A ducted propeller

Abstract

This invention proposes a ducted propeller, comprising a tube body, a propeller body, and protruding units. At least one groove is formed on the inner wall of the tube body. The propeller body is disposed within the tube body and located at one end of the tube body. The groove is spirally arranged around the central axis of the tube body. Several protruding units are continuously and uniformly arranged within the groove along its spiral line. Adjacent protruding units are connected end-to-end. By forming a spiral-shaped groove on the inner wall of the tube body, the propeller wake is rectified. As the wake flows towards the outlet at the free end of the tube body, the circumferential velocity component of the wake gradually decreases under the action of the groove. This results in the circumferential velocity component at the wake outlet being significantly smaller than that at the wake inlet, thereby improving propulsion efficiency and reducing noise.

Description

Technical Field

[0001] This invention relates to the field of aircraft propeller technology, and more particularly to a ducted propeller. Background Technology

[0002] A ducted propeller consists of a propeller and an externally mounted cylindrical guide tube. As a form of underwater propulsion, it is widely used in surface ships and underwater vehicles. Compared to ordinary propellers, ducted propellers offer advantages such as propeller protection, improved propulsion efficiency, and reduced noise. The continuous development of the shipbuilding industry has placed higher demands on the hydrodynamic and acoustic performance of surface ships and underwater vehicles, thus necessitating the development and innovation of propulsion technologies such as ducted propellers.

[0003] The wake of a propulsion device consists of axial and circumferential velocity components. To maximize propulsion efficiency and acoustic performance, it is desirable for the outflow to have only an axial velocity component and no circumferential velocity component. Therefore, flow control technology needs to be developed to rectify the wake through certain means, thereby minimizing the circumferential velocity component and achieving the goals of improving propulsion efficiency and reducing noise.

[0004] Furthermore, propeller tip vortices are one of the main sources of flow noise in propulsion systems and need to be controlled. The tiny gap between the duct and the blade tip of a ducted propeller is called the tip gap. During propeller operation, a suction zone forms in front of the blade, and a pressure zone is created behind it. Under the influence of this pressure difference, the fluid flows along the blade tip through the tip gap towards the suction zone. Upon entering the suction zone, it interacts with the low-pressure fluid, generating high-intensity vortices called tip gap vortices. This flow is called tip gap flow (TLV). Complex flow exists within the tip gap of a ducted propeller, with vortices of various sizes alternately shedding off. These unstable tip gap vortices not only affect propeller efficiency but also easily cause erosion damage to the propeller itself. In addition, the presence of tip gap vortices easily leads to cavitation in the low-pressure region of the vortex core, forming cavitation bubbles. The generation of cavitation bubbles directly increases the noise during propeller operation.

[0005] Therefore, how to reduce the circumferential velocity component of the wake and mitigate the adverse effects of tip gap vortices are important issues in the research and design of ducted propellers. Summary of the Invention

[0006] In view of this, the present invention proposes a ducted propeller to solve the problems of how to reduce the circumferential velocity component of the wake of the ducted propeller and reduce the adverse effects of tip gap vortices on the ducted propeller.

[0007] The technical solution of the present invention is implemented as follows: The present invention provides a duct propeller, including a tube body with at least one groove on the inner wall; a propeller body, disposed in the tube body and located at one end of the tube body; wherein the groove surrounds the central axis of the tube body in a spiral shape.

[0008] Based on the above technical solutions, preferably, it also includes a number of protruding units, which are continuously and evenly arranged in the groove along the spiral line of the groove; wherein, adjacent protruding units are connected end to end.

[0009] More preferably, the cross-sectional shape of the protruding unit along the spiral extension direction of the groove is trapezoidal or triangular; when the cross-sectional shape of the protruding unit is trapezoidal, the longer base of the protruding unit is fixed on the bottom surface of the groove and the shorter base of the protruding unit faces the inside of the pipe; when the cross-sectional shape of the protruding unit is triangular, one of the bases of the protruding unit is fixed on the bottom surface of the groove and one of the corners of the protruding unit faces the inside of the pipe.

[0010] More preferably, the cross-sectional shape of the protruding unit along the spiral extension direction of the groove is a right trapezoid or a right triangle, the extension line of the right-angled side of the protruding unit is aligned with the center of the radial cross-section of the tube, and the hypotenuse of the protruding unit faces the free end of the tube.

[0011] Based on the above technical solutions, preferably, the pitch of the grooved helix increases proportionally along the direction from the propeller body toward the free end of the tube.

[0012] Even more preferably, the depth of the groove increases proportionally with the increase of the helical pitch.

[0013] Even more preferably, the minimum pitch of the grooved helix is ​​the same as the pitch of the propeller body.

[0014] Based on the above technical solutions, preferably, the length of the grooved helix along the axial direction of the tube body is not less than the distance between the blade of the propeller body and the free end of the tube body.

[0015] Based on the above technical solutions, preferably, the rotation direction of the grooved helix is ​​the same as the rotation direction of the propeller body.

[0016] Based on the above technical solutions, preferably, the tube body includes a first tube with a groove on its inner wall and a paddle body inside; a second tube is fixedly sleeved outside the first tube; wherein, the first tube is made of sound-absorbing material.

[0017] The duct propeller of the present invention has the following advantages over the prior art:

[0018] (1) The present invention creates a spiral-shaped groove on the inner wall of the tube to rectify the propeller wake. When the wake flows toward the outlet of the free end of the tube, the circumferential velocity component of the wake gradually decreases under the action of the groove. This makes the circumferential velocity component at the wake outlet significantly smaller than that at the wake inlet, thereby improving propulsion efficiency and reducing noise.

[0019] (2) The present invention arranges several protruding units evenly along the groove inside, so that the protruding units form a wave-shaped rectification structure. When the wake passes through the groove, the wave-shaped rectification structure will generate a force on the wake opposite to the direction of the wake rotation. This can not only greatly reduce the circumferential velocity component of the wake, but also induce the blade tip vortex of the propeller to separate into smaller vortices, dissipate the energy in the blade tip vortex, thereby achieving the purpose of reducing the flow noise generated by the blade tip vortex.

[0020] (3) The tube body of the present invention is formed by two inner and outer tubes, which is convenient for disassembly and installation, and the design and manufacturing are relatively simple. The inner tube is made of sound-absorbing material, and grooves and protruding units are provided on the inner tube, which helps to absorb the flow noise generated by the wake and achieve the purpose of improving the acoustic performance of the propulsion device. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a side sectional view of the duct propeller of the present invention;

[0023] Figure 2 This is a perspective view of the tube body of the present invention;

[0024] Figure 3 This is a three-dimensional schematic diagram of the internal structure of the tube body of the present invention;

[0025] Figure 4 This is a side sectional view of the tube body of the present invention;

[0026] Figure 5 This is a perspective view of the protruding unit of the present invention;

[0027] Figure 6 This is a side sectional view of the protruding unit of the present invention.

[0028] In the diagram: 1. Tube body; 11. First tube; 12. Second tube; 101. Groove; 2. Paddle body; 3. Protruding unit. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, combined with Figure 2 and Figure 3 The present invention provides a ducted propeller, comprising a duct body 1 and a propeller body 2.

[0031] In this design, tube 1 is the duct section of the ducted propeller. Tube 1 is open at both ends; the end with the propeller is the wake inlet, and the end furthest from the propeller is the wake outlet. Although tube 1 is cylindrical in the accompanying drawings, in actual vehicles, it can also be conical, drum-shaped, or bottleneck-shaped. At least one groove 101 is formed on the inner wall of tube 1, spiraling around the central axis of tube 1. The function of the groove 101 is to rectify the wake, reducing its circumferential velocity component.

[0032] The propeller body 2 is the propeller part of the ducted propeller. The propeller body 2 has at least two blades arranged circumferentially. The shape of the blades is a spiral twist at a certain angle, so the design parameters of the blades also include the pitch. The propeller body 2 is set inside the tube 1 and located at the inlet end of the tube 1. After the water flows into the tube 1 from the inlet end of the tube 1, it is accelerated by the rotation of the propeller body 2 and becomes a tailflow. The tailflow is then ejected from the outlet end of the tube 1.

[0033] The principle of improving the rectification of the wake by the groove 101 in this case is as follows: assuming there is a moving point in the wake, it can be observed that after the wake is accelerated by the propeller body 2, it forms a spiral trajectory within the tube body 1. Therefore, the moving point always has axial velocity components during its movement. Since there are countless moving points in the wake, and the spiral trajectories of different moving points are not exactly the same, the circumferential velocity components of different moving points differ greatly, which is one of the reasons why the wake generates eddies. In this embodiment, by opening a spiral groove 101 on the inner wall of the tube body 1, it can be regarded as using the spiral trajectory of a moving point with a relatively small circumferential velocity component in the wake as a reference to guide different moving points in the wake. This allows the moving point with a relatively large circumferential velocity to be transformed into a moving point with a relatively small circumferential velocity under the guidance of the groove 101, thereby achieving the purpose of reducing the circumferential velocity component of the wake.

[0034] In addition, based on the different shapes and design parameters of the tube body 1, the axial velocity component and circumferential velocity component of the wake under the shape of the tube body 1 can be calculated, so as to design the corresponding groove 101.

[0035] exist Figure 5 In a preferred embodiment shown, a protruding unit 3 is also included.

[0036] Among them, several protruding units 3 are continuously and uniformly arranged in the groove 101 along the spiral line of the groove 101. Adjacent protruding units 3 are connected end to end to form a wave-shaped rectification structure. When the wake passes through the groove 101, the wave-shaped rectification structure will generate a force on the wake opposite to the direction of the wake rotation. This can not only greatly reduce the circumferential velocity component of the wake, but also induce the blade tip vortex of the propeller to separate into smaller vortices, dissipating the energy in the blade tip vortex, thereby achieving the purpose of reducing the flow noise generated by the blade tip vortex.

[0037] exist Figure 6 In a preferred embodiment shown, since it is necessary to form a wave-like rectifying structure with several protruding units 3, the cross-sectional shape of the protruding units 3 along the spiral extension direction of the groove 101 is trapezoidal or triangular. Specifically, when the cross-sectional shape of the protruding unit 3 is trapezoidal, the longer base of the protruding unit 3 is fixed to the bottom surface of the groove 101 and the shorter base of the protruding unit 3 faces the inside of the tube body 1; while when the cross-sectional shape of the protruding unit 3 is triangular, one of the bases of the protruding unit 3 is fixed to the bottom surface of the groove 101 and one corner of the protruding unit 3 faces the inside of the tube body 1. This causes the wave-like rectifying structure to generate a force on the wake that is opposite to the direction of the wake's rotation.

[0038] exist Figure 6 In a preferred embodiment shown, to ensure good rectification efficiency of the rectifying structure composed of several protruding units 3, the cross-sectional shape of the protruding unit 3 along the spiral extension direction of the groove 101 can be a right trapezoid or a right triangle, preferably a right triangle. The extension line of the right-angled side of the protruding unit 3 is aligned with the center of the radial cross-section of the tube body 1, and the hypotenuse of the protruding unit 3 faces the free end of the tube body 1. Typically, the apex corner of the triangle of the protruding unit 3 is rounded to avoid affecting the rectification efficiency.

[0039] exist Figure 3 In a preferred embodiment shown, the pitch of the helix of the groove 101 increases proportionally along the direction from the propeller body 2 toward the free end of the tube body 1. As previously mentioned, assuming there is a moving point in the wake, when the moving point moves along the groove 101, as the pitch of the groove 101 gradually increases, the circumferential velocity component of the moving point decreases accordingly, thus further reducing the circumferential velocity component of the wake.

[0040] exist Figure 4In a preferred embodiment shown, the depth of the groove 101 increases proportionally with the increase of the helical pitch. As previously mentioned, assuming there is a moving point in the wake, when the moving point moves along the groove 101, as the pitch of the groove 101 gradually increases, the helical length traversed by the moving point in one helical revolution becomes longer. The increase in the depth of the groove 101 is similar to expanding the circumference of the radial cross-section of that helical revolution, thereby further increasing the helical length that the moving point needs to traverse, which helps to further reduce the circumferential velocity component of the wake.

[0041] exist Figure 1 In a preferred embodiment shown, the minimum pitch of the helix of the groove 101 is the same as the pitch of the propeller body 2, so that the wake can be rectified by the groove 101 as quickly and with less impact.

[0042] exist Figure 1 In a preferred embodiment shown, the length of the spiral of the groove 101 along the axial direction of the tube body 1 is not less than the distance between the blade of the propeller body 2 and the free end of the tube body 1, so that the wake can enter the groove 101 as soon as possible and be rectified.

[0043] exist Figure 1 In a preferred embodiment shown, the rotation direction of the spiral of the groove 101 is the same as the rotation direction of the propeller body 2, so that the wake can be effectively rectified by the groove 101.

[0044] exist Figure 1 In a preferred embodiment shown, the tube body 1 includes a first tube 11 and a second tube 12.

[0045] The first tube 11 has a groove 101 on its inner wall and houses the propeller body 2 inside. The first tube 11 is made of sound-absorbing material, which helps absorb the flowing noise generated by the wake, thereby improving the acoustic performance of the propulsion device. Specifically, it can be foamed metal or foamed glass; foamed glass is preferred in surface ships or underwater vehicles to reduce adverse effects such as corrosion. The first tube 11 is preferably manufactured using additive manufacturing.

[0046] The second tube 12 is fixedly sleeved outside the first tube 11; the two tubes, one inside the other, form a ring, making the tube body 1 easy to disassemble and install, and simplifying the design and manufacturing process. The second tube 12 is usually made of metal, specifically high-strength stainless steel or titanium alloy, and mainly serves to shape and fix the tube.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ducted propeller, characterized in that, include: The inner wall of the pipe body (1) has at least one groove (101). The propeller body (2) is disposed inside the tube (1) and located at one end of the tube (1); Several protruding units (3) are continuously and evenly arranged in the groove (101) along the spiral line of the groove (101); The groove (101) is spiral around the central axis of the tube body (1); the rotation direction of the spiral of the groove (101) is the same as the rotation direction of the propeller body (2); The adjacent protruding units (3) are connected end to end, and the cross-sectional shape of the protruding unit (3) along the spiral extension direction of the groove (101) is trapezoidal or triangular; When the cross-sectional shape of the protruding unit (3) is trapezoidal, the longer bottom edge of the protruding unit (3) is fixed on the bottom surface of the groove (101) and the shorter bottom edge of the protruding unit (3) faces the inside of the tube body (1). When the cross-sectional shape of the protruding unit (3) is triangular, one of the bottom edges of the protruding unit (3) is fixed on the bottom surface of the groove (101) and one corner of the protruding unit (3) faces the inside of the tube body (1).

2. The ducted propeller according to claim 1, characterized in that: The cross-sectional shape of the protruding unit (3) along the spiral extension direction of the groove (101) is a right trapezoid or a right triangle. The extension line of the right-angled side of the protruding unit (3) is aligned with the center of the radial cross-section of the tube body (1). The hypotenuse of the protruding unit (3) faces the free end of the tube body (1).

3. The ducted propeller according to claim 1, characterized in that: The pitch of the groove (101) helix increases proportionally along the direction from the propeller body (2) toward the free end of the tube body (1).

4. A ducted propeller according to claim 3, characterized in that: The depth of the groove (101) increases proportionally with the increase of the helical pitch.

5. A ducted propeller according to claim 3, characterized in that: The minimum pitch of the groove (101) helix is ​​the same as the pitch of the propeller body (2).

6. A ducted propeller according to claim 1, characterized in that: The length of the groove (101) spiral along the axial direction of the tube body (1) is not less than the distance between the blade of the propeller body (2) and the free end of the tube body (1).

7. A ducted propeller according to claim 1, characterized in that: The tube body (1) includes, The first tube (11) has the groove (101) opened on its inner wall and the paddle body (2) is installed inside. The second tube (12) is fixedly sleeved outside the first tube (11); The first tube (11) is made of sound-absorbing material.

Images