FIG. 14 shows still another embodiment of the circumferential drive system of the propulsion fan 100 according to another embodiment. The embodiment shown in FIG. 14 is the same as the example described in FIG. 13. However, the drive system shown in FIG. 14 omits the central drive motor 215 and depends on the auxiliary motor 1303 for thrust generation.

[0073] Propellers arranged in plurality Figs. 15A and 15B are respectively a front view and a perspective view of a plurality of arranged propulsion fans 1500 according to an embodiment. In one embodiment, the plurality of arranged propulsion fans 1500 includes a plurality of propulsion fans 100 arranged horizontally so as to form a row of propulsion fans. In the example shown in Figs. 15A and 15B, the plurality of arranged propulsion fans 1500 includes a first propulsion fan 100A, a second propulsion fan 100B, and a third propulsion fan 100C. Each of the plurality of propulsion fans 100A to 100C includes a propulsion fan structure described herein. Although the plurality of arranged propulsion fans 1500 includes three propulsion fans 100, any number of propulsion fans more than two can be included in this plurality arrangement.

[0074] Fig. 16 shows an application example of a plurality of arranged propulsion fans 1600 according to an embodiment. As shown in Fig. 16, the plurality of arranged propulsion fans 1600 includes a plurality of propulsion fans as described herein. In one embodiment, the plurality of arranged propulsion fans 1600 is incorporated into the ducted wing 1603 of an aircraft 1605. A plurality of propulsion fans can be combined horizontally to form the ducted wing 1603. The ducted wing 1603 may be in the shape of a multi-leaf wing that passively generates lift and can be added with, for example, stagger, sweep, taper, dihedral angle, etc. of the multi-leaf wing as required. The total number and size of the propulsion fans included in the array 1600 depend on the requirements of the aircraft, such as the number of passengers boarding the aircraft, speed requirements, and altitude requirements of the aircraft 1605.

[0075] By arranging the propulsion fans continuously, several controls and thrust vectoring possibilities are expanded. The thrust can be varied between the respective propulsion fans 100 to induce yawing, rolling, and pitching moments. The relative pitch difference in the spanwise direction between the propulsion fans can be utilized to increase the climb speed and the descent speed. This can be further enhanced by additional control surfaces installed at the trailing edge.

[0076] The combinations of the duct in the span direction are suitable for integration along the wing or as the compound wing itself. The continuous array can be arranged and extended as a compound wing with sweep, stagger, dihedral, and taper according to the needs of the system. The choice of whether to integrate the continuously arranged propulsion fans as a complete compound wing depends not only on the relative size of the propulsion fans but also on the amount of thrust (thrust minus drag) required.

[0077] Use of the Propulsion Fan Figures 17A, 17B, and 17C are respectively a front view, a side view, and a top view of a hover drone 1700 according to an embodiment. The hover drone 1700 includes a plurality of arranged propulsion fans including a first propulsion fan 100A, a second propulsion fan 100B, and a third propulsion fan 100C. Although the hover drone 1700 only includes three propulsion fans, the hover drone 1700 can include more or fewer propulsion fans than the number shown in FIGS. 17A-17C.

[0078] The hover drone 1700 is a quiet electric vertical takeoff and landing (VTOL) drone and includes an array of propulsion fans as described herein. The hover drone 1700 can be used at close range such as in an urban environment. The hover drone 1700 has a 360-degree camera and sensors and can be used, for example, for hovering flight for more than 15 minutes. In one example, the propulsion fans 100A-100C can each have a diameter of 1 ft with an enhanced disk loading of 6.4 lb / ft 2 . The maximum takeoff weight of the hover drone 1700 is 30 pounds.

[0079] In the example shown in FIG. 17A, each of the propulsion fans 100A-100C includes a hub-driven centrally located motor 215, similar to the aforementioned auxiliary motor 1301. However, the hover drone 1700 may omit the auxiliary motor 1301 and include only the centrally located motor 215, or omit the centrally located motor 215 and include only the auxiliary motor 1301.

[0080] Figures 18A, 18B, and 18C are, respectively, a front view, a side view, and a top view of a cinema drone 1800 including a plurality of arranged propulsion fans according to an embodiment. Generally, the cinema drone 1800 is a quiet ducted fan VTOL drone used in movie shooting. The cinema drone 1800 may be all-electric or hybrid. The cinema drone 1800 can have, for example, a gimbal payload (e.g., a main camera) of up to 35 pounds. The cinema drone 1800 may have secondary cameras or sensors. The cinema drone 1800 can be used when the hovering flight time exceeds 20 minutes. The cinema drone may, in one embodiment, have a maximum cruise speed exceeding 50 miles per hour.

[0081] In one embodiment, the cinema drone 1800 is a compound aircraft and has a neutral stagger. As shown in FIG. 18A, the cinema drone 1800 includes a first wing 1801 and a second wing 1803. The first wing 1801 and the second wing 1803 each include a plurality of arranged propulsion fans. For example, the plurality of arranged propulsion fans included in the wing 1801 include propulsion fans 100A, 100B, 100C, 100D, while the plurality of arranged propulsion fans included in the wing 1803 include propulsion fans 100E, 100F, 100G, 100H. Therefore, half of the propulsion fans are on the first side of the fuselage 1805, and the other half of the propulsion fans are on the second side of the fuselage 1805. In the example shown in FIGS. 18A-18C, the plurality of arranged thrusters include eight thrusters, but any number of thrusters may be used.

[0082] The wings 1801 and 1803 of the cinema drone 1800 shown in FIGS. 18A-18C have an angled sweep formed between the two wings facing forward of the fuselage 1805. In the example shown in FIGS. 18-18C, the wings 1801 and 1803 can have a 20-degree dihedral angle and a 30-degree sweep angle. However, in different embodiments, other angles may be used.

[0083] In one embodiment, the cinema drone 1800 shown in FIGS. 18A to 18C has, as an example, a maximum takeoff weight of 75 pounds and a target maximum payload weight of 30 pounds. Each propulsion fan 100 can have a fan diameter of 1 ft with an enhanced disk loading of, for example, 6.0 lb / ft 2 . The fuselage 1805 of the cinema drone 1800 may be 5.5 ft long and 0.6 ft wide. For example, the wingspan of the cinema drone 1800 is 8.8 ft, the wing area is 17.4 ft 2 , and the wing loading may be 4.3 lb / ft 2 .

[0084] FIGS. 19A, 19B, and 19C are respectively a front view, a side view, and a top view of a transporter 1900 including a plurality of arranged propulsion fans according to one embodiment. The transporter 1900 may optionally be a manned VTOL aircraft. The transporter 1900 may be hybrid or fully electric. The transporter 1900 can have a flight endurance of 20 to 60 nautical miles at an operating altitude of, for example, 1,000 to 2,000 feet and a cruising speed of 130 to 250 knots.

[0085] In one embodiment, the transporter 1900 is a compound aircraft and has a slightly negative stagger. The transporter 1900 includes a first wing 1901 and a second wing 1903. An angle is formed between the wing 1901 and the wing 1903 toward the front of the fuselage 1905. In the example shown in FIGS. 19A to 19C, the dihedral angle of the wing may be 5 degrees and the sweep of the wing may be -25 degrees. However, in different embodiments, other angles may be used.

[0086] In one embodiment, a plurality of arranged propulsion fans are integrated with the wing 1901 and the wing 1903. The plurality of arranged first propulsion fans are on the first side of the fuselage 1905 and are incorporated into the wing 1901, and the plurality of arranged second propulsion fans are on the second side of the fuselage 1905 and are incorporated into the wing 1903. For example, the plurality of arranged propulsion fans included in the wing 1901 include the propulsion fans 100A, 100B, 100C, 100D, while the plurality of arranged propulsion fans included in the wing 1903 include the propulsion fans 100E, 100F, 100G, 100H. Therefore, half of the propulsion fans are on the first side of the fuselage 1905, and the other half of the propulsion fans are on the second side of the fuselage 1905. In the example shown in FIGS. 19A to 19C, the plurality of arranged thrusters include eight propulsion fans, but any number of propulsion fans may be used.

[0087] In one embodiment, the transporter 1900, as an example, has a maximum takeoff weight of 1000 pounds and a target maximum payload weight of 220 pounds. Each propulsion fan 100 can have a fan diameter of 3 ft with an enhanced disk loading of 6.0 lb / ft 2 . The fuselage 1905 of the transporter 1900 may be 9.2 ft in length and 3.75 ft in width. The wingspan of the transporter 1900 is 28.7 ft, the wing area is 106.3 ft 2 , and the wing loading is 9.4 lb / ft 2 .

[0088] FIGS. 20A, 20B, and 20C are respectively a front view, a side view, and a top view of a vertical takeoff and landing (VTOL) aircraft 2000 including a plurality of arranged propulsion fans according to one embodiment. The VTOL aircraft 2000 may optionally be a manned VTOL aircraft. The VTOL aircraft 2000 may be hybrid or fully electric. The VTOL aircraft 2000 can have a flight endurance of 20 to 400 nautical miles at an operating altitude of 1,000 to 2,000 feet and a cruising speed of 130 to 250 knots. In one embodiment, the VTOL aircraft 2000 is capable of hovering.

[0089] In the example shown in FIGS. 20A - 20C, the VTOL aircraft 2000 is a compound aircraft and has a slightly negative stagger. The VTOL aircraft 2000 includes a first wing 2001 and a second wing 2003. In one embodiment, an angle is formed between the wing 2001 and the wing 2003 towards the front of the fuselage 2005. The wing 2001 and the wing 2003 can have a dihedral angle of 5 degrees and a sweep angle of -25 degrees. However, in different embodiments, other angles may be used.

[0090] In one embodiment, a plurality of arranged propulsion fans are integrated into the wings 2001 and 2003. The plurality of arranged first propulsion fans are on the first side of the fuselage 2005 and are incorporated into the wing 2001, and the plurality of arranged second propulsion fans are on the second side of the fuselage 2005 and are incorporated into the wing 2003. For example, the plurality of arranged propulsion fans included in the wing 2001 include propulsion fans 100A, 100B, 100C, 100D, while the plurality of arranged propulsion fans included in the wing 2003 include propulsion fans 100E, 100F, 100G, 100H. Therefore, half of the propulsion fans are on the first side of the fuselage 2005, and the other half of the propulsion fans are on the second side of the fuselage 2005. In the example shown in FIGS. 20A - 20C, the plurality of arranged thrusters include eight propulsion fans, but any number of propulsion fans may be used.

[0091] As an example, the VTOL aircraft 2000 has a maximum takeoff weight of 5,000 pounds and a target maximum payload weight of 1,000 pounds (e.g., 3 - 4 passengers). Each propulsion fan 100 can have a fan diameter of 5 ft with an enhanced disk loading of 11.0 lb / ft 2 . The fuselage 2005 of the VTOL aircraft 2000 can have a length of, for example, 24.7 ft and a width of 5 ft. The VTOL aircraft 2000 can have, for example, a wingspan of 49 ft, a wing area of 300 ft 2 , and a wing loading of 16.7 lb / ft 2 .

[0092] Figures 21A, 21B, and 21C are respectively a front view, a side view, and a top view of a delivery drone 2100 including a plurality of arranged propulsion fans according to an embodiment. The delivery drone 2100 has a 360-degree camera and sensors and can be used for hovering flight for more than 20 minutes. In one embodiment, the maximum cruising speed of the delivery drone 2100 may exceed 50 miles per hour.

[0093] The delivery drone 2100 is an example of an electric tail sitter VTOL drone configured to accommodate cargo inside. In the illustrated example, the delivery drone 2100 is a compound aircraft and has a neutral stagger. The delivery drone 2100 includes, in one embodiment, a first wing 2101 and a second wing 2103 having an angular sweep formed between two wings toward the rear of the fuselage 2105.

[0094] In one embodiment, a plurality of arranged propulsion fans are integrated into the wings 2101 and 2103. The plurality of arranged first propulsion fans are on the first side of the fuselage 2105 and are incorporated into the wing 2101, and the plurality of arranged second propulsion fans are on the second side of the fuselage 2105 and are incorporated into the wing 2103. For example, the plurality of arranged propulsion fans included in the wing 2101 include propulsion fans 100A, 100B, and 100C, while the plurality of arranged propulsion fans included in the wing 2103 include propulsion fans 100D, 100E, and 100F. Therefore, half of the propulsion fans are on the first side of the fuselage 2105, and the other half of the propulsion fans are on the second side of the fuselage 2105. In the example shown in Figures 21A - 21C, the plurality of arranged thrusters includes six propulsion fans, but any number of propulsion fans may be used.

[0095] As an example, the delivery drone 2100 has a maximum takeoff weight of 55 pounds and a target maximum payload weight of 5.5 pounds. Each propulsion fan 100 is 6.0 lb / ft 2It can have a 1 ft fan diameter with an enhanced disk load. The fuselage 2105 of the delivery drone 2100 may be 6.7 ft long and 1.3 ft wide. For example, the wingspan of the delivery drone 2100 is 8.8 ft, the wing area is 21.9 ft 2 , and the wing loading may be 2.5 lb / ft 2 .

[0096] Free blade Since the propulsion fan 100 described in this specification has a high-speed capacity of 150 miles per hour or more, it is desirable to improve the propulsion efficiency by either blade angle variability or mass flow rate throttling. As described above, the propulsion fan 100 includes a significantly larger number of blades than conventional propellers. However, implementing a general variable pitch propeller mechanism would be an excessive burden from the perspective of mechanical complexity.

[0097] In one embodiment, an array of propulsion fans as described above is incorporated into an aircraft using a free wing blade structure. The free wing blade structure can be implemented in any of the aircraft described above, for example, in FIGS. 17 - 21. The free wing blade is a propulsion fan that can rotate freely along the radial axis because the mass balance is achieved in front of the aerodynamic center of each blade. That is, the blade fan 209 can rotate freely along the radial axis because the mass balance is achieved in front of the aerodynamic center of each blade. With the free wing blade, by combining airfoil design, wing mass balance, and wing pivot, the wing can pivot freely while self-trimming to a zero pitching moment with a constant CL under all flight conditions.

[0098] The combination of the free blade structure and the propulsive fan 100 constructs a passive system that varies the angle of attack (AoA) of the blade while keeping the blade load constant. Since the electric motor can operate with high efficiency over a wide range of rotational speeds, this may bring a unique synergistic effect to the electric motor-driven propulsive fan 100. The electric motor can be operated to increase or decrease the radial flow velocity among different inflow velocities, and the blade "floats" and adjusts the AoA to maintain the same lift coefficient (CL). This ability may also provide the value of reducing noise as a method to avoid blade stall where the noise increases when the flight conditions and turbulence levels are different.

[0099] There are many advantages to using free blades. For example, the free blade balances the pitch so that it always has an AoA near L / Dmax CL (usually 0.5 - 1.0) by adding the mass of the leading-edge blade. As a result, the AoA of the blade always matches the inflow and the flow does not separate. Furthermore, since the propulsive fan 100 is rim-driven, it is possible to balance the mass when the inner hub region is empty, enabling the lightest mass balance counterweight to be mounted in front of the blade (without being exposed to the airflow). Thereby, the propulsive fan 100 can vary the rotational speed by about ~50% during different flight segments and can always bring the blade closer to the optimal angle of advance ratio. Different from turbines and IC engines, since the electric motor exhibits high efficiency over a wide rotational range, there are particular advantages to using free blades in combination with the electric motor. Therefore, while turbines and IC engines need to operate at a constant rotational speed for a certain output, the electric motor does not. Thereby, the propulsor can vary the rotational speed by about ~50% during different flight segments and can always bring the blade closer to the optimal angle of advance ratio. Finally, the free blade may also enable more extensive VTOL integration due to the wider AoA adjustment range and the need for thrust.

[0100] Circulation duct control In one embodiment, the circulation control mechanism is disposed in the duct lip 201. The circulation control mechanism is configured to eject air toward the duct lip 201. By introducing air into the duct lip 201, the suction amount at the duct lip 201 increases. In one embodiment, an electric motor combined with a centrifugal or axial flow compressor is incorporated into the remaining area within the duct to increase the circulation control injection and / or suction at the duct lip 201. By applying distributed electric propulsion (DEP) to the circulation control injection within the duct lip 201, the static thrust and low-speed thrust can be enhanced with lower power than applying additional power to the thruster. By this internal application of DEP, the aerodynamic integration advantages are maximized in both the propulsion fan 100 and the aircraft integration level. Applying circulation control at the duct lip 201, for example, increases the static thrust by up to 40% at the same fan output.

[0101] In one embodiment, an emergency power ram air turbine with a high PR and intake flow rate required a high circulation control jet injection flow rate (i.e., a jet close to sonic noise). A quiet low flow rate jet (~300 ft / sec) can be used and a small internal duct electric centrifugal blower can be used as the power source.

[0102] Slower circulation control jets may have a similar impact in terms of enhancing the thruster's thrust, considering that the PR and the static duct inflow velocity are much lower. The effectiveness of circulation control is a function of Vjet / Vintake. Another interesting aspect of applying circulation control injection within the duct lip is the avoidance of duct lip separation within the duct at high angles of attack (i.e., during transition). This is an important consideration for ducted eVTOLs. This is because when the intake flow separates at the duct lip, oscillating flow is generated by the fan blades, resulting in periodic blade loading and a significant increase in noise.

[0103] Within the duct lip 201, by applying circulation control at an injection velocity of approximately 300 ft / sec, the suction force of the duct lip can be increased to about 75% of the total static thrust. Blowing air onto the duct lip 201 effectively imparts aerodynamic shape morphing to the duct lip, further entraining the surrounding air. When injection is applied, the incoming air will (apparently) touch a much larger bellmouth duct lip than desired in the static state. However, the actual inlet of the bellmouth duct causes a large resistance during cruise. The circulation control injection within the duct can be turned off during cruise flight when the injection is relatively ineffective. A compact high-speed centrifugal blower operates at a speed that raises the blade band to ultrasonic frequencies for internal injection. Circulation control injection is most effective with a high nozzle injection velocity (a velocity close to the speed of sound is optimal), but the nozzle injection of the present invention is designed with a low injection velocity to achieve low noise (the injection sound varies with the tenth power of the nozzle injection velocity). The purpose of applying injection at the duct leading edge is to maximize the incoming swirl angle and prevent stall of the leading edge duct lip.

[0104] In one embodiment, the circulation control duct can be applied to the duct lip 201 of any of the aircraft embodiments described herein.

[0105] A blade fan having mounting pin roots, tip shrouds, and knife-edge seals In one embodiment, the blade fan for use with the propulsion fan 100 described above includes blades having pin roots for attaching the blades to the hub, rather than the lock ends described above with respect to FIGS. 7A, 7B, and 7C. FIGS. 22A, 22B, and 22C are respectively a front view, a side view, and a top view of a blade 2200 having a double pin-hole type root according to a second embodiment. FIGS. 23A, 23B, and 23C are respectively a perspective view of a blade 2200 having a double pin root, a perspective view of a shroud segment 2207 of the blade 2200, and a perspective view of the double pin root of the blade 2200 according to the second embodiment.

[0106] In one embodiment, each blade 2200 includes a first end 2201, a second end 2203 located on the side opposite to the first end 2201, and an airfoil portion 2205 between the first end 2201 and the second end 2203 of the blade 2200. The blade 2200 may include features other than those described herein in other embodiments. The first end 2201 is located at the tip of the blade 2200.

[0107] In one embodiment, the first end 2201 of each blade 2200 includes a shroud segment (e.g., a shroud portion) 2207. Each shroud segment 2207 of the blade 2200 is configured to be connected to a plurality of shroud segments 2207 of other blades 2200 included in the blade fan. The shroud segments 2207 interlock with each other to form an interlocking tip shroud as a whole. The tip shroud is arranged along the circumference of the blade fan, as will be described in more detail below.

[0108] By interlocking the first end 2201 (e.g., the tip) of the blade 2200 using the shroud segment 2207, the first end 2201 of the blade 2200 is tensioned such that the pitch of the first end 2201 of the blade 2200 during thrust generation is substantially the same as the pitch of the first end 2201 of the blade 2200 at rest, thereby reducing the noise caused by the change in the angle of the blade 2200. Thus, the blade 2200 does not require a locking ring 211 for applying tension to the tip of the blade 2200, as described in the embodiment of FIG. 7, by the interlocking shroud segment 2207.

[0109] In one embodiment, each shroud segment 2207 is integrated with the blade 2200 that includes the shroud segment 2207. The shroud segment 2207 can extend from an end of the airfoil portion 2205 of the blade 2200 that is farthest from the second end 2203 of the blade 2200. The shroud segment 2207 has a width that is wider than the width of the end of the airfoil portion 2205. In one embodiment, in the top view of the shroud segment 2207 shown in FIG. 22C, the shroud segment 2207 is quadrilateral (e.g., parallelogram, rectangle, square). The shroud segment 2207 also has a curvature on the top and bottom surfaces of the shroud segment 2207, as shown in FIGS. 22A and 22B. The shroud segment 2207 curves to form a circular tip shroud around the circumference of the blade fan when the shroud segments 2207 of the blade 2200 are interlocked.

[0110] In one embodiment, each shroud segment 2207 includes a connection mechanism for connecting the shroud segment 2207 of the blade 2200 to another shroud segment 2207 of another blade 2200. In one embodiment, the connection mechanism includes a protrusion 2209 on a first side of the shroud segment 2207 and a recess 2210 on a second side of the shroud segment 2207 that is opposite the first side of the shroud segment 2207. In one embodiment, the second side is parallel to the first side of the shroud segment 2207. There are no protrusions 2209 and recesses 2210 on the remaining sides of the shroud segment 2209.

[0111] Generally, the protrusion 2209 of a given shroud segment 2207 is configured to be inserted into the recess 2210 of another shroud segment 2207, and the recess 2211 of a given shroud segment 2207 is configured to receive the protrusion 2209 of another shroud segment 2207 to fix the shroud segments 2207 to each other. For example, the protrusion 2209 of the shroud segment 2207 of the first blade 2200 is configured to be inserted into the recess 2210 of the second shroud segment 2207 of the second blade 2200. The protrusion 2209 contacts a part of the second shroud segment 2207 that constitutes the recess 2210 of the second shroud segment, whereby the second side of the shroud segment 2207 of the first blade 2200 contacts the first side of the shroud segment 2207 of the second blade 2200. Similarly, the recess 2210 of the shroud segment 2207 of the first blade 2200 is configured to receive the protrusion 2209 of the shroud segment 2207 of the third blade 2200, whereby the protrusion 2209 comes into contact with a part of the first blade 2200's shroud segment 2207 that constitutes the recess 2210 of the first shroud segment. As a result, the second side of the shroud segment 2207 of the first blade contacts the first side of the shroud segment 2207 of the third blade 2200.

[0112] The second end 2203 of the blade 2200 is located at the root of the blade 2200. In one embodiment, the second end 2203 has a pin root design for fixing the second end 2203 of the blade 2200 to the hub 2700 shown in FIGS. 27A and 27B. In one embodiment, the blade 2200 includes a dual pin root design, as further described below.

[0113] In one embodiment, the second end portion 2203 includes a base portion 2211 and a plurality of mounting tabs 2213 (e.g., mounting portions, mounting pins, or pin bases) that extend vertically away from the lower surface of the base portion 2211. As shown in FIG. 23C, the base portion 2211 extends from the end portion of the airfoil portion 2205, i.e., the end portion farthest from the first end portion 2201 of the blade, such that a radius is formed between the surface of the base portion 2211 and the end portion of the airfoil portion 2205. The radius is formed to increase the strength of the blade 2200, thereby reducing the possibility of the blade cracking at the interface between the base portion 2211 and the airfoil portion 2205.

[0114] In one embodiment, the base portion 2211 is curved along the length of the base portion 2211. More specifically, the base portion 2211 includes a first end portion and a second end portion opposite the first end portion. The portion between the first end portion and the second end portion of the base portion 2211 is curved such that the first end portion and the second end portion of the base are offset (e.g., offset from each other). The base portion 2211 includes a connection surface 2219 (e.g., an edge) on the right side (e.g., left side) of the base and a connection surface 2219 on the second side (e.g., left side) of the base portion 2211, and each connection surface 2219 follows the curvature of the base portion 2211. The connection surface 2219 of the blade 2200 is configured to connect (e.g., contact) with the connection surface 2219 of another blade 2200. In one embodiment, as shown in FIG. 22B, the base portion 2211 is angled upward from the first end portion of the base portion 2211 toward the second end portion of the base portion 2211.

[0115] In one embodiment, the mounting tabs 2213 are configured to attach the blade 2200 to the hub 2700. The mounting tabs 2213 include a first mounting tab 2213A and a second mounting tab 2213B. In one embodiment, the first mounting tab 2213A extends vertically from the lower surface of the first end portion of the base portion 2211, and the second mounting tab 2213B extends vertically from the lower surface of the second end portion of the base portion 2211 opposite the first end portion of the base portion 2211.

[0116] Due to the curvature of the base 2211 from the first end of the base 2211 to the second end of the base 2211, the first mounting tab 2213A and the second mounting tab 2213B are offset from each other such that the second mounting tab 2213 is offset from the first mounting tab 2213 in the horizontal direction, as shown in the front view of the blade 2200 shown in FIG. 22A. In one embodiment, the width of the first mounting tab 2213A and the width of the second mounting tab 2213B are the same, and the offset corresponds to the matching width.

[0117] Furthermore, the length of the first mounting tab 2213A may be different from the length of the second mounting tab 2213B. In one embodiment, as shown in FIG. 22B, since the base 2211 is inclined upward from the first end of the base 2211 toward the second end of the base 2211, the length of the second mounting tab 2213B exceeds the length of the first mounting tab 2213A. Although the first mounting tab 2213A and the second mounting tab 2213B have different lengths, the lowermost point of the first mounting tab 2213A is aligned with the lowermost point of the second mounting tab 2213B, as shown in FIG. 22B.

[0118] Finally, as shown in the side view of the blade 2200 in FIG. 22B, the thicknesses of the mounting tabs 2213 may be different. In one embodiment, the thickness of the second mounting tab 2213B exceeds the thickness of the first mounting tab 2213A. However, in other embodiments, the first mounting tab 2213A and the second mounting tab 2213B have the same thickness.

[0119] In one embodiment, the mounting tabs 2213 each include a hole. For example, the first mounting tab 2213A includes a first hole 2215A, and the second mounting tab 2213B includes a second hole 2215B. The center of the first hole 2215A and the center of the second hole 2215B are offset from each other (offset) due to the displacement of the mounting tabs 2213, as shown in the front view of the blade 2200 in FIG. 22A.

[0120] As will be described in further detail below, a fastening mechanism, such as a fastening pin, is configured to be inserted into a first hole 2215A of one blade 2200 and further into a second hole 2215B of a second blade to connect the first and second blades to a hub 2700. By fixing the base of the blade 2200 with a double pin, the pitch (e.g., angle) of the base of the blade 2200 remains substantially the same during thrust generation or while the propulsion fan 100 is stationary, thereby reducing noise pollution.

[0121] The airfoil 2205 is disposed between a first end 2201 and a second end 2203 of the blade 2200. In one embodiment, the airfoil 2205 includes a geometric twist 2217 of the airfoil 2205. The geometric twist 2217 is a change in the angle of incidence of the airfoil measured with respect to the base of the blade 2200. That is, the airfoil 2205 includes a plurality of different angles of incidence over the length of the airfoil 2205 due to the geometric twist 2217. For example, the airfoil 2205 may have a first angle of incidence on a first side of the geometric twist 2217 (e.g., below the geometric twist 2217 in FIG. 22A), and may have a second angle of incidence on a second side of the geometric twist 2217 (e.g., above the geometric twist 2217 in FIG. 22A).

[0122] As a result of the geometric twist 2217, as shown in FIG. 22C, when viewed from a top view of the blade 2200, the first end 2201 and the second end 2203 are offset from each other. In one embodiment, the geometric twist 2217 begins at a portion of the airfoil 2205 closer to the second end 2203 (e.g., the base) than the first end 2201 (e.g., the tip) of the blade 2200. The geometric twist between the chord of the base and the tip may vary up to 45 degrees.

[0123] Figures 24A, 24B, and 24C are respectively a front view, a side view, and a perspective view of a plurality of interlocking blades 2200 each having a double pin root according to the second embodiment. As shown in FIGS. 24A - 24C, the plurality of blades 2200 includes a first blade 2200A, a second blade 2200B on a first side (e.g., the right side) of the first blade 2200A, and a third blade 2200C on a second side (e.g., the left side) of the first blade 2200A. The plurality of blades 2200 are interlocked such that the shroud segments 2207 of the blades 2200 mesh with each other to form a part of the tip shroud disposed on the circumference of the blade fan.

[0124] For example, the protrusion 2209 of the first shroud 2207A of the first blade 2200A is inserted into the recess 2210 of the second shroud 2207B of the second blade 2200B such that the edge on the first side of the first shroud 2207A contacts the edge on the second side of the second shroud 2207B, as shown in FIGS. 24A - 24C. Similarly, the protrusion 2209 of the third shroud 2207C of the third blade 2200C is inserted into the recess 2210 of the first shroud 2207A of the first blade 2200A such that the edge on the first side of the third shroud 2207C contacts the edge on the second side of the first shroud 2207A, as shown in FIGS. 24A - 24C.

[0125] Furthermore, the connection surfaces 2219 of the bases 2211 of each blade 2200 are in contact with the connection surfaces 2219 of the bases 2211 of adjacent blades 2200. For example, the connection surface 2219 on the right side of the base 2211 of the first blade 2200A is in contact with the connection surface 2219 on the left side of the base 2211 of the second blade 2200B. Similarly, the connection surface 2219 on the right side of the base 2211 of the third blade 2200C is in contact with the connection surface 2219 on the left side of the base 2211 of the first blade 2200A.

[0126] As described above, the mounting tabs 2213 of the predetermined blades 2200 are offset from each other. However, while the blades 2200 are connected to each other as shown in FIGS. 24A to 24C, the center of the first hole 2215A included in the first mounting tab 2213A of the predetermined blade 2200 is aligned with the center of the second hole 2215B included in the second mounting tab 2213B of another blade 2200. For example, the center of the first hole 2215A of the first mounting tab 2213A of the first blade 2200A is aligned with the center of the second hole 2215B of the second mounting tab 2213B of the third blade 2200C.

[0127] FIGS. 25A and 25B are a front view and a perspective view, respectively, of a shroud segment 2500 according to another embodiment. The shroud segment 2500 includes the features of the aforementioned shroud segment 2207. Further, in one embodiment, the shroud segment 2500 includes a plurality of knife-edge segments 2501. The knife-edge segments 2501 improve the control of end air leakage throughout the interlocking tip shroud and improve the fan blade clearance-to-span ratio, thereby improving performance and retention. That is, the knife-edge segments function as dams that reduce air leakage to the rear region of the blade fan.

[0128] In one embodiment, the plurality of knife-edge segments 2501 includes a first edge segment 2501A and a second edge segment 2501B. Each knife-edge segment 2501 is a protrusion that projects from the upper surface of the shroud segment 2500. In one embodiment, each knife-edge segment 2501 extends from the first side of the shroud segment 2500 having the protrusion 2209 to the second side of the shroud segment 2500 having the recess 2210. In the example shown in FIGS. 25A and 25B, the heights of the plurality of knife-edge segments 2501 are the same. That is, the first knife-edge segment 2501A has the same height as the second knife-edge segment 2501B.

[0129] In one embodiment, the side surfaces of each knife edge segment 2501 include a plurality of steps 2503 that increase the surface area of the shroud segment 2500 to further reduce air leakage across the blade fan. Accordingly, the side surfaces of each knife edge segment 2501 do not extend linearly from the upper surface of the shroud segment 2500 to the tip of the knife edge segment 2501. Rather, each side surface includes one or more steps for increasing the surface area of the shroud segment 2500. For example, the first knife edge segment 2501A includes a first step 2503A on a first side of the first knife edge segment 2501A and a second step 2503B on a second side of the first knife edge segment 2501A. Similarly, the second knife edge segment 2501B includes a first step 2503A on a first side of the second knife edge segment 2501B and a second step 2503B on a second side of the second knife edge segment 2501B.

[0130] In one embodiment, each knife edge segment 2503 has a plurality of connection surfaces 2505 configured to connect (e.g., contact) to the connection surfaces of other knife edge segments 2503. Each knife edge segment 2503 has a first connection surface 2505 on a first side of the shroud segment 2500 and a second connection surface 2505 on a second side of the shroud segment 2500. The connected knife edge segments 2503 collectively form one or more knife edge seals on the outer periphery of the tip shroud, as further described below.

[0131] Figure 26A is a front view of a shroud segment 2600 according to another embodiment. The shroud segment 2600 includes features similar to those of the shroud segment 2500 described in FIGS. 25A and 25B. For example, the shroud segment 2600 includes knife edge segments 2601A and 2601B each including steps 2503A and 2503B, respectively. However, the knife edge segment 2601 has different heights in the embodiment shown in FIG. 26A. For example, the first knife edge segment 2601A is slightly lower than the height of the second knife edge segment 2601B. The second knife edge segment 2601B is closer to the rear end of the blade fan than the first knife edge segment 2601B, further preventing unwanted air from propagating to the rear end of the blade fan.

[0132] Figure 26B is a front view of a shroud segment 2603 according to another embodiment. The shroud segment 2603 includes features similar to those of the shroud segment 2207 in addition to a single knife edge segment 2605. The single knife edge segment 2605 is aligned with the recess 2210 and the protrusion 2205 and, in one embodiment, extends from a first side of the shroud segment 2603 having the protrusion 2209 to a second side of the shroud segment 2603 having the recess 2210. However, in other embodiments, the single knife edge segment 2605 may be disposed at other positions along the upper surface of the shroud segment 2603.

[0133] FIGS. 27A and 27B are a front view and a side view, respectively, of a hub 2700 according to an embodiment. FIGS. 28A and 28B are a perspective view of a first end 2701 of the hub 2700 and a perspective view of a second end 2703 of the hub 2700, respectively, according to an embodiment. The hub 2700 is configured to be connected to the blade 2200 having the double pin root described above.

[0134] The hub 2700 is the central part of the blade fan and is arranged at the center of the blade fan as will be described later. In one embodiment, the hub 2700 is configured to connect to the nose cone 203 and the motor 215. Since the design of the hub 2700 is different from that of the aforementioned hub 205, the connection points of the nose cone 203 and the motor 215 have been changed according to the connection points of the hub 2700.

[0135] As shown in FIGS. 27A, 27B, 28A, and 28B, the hub 2700 is cylindrical in one embodiment. In one embodiment, the diameter of the first end 2701 of the hub 2700 is different from the diameter of the second end of the hub 2700. In one embodiment, the first end 2701 of the hub 2700 has a diameter that matches the diameter of the second end of the nose cone 203, while the second end 2703 of the hub 2700 has a diameter that matches the diameter of the motor 215.

[0136] The hub 2700 can include a raised portion 2707 as shown in FIGS. 28A and 28B. In one embodiment, the raised portion 2707 has a conical shape extending from the second end 2703 of the hub 2700 toward the first end 2701 of the hub 2700. As shown in FIG. 27B, the raised portion 2707 extends beyond the first end 2701 of the hub 2700. That is, the end of the raised portion 2707 protrudes beyond the first end 2701 of the hub 2700. As shown in FIG. 28B, the raised portion 2707 forms a cavity 2709 in the second end 2703 of the hub 2700, and at least a part of the motor 215 can be arranged therein. By arranging at least a part of the motor 215 within the cavity 2709 of the hub 2700, the overall length of the propulsion fan 100 can be shortened.

[0137] In one embodiment, the nose cone attachment point 2711 is located at the end of the raised portion 2707. The nose cone attachment point 2711 is configured to contact the nose cone 213. The nose cone attachment point 2711 may be cylindrical with a flat surface. In one embodiment, the nose cone attachment portion includes an opening 2705. The opening 2705 is located at the center of the hub 2700 and extends through the thickness of the hub 2700. The center of the opening 2705 is configured to be aligned with the center of the air flow path 413 of the nose cone 203. Therefore, the air flow exiting the air flow path 413 of the nose cone 203 flows through the opening 2705 of the hub 2700 to cool the motor 215.

[0138] In one embodiment, the motor attachment point 2713 is disposed within the cavity 2709. The motor attachment point 2713 is configured to contact the motor 215. The motor attachment point 2713 may be cylindrical with a flat surface. In one embodiment, the opening 2705 extends through the thickness of the motor attachment point 2713 as shown in FIG. 28B. The center of the opening 2705 of the motor attachment point 2713 is aligned with the center of the opening 2705 of the nose cone attachment point 2711.

[0139] In one embodiment, the diameter of the opening 2705 of the nose cone attachment point 2711 is different from the diameter of the opening 2705 of the motor attachment point 2713 as shown in FIGS. 28A and 28B. For example, the diameter of the opening 2705 of the motor attachment point 2713 is larger than the opening 2705 of the nose cone attachment point 2711. In one embodiment, the opening 2705 of the motor attachment point 2713 is configured to receive the output shaft of the motor 215. That is, the output shaft of the motor 215 is inserted into the opening 2705 of the motor attachment portion 2713. The output shaft of the motor 215 contacts the inner surface of the hub 2700 disposed within the opening 2705 to connect the output shaft of the motor 215 to the hub 2700. When the output shaft of the motor 215 rotates, the hub 2700 also rotates, thereby rotating the blade fan connected to the hub 2700.

[0140] The hub 2700 includes a plurality of blade mounting flanges 2715 configured to connect the blades 2200 to the hub 2700. In one embodiment, the plurality of blade mounting flanges 2715 includes a first blade mounting flange 2715A, a second blade mounting flange 2715B, a third blade mounting flange 2715C, and a fourth blade mounting flange 2715D. Each blade mounting flange 2715 is an annulus extending radially from the outer surface of the hub 2700. The blade mounting flanges 2715 are disposed on a portion of the outer surface of the hub between the first end 2701 and the second end 2703 of the hub.

[0141] In one embodiment, the blade mounting flanges 2715 are spaced apart from each other such that slots 2717 are formed between the blade mounting flanges 2615, as shown in FIG. 27B. The slots 2717 are formed along the circumference of the hub 2700. For example, as shown in FIG. 27B, a first slot 2717A is formed between the first blade mounting flange 2715A and the second blade mounting flange 2715B. Further, as shown in FIG. 27B, a second slot 2717B is formed between the third blade mounting flange 2715C and the fourth blade mounting flange 2715D. The width of the first slot 2717A matches the thickness of the first mounting tab 2213A, and the width of the second slot 2717B matches the thickness of the second mounting tab 2213B.

[0142] In one embodiment, the blade mounting flange 2715 includes a plurality of holes 2719. Each blade mounting flange 2715A, 2715B, 2715C, 2715D includes a set of holes 2719 respectively. For example, the first blade mounting flange 2715A includes a plurality of first holes 2719A that penetrate the entire thickness of the first blade mounting flange 2715A. The first holes 2719A are spaced apart from each other at uniform intervals on the circumference of the first blade mounting flange 2715A. The second blade mounting flange 2715B includes a plurality of second holes 2719B that penetrate the entire thickness of the second blade mounting flange 2715B. The second holes 2719B are spaced apart from each other at uniform intervals on the circumference of the second blade mounting flange 2715B. The third blade mounting flange 2615C includes a plurality of third holes 2719C that penetrate the entire thickness of the third blade mounting flange 2715C. The third holes 2719C are spaced apart from each other at uniform intervals on the circumference of the third blade mounting flange 2615C. Finally, the fourth blade mounting flange 2715D includes a plurality of fourth holes 2719D. Different from the first to third holes 2719A - 2719C, the fourth holes 2719D extend partially through the entire thickness of the fourth blade mounting flange 2715D. That is, the fourth holes 2719 do not penetrate the entire thickness of the fourth blade mounting flange 2715D. The fourth holes 2719D are spaced apart from each other at uniform intervals on the circumference of the fourth blade mounting flange 2715D.

[0143] In one embodiment, the centers of the first holes 2719A, the centers of the second holes 2719B, the centers of the third holes 2719C, and the centers of the fourth holes 2719B are aligned to collectively form a row of holes 2719 around the circumference of the hub 2700. That is, the center of each first hole 2719A is aligned with the center of the corresponding second hole 2179B, the center of the corresponding third hole 2719B, and the center of the corresponding fourth hole 2719D, where the first holes 2719A, the second holes 2719B, the third holes 2719C, and the third row 2719D are in the same row of holes. In one embodiment, the slots 2717 and holes 2719 of the hub 2700 are configured to connect the blade 2200 to the hub 2700 as further described below.

[0144] Figure 29 is a cross-sectional view of the hub 2700 along line A-A' of FIG. 27B according to an embodiment. As shown in FIG. 29, the hub 2700 includes a webbing 2900 that extends from the center of the hub 2700 toward the second end 2703 of the hub 2703. The thickness of the webbing 2900 varies along the length direction of the webbing 2900. As shown in FIG. 29, the end of the webbing 2900 at the second end 2703 of the hub 2700 is thicker than the middle portion of the webbing 2900, which is located between the second end 2703 of the hub and the end of the webbing 2900 extending from the central portion of the hub 2703. The end of the webbing 2900 at the second end of the hub 2700 includes a radius portion 2901 for enhancing the strength of the hub 2700.

[0145] FIGS. 30A, 30B, and 30C are respectively a front view, a side view, and a perspective view of a blade 2200 having a double pin-hole type root connected to the hub 2700 according to an embodiment. The mounting tab 2213 of the blade 2200 is configured to be inserted into the slot 2717 of the hub 2700. Specifically, the first mounting tab 2213A of the blade 2200 is inserted into a first slot 2171A formed between a first blade mounting flange 2715A and a second blade mounting flange 2715B. Further, the second mounting tab 2213B of the blade 2200 is inserted into a second slot 2171B formed between a third blade mounting flange 2715C and a fourth blade mounting flange 2715D.

[0146] When the first mounting tab 2213A is inserted into the first slot 2717A, the center of the first hole 2215A of the first mounting tab 2213A is aligned with the center of the hole 2719A of the first blade mounting flange 2715A and the center of the hole 2719B of the second blade mounting flange 2715A, where the centers of the holes 2719A and 2719B of the first and second blade mounting flanges 2715A are aligned with each other. Similarly, when the second mounting tab 2213B is inserted into the second slot 2717B, the center of the second hole 2215B of the second mounting tab 2213B is aligned with the center of the hole 2719C of the third blade mounting flange 2715C, and the centers of the holes 2719C and 2719D of the third and fourth blade mounting flanges 2715D, where the centers of the holes 2719C and 2719D of the third and fourth blade mounting flanges 2715D are aligned with each other. However, due to the offset between the first mounting tab 2213A and the second mounting tab 2213B, the centers of the holes 2719A and 2719B that align with the center of the first hole 2215A of the first mounting tab 2213A are offset from the centers of the holes 2719C and 2719D that align with the center of the second hole 2215B of the second mounting tab 2213B. This is because the holes 2719A and 2719B of the first and second blade mounting flanges 2715A and 2715B are in the first hole row, while the holes 2719B and 2719D of the third and fourth blade mounting flanges 2715C and 2715D are in the second hole row adjacent to the first hole row.

[0147] Figures 31A and 31B are a perspective view and a side view, respectively, of a plurality of interconnected blades 2200 having a double pin-hole type base connected to a hub 2700 according to an embodiment. As shown in FIGS. 31A and 31B, the plurality of blades 2200 are connected to the hub 2700 using a plurality of fasteners 3100. In one embodiment, the fasteners are of the pin type as shown in FIGS. 31A and 31B, although other types of fasteners may be used. When the plurality of blades 2200 are connected to the hub 2700, the shroud segments 2707 of the blades 2200 are interlocked, and the connection surfaces 2219 of the bases 2211 of the blades 2200 are interlocked as described in FIGS. 24A - 24C. When all of the plurality of blades are attached to the hub 2700, a circular tip shroud is formed at the second end of the blade 2200 as further described below.

[0148] Figures 32A and 32B are a detailed perspective view of region A of FIG. 31A as seen from the first end 2701 of the hub 2700 with the plurality of blades 2200 attached to the hub 2700 using the fasteners 3100, and a detailed perspective view of region A of FIG. 31A as seen from the second end 2703 of the hub 2700 with the plurality of blades 2200 attached to the hub 2700 using the fasteners 3100, respectively. FIG. 33 is a wireframe view of the first end 2701 of the hub 2700 with the plurality of blades 2200 attached to the hub 2700 using the fasteners 3100.

[0149] Due to the offset between the first mounting tab 2213A and the second mounting tab 2213B of each blade, a single fastener 3100 cannot connect the blade 2200 to the hub 2700. Rather, a plurality of fasteners 3100 (e.g., two) are required to connect each blade 2200 to the hub 2700. The plurality of fasteners 3100 for connecting each blade 2200 to the hub 2700 includes a first fastener and a second fastener.

[0150] The first fastener is inserted through the first hole 2215A of the first attachment tab 2213A of the blade 2200, which is disposed between the first hole of the blade attachment flange 2715A, the first hole of the second blade attachment flange 2715B aligned with the first hole of the first blade attachment flange 2715A, and the hub 2700 to fix the first attachment tab 2213A of the first blade to the hub 2700. The first fastener also passes through 4) the first hole of the third blade attachment flange 2715C aligned with the first holes of the first and second blade attachment flanges 2715B, and 5) the first hole of the fourth blade attachment flange 2715D, and 6) is inserted into the second attachment tab 2213B of the first adjacent blade 2200 disposed between the first hole of the third blade attachment flange 2715C and the first hole of the fourth blade attachment flange 2715D, where the first adjacent blade 2200 is directly adjacent to the blade 2200 on the first side (e.g., the left side).

[0151] Since the second attachment tab 2213B of the blade 2200 is offset from the first attachment tab 2213A of the blade 2200, the second attachment tab 2213B of the blade is not connected to the hub 2700 using the first fastener. Rather, the second attachment tab 2213B of the blade 2200 is connected to the hub 2700 using a second fastener. This second fastener is used to connect the first attachment tab 2213A of the second adjacent blade 2200 to the hub 2700 where the second adjacent blade 2200 is directly adjacent to the second side (e.g., the right side) of the blade 2200.

[0152] The second fastener is inserted through 1) a second hole of the first blade mounting flange 2715A that is directly adjacent to the first hole of the first blade mounting flange 2715A, 2) a second hole of the second blade mounting flange 2715B that is aligned with the second hole of the first blade mounting flange 2715A and is directly adjacent to the first hole of the second blade mounting flange 2715B, and 3) a first hole 2215A of a first mounting tab 2213A of the second adjacent blade 2200 to fix the first mounting tab 2213A of the second adjacent blade 2200 to the hub 2700, where the first hole 2215A is between the second hole of the first blade mounting flange 2715A and the second hole of the second blade mounting flange 2715B.

[0153] The second fastener also 4) passes through a first hole of the third blade mounting flange 2715C, 5) a first hole of the fourth blade mounting flange 2715D that is aligned with the first holes of the first and second blade mounting flanges 2715B, and 6) is inserted into a second mounting tab 2213B of the blade 2200 that is disposed between the first hole of the third blade mounting flange 2715C and the first hole of the fourth blade mounting flange 2715D to fix the blade to the hub 2700.

[0154] FIG. 33 is an example showing how the first blade 2200A is connected to the hub 2700, where the first fastener 3100B is inserted through the first hole 2719 of the first blade mounting flange 2715A, the first hole 2719 of the second blade mounting flange 2715B, and the first mounting tab 2213A of the first blade 2200A. However, the first fastener 3100B does not fix the second mounting tab 2213B of the first blade 2200A to the hub 2700. Rather, the second fastener 3100C is used to fix the second mounting tab 2213B of the first blade 2200A to the hub 2700.

[0155] The second fastener 3100C is inserted through the second hole 2719 of the first blade mounting flange 2715A directly adjacent to the first hole 2719 of the first blade mounting flange 2715A into which the first fastener 3100B is inserted, the second hole 2719 of the second blade mounting flange 2715B directly adjacent to the first hole 2719 of the second blade mounting flange 2715B into which the first fastener 3100B is inserted, and the first hole of the first mounting tab 2213A of the second blade 2200C adjacent to the first blade 2200A. Further, the second fastener 3100C is inserted through the second hole 2215B of the second mounting tab 2213B of the first blade 2200A which is inserted between the second hole 2719 of the third blade mounting flange 2715C, the second hole 2719 of the fourth blade mounting flange 2715D, and the second hole 2719 of the third blade mounting flange 2715C and the second hole 2719 of the fourth blade mounting flange 2715D to fix the first blade 2200A to the hub 2700. The remaining blades 2200 are attached to the hub 2700 in this way to form a blade fan with blades having double pin roots and tip shrouds.

[0156] Figures 34A, 34B, and 34C are a front view, a side view, and a perspective view, respectively, of a blade fan 3400 with a tip shroud 3401 for use in a propulsion fan 100 according to one embodiment. As described above, the tip shroud 3401 is collectively formed by connected shroud segments 2207. The blade fan 3400 includes blades 2200 having the double pin roots described above. The blade fan 3400 may include any number of blades 2200 depending on the application. In one embodiment, the material of the blades 2200 of the blade fan 3400 also depends on the type of application of the blade fan 3400. The blades 2200 may be made of a metal such as aluminum or titanium, or a composite material such as carbon fiber. It should be noted that in other embodiments, the blade fan can have double pin roots as described above without the tip shroud 3401.

[0157] As shown in FIGS. 34A, 34B, and 34C, a plurality of blades 2200 are arranged to form an annular shape having a hollow center in which the hub 2700 is disposed. Each blade 2200 is arranged such that at least a part of the leading edge and the trailing edge of the blade 2200 overlaps with an adjacent blade 2200. For example, the leading edge of a certain blade 2200 overlaps with the trailing edge of the blade 2200 on the left side of that blade 2200, and the trailing edge of a certain blade 2200 overlaps with the leading edge of the blade 2200 on the right side of that blade 2200. By arranging the plurality of blades 2200 to overlap each other, the robustness against the inflowing air flow is improved. This robustness can be adjusted in consideration of the local aerodynamic effects and the Reynolds number effect that affects the laminar flow attachment of the flow within and between the blades 2200.

[0158] As shown in FIGS. 34A, 34B, and 34C, the shroud segment 2207 of the blade 2200 is interlocked to apply tension to the tip of the blade 2200 such that the pitch of the blade 2200 during thrust generation changes. That is, by applying tension to the tip of the blade 2200, the same shape and twist of the blade can be maintained both during thrust generation and at rest, and the noise caused by the change in the blade angle can be reduced. The interlocking shroud segments 2207 of the blade 2200 collectively form a tip shroud that prevents or at least reduces blade vibration at the tip of the blade 2200. The reduction of blade vibration enables a high blade number, high aspect ratio fan rotor design.

[0159] Figures 35A, 35B, and 35C are, respectively, a front view, a side view, and a perspective view of the blade fan 3500 of the propulsion fan 100 according to one embodiment. The blade fan 3500 is similar to the blade fan 3400, except that it includes a plurality of knife edge seals 3501 formed on the outer periphery of the blade fan 3500 (for example, the outer periphery of the tip shroud). In one embodiment, the knife edge seal 3501 includes a first knife edge seal 3501A formed on the outer periphery of the blade fan 3500 and a second knife edge seal 3501B formed on the outer periphery of the blade fan 3500. In one embodiment, the first knife edge seal 3501A and the second knife edge seal 3501B are arranged at intervals from each other. The first knife edge seal 3501A is disposed closer to the first side of the blade fan 3500 configured to connect to the nose cone 203, while the second knife edge 3501B is disposed closer to the second side of the blade fan 3500 configured to connect to the motor 215.

[0160] The first knife edge seal 3501A includes a plurality of first knife edge segments 2501A extending from a plurality of shroud segments 2500 of the plurality of blades 2200. As described above, each of the first knife edge segments 2501A is configured to be connected to other first knife edge segments 2501A of the plurality of blades 2200. Similarly, the second knife edge 3501B includes a plurality of second knife edge segments 2501B extending from a plurality of shroud segments 2500 of the plurality of blades 2200 within the blade fan 3500. As described above, each of the second knife edge segments 2501B is configured to be connected to other second knife edge segments 2501B of the plurality of blades 2200. The mutually connected first knife edge segments 2501A form the first knife edge seal 3501A, and the mutually connected second knife edge segments 2501B form the second knife edge seal 3501B.

[0161] As described above with respect to FIGS. 25A and 25B, the blade fan 3500 shown in FIG. 35 has a first knife-edge seal 3501A and a second knife-edge seal 3501B having the same height because the first knife-edge segment 2501A and the second knife-edge segment 2501B have the same height. In an alternative embodiment, the first knife-edge seal 3501A and the second knife-edge seal 3501B may have different heights because the first knife-edge segment 2601A and the second knife-edge segment 2601B have different heights, as described above with respect to FIGS. 26A and 26B.

[0162] FIG. 36 is a perspective view of a blade fan 3600 of a propulsion fan 100 according to an embodiment. The blade fan 3600 is similar to the blade fan 3500 except that it includes a single knife-edge seal 3601 formed on the outer periphery of the blade fan 3600. The single knife-edge seal 3601 is formed along the center of the tip shroud surrounding the blade. The single knife-edge seal 3601 includes a plurality of single knife-edge segments 2605 (shown in FIG. 26B) of the plurality of blades 2200 included in the blade fan 3600. As described above, each of the single knife-edge segments 2605 is configured to be connected to other single knife-edge segments 2605 of the plurality of blades 2200.

[0163] Figures 37A and 37B are respectively a side view and a perspective view of a blade 3700 having a plurality of knife-edge segments and a single pin-hole type root according to the third embodiment. The blade 3700 includes a shroud segment 2500 having knife-edge segments 2501A and 2501B at a first end of the blade 3700, and a base 2211 at a second end of the blade 3700, and includes features similar to those of the blade 2200 described above with respect to FIGS. 22-23 and 25A and 25B. Therefore, for the sake of simplicity, the description of similar features is omitted. In contrast to the blade 2200, the blade 3700 includes a single mounting tab 3701 that extends vertically from the lower surface of the base 2211. The single mounting tab 3701 includes a hole 3703 for fixing the blade 3700 to the hub 2700.

[0164] Figure 38 is a front view of a blade fan 3800 of a propulsion fan 100 according to an embodiment. The blade fan 3800 includes features similar to those of the blade fan 3500, such as a plurality of blades 3700 and a plurality of knife-edge seals 3501 on the circumference of the blade fan 3800. Therefore, for the sake of simplicity, the description of similar features is omitted. In contrast to the blade fan 3800, each blade 3700 is attached to the hub 2700 using a single fastener 3100, while each of the blades 2200 included in the blade fan 3800 requires a plurality of fasteners 3100 to attach a single blade 2200 to the hub 2700 as described above.

[0165] References in the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic is included in at least one embodiment of the present disclosure. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily referring to the same embodiment.

[0166] Although the present disclosure has been specifically shown and described with reference to one embodiment and several alternative embodiments, it will be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention.

Claims

1. I am a fan of the promotion, A hub including a first end and a second end, Each of the plurality of blades includes a first end of the blade, a second end of the blade opposite to the first end, and an airfoil between the first end and the second end of the blade, wherein the second end of each blade includes a first mounting tab and a second mounting tab that are inserted into a hub, A plurality of fasteners configured to connect the plurality of blades to the hub, each fastener configured to connect the first mounting tab of the first blade among the plurality of blades and the second mounting tab of the second blade among the plurality of blades to the hub, the second blade being directly adjacent to the first blade and the plurality of fasteners, One or more seals protruding from the upper surfaces of the multiple first ends of the multiple blades, each of the one or more seals extending around the circumference of the blade fan, A nose cone connected to the first end of the hub, A motor connected to the second end of the hub, A propulsion fan comprising the blade fan, the hub, the nose cone, and a duct that at least partially surrounds the motor.

2. I'm a Blade fan, Hub and, Each of the plurality of blades includes a first end, a second end opposite the first end, and an airfoil portion between the first end and the second end, wherein the second end of each blade includes a first mounting tab and a second mounting tab inserted into a hub, the first mounting tab being radially offset from the second mounting tab, and the plurality of blades, A plurality of fasteners configured to connect the plurality of blades to the hub, each fastener of the plurality of fasteners configured to connect the first mounting tab of a first blade among the plurality of blades and the second mounting tab of a second blade among the plurality of blades to the hub, wherein the second blade is directly adjacent to the first blade and the first blade is radially offset from the second blade, the plurality of fasteners A blade fan in which the first mounting tab has a first length, and the second mounting tab has a second length, the second length being longer than the first length.

3. The aforementioned hub is A first end and a second end on the opposite side of the first end, A plurality of mounting flanges, located between the first end and the second end of the hub, projecting from the upper surface of the hub, comprising a first mounting flange and a second mounting flange toward the first end of the hub, and a third mounting flange and a fourth mounting flange toward the second end of the hub, A plurality of slots provided on the outer circumference of the hub, including a first slot provided between the first mounting flange and the second mounting flange, and a second slot provided between the third mounting flange and the fourth mounting flange, A hub comprising a plurality of holes provided in the plurality of mounting flanges, the plurality of holes including a first hole provided in the first mounting flange, a second hole provided in the second mounting flange, a third hole provided in the third mounting flange, and a fourth hole provided in the fourth mounting flange, The blade fan according to claim 2, wherein the center of each of the first holes is aligned with the center of the corresponding second hole, the center of the corresponding third hole, and the center of the corresponding fourth hole.

4. The blade fan according to claim 3, wherein the first mounting flange, the second mounting flange, the third mounting flange, and the fourth mounting flange each extend around the circumference of the hub.

5. The blade fan according to claim 3, wherein each of the plurality of blades has a first mounting tab that includes a first hole, each of the plurality of blades has a second mounting tab that includes a second hole, and the first and second mounting tabs of each of the plurality of blades are offset from each other such that the center of the first hole of the first mounting tab and the center of the second hole of the second mounting tab are misaligned.

6. The blade fan according to claim 5, wherein each of the plurality of blades has a first mounting tab inserted into the first slot, and each of the plurality of blades has a second mounting tab inserted into the second slot.

7. The center of the first hole in the first mounting tab of each of the plurality of blades is aligned with the center of one of the first holes in the first mounting flange and the center of one of the second holes in the second mounting flange, and the center of the second hole in the second mounting tab of each of the plurality of blades is aligned with the center of one of the third holes in the third mounting flange and the center of one of the fourth holes in the fourth mounting flange, The blade fan according to claim 6, wherein the center of one of the first holes and the center of one of the second holes, which are aligned with the first hole of the first mounting tab of the blade, are not aligned with the center of one of the third holes and the center of one of the fourth holes, which are aligned with the second hole of the second mounting tab of the blade.

8. The blade fan according to claim 6, wherein each of the plurality of fasteners is configured to be inserted into one of the first holes of the first mounting flange, one of the first holes of the first mounting tab of the corresponding blade, one of the second holes of the second mounting flange, one of the third holes of the third mounting flange, one of the second holes of the second mounting tab of another blade adjacent to the corresponding blade, and one of the fourth holes of the fourth mounting flange.

9. The second end of each of the plurality of blades is The blade fan according to claim 2, further comprising a base including a lower surface, a first connecting surface on a first side of the base, and a second connecting surface on a second side of the base opposite to the first side of the base, wherein the first mounting tab and the second mounting tab extend perpendicularly from the lower surface of the base away from the lower surface.

10. The blade fan according to claim 9, wherein the first connecting surface of each of the plurality of blades is connected to the second connecting surface of an adjacent first blade on the first side of the blade, and the second connecting surface of each of the plurality of blades is connected to the first connecting surface of an adjacent second blade on the second side of the blade.

11. Each of the plurality of blades has a first end comprising a shroud segment. The blade fan according to claim 2, wherein the shroud segment is wider than a portion of the airfoil connected to the shroud segment, and is configured to connect to other shroud segments of other blades among the plurality of blades.

12. The aforementioned blade fan is further provided with a tip shroud around its circumference, The blade fan according to claim 11, wherein the tip shroud comprises shroud segments on which the plurality of blades are interconnected.

13. The blade fan according to claim 12, wherein each of the plurality of blades' shroud segments includes a projection on a first side of the shroud segment and a recess on a second side of the shroud segment opposite to the first side of the shroud segment, the projection of each shroud segment being inserted into the recess of another shroud segment to connect the shroud segment to another shroud segment.

14. The first end of each of the plurality of blades is The blade fan according to claim 12, further comprising a plurality of projections extending from the upper surface of the shroud segment of the blade and extending away from the upper surface of the shroud segment.

15. The blade fan according to claim 14, wherein each of the plurality of protrusions is connected to other protrusions of other blades among the plurality of blades, and together along the upper surface of the tip shroud, a plurality of seals are collectively formed around the circumference of the blade fan.

16. The blade fan according to claim 14, wherein each of the plurality of protrusions of each shroud segment includes a side surface having one or more steps.

17. The blade fan according to claim 14, wherein each of the plurality of protrusions of each shroud segment includes a first protrusion having a first height and a second protrusion having the same second height as the first height.

18. The blade fan according to claim 14, wherein each of the plurality of protrusions of each shroud segment includes a first protrusion having a first height and a second protrusion having a second height different from the first height.

19. A hub including a first end and a second end on the opposite side of the first end, A plurality of blades comprising a plurality of first ends, a plurality of second ends facing the plurality of first ends and mounted on the circumference of the hub, and a plurality of airfoil portions between the plurality of first ends and the plurality of second ends, wherein the second end of each blade includes a first mounting tab and a second mounting tab, the first mounting tab being radially offset from the second mounting tab, and Equipped with, A blade fan in which the first mounting tab has a first length, and the second mounting tab has a second length, the second length being longer than the first length.

20. Each of the plurality of blades has a first end comprising a shroud segment. The blade fan according to claim 19, wherein the shroud segment is wider than a portion of the plurality of airfoils connected to the shroud segment, and is configured to be connected to other shroud segments of other blades among the plurality of blades.

21. The aforementioned blade fan is further provided with a tip shroud around its circumference, The blade fan according to claim 20, wherein the shroud is composed of shroud segments in which the plurality of blades are interconnected.

22. The blade fan according to claim 21, wherein each of the plurality of blades' shroud segments includes a projection on a first side of the shroud segment and a recess on a second side of the shroud segment opposite to the first side of the shroud segment, the projection of each shroud segment being inserted into the recess of another shroud segment to connect the shroud segment to another shroud segment.

23. The blade fan according to claim 21, further comprising one or more seals protruding from the upper surfaces of the plurality of first ends of the plurality of blades, wherein each of the one or more seals extends around the circumference of the blade fan and the one or more seals protrude from the upper surface of the shroud.

24. The first end of each of the plurality of blades is The blade further comprises a plurality of projections extending from the upper surface of the shroud segment and extending away from the upper surface of the shroud segment, The blade fan according to claim 20, wherein each of the plurality of protrusions of the shroud segment of the blade is configured to connect to other protrusions of other shroud segments of other blades among the plurality of blades, and to collectively form one or more seals.

25. The blade fan according to claim 24, wherein each of the plurality of protrusions of each shroud segment includes a side surface having one or more steps.

26. The blade fan according to claim 24, wherein each of the plurality of protrusions of each shroud segment includes a first protrusion having a first height and a second protrusion having the same second height as the first height.

27. The blade fan according to claim 24, wherein each of the plurality of protrusions of each shroud segment includes a first protrusion having a first height and a second protrusion having a second height different from the first height.

28. The aforementioned hub is A first end and a second end on the opposite side of the first end, A plurality of mounting flanges, located between the first end and the second end of the hub, projecting from the upper surface of the hub, comprising a first mounting flange and a second mounting flange toward the first end of the hub, and a third mounting flange and a fourth mounting flange toward the second end of the hub, A plurality of slots provided on the outer circumference of the hub, including a first slot provided between the first mounting flange and the second mounting flange, and a second slot provided between the third mounting flange and the fourth mounting flange, A hub comprising a plurality of holes provided in the plurality of mounting flanges, the plurality of holes including a first hole provided in the first mounting flange, a second hole provided in the second mounting flange, a third hole provided in the third mounting flange, and a fourth hole provided in the fourth mounting flange, The blade fan according to claim 19, wherein the center of each of the first holes is aligned with the center of the corresponding second hole, the center of the corresponding third hole, and the center of the corresponding fourth hole.

29. The blade fan according to claim 28, wherein the first mounting flange, the second mounting flange, the third mounting flange, and the fourth mounting flange each extend around the circumference of the hub.

30. The blade fan according to claim 28, wherein the first mounting tab and the second mounting tab are inserted into the hub, the first mounting tab of each of the plurality of blades includes a first hole, the second mounting tab of each of the plurality of blades includes a second hole, and the first mounting tab and the second mounting tab of each of the plurality of blades are offset from each other such that the center of the first hole of the first mounting tab and the center of the second hole of the second mounting tab are misaligned.

31. The blade fan according to claim 30, wherein each of the plurality of blades has a first mounting tab inserted into the first slot, and each of the plurality of blades has a second mounting tab inserted into the second slot.

32. The center of the first hole in the first mounting tab of each of the plurality of blades is aligned with the center of one of the first holes in the first mounting flange and the center of one of the second holes in the second mounting flange, and the center of the second hole in the second mounting tab of each of the plurality of blades is aligned with the center of one of the third holes in the third mounting flange and the center of one of the fourth holes in the fourth mounting flange, The blade fan according to claim 31, wherein the center of one of the first holes and the center of one of the second holes, which are aligned with the first hole of the first mounting tab of the blade, are not aligned with the center of one of the third holes and the center of one of the fourth holes, which are aligned with the second hole of the second mounting tab of the blade.

33. A plurality of fasteners configured to connect the plurality of blades to the hub, each fastener configured to connect the first mounting tab of a first blade among the plurality of blades and the second mounting tab of a second blade among the plurality of blades to the hub, the further comprising the plurality of fasteners, the second blade being directly adjacent to the first blade, The blade fan according to claim 31, wherein each of the plurality of fasteners is configured to be inserted into one of the first holes of the first mounting flange, one of the first holes of the first mounting tab of the corresponding blade, one of the second holes of the second mounting flange, one of the third holes of the third mounting flange, one of the second holes of the second mounting tab of another blade adjacent to the corresponding blade, and one of the fourth holes of the fourth mounting flange.

34. The second end of each of the plurality of blades is The blade fan according to claim 30, further comprising a base including a lower surface, a first connecting surface on a first side of the base, and a second connecting surface on a second side of the base opposite to the first side of the base, wherein the first mounting tab and the second mounting tab extend perpendicularly from the lower surface of the base away from the lower surface.

35. The blade fan according to claim 34, wherein the first connecting surface of each of the plurality of blades is connected to the second connecting surface of an adjacent first blade on the first side of the blade, and the second connecting surface of each of the plurality of blades is connected to the first connecting surface of an adjacent second blade on the second side of the blade.

36. A propulsion device configured to generate thrust, A hub including a first end and a second end on the opposite side of the first end, A blade fan comprising a plurality of blades arranged in an annular shape, each blade including a first end, a second end opposite the first end, and an airfoil portion between the first and second ends, wherein the second end of each blade comprises a first mounting tab and a second mounting tab inserted into a portion of the hub between the first and second ends of the hub, the first mounting tab having a first length, the second mounting tab having a second length, the second length being longer than the first length, and the first mounting tab being radially offset from the second mounting tab, A plurality of fasteners configured to connect the blade fan to the hub, wherein each fastener of the plurality of fasteners is configured to connect the first mounting tab of a corresponding blade from the plurality of blades to the hub, and the second mounting tab of another blade from the plurality of blades to the hub, the other blades being directly adjacent to the corresponding blades, and each blade of the plurality of blades being radially offset from one another, A nose cone connected to the first end of the hub, A motor connected to the second end of the hub, A propulsion system comprising the blade fan, the hub, the nose cone, and a duct that at least partially surrounds the motor.

37. A propulsion device configured to generate thrust, A hub including a first end and a second end on the opposite side of the first end, A blade fan comprising a plurality of blades including a plurality of first ends, a plurality of second ends facing the plurality of first ends and mounted on the circumference of the hub, and a plurality of blades including a plurality of airfoil sections disposed between the plurality of first ends and the plurality of second ends, One or more seals protruding from the upper surfaces of the plurality of first ends of the plurality of blades, wherein each of the one or more seals extends around the circumference of the blade fan, A nose cone connected to the first end of the hub, A motor connected to the second end of the hub, A propulsion system comprising the blade fan, the hub, the nose cone, and a duct that at least partially surrounds the motor.

Images