An adaptive morphing cross-medium vehicle propeller

Abstract

The application discloses a self-adaptive variable-configuration cross-medium vehicle propeller and belongs to the technical field of cross-medium vehicle propulsion. The existing fixed propeller cannot simultaneously consider cross-medium high-efficiency propulsion, and the composite power device structure is complex and heavy. Although the variable-body scheme can change the diameter, it cannot change the pitch synchronously. The application comprises a hub, a plurality of blades and a hinge assembly. The blades are sequentially provided with a root section, a stem section and a tip section along the span direction, and the tip section is reversely bent downward relative to the stem section. When unfolded, the stem section and the reversely bent tip section jointly propel; when folded, the stem section tends to be flat and has no propulsion, and only the reversely bent tip section propels, so that the effective working area of the blade is reduced, and the resistance moment is reduced. The application realizes self-adaptive switching of the configuration according to the medium density by synchronously folding the three-section blade and cooperating with the spatial inclination of the hinge shaft, has the advantages of light structure and high reliability, and solves the technical problems of low efficiency or blocked rotation heat burning of the traditional air propeller when running in the cross-medium.

Description

Technical Field

[0001] This invention relates to the field of cross-medium vehicle propulsion technology, specifically to an adaptive variable configuration cross-medium vehicle propeller, which is particularly suitable for cross-medium unmanned vehicles that need to operate alternately in air and water media with different densities. Background Technology

[0002] With the rapid development of cross-medium unmanned aerial vehicle technology, the same propulsion device needs to meet the dual requirements of air flight (low-density medium) and underwater navigation (high-density medium). However, water is about 800 times denser and about 50 times more viscous than air. The huge difference in physical properties between the two media brings fundamental technical challenges to the design of the propulsion system.

[0003] Traditional single fixed propellers cannot meet the working requirements of both media: if designed for aerial operation, the blade diameter and pitch are large, and the fluid resistance increases sharply when working in water, resulting in a significant decrease in the prime mover speed, excessive operating current and severe heat generation, and even the risk of burning out the prime mover; if designed for underwater operation, the blade diameter and pitch are small, and it cannot provide sufficient lift and thrust in the air, making it difficult for the vehicle to achieve normal flight.

[0004] To address these issues, various technical solutions have emerged in the existing technology. For example, some solutions employ a hybrid propulsion system, which equips the vehicle with separate air and underwater propulsion systems. While this can meet the propulsion requirements of both media, it results in complex structures and significantly increased weight, severely impacting the vehicle's payload and endurance. Another approach involves using foldable or variable-diameter propeller structures, utilizing hinges to deploy and retract the blades.

[0005] Chinese patent application CN121106654A discloses a transmedium variable-body propeller, whose blades are connected to a shaft via hinges. The blades are configured to switch between an unfolded state and a folded state when rotating around the hinge axis. In air, they unfold using centrifugal force, and in water, they fold using the viscous drag of the water. However, the blades in this design are a single-piece structure. When folded, the blade segments still propel as a whole, achieving only a change in blade diameter. It fails to achieve adaptive adjustment of the blade pitch according to the medium, leaving significant room for improvement in propulsion efficiency in both media. Furthermore, some designs employ active control mechanisms such as electric telescopic rods to simultaneously adjust diameter and pitch. However, active control schemes require sensors, controllers, drive motors, and corresponding power supply lines, resulting in complex structures, high costs, and increased potential failure points, reducing the reliability of the transmedium vehicle in complex environments.

[0006] Therefore, it is evident that there is currently a lack of a purely mechanical passive propeller solution that can achieve synchronous adaptive changes in diameter and pitch without requiring a complex electronic control mechanism. Summary of the Invention

[0007] (a) The technical problem that the invention aims to solve This invention addresses the aforementioned technical deficiencies of existing cross-medium vehicle propellers by providing an adaptive variable-configuration cross-medium vehicle propeller. This propeller, through a three-segment blade design and the coordination of spatial tilting of the hinge axis, achieves passive adaptive switching of blade configuration. Without any electronically controlled pitch mechanism or power switching device, it can automatically match the optimal propulsion configuration in media of different densities, while simultaneously achieving synchronous and coordinated changes in diameter and pitch.

[0008] (II) Technical Solution To achieve the above-mentioned objectives, the present invention provides the following technical solution: An adaptive variable configuration transmedium vehicle propeller includes a hub, a plurality of blades circumferentially distributed on the outside of the hub, and a hinge assembly connecting the blades and the hub.

[0009] The blade consists of a root section, a trunk section, and a tip section along its span from the inside out. The blade is hinged to the hinge assembly via the root section, and the tip section is bent downward relative to the trunk section to form a downward-curving tip.

[0010] During the rotation of the blades around the hinge axis, either retracting or unfolding: When the blades are deployed, the blade shaft and the downward-facing blade tip together generate propulsion. When the blades are folded, the blade shaft tends to be straight and loses its propulsive function. The downward-facing blade tip generates propulsive force independently. The radial working length and pitch angle of the blades decrease simultaneously, resulting in a reduction in the effective working area of ​​the blades.

[0011] Furthermore, the adaptive variable configuration transmedium propeller also includes a restoring linkage device connecting the blades and the hub. One end of the restoring linkage device is connected to the hub, and the other end is connected to the root of the blade. The force direction of the restoring linkage device is offset from the axis of the hinge shaft on the radial section of the hub, so as to generate a restoring torque that increases with the folding angle when the blade rotates. The restoring linkage device includes a return mechanism, a linkage, and a connector. The connector connects the blade and the return mechanism, and the linkage ensures that each blade moves synchronously under the combined action of the return mechanism and the medium resistance.

[0012] In a preferred embodiment, the hinge assembly includes a hinge seat fixedly connected to the propeller hub and a hinge shaft rotatably engaged within the hinge seat. The spatial axis of the hinge shaft is simultaneously inclined relative to both the radial and axial directions of the propeller hub, so that the propeller shaft tends to be straight when the propeller blade is folded.

[0013] In a preferred embodiment, the ratio of the spanwise length of the propeller tip section to the spanwise length of the propeller trunk section is 0.1 to 2, and the angle range of the downward dihedral angle between the propeller tip section and the propeller trunk section is 5° to 45°.

[0014] In a preferred embodiment, the radial offset distance between the force direction of the return linkage device and the axis of the hinge shaft on the radial section of the propeller hub is 1 / 5 to 1 / 2 of the width of the propeller root.

[0015] In a preferred embodiment, the propeller hub includes an upper hub plate and a lower hub plate that overlap each other. The upper hub plate and the lower hub plate are fixedly connected by a plurality of fasteners evenly distributed along the circumference, and the upper hub plate and the lower hub plate enclose a limiting cavity to accommodate the root of the propeller blade and the connecting parts. A limiting structure is provided in the limiting cavity to limit the maximum unfolded position and the maximum folded position of the propeller blade. Further, the limiting structure is adjustable, and the limiting structure is an adjustable limiting boss or a limiting stop. Preferably, the adjustment adopts a threaded mechanism.

[0016] In a preferred embodiment, the number of blades is two or more and they are evenly distributed along the circumference of the hub. The blades are made of carbon fiber composite material, and the return linkage device is a stainless steel or titanium alloy spring.

[0017] The present invention also provides a method for operating an adaptive variable configuration transmedium vehicle propeller, the propeller comprising a hub, a plurality of blades circumferentially distributed on the outside of the hub, and a hinge assembly connecting the blades and the hub, wherein the blades, along their spanwise direction from the inside to the outside, are sequentially a root section, a stem section, and a tip section, the tip section being bent downward relative to the stem section to form a downward-curving tip; the method of operation includes the following steps: When the propeller rotates in a low-density medium, the blades expand outward around the hinge axis under the action of centrifugal force. The propeller trunk and the lower counter-rotating tip together generate propulsion force. The radial working length of the blades increases and the pitch angle increases, that is, the effective working area of ​​the blades increases to a propulsion configuration that is adapted to the low-density medium. When the propeller rotates in a high-density medium, the blades fold inward around the hinge axis under the combined action of fluid resistance and the restoring torque of the return linkage device. The propeller shaft tends to be straight and loses its propulsive function. The lower anti-propeller tip generates propulsive force independently. The radial working length of the blades decreases and the pitch angle decreases, that is, the effective working area of ​​the blades is reduced to a propulsive configuration adapted to the high-density medium. During the rotation process of the blades unfolding and retracting, their radial working length and pitch angle change synchronously with the change of rotation position.

[0018] (III) Beneficial Effects Compared with the prior art, the present invention has the following advantages: True cross-medium versatility. This invention achieves simultaneous, linked changes in radial working length and pitch angle of the propeller blade under a single rotational degree of freedom through a three-segment structure design—root section, stem section, and tip section—in conjunction with the spatial tilt of the hinge axis. Compared to existing folding propellers (such as CN121106654A) that can only achieve diameter changes, the stem section of this invention tends to be straight and actively withdraws from propulsion when folded, with propulsion solely driven by the downward-facing tip. This "structural partitioning + functional division" design concept is completely absent in existing technologies. This invention can match better aerodynamic / hydrodynamic parameters in both media, significantly improving cross-medium propulsion efficiency. Simultaneously, this invention achieves "one propeller, two uses" through passive and timely adaptive control of a purely mechanical structure (comprehensive balancing of centrifugal force, fluid resistance, spring force, etc.), without any electronically controlled pitch mechanism or power switching device.

[0019] Effective protection of the power system. When operating in water, the propeller blades automatically fold, the propeller shaft becomes flat and loses its propulsive function, with only the downward-facing tip providing propulsion. This reduces the radial working length and pitch angle of the propeller blades, significantly decreasing the effective working area. This substantially reduces the drag torque of high-density media, such as water, on the propeller blades, allowing the prime mover to maintain normal operation within its rated speed range. This fundamentally solves the technical problems of traditional air-operated propellers experiencing a sharp drop in speed, excessive current, severe overheating, and even burnout of the prime mover after entering water, significantly improving the service life and operational safety of the prime mover and ESC.

[0020] Lightweight and highly reliable. Compared to multiple power systems or complex active pitch control mechanisms (such as electric telescopic boom drive schemes), this invention features a compact structure, fewer components, and lighter weight. Since it eliminates the need for sensors, controllers, drive motors, and power supply lines, its reliability in underwater high-pressure, high-humidity, and high-salt-spray environments is significantly superior to active control schemes, greatly improving the payload and endurance of cross-medium vehicles.

[0021] The advantages of purely mechanical passive control. This invention abandons the complex path of relying on electronic control systems for mode switching in existing technologies, and instead adopts a purely mechanical passive control method based on fluid dynamics principles. When the vehicle crosses the water-air interface, the propeller configuration switching is automatically triggered by changes in the external medium environment, without any active intervention from the vehicle's flight control system. It has a fast response speed, no delay, and no additional energy consumption. Attached Figure Description

[0022] Figure 1 This is an exploded view of the overall structure of the adaptive variable configuration transmedium vehicle propeller of the present invention.

[0023] Figure 2 This is a top view of the propeller of the present invention in its deployed state, showing the maximum working diameter of the blades when deployed.

[0024] Figure 3 This is a schematic diagram of the side cross-section of the propeller of the present invention in the deployed state, showing the posture of the propeller trunk and the downward-facing tip of the propeller being propelled together in the deployed state.

[0025] Figure 4 for Figure 3 A schematic diagram showing the angle of the blade section at 75% of the rotation radius of the propeller, illustrating the pitch angle in the deployed state.

[0026] Figure 5 This is a top view of the propeller of the present invention in a folded state, showing the working diameter of the propeller blades after they are retracted.

[0027] Figure 6 This is a schematic diagram of the side cross-section of the propeller of the present invention in a folded state, showing the posture in which the propeller shaft tends to be straight and the downward-facing propeller tip propels independently in the folded state.

[0028] Figure 7 for Figure 6 A schematic diagram showing the angle of the blade section at 75% of the rotation radius of the propeller, illustrating the pitch angle in the folded state.

[0029] Figure 8 This is a partially enlarged schematic diagram of the spatially tilted arrangement of the hinge shaft of the present invention, showing the spatial orientation of the hinge shaft tilted simultaneously relative to the radial and axial directions of the propeller hub.

[0030] Figure 9 This is a partial schematic diagram of the offset arrangement of the return linkage device of the present invention, showing the radial offset relationship between the force direction of the return linkage device and the hinge axis centerline.

[0031] Figure 10 This is an exploded view of the blade folding and hub split-layer structure of the present invention, showing the structural relationship between the upper hub plate, the lower hub plate and the limiting cavity between them.

[0032] Explanation of the main component markings in the attached drawings: 100-blade, 101-blade root section, 102-blade trunk section, 103-blade tip section; 200-blade hub, 201-upper hub plate, 202-lower hub plate, 300-fastener, 400-reset linkage device, 401-returner, 402-linker, 403-connector, 500-hinge assembly, 501-hinge seat, 502-hinge shaft, 600-limiting structure, 700-prime mover, α-blade downward reversal angle, β1-hinge shaft spatial tilt angle 1, β2-hinge shaft spatial tilt angle 2, D1-working diameter in deployed state, D2-working diameter in folded state, θ1-blade trunk pitch angle in deployed state, θ2-blade trunk pitch angle in folded state, O-hinge shaft center, F-force direction of the return linkage device, d-radial offset distance. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Example 1

[0034] The basic principles and working principles of this invention are as follows: Figure 1 As shown. The adaptive variable configuration transmedium vehicle propeller provided by the present invention includes a hub 200, a plurality of blades 100 circumferentially distributed on the outside of the hub 200, and a hinge assembly connecting the blades 100 and the hub 200.

[0035] The rotor hub 200 is used to mount the propeller as a whole onto the output shaft of the prime mover 700, transmitting the torque of the prime mover 700 to each blade 100. The rotor hub 200 can be made of metal materials (such as aluminum alloy, titanium alloy) or high-strength engineering composite materials, and its specific shape and size are determined according to the model of the prime mover and the overall layout of the aircraft.

[0036] like Figure 1 As shown, the blade 100 consists of a root section 101, a stem section 102, and a tip section 103 along its span from the inside to the outside. The blade 100 is hinged to the hinge assembly via the root section 101. The tip section 103 bends downward relative to the stem section 102 to form a downward-facing tip, which serves as the propulsion area after the blade is folded. It also reduces tip vortex intensity, lowers induced drag and vortex interference noise, and improves the aerodynamic stability of the rotor / propeller.

[0037] The hinge assembly 500 includes a hinge seat 501 fixedly connected to the rotor hub 200 and a hinge shaft 502 rotatably engaged within the hinge seat 501. The root section 101 of the blade 100 is rotatably connected to the hinge seat 501 via the hinge shaft 502, so that each blade 100 can rotate independently relative to the rotor hub 200 around the hinge shaft 501, thereby unfolding or retracting. Example 2

[0038] The blade has a three-section structure, as shown below. Figure 2 and Figure 3 As shown, the blade 100 consists of a root section 101, a stem section 102, and a tip section 103 along its radial direction from the inside to the outside.

[0039] The root section 101 is located at the innermost side of the blade 100 and is used to connect with the hinge assembly. The length of the root section 101 should ensure sufficient connection strength and rotational stiffness, and its specific length is determined according to the total length of the blade and the stress state.

[0040] The rotor stem section 102 is located in the middle of the rotor blade 100 and is the main load-bearing section of the rotor blade 100. In the deployed state, the rotor stem section 102 has a large radial length and a certain pitch angle, which can effectively propel the medium. The airfoil of the rotor stem section 102 can be a conventional airfoil suitable for low-speed aircraft (such as Clark Y, Eppler E193, etc.), or a special airfoil that combines hydrodynamic and aerodynamic characteristics can be designed according to the special requirements of cross-medium operation.

[0041] The blade tip 103 is located on the outermost side of the blade 100 and bends downward relative to the blade shaft 102 to form a downward-curving blade tip. The downward-curving design of the blade tip 103 ensures that even when the blade shaft 102 becomes flat and loses its propulsive function in the folded state, the downward-curving blade tip can still maintain a certain effective angle of attack and generate propulsion force on the medium.

[0042] like Figure 3 and Figure 4 As shown, the downward flare angle α between the propeller tip section 103 and the propeller trunk section 102 is preferably in the range of 5° to 45°. When α is less than 5°, the effective angle of attack of the downward flare propeller tip in the folded state is insufficient, making it difficult to generate sufficient thrust; when α is greater than 45°, the bending of the propeller tip section 103 is too severe, which may lead to a decrease in structural strength and an increase in flow separation. Those skilled in the art can select an appropriate α value within the above range according to the specific design conditions of the aircraft.

[0043] like Figure 3 As shown, the ratio of the spanwise length of the propeller tip section 103 to the spanwise length of the propeller trunk section 102 is preferably 0.1 to 2. This ratio determines the size of the effective working area when the folded, downward-reversing propeller tip propels alone. When this ratio is small (e.g., 0.1 to 0.5), the spanwise length of the downward-reversing propeller tip is short, and the propulsion area after folding is small, which is suitable for working conditions where there is a large difference between high and low density media, such as entering or exiting water at low altitudes; when this ratio is large (e.g., 1 to 2), the spanwise length of the downward-reversing propeller tip is long, and the propulsion area after folding is relatively large, which is suitable for working conditions where there is a small difference between high and low density media or where higher underwater propulsion is required. Example 3

[0044] Responding linkage device such as Figure 9 As shown, the present invention also includes a return linkage device 400 connecting the blade 100 and the hub 200. One end of the return linkage device 400 is connected to the hub 200, and the other end is connected to the root of the blade 100 (root section 101).

[0045] The force direction F of the return linkage 400 deviates from the axis O of the hinge shaft 502 on the radial section of the rotor hub 200. That is, there is a certain radial offset distance d between the line of action of the force of the return linkage 400 and the rotation center of the hinge shaft 502 (see...). Figure 9 This offset arrangement causes the force applied by the return linkage device 400 to generate a certain restoring torque at the root of the blade 100, and this restoring torque changes in a positively correlated (monotonically increasing) manner with the increase of the folding angle of the blade 100.

[0046] The radial offset distance d of the return linkage device 400 is preferably 1 / 5 to 1 / 2 of the root width W of the blade 100. When d is within this range, the return linkage device 400 can provide sufficient return torque to ensure that the blade 100 retracts reliably in water, while not being too large so that the centrifugal force cannot overcome the return force to achieve deployment when rotating at high speed in air.

[0047] like Figure 9 As shown, the return linkage device 400 includes a returner 401, a linkage 402, and a connector 403. The connector 403 connects the blade 100 and the returner 401, transmitting the return force of the returner 401 to the root of the blade 100. The linkage 402 establishes a linkage constraint between each blade 100, limiting each blade 100 to move synchronously under the combined action of the returner 401 and the medium resistance.

[0048] The return mechanism 401 provides elastic restoring force, preferably a tension spring, but torsion springs, gas springs, or elastomers (such as rubber blocks) with elastic restoring function can also be used. The connector 403 is preferably a hook, pin, or flexible connector. The linkage 402 can employ a synchronizing ring, linkage mechanism, or cable-pulley mechanism to achieve multi-blade linkage constraint.

[0049] The elastic coefficient k and preload of the return mechanism 401 should be determined based on the following two boundary conditions: Boundary condition 1 (air deployment): At the rated speed in the air, the deployment torque generated by the centrifugal force on the blade 100 must be greater than the sum of the restoring torque of the returner 401 and the air resistance torque.

[0050] Boundary condition 2 (underwater retraction): At the rated speed in water, the sum of the retraction torque generated by the fluid resistance on the blade 100 and the restoring torque of the return device 401 must be greater than the unfolding torque generated by the centrifugal force.

[0051] By reasonably selecting the elastic coefficient and preload of the return device 401, the propeller can satisfy the above two boundary conditions in air and water respectively, thus achieving reliable dual-mode adaptive switching.

[0052] The material of the recovery linkage device 400 is preferably stainless steel or titanium alloy to adapt to the corrosive working environment of high humidity and high salt spray underwater, and to ensure the stability of mechanical properties during long-term use. Example 4

[0053] Hinge axis space tilt as Figure 8 As shown, the spatial axis of the hinge shaft 502 is not simply arranged along the radial or axial direction of the hub 200, but is simultaneously inclined relative to both the radial and axial directions of the hub 200.

[0054] Specifically, the spatial axis of the hinge shaft 502 has a preset spatial tilt angle β1, β2 between it and the rotation plane of the propeller hub 200 (see...). Figure 8 This tilt angle causes the blade 10000 to exhibit coupled characteristics in three-dimensional space when it rotates around the hinge axis 502—that is, the radial displacement of the blade 10000 and the change in the spatial attitude angle of the blade 10000 are simultaneously achieved by the same rotational degree of freedom.

[0055] When the blade 10000 unfolds outward around the hinge axis 502, the blade stem section 102 rises with the rotation, and its pitch angle increases to θ1 (see...). Figure 3 and Figure 4 At this point, the propeller stem section 102 has a large effective angle of attack, which can generate thrust together with the downward-facing propeller tip.

[0056] When the blade 10000 retracts inward around the hinge shaft 502, due to the spatially tilted arrangement of the hinge shaft 502, the spatial attitude angle of the blade section 102 changes synchronously during the retraction process—the blade section 102 tends to be parallel to the plane of rotation (i.e., the pitch angle approaches 0°). At this time, the effective angle of attack of the blade section 102 approaches zero, and it cannot generate effective thrust on the medium, essentially ceasing to perform propulsive work (see...). Figure 6 and Figure 7 Meanwhile, the downward-reverse propeller tip, due to its preset downward-reverse angle α, still maintains a certain effective angle of attack θ2 in the folded state, and can generate propulsion force on the medium independently.

[0057] The values ​​of the hinge axis spatial tilt angles β1 and β2 should be determined comprehensively based on the required diameter and pitch changes of the vehicle in the air and underwater. Generally, the preferred range for β is 2° to 30°. Example 5

[0058] The hub structure of the present invention is as follows Figure 10 As shown, the rotor hub 200 preferably adopts a split-layer structure, including an upper hub plate 201 and a lower hub plate 202 that are stacked together. The upper hub plate 201 and the lower hub plate 202 are fixedly connected by a number of fasteners 300 evenly distributed along the circumference. The upper hub plate 201 and the lower hub plate 202 form a limiting cavity to accommodate the root of the rotor blade 100 (rotor root section 101) and the end of the return linkage device 400.

[0059] A limiting structure 600 is provided within the limiting cavity to limit the maximum unfolded position and the maximum folded position of the blade 100. When the blade 100 rotates to the maximum unfolded position, the root of the blade 100 abuts against the limiting structure 600, preventing the blade 100 from continuing to unfold outward; when the blade 100 rotates to the maximum folded position, the root of the blade 100 abuts against the limiting structure 600, preventing the blade 100 from continuing to fold inward.

[0060] The limiting structure 600 is preferably an adjustable limiting boss or limiting block. By adjusting the position of the limiting structure 600, the maximum deployed position and the maximum folded position of the blade 1 can be changed, thereby adjusting the working configuration of the propeller in the two media to adapt to different navigation conditions.

[0061] The fastener 300 is preferably provided with an anti-loosening locking structure, such as a self-locking nut, a spring washer, or a thread anti-loosening adhesive, to prevent the fastener from loosening due to vibration during high-speed rotation of the propeller.

[0062] The upper hub plate 201 and the lower hub plate 202 are preferably made of aluminum alloy or titanium alloy, and the weight is reduced as much as possible while ensuring sufficient structural strength. Example 6

[0063] The following combination Figures 2 to 7 The invention describes in detail the working process of the propeller in two different media.

[0064] (a) Working process in low-density medium (air) When the aircraft is in the air, the propeller rotates at high speed driven by the prime mover 700. Due to the low density and viscosity of air, the propeller blades 100 experience relatively little fluid resistance during rotation. Under this condition, the centrifugal force on the propeller blades 100 is dominant and sufficient to overcome the restoring torque of the return linkage device 400 and the slight air resistance, forcing each propeller blade 100 to unfold outward around the hinge axis 502.

[0065] like Figure 2 As shown, in the fully deployed state, each blade 100 extends radially outward to its maximum position, and the effective working diameter of the propeller reaches its maximum value D1. Simultaneously, due to the spatially tilted arrangement of the hinge shaft 502, the spatial attitude angle of the blades 100 changes synchronously during deployment—as... Figure 3 and Figure 4 As shown, the pitch angle of the propeller shaft section 102 at 75% of the turning radius reaches θ1. This pitch angle, together with the downward dihedral angle α of the propeller tip section 103, determines the aerodynamic performance of the propeller in the air. In this configuration, the propeller shaft section 102 and the downward dihedral tip jointly generate thrust. The propeller has a large diameter and a large combined pitch, which can generate sufficient aerodynamics under high flow and low pressure conditions to ensure the normal flight of the aircraft.

[0066] (II) Working process in high-density medium (water) When the vehicle enters the water, the working medium around the propeller changes from air to water. Water is about 800 times denser than air and about 50 times more viscous, causing the fluid resistance experienced by the propeller blades to increase dramatically during rotation.

[0067] Under this condition, the enormous fluid resistance acts on the surface of the blade 100, generating a torque that causes the blade 100 to fold and rotate in the retracting direction. This torque, combined with the restoring torque of the return linkage device 400, overcomes the centrifugal force (due to the increased resistance in the water, the speed of the prime mover decreases, and the centrifugal force decreases accordingly), forcing each blade 100 to retract inward around the hinge shaft 502.

[0068] like Figure 5 As shown, in the fully folded state, each blade 100 retracts inward to its minimum radial position, reducing the effective working diameter of the propeller to D2 (D2 is significantly smaller than D1). Simultaneously, due to the spatially tilted arrangement of the hinge shaft 502, the spatial attitude angle of the propeller stem section 102 changes synchronously in opposite directions during the retraction process—as... Figure 6 and Figure 7 As shown, the pitch angle of the propeller stem section 102 at 75% of the turning radius decreases to θ2 (θ2 is significantly smaller than θ1, approaching 0°), and the propeller stem section 102 tends to be straight and loses its propulsive function. The downward-facing propeller tip, due to its preset downward-facing angle α, still maintains a certain effective angle of attack in the folded state, generating thrust independently. In this configuration, the propeller has a smaller diameter and a smaller pitch, significantly reducing the effective working area of ​​the blades and effectively lowering the drag torque of the water medium on the blades. This allows the prime mover 700 to operate within its normal rated speed range, ensuring smooth output of torque and thrust.

[0069] (III) Automaticity and reversibility of configuration switching The configuration switch from air mode to underwater mode described above is automatically triggered by changes in the medium environment, requiring no electronic control signals or manual intervention. When the vehicle returns from the water to the air, as the medium resistance decreases significantly and the prime mover's speed increases (700 rpm), centrifugal force regains dominance, and the propeller blades (100) automatically deploy outward, restoring the air flight configuration. This reversible adaptive switching process can be automatically repeated each time the vehicle crosses the water-air interface, ensuring the continuous and normal operation of the propulsion system during repeated water entry and exit processes. Example 7

[0070] The number and distribution of blades in this invention: The number of blades 100 is two or more, and they are evenly distributed along the circumference of the hub 200.

[0071] When there are two blades (100), the structure is the simplest and the lightest, making it suitable for small, cross-medium vehicles. The two blades are symmetrically distributed at 180°, which facilitates dynamic balance adjustment.

[0072] When the number of blades 100 is three, each blade is evenly distributed at 120° along the circumference. The three-blade scheme achieves a good balance between aerodynamic / hydrodynamic performance and structural complexity, and is one of the preferred embodiments of the present invention.

[0073] When the number of blades 100 is four, each blade is evenly distributed at 90° around the circumference. The four-bladed design can provide a larger total thrust area, which is suitable for large transmedium vehicles with high propulsion power requirements, but the structural weight and moment of inertia will also increase accordingly.

[0074] Those skilled in the art can select the appropriate number of propellers from the above schemes based on the specific power requirements and weight limitations of the aircraft. Example 8

[0075] The material selection of this invention takes into account that the transmedium vehicle needs to work alternately in both air and water media. The selection of materials for each component of the propeller needs to take into account multiple requirements such as lightweight, high strength and corrosion resistance.

[0076] The propeller blade 100 is preferably made of carbon fiber composite material. Carbon fiber composite material has advantages such as high specific strength, high specific stiffness, low density, and good fatigue resistance. It can minimize weight, reduce rotational inertia, and improve propeller response speed while ensuring sufficient structural strength of the blade. The layup scheme and curing process of carbon fiber composite material are determined according to the stress state and airfoil requirements of the blade.

[0077] The recovery linkage device 400 is preferably made of stainless steel or titanium alloy. Stainless steel (such as 304, 316L) has good corrosion resistance and moderate elastic modulus, and is relatively inexpensive, making it suitable for general working environments. Titanium alloy (such as TC4) has higher specific strength and superior corrosion resistance, making it suitable for deep-sea working environments where weight and corrosion resistance requirements are more stringent.

[0078] Metal structural components such as the propeller hub 200, hinge seat 501, and hinge shaft 502 are preferably made of aluminum alloy (such as 7075) or titanium alloy to achieve lightweighting while ensuring structural strength. Fasteners 300 are preferably made of stainless steel or alloy steel and are equipped with anti-loosening structures.

[0079] A self-lubricating bushing or sealed bearing is preferably provided between the hinge shaft 502 and the propeller root section 101 to reduce rotational friction, improve rotational flexibility, and prevent impurities such as mud and sand from entering the rotational interface, thus ensuring the long-term reliability of the propeller in turbid waters. Example 9

[0080] To more clearly illustrate the technical contributions of this invention, a comparative analysis will be conducted below with the closest prior art, CN121106654A.

[0081] CN121106654A discloses a propeller with a cross-medium variable body, in which the blades are connected to a shaft via hinges, and the blades are configured to switch between an unfolded state and a folded state when rotating around the hinge axis. In this design, the blades are a single-piece structure, and when folded, the segments still propel the propeller as a whole, only changing the radial extension length of the blades (i.e., the working diameter), while the pitch angle of the blades remains constant during rotation. Therefore, although this design achieves diameter change, it fails to achieve adaptive synchronous adjustment of the pitch.

[0082] In contrast, this invention divides the blade 100 along its span into three functionally distinct sections: the root section 101, the trunk section 102, and the tip section 103. The tip section 103 is bent downward relative to the trunk section 102 to form a downward-curving tip. When the blade 100 is unfolded, the trunk section 102 and the downward-curving tip together generate propulsion. When the blade 100 is folded, the trunk section 102 tends to be straight and loses its propulsion function, while the downward-curving tip generates propulsion independently. Furthermore, the radial working length of the blade decreases synchronously with the pitch angle.

[0083] This "three-segment structure + functional division of labor" design concept is the essential difference between this invention and existing technologies. Existing technology CN121106654A uses a single-piece blade structure, where all segments still propel the blade together when folded. In contrast, the blade of this invention achieves functional division through a three-segment structure—the blade shaft and tip work together when unfolded, and the blade shaft actively withdraws from propulsion when folded, while the downward-facing tip independently completes propulsion. This synergistic effect of structural partitioning and functional division of labor enables this invention to achieve efficient propulsion in both water and air media, a capability completely absent in existing technologies.

[0084] Furthermore, compared to solutions that use active control mechanisms such as electric telescopic rods to simultaneously adjust the diameter and pitch, this invention requires no sensors, controllers, drive motors, or power supply lines. Its structure is simpler, more reliable, and lower in cost, making it particularly suitable for harsh underwater working environments with high pressure, high humidity, and high salt spray. The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An adaptive variable-configuration transmedium vehicle propeller, comprising a hub, a plurality of blades circumferentially distributed on the outer side of the hub, and a hinge assembly connecting the blades and the hub, characterized in that: The blade consists of a root section, a trunk section, and a tip section along its span from the inside to the outside. The blade is hinged to the hinge assembly through the root section, and the tip section is bent downward relative to the trunk section to form a downward-facing tip. During the rotation of the blade around the hinge axis, when the blade is extended, the blade shaft and the downward-reversing blade tip together generate propulsion force; when the blade is folded, the blade shaft tends to be straight and loses its propulsion function, the downward-reversing blade tip generates propulsion force alone, and the radial working length and pitch angle of the blade decrease synchronously, resulting in a reduction in the effective working area of ​​the blade.

2. The adaptive variable configuration transmedium vehicle propeller according to claim 1, characterized in that: It also includes a return linkage device connecting the blade and the hub; one end of the return linkage device is connected to the hub and the other end is connected to the root of the blade, and the force direction of the return linkage device is deviated from the axis of the hinge shaft on the radial section of the hub, so as to generate a return torque that increases with the increase of the folding angle when the blade rotates. The recovery linkage device includes a recoverer, a linkage, and a connector. The connector connects the blades and the recoverer, and the linkage limits the synchronous movement of each blade under the combined action of the recoverer and the medium resistance.

3. The adaptive variable configuration transmedium vehicle propeller according to claim 1, characterized in that: The hinge assembly includes a hinge seat fixedly connected to the propeller hub and a hinge shaft rotatably engaged within the hinge seat. The spatial axis of the hinge shaft is simultaneously inclined relative to both the radial and axial directions of the propeller hub, so that the propeller shaft tends to be straight when the propeller blade is folded.

4. The adaptive variable configuration transmedium vehicle propeller according to claim 1, characterized in that: The ratio of the spanwise length of the propeller tip section to the spanwise length of the propeller trunk section is 0.1 to 2, and the angle range of the downward dihedral angle between the propeller tip section and the propeller trunk section is 5° to 45°.

5. The adaptive variable configuration transmedium vehicle propeller according to claim 2, characterized in that: The radial offset distance between the force direction of the return linkage device and the axis of the hinge shaft on the radial section of the propeller hub is 1 / 5 to 1 / 2 of the width of the propeller root.

6. The adaptive variable configuration transmedium vehicle propeller according to claim 1, characterized in that: The propeller hub includes an upper hub plate and a lower hub plate that are stacked on top of each other. The upper hub plate and the lower hub plate are fixedly connected by a number of fasteners that are evenly distributed along the circumference. The upper hub plate and the lower hub plate form a limiting cavity to accommodate the root of the propeller blade and the connecting parts.

7. The adaptive variable configuration transmedium vehicle propeller according to claim 6, characterized in that: The limiting cavity is provided with a limiting structure to limit the maximum unfolded position and the maximum folded position of the blade.

8. The adaptive variable configuration transmedium vehicle propeller according to claim 7, characterized in that: The limiting structure is adjustable, and further, the limiting structure is an adjustable limiting boss or a limiting block.

9. The adaptive variable configuration transmedium vehicle propeller according to any one of claims 1 to 8, characterized in that: The number of blades is two or more and they are evenly distributed along the circumference of the hub. The blades are made of carbon fiber composite material, and the return linkage device is a stainless steel or titanium alloy spring.

10. A method for operating an adaptive variable-configuration transmedium vehicle propeller, the propeller comprising a hub, a plurality of blades circumferentially distributed outside the hub, and a hinge assembly connecting the blades and the hub, wherein the blades, along their spanwise direction from the inside to the outside, are sequentially a root section, a stem section, and a tip section, the tip section being bent downward relative to the stem section to form a downward-curving tip, characterized in that... Includes the following steps: When the propeller rotates in a low-density medium, the blades expand outward around the hinge axis under the action of centrifugal force. The propeller trunk and the lower counter-rotating tip together generate propulsion force. The radial working length of the blades increases and the pitch angle increases, that is, the effective working area of ​​the blades increases to a propulsion configuration that is adapted to the low-density medium. When the propeller rotates in a high-density medium, the blades fold inward around the hinge axis under the combined action of fluid resistance and the restoring torque of the return linkage device. The propeller shaft tends to be straight and loses its propulsive function. The lower anti-propeller tip generates propulsive force independently. The radial working length of the blades decreases and the pitch angle decreases, that is, the effective working area of ​​the blades is reduced to a propulsive configuration adapted to the high-density medium. During the rotation process of the blades unfolding and retracting, their radial working length and pitch angle change synchronously with the change of rotation position.

Images