A folding propeller with a blade hub conforming

Abstract

The present application belongs to the field of aircraft technology, and particularly relates to a folding propeller with conformal blades and hub. The center of gravity of the propeller blade is set, and the mass of a single propeller blade and the distance from the center of gravity of the propeller blade to the rotation center are designed, so that the aerodynamic thrust is equal to and opposite to the component of the centripetal force of the propeller blade in the negative direction of the normal line. Thus, the deformation of the propeller blade caused by the thrust is compensated, the center line of the propeller blade is coincident with the rotation plane, and the propeller blade and the propeller hub form a complete integrated propeller. Through the shape and structure design of the propeller blade, the center of gravity is offset from the rotation plane and offset by a certain distance in the thrust direction, so that the axial aerodynamic force and the axial component of the centrifugal force of the propeller blade are balanced when the propeller blade rotates, the folding propeller is in the design point state when working, the propeller efficiency is improved, and the propeller is more stable when rotating.

Description

Technical Field

[0001] This invention belongs to the field of aircraft technology, and specifically relates to a folding propeller with conformal blade and hub design. Background Technology

[0002] As a core power component of drones, aircraft, and other equipment, propellers typically consist of blades and a hub, and their performance directly affects the equipment's range, efficiency, and safety. While traditional non-folding propellers can provide stable thrust, they occupy a large space when stored, especially in shipborne or tube-launched scenarios, where size limitations can easily affect the efficiency of equipment transportation and deployment.

[0003] Chinese invention patents CN108688792A, CN108621725B, and Chinese utility model patent CN221163312U each provide a folding propeller device. The propeller is folded by adding external devices such as elastic elements and electromagnetic blocks at the connection between the hub and the blades. Although the folding function is achieved, the irregularly shaped hub will bring greater resistance and will not generate lift, which will reduce the efficiency of the propeller and thus reduce the range and flight time of the aircraft.

[0004] Chinese utility model patents CN207417150U and CN210455185U respectively provide a folding propeller device, which folds axially using bolts and hinges and uses centrifugal force to achieve autonomous propeller deployment. However, it lacks a precise locking mechanism. After the blades rotate, they will fold at a certain angle around the folding axis along the thrust direction. At this time, the propeller rotation surface is a cone surface with a large angle, which deviates from the propeller design point. At the same time, the blades will also wobble when rotating at high speed or changing speed, causing unstable thrust and reduced efficiency.

[0005] Existing folding propellers, due to the need to consider the folding function, have a hub that occupies a large proportion of the total propeller length. This hub is an irregularly shaped component and not a lifting body; during operation, it only generates rotational drag, not thrust. At high speeds, the hub contributes entirely to negative drag, affecting the overall aerodynamics of the propeller. Furthermore, the design of the blade's center of gravity in a folding propeller is crucial. As the propeller rotates, the thrust causes the blades to rotate around the folding axis. The center of gravity needs to be offset from the plane of rotation by a certain distance, allowing centrifugal force to generate a force of equal magnitude in the opposite direction of the thrust. This ensures the propeller's plane of rotation is a flat plane, representing the ideal design state, rather than the propeller becoming a cone under the influence of thrust after rotation. Summary of the Invention

[0006] (a) Technical problems to be solved The technical problems to be solved by the present invention are: 1) The existing folding propeller hub is an irregular part, which only generates resistance and not thrust when rotating, thus reducing the propeller efficiency; 2) When the folding propeller rotates, the blades will rotate around the folding axis at a certain angle under the action of thrust. At this time, the propeller deviates from the design point, thus reducing the propeller efficiency.

[0007] (II) Technical Solution To solve the above-mentioned technical problems, the present invention provides a folding propeller with conformal blade and hub design, such as... Figure 1 As shown, the folding propeller includes: a propeller hub (1), propeller blades (2), and a folding shaft (3). The propeller blades (2) are provided in two, located on both sides of the propeller hub (1) and connected to the propeller hub (1). The two propeller blades (2) are respectively provided with connecting holes in the connecting parts of the two propeller blades (2) and the propeller hub (1). The connection means is to achieve hinge connection through the folding shaft (3). Specifically, by setting the center of gravity position of the propeller blades, and designing the mass of a single propeller blade and the distance from the center of gravity of the propeller blade to the center of rotation, the aerodynamic thrust is increased. F The component of the centripetal force in the negative direction of the normal to the propeller blade (2) F nY Equal and opposite in direction, thereby compensating for the blade deformation caused by thrust, and enabling the center line of the propeller blade (2) to coincide with the plane of rotation. At this time, the propeller blade (2) and the propeller hub (1) form a complete integrated propeller.

[0008] Define the two propeller blades (2) as extending radially when deployed; When the propeller blade (2) rotates, the plane formed is a rotating plane that covers the radial direction, and the normal direction of this rotating plane is the axial direction; When the propeller blades (2) need to be stored in a small space, they are in an axially folded state, such as... Figure 2 As shown; when the aircraft is operating, the propeller rotates at high speed, and the propeller blades unfold under the action of centrifugal force, as... Figure 1 As shown.

[0009] When the folding propeller rotates at high speed, it generates a positive aerodynamic thrust along the direction of the aircraft's flight, i.e., in the direction normal to the aforementioned plane of rotation. F This aerodynamic thrust F The force acts on the propeller blade (2), causing the propeller blade (2) to rotate around the folding axis (3) in the direction of thrust. At this time, the connection between the propeller blade (2) and the propeller hub (1) is not flush, deviating from the propeller design point, resulting in aerodynamic loss and unstable rotation.

[0010] The propeller blade (2) has the following shape and structure: (1) Setting the center of gravity of the propeller blades; With the propeller blade (2) in a horizontally laid-out state, its center of gravity is set to be offset by a certain distance H relative to the plane of rotation in the positive normal direction, and the method for determining this distance H is as follows: like Figure 3 and Figure 4 According to geometric relationships, after the center of gravity shifts a distance H in the positive direction of the normal to the plane of rotation, the line connecting the center of gravity to the center of rotation, which is the line of action of the centripetal force, makes an angle with the plane of rotation. θ Satisfy: sin θ = H / L cg ; in, L cg This is the distance from the center of gravity of the propeller blade to the center of rotation. Combining the centripetal force formula F n = mω 2 L cg m is the mass of a single blade, and represents the foldable portion; F n The centripetal force is the force from the center of gravity of the propeller blade (2) to the rotation center of the propeller hub (1); The component of centripetal force in the negative normal direction F nY Represented as: F nY = F n sin θ = mω 2 L cg × H / L cg = mω 2 H According to "aerodynamic thrust" F The centripetal force normal to the propeller blade (2) F nY The equilibrium condition of "equal in magnitude and opposite in direction" allows F = F nY Substituting into the above formula, we get: H = F / mω 2 .

[0011] In practical engineering design, the H value is verified and corrected in the following ways: If the calculated H value is too large, causing the propeller blade's center of gravity to shift beyond the structural profile, it is necessary to increase the number of blades, reduce the design value of F for a single blade, or appropriately increase the propeller's design speed. ω Increase F nY Quantity.

[0012] (2) Parameter settings for propeller blades; The centripetal force on the propeller blade (2) whose center of gravity points towards the center of rotation of the propeller hub (1). F n = mω 2 L cg Decompose the forces into components along the negative normal. F nY And the component force along the radial direction in the plane of rotation; The angle between the direction of the centripetal force and the plane of rotation is θ In this case, F nY = F n ×sin θ = mω 2 L cg ×sin θ ; Therefore, in order to achieve F nY For parameters equal in magnitude to F but opposite in direction, the following types of parameters need to be preset: 1) The mass m of a single blade is predetermined through material selection and structural optimization. Carbon fiber composite material with a density of 1.7 g / cm³ is used, and the uniformity of mass distribution is verified by finite element analysis to avoid excessive local mass leading to center of gravity shift error. The mass deviation of a single blade is controlled within ±3% to ensure the force balance of the two blades. 2) Distance from the center of gravity to the center of rotation L cg The shape of the blade is determined by both its external profile and internal reinforcing structure, and is pre-calibrated using three-dimensional center of gravity analysis software. L cg The design value and the blade radius R satisfy 0.4R≤ L cg ≤0.6R, to ensure the effective proportion of the centripetal force; In addition, the design speed ωThe rated speed and reduction ratio of the motor in the aircraft's power system are preset, and the speed is in line with the most commonly used cruise speed conditions of the aircraft. In addition, the aerodynamic thrust F is designed and determined in advance based on the rated flight speed required by the aircraft design. This parameter directly affects the calculation result of the aerodynamic thrust F. It needs to be calculated in the aerodynamic simulation software Fluent to ensure that the aerodynamic thrust F is stable at the design speed.

[0013] This results in aerodynamic thrust F Component of the force in the negative direction of the centripetal force normal F nY Equal and opposite in direction, thereby compensating for the blade deformation caused by thrust, and enabling the center line of the propeller blade (2) to coincide with the plane of rotation. At this time, the propeller blade (2) and the propeller hub (1) form a complete integrated propeller.

[0014] (III) Beneficial Effects To improve the performance of folding propeller devices, this invention proposes a folding propeller with conformal blade and hub design. Instead of using a separate folding hub, a portion of the blade root structure is directly used as the hub, connected via a rotating shaft to achieve folding and unfolding functions. Simultaneously, the blade's center of gravity is rationally designed to balance the component of centrifugal force in the thrust direction with the blade thrust, ensuring that the propeller's rotational plane is a single plane in the unfolded (working) state. In this state, the propeller remains at its designed point after unfolding, guaranteeing propeller efficiency.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The present invention provides a folding propeller with conformal blade and hub. In the folded state, the radial dimension is greatly reduced, which facilitates the storage and transportation of aircraft and deployment in confined spaces such as shipborne and tube-launched environments, and reduces the requirements for storage space.

[0016] 2. The present invention provides a folding propeller with conformal blade and hub, consisting only of a conformal hub, blades and folding shaft. It has a simple structure, requires no external force to drive, and can automatically unfold by centrifugal force. The structure is simple and easier to design for lightweight applications.

[0017] 3. The present invention provides a folding propeller with conformal blade and hub. The hub part itself is part of the blade. After unfolding, it forms a complete propeller with the blade. Compared with existing folding propellers, the hub part has less rotational resistance and can generate additional thrust, which reduces losses and increases thrust.

[0018] 4. This invention provides a folding propeller with conformal blade and hub design. The shape and structure of the blade are designed so that the center of gravity is offset from the plane of rotation and shifted a certain distance in the direction of thrust. This balances the axial aerodynamic force and the axial component of the centrifugal force on the blade during rotation, ensuring that the folding propeller is in the designed state during operation. This improves the propeller efficiency and makes the propeller more stable during rotation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a folding propeller with conformal blade and hub design according to this embodiment. Figure 2 This is a schematic diagram of the folded state of a folding propeller with conformal blade and hub according to this embodiment. Figure 3 This is a side force diagram of a folding propeller with conformal blade and hub according to this embodiment. Figure 4 This is a schematic diagram illustrating the mechanical and geometric relationships involved in the technical solution of this invention. In the picture: 1. Propeller hub, 2. Propeller blades, 3. Folding shaft. Detailed Implementation

[0020] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0021] To address the problems of existing technologies, this invention provides a folding propeller with conformal blade and hub design, such as... Figure 1 As shown, the folding propeller includes: a propeller hub (1), propeller blades (2), and a folding shaft (3). The propeller blades (2) are provided in two, located on both sides of the propeller hub (1) and connected to the propeller hub (1). The two propeller blades (2) are respectively provided with connecting holes in the connecting parts of the two propeller blades (2) and the propeller hub (1). The connection means is to achieve hinge connection through the folding shaft (3). Specifically, by setting the center of gravity position of the propeller blades, and designing the mass of a single propeller blade and the distance from the center of gravity of the propeller blade to the center of rotation, the aerodynamic thrust is increased. F The component of the centripetal force in the negative direction of the normal to the propeller blade (2) F nY Equal and opposite in direction, thereby compensating for the blade deformation caused by thrust, and enabling the center line of the propeller blade (2) to coincide with the plane of rotation. At this time, the propeller blade (2) and the propeller hub (1) form a complete integrated propeller.

[0022] Define the two propeller blades (2) as extending radially when deployed; When the propeller blade (2) rotates, the plane formed is a rotating plane that covers the radial direction, and the normal direction of this rotating plane is the axial direction; When the propeller blades (2) need to be stored in a small space, they are in an axially folded state, such as... Figure 2 As shown; when the aircraft is operating, the propeller rotates at high speed, and the propeller blades unfold under the action of centrifugal force, as... Figure 1 As shown.

[0023] When the folding propeller rotates at high speed, it generates a positive thrust along the direction of the aircraft's flight, i.e., in the direction normal to the aforementioned plane of rotation. F The thrust F The force acts on the propeller blade (2), causing the propeller blade (2) to rotate around the folding axis (3) in the direction of thrust. At this time, the connection between the propeller blade (2) and the propeller hub (1) is not flush, deviating from the propeller design point, resulting in aerodynamic loss and unstable rotation.

[0024] The propeller blade (2) has the following shape and structure: (1) Setting the center of gravity of the propeller blades; With the propeller blade (2) in a horizontally laid-out state, its center of gravity is set to be offset by a certain distance H relative to the plane of rotation in the positive normal direction, and the method for determining this distance H is as follows: like Figure 3 and Figure 4 According to geometric relationships, after the center of gravity shifts a distance H in the positive direction of the normal to the plane of rotation, the line connecting the center of gravity to the center of rotation, which is the line of action of the centripetal force, makes an angle with the plane of rotation. θ Satisfy: sin θ = H / L cg ; in, L cg This is the distance from the center of gravity of the propeller blade to the center of rotation. Combining the centripetal force formula F n = mω 2 L cg m is the mass of a single blade, and represents the foldable portion; F n The centripetal force is the force from the center of gravity of the propeller blade (2) to the rotation center of the propeller hub (1); The component of centripetal force in the negative normal direction F nY Represented as: F nY =F n sin θ = mω 2 L cg × H / L cg = mω 2 H According to "aerodynamic thrust" F With the negative component of the centripetal force F nY The equilibrium condition of "equal in magnitude and opposite in direction" allows F = F nY Substituting into the above formula, we get: H = F / mω 2 .

[0025] In practical engineering design, the H value is verified and corrected in the following ways: If the calculated H value is too large, causing the propeller blade's center of gravity to shift beyond the structural profile, it is necessary to increase the number of blades, reduce the design value of F for a single blade, or appropriately increase the propeller's design speed. ω Increase F nY Quantity.

[0026] (2) Parameter settings for propeller blades; The centripetal force on the propeller blade (2) whose center of gravity points towards the center of rotation of the propeller hub (1). F n = mω 2 L cg Decompose the forces into components along the negative normal. F nY And the component force along the radial direction in the plane of rotation; The angle between the direction of the centripetal force and the plane of rotation is θ In this case, F nY = F n ×sin θ = mω 2 L cg ×sin θ ; Therefore, in order to achieve F nYFor parameters equal in magnitude to F but opposite in direction, the following types of parameters need to be preset: 1) The mass m of a single blade is predetermined through material selection and structural optimization. Carbon fiber composite material with a density of 1.7 g / cm³ is used, and the uniformity of mass distribution is verified by finite element analysis to avoid excessive local mass leading to center of gravity shift error. The mass deviation of a single blade is controlled within ±3% to ensure the force balance of the two blades. 2) Distance from the center of gravity to the center of rotation L cg The shape of the blade is determined by both its external profile and internal reinforcing structure, and is pre-calibrated using three-dimensional center of gravity analysis software. L cg The design value and the blade radius R satisfy 0.4R≤ L cg ≤0.6R, to ensure the effective proportion of the centripetal force; In addition, the design speed ω The rated speed and reduction ratio of the motor in the aircraft's power system are preset, and the speed is in line with the most commonly used cruise speed conditions of the aircraft. In addition, the aerodynamic thrust F is designed and determined in advance based on the rated flight speed required by the aircraft design. This parameter directly affects the calculation result of the aerodynamic thrust F. It needs to be calculated in the aerodynamic simulation software Fluent to ensure that the aerodynamic thrust F is stable at the design speed.

[0027] This results in aerodynamic thrust F Component of the force in the negative direction of the centripetal force normal F nY Equal and opposite in direction, thereby compensating for the blade deformation caused by thrust, and enabling the center line of the propeller blade (2) to coincide with the plane of rotation. At this time, the propeller blade (2) and the propeller hub (1) form a complete integrated propeller.

[0028] In summary, the present invention provides a folding propeller with conformal blade and hub design. By directly using a portion of the structure at the root of the blade as the hub, the propeller is deployed in a manner that conforms to the blade and hub design, thereby improving propeller performance and reducing aerodynamic losses. All of these improvements fall within the scope of protection of the present invention.

[0029] This invention designs the blade's center of gravity to deviate from the plane of rotation and shift it a certain distance in the direction of thrust. This balances the axial aerodynamic thrust and the axial component of the centrifugal force experienced by the blade during rotation, ensuring that the folding propeller is in the designed state during operation. This improves the propeller's efficiency and stability, all of which are within the scope of protection of this invention.

[0030] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A folding propeller with conformal blade and hub design, characterized in that, The folding propeller includes: a propeller hub (1), a propeller blade (2), and a folding shaft (3). The propeller blades (2) are provided in two, located on both sides of the propeller hub (1) and connected to the propeller hub (1). The two propeller blades (2) are respectively provided with connecting holes in the connecting parts of the two propeller blades (2) and the propeller hub (1). The connection means is to achieve hinge connection through the folding shaft (3). Specifically, by setting the center of gravity position of the propeller blades, and designing the mass of a single propeller blade and the distance from the center of gravity of the propeller blade to the center of rotation, the aerodynamic thrust is increased. F The component of the centripetal force in the negative direction of the normal to the propeller blade (2) F nY Equal and opposite in direction, thereby compensating for the blade deformation caused by thrust, and enabling the center line of the propeller blade (2) to coincide with the plane of rotation. At this time, the propeller blade (2) and the propeller hub (1) form a complete integrated propeller. Among them, the two propeller blades (2) are defined to extend radially when deployed; When the propeller blade (2) rotates, the plane formed is a rotating plane that covers the radial direction, and the normal direction of this rotating plane is the axial direction; When the propeller blades (2) need to be stored in a small space, they are in an axially folded state; when the aircraft is working, the propeller rotates at high speed and the propeller blades unfold under the action of centrifugal force. The center of gravity of the propeller blade (2) is set as follows: With the propeller blade (2) in a horizontally laid-out state, its center of gravity is set to be offset by a certain distance H relative to the plane of rotation in the positive normal direction, and the method for determining this distance H is as follows: After the center of gravity shifts a distance H in the positive direction normal to the plane of rotation, the line connecting the center of gravity to the center of rotation (the line of action of the centripetal force) makes an angle with the plane of rotation. θ Satisfy: sin θ = H / L cg ; in, L cg This is the distance from the center of gravity of the propeller blade to the center of rotation. Combining the centripetal force formula F n = mω 2 L cg m is the mass of a single blade, and represents the foldable portion; F n The centripetal force is the force from the center of gravity of the propeller blade (2) to the rotation center of the propeller hub (1); The component of centripetal force in the negative normal direction F nY Represented as: F nY = F n sin θ = mω 2 L cg × H / L cg = mω 2 H According to "aerodynamic thrust" F With the negative component of the centripetal force F nY The equilibrium condition of "equal in magnitude and opposite in direction" allows F = F nY Substituting into the above formula, we get: H = F / mω 2 ； The propeller blade parameters are set as follows: The centripetal force on the propeller blade (2) whose center of gravity points towards the center of rotation of the propeller hub (1). F n = mω 2 L cg Decompose the forces into components along the negative normal. F nY And the component force along the radial direction in the plane of rotation; The angle between the direction of the centripetal force and the plane of rotation is θ In this case, F nY = F n ×sin θ = mω 2 L cg ×sin θ ; Therefore, in order to achieve F nY For parameters equal in magnitude to F but opposite in direction, the following types of parameters need to be preset: 1) The mass m of a single blade is predetermined through material selection and structural optimization. Carbon fiber composite material with a density of 1.7 g / cm³ is used, and the uniformity of mass distribution is verified by finite element analysis to avoid excessive local mass leading to center of gravity shift error. The mass deviation of a single blade is controlled within ±3% to ensure the force balance of the two blades. 2) Distance from the center of gravity to the center of rotation L cg The shape of the blade is determined by both its external profile and internal reinforcing structure, and is pre-calibrated using three-dimensional center of gravity analysis software. L cg The design value and the blade radius R satisfy 0.4R≤ L cg ≤0.6R, to ensure the effective proportion of the centripetal force; Among them, the design speed ω The rated speed and reduction ratio of the motor in the aircraft's power system are preset, and the speed is in line with the most commonly used cruise speed conditions of the aircraft. Among them, the design aerodynamic thrust F is predetermined based on the rated flight speed required by the aircraft design. This parameter directly affects the calculation result of the aerodynamic thrust F. It needs to be calculated in the aerodynamic simulation software Fluent to ensure that the aerodynamic thrust F is stable at the design speed. This results in aerodynamic thrust F Component of the force in the negative direction of the centripetal force normal F nY Equal and opposite in direction, thereby compensating for the blade deformation caused by thrust, and enabling the center line of the propeller blade (2) to coincide with the plane of rotation. At this time, the propeller blade (2) and the propeller hub (1) form a complete integrated propeller.

2. The folding propeller with conformal blade and hub as described in claim 1, characterized in that, In practical engineering design, the H value is verified and corrected in the following ways: If the calculated H value is too large, causing the propeller blade's center of gravity to shift beyond the structural profile, it is necessary to increase the number of blades, reduce the design value of the aerodynamic thrust F of a single blade, or appropriately increase the propeller's design speed. ω Increase F nY Quantity.

3. The folding propeller with conformal blade and hub as described in claim 1, characterized in that, The folding propeller directly uses a part of the root structure of the blade as the hub, which is connected by a rotating shaft to achieve the function of folding and unfolding.

4. The folding propeller with conformal blade and hub as described in claim 1, characterized in that, The folding propeller has a rationally designed blade center of gravity, which balances the component of centrifugal force in the thrust direction with the blade thrust, so that the rotation surface of the propeller in the unfolded state is a plane. At this time, the propeller still maintains the design point state after unfolding, ensuring the efficiency of the propeller.

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